neuro guide 2

Module 6

Visual system

• Eyes are part of your brain 

Light is electromagnetic radiation

• Wave amplitude = brightness

  • Amplitude - height of wave  

• Wavelength = color

  • Wavelength - length of wave 

The retina

• Back of your eyes

• Where transduction happens

  • Transduction - energy from environment converted to change membrane potential

• Light-sensitive 

• Receptor cells + neurons 

• We’re actually viewing the world upside down

• 2 types of photo receptors, rods and cones 

Rods and cones

120 million rods 

• sensitive to dim light, but not color

• night vision – best in dim light

• function well in low light

• more toward outsides of retina

6 million cones 

• operate best in light

• responds to color

• 3 types, sensitive to red, green, blue

• more toward middle of retina

• 3 types of cones: red, green, and blue

• Light get translated into the language of the nervous system

Phototransduction

photopigment molecules: 

• rhodopsin (rods) 

• iodopsin (cones; 3 types)

• Photoreceptors constantly are releasing neurotransmitters in the dark 

Receptive field

• Refers to the portion of space that can make a neuron respond when to move

• Refers to what part of the visual field (or what part of the world that’s in front of me) that one particular neuron in my retina is paying attention to

• Retina contains a map of the world in front of you upside down

The visual field

Optical chiasm 

• nasal information crosses, temporal information does not 

• so, left visual field goes to right side of brain and vice-versa

• Retinal disparity - helps estimate the distance of how far away objects are from you 

nasal = by the nose (medial) 

temporal = by the temples (lateral)

The main visual pathway (for conscious vision)

• retinal ganglion cells -> LGN of thalamus -> primary visual cortex

• retinotopic map in retina, LGN, and V1. 

• receptive fields along the whole pathway. 

• retinal cells code light/dark contrast and color 

• primary visual cortex cells code (aka communicate information) color, orientation, movement, spatial frequency, texture, retinal disparity 

• visual association cortex cells code color, form, movement, spatial location 

• simple processing → complex

• 10-20% of the visual cortex is devoted to encoding the fovea  

The main pathway isnt the ONLY pathway

• retinal ganglion cells project to one of five targets: 

  • suprachiasmatic nucleus accessory 

  • optic system 

  • pretectum 

  • superior colliculus 

  • lateral geniculate nucleus

Blindsight - an individual who is blind, who cannot see, who has no conscious experience in the visual world 

• Video was shown of a blind person being able to complete this obstacle course without bumping into any of the objects. How was this possible? Because the brain was damaged, specifically the visual primary cortex. The eyes however are fine, and are receiving information through the retinal ganglion cells which influences their behavior.

V1 = striate cortex 

• Each spot in your visual field has a location column or hypercolumn

• Orientation selective neurons are one example of feature detectors

Feature detectors are neurons that basically display a preference for a particular type of input

• They can be simple 

• They monitor a particular region of space and they have excitatory areas 

• They can also be complex (or even hyper complex)

  • Basically complex versions of the simple ones 

Modules 

• V1 is organized into what is called modules

• Each module is responsible for detecting all the different kinds of features that are found in the same chunk of visual space

• Each module receives input from both eyes 

~2500 modules

each one analyze various visual

features in a very small chunk of

visual space

• orientation

• texture

• color

• retinal disparity (for depth

perception)

• black lines = borders between columns receiving signals from L & R eyes (ocular dominance columns); responsible for depth perception

• white ovals = groups of neurons responsible for color perception (“blobs”).

• ‘pinwheels' are formed by neurons involved in the perception of shape, with each color marking neurons responsible for a particular orientation in space.

Extrastriate cortex (extrastriate means outside of the straight cortex)

• 2 different “streams” of information:

  • Dorsal stream: where? (analysis of motion) 

  • Ventral stream: what? (object recognition) 

• 2 different pathways; one for figuring out where things are and another for figuring out what things are

• At least 20 other visual cortical areas that are outside the primary visual cortex

Ventral stream; the ‘what’ pathway

• Ventral occipital lobe & temporal lobe

• Task is object recognition 

• (it would be viewpoint-independent (or invariant) if the same cell fired for all of these images)

• Viewpoint invariant - they would fire to an object no matter which way the object is turned

• Viewpoint dependent or view centered - they only fire if something’s in a particular viewpoint

Problems with perception 

• Agnosia is caused by brain damage 

• Agnosia - loss of the ability to recognize some things 

Dorsal stream; the ‘where’ pathway 

• Dorsal  occipital lobe & parietal lobe

• Figures out where the object is in space 

• main functions: visuo-motor control (actions) e.g., locomotion, grasping

• Handles a lot of automatic computations

  • For example, when ur tired and u need to brush ur teeth, and without thinking about it ur toothbrush is already in ur hands 

• ‘’Vision for action’

• Critical for locating objects in space and figuring out how to take action involving objects, such as things like grabbing 

• parietal lobe has many specialized areas for using vision to guide actions in space 

different functions require different information

• dorsal stream: viewer centered viewpoint-dependent recognition 

  • detect spatiotemporal variability

• ventral stream: object-centered viewpoint-independent recognition 

  • ignore spatiotemporal variability 

• In everyday behavior, both streams work together e.g. they are integrated) 

Dorsal stream damage

• akinetopsia or movement agnosia

  • can’t perceive movement

  • damage to V5/MT

• Balint’s syndrome

  • can’t perceive the location of objects

  • damage to bilateral posterior parietal cortex

Direction of information flow 

• feedforward: sensory->association 

• feedback: association->sensory

Assignment 6 

1. Which of the following are true about the direction of information flow in the visual system?

ANSWERS; 

• The optic chiasm is where some visual information crosses over to the contralateral hemisphere (while some other information doesn’t cross over)

• Each eye gets information from both halves (both the left and the right) of the visual field

• Information in the left visual field ends up in the right hemisphere

2. Select the items about receptive fields of neurons in the visual system that are correct.

ANSWERS; 

• the retinal ganglion cells with smaller receptive fields are responsible for things like reading very fine print

• the receptive fields of retinal ganglion cells in the fovea are smaller; receptive fields of retinal ganglion cells in the periphery are larger

• retinal ganglion cells that synapse on more photoreceptors have larger receptive fields

3. All the visual information coming in from your retinas is sent to all the same areas of your brain for processing.

ANSWER; False

4. Why might people who are blind still be able to use some visual information to guide their behavior?

ANSWER; they might have damage to parts of the pathway associated with conscious awareness of visual information, but visual information might still be getting through to other pathways they are not aware of.

5. A person with prosopagnosia has difficulty with what:

ANSWER: face recognition 

6. Which of these is more accurate about the organization of V1 (primary visual cortex)?

ANSWER: It has all these little processing units responsible for doing different things, like responding to different orientations, textures, etc. All the neurons responsible for monitoring one specific area of space (like part of Chuck Close’s nose) live together in the same part of V1, and inside the part where they live, there are some neurons that detect one specific orientation (like “/”) and there are other neurons that detect other specific orientations (like “\”). Then, the neurons that are responsible for monitoring other parts of space (like part of Chuck Close’s ear) live in a different part of V1.

7. All neurons in V1 receive inputs from both the left eye and the right eye, in equal proportion (e.g. 50/50).

ANSWER: False

8. Which of these cells fires an action potential that is sent directly down the optic nerve? (by direct, I mean without synapsing on another neuron).

ANSWER: retinal ganglion cell 

9. Transduction means:

ANSWER: converting energy out in the world to a language that neurons speak

10. A neuron that is orientation-selective would:

ANSWER: fire the most when a specific angle is visible, and fire less (or not at all) in response to different angles

11. Cell A responds to only one exact angle at one exact part of the visual field. Cell B responds to the same angle as Cell A, but also responds to a few similar angles as well, even at slightly different locations. Cell A is a ____ and Cell B is a ____.

ANSWER: simple cell; complex cell.

12. There is only one pathway for visual information in the brain.

ANSWER: False 

13. Which of these properties are true of cones: (read carefully -- select all the correct responses!)

ANSWERS: 

• they are responsible for clarity 

• they are responsible for color vision 

• they are primarily located in the center of the retina 

14. What is the primary (and first) destination of the axons of most of the retinal ganglion cells? (E.g. where will they synapse on the next neurons in the pathway).

ANSWER: the lateral geniculate nucleus of the thalamus 

15. Humans can see all possible light wavelengths.

ANSWER: False 

16. The retina is located at which part of the eye:

ANSWER: the very back (closest to your thalamus) 

17. Your roommate slid a nice warm mug across the table to you on a cold day. You are looking at it and wondering whether it is coffee, tea, or cocoa, and since you like them all, you’re thinking about having a sip to warm you up. As you prepare to lift the mug, which bit of information does your ventral stream care more about, in recognizing what’s in the mug before you have your first sip?

ANSWER: what color the liquid is 

18. If you are a neurologist and seeing a patient who had a stroke and is now having trouble with categorizing the objects in front of them (e.g. that’s a cube, that’s a hammer), which part of their visual system would you suspect the stroke had damaged most?

ANSWER: ventral

19. Your roommate slid a nice warm mug across the table to you on a cold day. You are looking at it and wondering whether it is coffee, tea, or cocoa, and since you like them all, you’re thinking about having a sip to warm you up. As you prepare to lift the mug, which bit of information does your dorsal stream care more about than your ventral stream?

ANSWER: which way the handle is pointing 

20. In a soccer match, visual processing of the ball that’s coming toward you so that your foot can make contact with it successfully is more of a ____ stream task.

ANSWER; dorsal 

21. You are a neurologist examining a patient and give them two pictures, one of a rectangle the long way (like a truck) and the other of a rectangle the tall way (like a skyscraper). The patient reports that they are the same: they cannot see any difference. You then show the same shapes to the patient, one at a time, and ask them to pretend they are picking up the shape with their hand, and you make note of how they form their hand. You observe that they correctly calibrate their grip to the different shapes, even though they reported that the shapes looked the same. Where do you suspect this patient is having problems?

ANSWER: extrastriate cortex in the ventral stream 

22. You are a med student studying a case report. A patient is admitted with brain damage due to hypoxia (lack of oxygen) and presents with some specific impairments. Basic visual capabilities are preserved. They can detect when light is in a part of their visual field, and they have normal shape processing, and successfully recognize all the categories of objects they were tested on. If you ask them to look in a particular part of space, though, they can’t follow the instruction, and if you ask them to move their hand toward an object you are holding up, while they say they can see it, they can’t quite get their hand to the right spot. Which lobe do you conclude has damage?

ANSWER: parietal

Module 7 

Sensation - converting energy out in the world into a language the nervous system can understand

• When an object moves or vibrates, this causes pressure changes in the air 

• Changes in pressure are sound waves 

• Sound waves can be both simple and complex

Loudness

• We measure loudness on a decibel scale dB

• Wavelength is how long until the pattern repeats and frequency is how many times the pattern repeats in a particular time

• Higher frequency = more repeats aka more bumps 

• Frequencies are measured in units of hertz

  • Hz = hertz = how many cycles (or pattern repeats) per second

Audition

• Transduction - we take the energy of the world and convert it to the language of neurons

• Audition is the transduction of sound waves into neural code

• Humans detect ~ 20 – 20,000 Hz

• most sensitive to 2,000 – 4,000 Hz (speaking range) 

ear transduces air pressure → mechanical energy → neural activity

Transduction occurs in the cochlea.

Fluid in the cochlea is rich in potassium. 

Cochlear nerve

• The nerves that make up the cochlear nerve are bipolar

• Cochlear nerve is one of your cranial nerves and connects to the medulla

transduction summary

vibration of ossicles →

deflects membrane →

stretches hair cells →

opens K+ and Ca++ channels →

K+ and Ca++ influx →

hair cells release NT →

excites neurons of cochlear (auditory) nerve →

Brain

Different frequency sound waves cause different parts of the vascular membrane to move

• The brain uses rate coding to encode the very lowest sound frequencies 

• Place coding is used in cochlear implants to help those who have hearing loss

  • medium-to-high frequencies: place coding 

  • low frequencies: rate coding

Loudness 

• Louder sounds make the eardrums and ossicles of the bone vibrate more 

• medium-to-high frequencies: firing rate (louder = fire faster)

• low frequencies: number of neurons firing (louder = more neurons)

Localization - determining where a sound is coming from 

**left off on lecture video 2 at timestamp 6:35. I just cant do this rn bro TAT im still tired, still sick, havent gotten decent sleep in days now i cant do this. 

Assignment 7 

1. Say you are a robotics engineer working on robots to be good company for lonely elderly nursing home residents. (This is a real thing!) You are currently trying to design the robot equivalent of cutaneous sensory receptors and you are taking your inspiration from your extensive knowledge of human cutaneous sensory receptors. Your goal is to specifically design sensory receptors that detect the sustained pressure associated with resting a head on a shoulder or holding a hand (as opposed to a sensory receptor that would detect a quick tap on the shoulder, like someone trying to get the robot’s attention). Based on what you know about human somatosensation, do you want these receptors to be:

Answer: slowly adapting (they fire immediately when they detect pressure, and then keep firing as long as the same pressure stimulus is there)

2. The area of skin supplied by a single spinal nerve is:

Answer: a dermatome, and adjacent spinal nerves supply nearby areas of skin.

3. Say you are sitting on the floor with your legs criss-crossed and your eyes closed. Which of these types of information reflects proprioceptive sensation?

Answer: you know that your left ankle is on top of your right thigh.

4. All kinds of somatosensory information (touch, pressure, pain, temperature, proprioception) takes exactly the same pathway (sequence of regions & tracts) from the periphery (e.g. the skin) all the way up to the brain.

Answer: False

5. Damage to which part of auditory association cortex can impair the ability to extract the emotional content of speech?

Answer: right

6. Which of these types of somatosensory receptors responds to pain?

Answer: free nerve endings

7. While the retina has a map of the visual world (retinotopic map), there is nothing similar in the auditory system that encodes sound information (like pitch) in an orderly spatial organization.

Answer: False

8. If a group of hair cells in the cochlea is moved in the direction of the longest hair in the bunch, which of these would occur? [ Mark all the correct responses ].

Answers:

•  ions enter channel

• increased rate of action potentials

• ion channel pulled open

9. You are born with the somatosensory cortex organization you will have throughout your entire life; there is no plasticity in that system.

Answ: False

10. Which of the following aspects of information does the auditory system make use of for localizing sound? [ Mark all the correct responses ].

Answers: 

• timbre differences

• intensity differences

• phase differences

11. Sudden head rotations (with acceleration) are detected in ______, specifically by ____.

A: a semicircular canal; hair cells

12. If a group of hair cells in the cochlea is moved in the direction of the shortest hair in the bunch, which of these would occur? [ Mark all the correct responses ].

Answers: 

• ion channel no longer pulled open

• reduced tension on tip link

• ions cannot enter channel

13. What principle of how the auditory system is organized is the reason cochlear implants work?

A:  place coding of pitch information 

14. Which part of the vestibular system starts to respond as you move your head from an upright position to a horizontal position (like a pillow)?

A: saccule

15. Say Cherese is experiencing chronic pain and it is not possible to eliminate the underlying cause of the pain. Her doctors are trying to help diminish her experience of the pain and the emotional suffering it is causing here, even though they know they cannot change the pain sensation itself. What part of the brain are her doctors trying to target? (They are trying to target the brain regions associated specifically with her emotional experience of the pain, and not the regions associated with pain sensations in themselves.)

A;  anterior cingulate cortex 

16. Humans can hear all frequencies of sound.

A; False

17. You are about to win the Nobel prize due to your recent discovery of a brand new sense you discovered that humans have. Congratulations! This new sense is processed by a specialized organs in our pineal glands and it picks up on all wavelengths of light, not just the visible spectrum -- and we don’t experience this sense as seeing light, it’s more of a feeling of light instead, because the receptors for this sense are cutaneous – they are in the skin – and then project to the spinal cord and finally the to the new sensory organ in the pineal gland.  You found that this new specialized sensory organ in the pineal gland has a topographic organization, consistent with what we saw in the other senses. What would having a topographic organization mean for this new sense?

A; the spatial organization of neurons in the specialized organ in the pineal gland reflects the spatial organization of the receptors on your skin. neurons detecting full-spectrum light on one finger are nearby to neurons detecting full-spectrum light on another finger, but far away from neurons detecting full-spectrum light on your toe.

18. Which of these parts of the auditory system is most analogous to photoreceptors in the visual system (e.g. performs a comparable role)?

A;  hair cells 

19. Which of these is both correct and an example of place coding of pitch?

A; the basilar membrane is stimulated closer to the eardrum for a flute, and further away from the eardrum for a sound like an oboe.

20. Sound 1 has a low amplitude and a high frequency. Sound 2 has high amplitude and low frequency. Which of these is most plausible?

•  Object 1 is a flute played quietly so as not to wake someone. Object 2 is the bass from the stereo you can hear from the next car at a stoplight. 

21. Match the pathway with the type of information it carries.

• spinothalamic tract - temperature & pain; dorsal columns - touch & kinesthesia

22. Receptors for the cutaneous senses respond to what:

•  pressure, vibration, temperature 

23. Similarly to information from vision and audition, somatosensory information gets sent to specific thalamic nuclei on the way to the rest of the brain.

• True

24. The concept of labeled lines in neuroscience refers to which of these ideas: (note: when I say kinds or types of “information”, think of things like light vs sound vs pressure vs temperature)

• in principle, someone could label bundles of axons according to the type of information they carry (if they had the right kind of labeling technology, or a detailed neuroanatomical model). This is because different types of information are detected by different receptors, and sent to the brain along different axons, and that information is kept separate rather than being mingled together before it gets to the brain.

25. Give and explain an example of hierarchical processing in the brain – the idea that the brain does simple things first, and those simple things get combined into more complicated things, and even more complicated things, as information gets further and further from sensory areas. Your answer needs to have an explanation – just a single word is not sufficient. (There are many possible examples, you only need to describe one. Your answer should discuss both different brain AREAS, and their different JOBS -- e.g. what types of information is processed in the brain areas you are discussing. Some examples were covered in both this and the previous module, and your examples can come from either one. )

• (THIS WAS MY ANSWER) Our visual system is an example of hierarchical processing in the brain. This process begins at the retinal ganglion cells where they process the lightness, darkness, and contrast. Then it goes to the lateral geniculate nucleus of the thalamus where it receives the information from the ganglion cells and sends the information to the primary visual cortex. From there, the primary visual cortex codes the color, orientation, and movement. Finally, the visual association cortex processes the information received from the primary visual cortex to analyze.

• Prof answer: There are many possible examples, but here are some. Examples of simple types of information in the auditory system would be tones (processed in primary auditory cortex) and more complex information would be melodies or voices (processed in auditory association cortex). (Have a look at slide 24 in the lecture PDF for more info on this). Or, in the visual system, simple lightness/darkness in the retina->LGN->V1 and more complex shapes/letters/faces in visual association areas

Module 8

Movement and Sleep

Skeletal ‘striated’ muscle 

• Consists of  hundreds of muscle fibers

• each fiber innervated by a single motor neuron axon

Muscles come in anatongist pairs 

• Movement occurs because muscles contract 

• Muscles contracting can only pull, they cannot push

• We can create a full range of movements bc we have muscles in different locations that counteract one another. These are considered antagonist pairs 

  • These pairs consists of flexors which pull things toward the body, and extensors which pull away from the body 

The ‘final common pathway’

• all motor pathways ultimately converge on simple circuits in the spinal cord that go directly to effector muscle

  • lower motor neurons in ventral horn

  • exit via ventral root 

  • innervate muscles, cause contraction 

The motor unit 

• Motor units are the site of one motor neuron and all the different muscle fibers it innervates

• Different sizes of motor units across different areas of the body

  • leg: 1 motor neuron : 1000+ muscle fibers 

  • finger: 1 motor neuron : 3 muscle fibers

• Motor units are activated by the nervous system in a specific order

• Smaller motor units are going to be activated before larger motor units

  • small first (less force) 

  • large last (more force)

Neuromuscular junction 

• Synapse between the axon of the motor neuron and muscle fiber

  • Synapse is called neuromuscular junction

• action potential in axon → ACh release 

• ACh binds to receptors on muscle fiber → depolarization 

• Na+ channels open → action potential in fiber 

• action potential → sarcoplasmic reticulum releases Ca2+

Excitation-contraction coupling

• Muscle fibers are made of 2 different types of filaments; actin and myosin

  • Actin is think

  • Myosin is thick

• When the action potential in the muscle fiber itself causes calcium ions to be released, the myosin filaments interact with the actin filaments 

• muscle length shortens = muscle contraction!

Motor neurons & muscle fibers

• Extrafusal fibers are innervated by alpha motor neurons

• intrafusal fibers (spindles) are innervated by gamma motor neurons (and sensory neurons) 

• stretch is detected by both intrafusal fibers and Golgi tendon organ

• Golgi tendon organ’s main job is to measure the total amount of stretch that’s exerted by the muscle on the bones

Spinal control of movement

• Monosynaptic stretch reflex

  • Example is when the doctor taps your knee to test your reflex

  • This reflex only involves 2 neurons: a sensory neuron that registers the tap and a motor neuron that causes muscle contraction 

• Polysynaptic stretch reflex 

• This sort of movement is done without the brain– it’s only done by the spinal cord

Spinal control of complex movement 

• Types of spinal movement: 

  • reflexes (e.g., stretch) 

  • fancier (e.g., reciprocal inhibition) 

  • fanciest (e.g., swimming, walking) – central pattern generators 

Control of movement by the brain 

• Motor system is hierarchical 

  • highest level - association cortex + basal ganglia - strategy

  • middle level - motor cortex+cerebellum - tactics

  • lowest level - brain stem+spinal cord - execution

Descending spinal tracts 

• Lateral pathways 

  • Under cortical control

  • Responsible for voluntary movement 

• Ventromedial pathways

  • Big role in posture, stabilization and locomotion

  • Under control of the brain stem, which means we’re not thinking about it

Lateral pathways 

• Most of these pathways originate in the cortex

• Most originate in the motor cortex

• Corticospinal tract 

  • Starts at cortex, ends at spinal cord

  • Synapses on the spinal nerves 

  • independent limb movements

  • arm, hand, finger movements

  • trunk, legs, feet

• Corticobulbar tract

  • Cranial nerves; responsible for the movement of facial muscles 

  • face, neck, tongue, some eye muscles

  • Doesn't go all the way to the spinal cord, going to sit at the medulla bc that’s where most of the cranial nerve roots are

  • Another name for the medulla is bald; which is why it’s called corticobulbar

• Rubrospinal tract

  • Evolutionary older tract

  • Originates in the red nucleus of the brain stem

  • Involved in independent movements of forearms, hands (not fingers)

  • Synapses on the spinal cord 

Ventromedial pathways 

• Responsible for automatic movements 

• Uses sensory information about balance, body position, and the visual world to maintain your balance and maintain body posture

• Originates in the brain stem, and projects onto the spinal neurons that control the trunk muscles as well as the large muscles like the shoulder, elbow, pelvis, knee

• Vestibulospinal tracts

  • Carries vestibular information about the location of the body in the world 

  • Plays an important role in keeping your head stabilized and helping you maintain an upright and balanced posture

  • head stability, upright & balanced posture

• Tectospinal tract 

  • Originates in the curricula of the midbrain 

  • orient to new sensory information 

  • Ex. helps u swivel your head in the direction of a sound, or move your head towards where a light was flashed 

• Reticulospinal tracts 

  • Originates in the reticular nuclei throughout the brain stem

  • 2 different tracts; lateral and medial 

  • (semi)automatic functions 

  • Responsible for things like sneezing, coughing, vomiting

  • muscle tone 

  • posture 

  • locomotion 

Hierarchical organization of motor systems

• basic patterns generated at each level 

• progressively higher levels select and modify patterns

The motor system is a collection of loops

Motor cortex

• Premotor cortex, supplementary motor areas:

  • Where planning and coordinating happens 

  • Plans what movement you’re gonna do and how you’re gonna do it 

  • ”what” -> ”how”

• Primary motor cortex:

  • execution of motor patterns 

  • go” 

Premotor cortex

• Involved in planning and coordinating voluntary movements 

• cells are active during intention to make particular movements  

• Has a somatotopic organization 

Supplementary motor area (SMA)

• Also involved in motor planning 

• Involved in sequences of behaviors 

• Also plays an important role in coordinating movements across both sides of the body 

Primary motor cortex (M1)

• execution of movement 

• fine motor control 

• topographical organization 

• ~ 20% of upper motor neurons directly innervate contralateral motor neurons

  • but typically more synapses are involved! 

Motor cortex damage 

• Motor cortex damage is associated with disruptions of fine motor control

  • Using hands and fingers 

• partial paralysis (paresis, not plegia) 

  •  “disinclined” to use affected limb

• fine motor control disrupted 

  • decreased speed, accuracy, force (“clumsy”)

• Disrupts people’s abilities to do tasks like play multiple musical instruments, handwriting, sewing

Basal Ganglia modulation

• Plays an important role in the selection of movement and in motivation 

• Has no direct input from periphery sensory systems and no direct outputs to the spinal motor circuits. It modulates things that are going on, but gets no direct sensory input or output

• Plays an important role in motor systems

Basal Ganglia 

• Direct pathway 

• Striatum = caudate + putamen

• at rest, globus pallidus inhibits thalamic activation of cortex. (spontaneous neural activity)

  • cortex ↓ caudate ↓ putamen ↓ globus pallidus (excitation) ↓ thalamus (inhibition)

  • Note: excitation means what it sounds like: excite, going up, firing action potentials. Inhibition means to quiet down, calm down, shut up!! Shhh!! Ur being too loud!!

• when striatum is activated, globus pallidus is inhibited, allowing thalamus to activate cortex.

  • cortex ↓ caudate (excitation) ↓ putamen (excitation) ↓ globus pallidus (inhibition) ↓ thalamus (excitation)

• Neurons kinda fire randomly in the nervous system for no reason sometimes 

Basal Ganglia: Function 

• Controls the amplitude + direction of movement 

  • Basically how much movement and the direction of the movement. 

• Plays a role in the selection and initiation of slow continuous voluntary movements

  • Eg. smooth pursuit. Smooth pursuit is basically following a moving object with your eye. For example, a red cross moving across the screen. 

Basal Ganglia: Dysfunction 

• Parkinson’s Disease

  • degeneration of substantia nigra 

  • loss of DA → inhibition of thalamocortical loop → less movement 

    • Excitatory inputs to the striatum inhibit the globus pallidus, which has the effect of removing the brakes on the thalamus and allowing the thalamus to communicate up to the cortex 

    • In healthy individuals, the dopaminergic inputs from the substantia nigra to the putamen are responsible for putting the brakes on the globus pallidus, which in turn removes the brakes from the thalamocortical loop which allows the thalamus to excite the cortex which helps us initiate and select movements 

    • In Parkinson’s disease, we lose those dopaminergic inputs to the putamen. The globus pallidus stays at rest bc it’s not getting activated which means it keeps those breaks on the thalamocortical loop which results in less movement. 

  • symptoms: 

    • tremors at rest 

    • muscular rigidity 

    • akinesia: difficulty in initiating voluntary movement

• Huntington’s Disease

  • Genetic disorder + more rare than Parkinson’s 

  • Characterized by progressive and selective neurodegeneration 

  • degeneration results in disinhibition of thalamocortical loop → too much movement 

  • symptoms: 

    • uncontrollable, involuntary ballistic arm movements, facial twitches 

    • writhing movements of limbs, tremors, dementia

Cerebellum 

• Has an important role in error correction, timing, and motor learning

• Cerebellum gets input from the spinal cord, cortex (via pons)

• Cerebellum sends outputs to the thalamus, just like the basal ganglia does

  • It has a way to talk to motor neurons indirectly 

  • Also sends outputs to the red nucleus 

  • Purkinje cells → deep nuclei → thalamus, red nucleus

• Contains more than half of the neurons in the entire central nervous system  

Cerebellum: Function 

• Gets 2 types of information: intended movement and about what’s happening in the world 

• It can compare intentions with reality and then instruct the motor cortex indirectly via those connections 

• error correction of ongoing movement 

• motor learning 

• especially critical in programming rapid movements 

• timing 

• maintains muscle tone 

• Balance

Cerebellum: Dysfunction 

• Jerky, inaccurate movements, loss of balance 

• Loss of muscle tone or weakness

• Intention tremor

  • tremor during movement

• Decomposition/fragmentation of movement

  • small, trial-and-error movements toward goal instead of single, efficient ballistic movements

• ataxia 

  • balance, posture, coordination problems

posterior parietal & prefrontal cortex

Why sleep? 

• All vertebrates sleep 

• Hypothesized functions of sleep

  • Converving energy (probably not)

  • Restoration of body (maybe)

  • Consolidation of memory (yes)

  • “Cleaning in the brain” (yes)

• Sleep deprivation is a major public health problem. Even losing 1 hour of sleep can have profound negative consequences. 

• When the clock goes forward and we loose an hour of sleep (bc daylight saving’s time or whatnot), there’s a 24% increase in heart attacks

• When the clock goes backward and we gain an hour of sleep, there’s a 25% reduction in heart attacks

  • Similar patterns for car accidents 

• There’s a strong link between sleep and immune function 

• People who had 4 hours of sleep had a 70% reduction in natural killer cells, which are critical parts in your immune system

restricted/short/poor quality sleep is linked with…..

• impaired memory, judgement 

• immune suppression, increased cancer risk 

• obesity, type II diabetes 

• dementia 

• can precede and/or exacerbate some forms of mental illness (sz, bp)

• decreased reproductive health 

• decreased life span

Studying sleep in humans

• EEG is usually the way sleep is studied in humans

• EEG – electroencephalogram 

• EOG – electrooculogram 

• EMG – electromyogram

EEG Activity

• When all neurons are firing at about the same time, their electrical messages are synchronized and they appear as a large wave 

• If neurons are firing in a less coordinated way, their electrical messages are desynchronized and they appear as a small, more chaotic looking wave form without a clear pattern

• Desynchronization typically appears when someone is alert and paying attention to events in the environment or is thinking actively 

EEG when awake

• Alpha activity 

  • Associated with being more drowsy and relaxed 

  • 8–12Hz

• Beta activity 

  • Associated with being attentive, like your brain is busy processing things

  • 13–30Hz

  • Amplitude is lower 

  • Beta activity is more desynchronized 

EEG when asleep

• Stage 1: NonREM, theta (3.5-7.5 Hz) 

  • Transition between being awake and being asleep

  • Your muscles are still active, your eyes are rolling, and it’s easy to get woken up 

  • Theta activity is a slower frequency, higher amplitude pattern that indiciates that the firing of neurons is becoming more synchronized 

  • Stage where you may experience hypnotic jerk 

• Stage 2: NREM, sleep spindles, K complexes 

  • Sleep spindles are high frequency bursts 

  • Sleep spindles play a role in memory consolidation 

  • K complexes are sudden big spikes

  • K complexes reflect a quick inhibition of neural activity that keeps you asleep when there’s an unimportant external stimulus eg when the house creaks 

• Stage 3: slow wave sleep, delta (<3.5Hz)

  • Frequencies are even lower, and amplitude is higher 

  • Amplitude reflects neurons firing in a very coordinated way 

  • Deepest stage of sleep 

  • Unresponsive to external stimuli, and if they do get awaken, they will be groggy and confused 

  • Metabolic activity of the cortex decreases considerably, which suggests that the cortex rests during sleep 

  •  

• REM: REM, theta+beta

  • Occurs an hour and a half after you fall asleep 

  • EEG activity differs considerably during REM sleep

  • High frequency, low amplitude + desynchronized 

  • No clear pattern 

  • Combination of theta and beta activity 

REM (Rapid Eye Movement) Sleep 

• When we dream

• Difference in EEG during this stage is thought to represent the brain’s activity during dreaming 

• Heart rate and respiration are irregular

• Muscles are paralyzed during REM sleep, other than the twitching of your hands and your feet + your eyes darting around 

• This sleep paralysis keeps you from acting out your dreams 

• You can be easily awakened during REM sleep 

• Low activity during rem sleep in the visual cortex, or striate cortex (bc ur not getting visual input bc ur sleep… duh)

• High activity in extrastriate cortex, which reflects the visual components to your dreams 

• Low activity in prefrontal cortex (bc ur not doing a lot of planning or organization in your dreams)

Cycle of sleep stages 

• Cycle thru the sleep stages 4-5 times a night, each cycle lasting 90 minutes each

• periods of REM increase in length and frequency

• Experience more REM sleep in the later parts of the nights 

Sleep stages and learning 

• Sleep is really important in learning + consolidating memories 

• Learning and memory formation involves modification to the synapses between neurons in your brain. That is what learning is. It is a change in your brain conductivity

• The more important functions of sleep is consolidating the synapses that reflect the really important stuff that you need to remember and discarding the changes that aren’t so important 

• Different stages of sleep help different kinds of memories 

• memory consolidation requires both SWS aka short wave sleep & REM, but …. 

• SWS consolidates declarative memories 

  • Eg; Springfield is the capital of Illonois

• REM sleep consolidates nondeclarative memories 

  • Eg; how to ride a bike 

  • mice deprived of REM sleep learn maze slower 

  • rats and people increase REM sleep when learning new task 

  • hippocampal place cells fire at certain places in maze and then exhibit same pattern during REM sleep, as if “remembering” maze

• When people are learning how to do a task, they are naturally increasing their rem sleep 

• An important function of REM sleep is to let the brain replay or rehearse a new thing you learned 

• After you teach a rat to learn a brand new maze, during REM sleep, their hippocampal place cells fire in the exact same order that they were activated when they were firing as the rat was doing the maze itself 

Brain mechanisms; sleep

• Adenosine

  • Neuromodulator 

  • Has a supply of glycogen, which is a nutrient 

  • Glycogen gets converted into fuel for the brain when awake 

  • Fall in the level of glycogen causes the level of extracellular adenosine to increase 

  • Adenosine inhibits neural activity and promotes sleep. While asleep, glycogen supply gets replenished during short wave sleep and the cycles continue 

  • Caffeine blocks adenosine receptors. This prevents the inhibitory effect on neural activity and reduces the effects of sleep deprivation 

Brain mechanisms: wakefulness

All of these have high levels during wakefulness and low levels during SWS. All except Ach are also low during SWS

• acetylcholine (pons, basal forebrain (BF), medial septum) 

  • Related to adenosine

  • cortical desynchrony, cortical/hippocampal activation 

  • alertness, behavioral arousal

• norepinephrine (locus coeruleus) 

  • attention: vigilance, noticing important stimuli 

• serotonin (raphe nuclei) 

  • activating behavior 

  • maintaining concentration

• histamine (tuberomammillary nucleus) 

  • directly increase activation/arousal, indirectly increase Ach

  • Makes you awake 

• orexin (lateral hypothalamus)

Orexin 

• Peptide neurotransmitter that’s released by neurons in the lateral hypothalamus 

• projects nearly everywhere in brain, excitatory effect

• Sleep and wakefullness are some of the functions 

• Has a large role in appetite 

• Involved in thermoregulation 

• High during wakefulness and especially during exploratory activity 

• Orexin neurons fire fast during alert or active waking and have their highest rate of firing during this exploratory behavior 

  • Fires more slowly during quiet waking, slow wave sleep, and REM sleep 

• Modafinal (drug used to treat narcolepsy) produces a learning effect by stimulating the release of orexin 

sleep <-> wake transitions 

• neurons triggering SWS are in ventrolateral preoptic area (VLPOA): 

  • reciprocally connected via GABAergic neurons to “wake” areas: BF, LC, TMN, raphe 

  • active during sleep (stimulation → animal falls asleep) 

  • destruction → insomnia, coma, death 

  • sleep is not a passive process! actively generated/maintained.

• You cant be asleep and awake at the same time

Circadian rhythms / biological clock

• Controlled by the suprachiasmatic nucleus (SCN) of the hypothalamus

• light cues (zeitgebers = “time-givers”) resets clock 

  • melanopsin in some retinal ganglion cells 

  • retinohypothalamic pathway (retina->SCN)

• projects indirectly to vIPOA & orexinergic neurons 

• suppresses pineal gland secretion of melatonin

Assignment 8 

1. ____ is associated with difficulty initiating voluntary movements and ____; ____ is associated with uncontrollable involuntary movements and _____.

• Parkinsons’s, degeneration of dopaminergic inputs to the basal ganglia; Huntington’s, degeneration of the basal ganglia

2. Simon is a game from the 80s. The different colors light up in a sequence (say, red->blue->yellow->blue) and you have to remember the sequence and touch the buttons in the right order. Say someone had damage to a part of the motor and this damage made them unable to play Simon, but they could still perform other types of movements normally. Which part of the motor system is most consistent with this profile?

•  supplementary motor area (SMA) 

3. What happens in the basal ganglia loop (“the direct pathway”) when the striatum is activated?

•  the globus pallidus is inhibited. This removes the inhibition the globus pallidus was supplying to the thalamus, which allows the thalamus to send excitatory input to the cortex. 

4. No matter how complex, all movements involving your arms and/or legs ultimately involve lower motor neurons in the spinal cord.

•  True 

5. Electrically stimulating the “hand area” in primary motor cortex causes what?

•  one movement of the contralateral hand 

6. When the globus pallidus is “at rest”, that means it is not firing any action potentials at all.

• False

7. What is the effect of on the basal ganglia loop (the “direct pathway”) when the basal ganglia is “at rest”?

•  the thalmus is inhibited, and therefore does not send excitatory input to motor cortex

8. Which of these motor system components is involved in error correction, in part by comparing the intended movement with what is actually happening?

• Cerebellum

9. Which of these muscle components are involved in detecting sensory information related to proprioception? (hint: think stretch) Mark all correct responses.

•  intrafusal muscle fibers 

•  Golgi tendon organ 

10. If you are interested in facial movements, which of these tracts should you read about first?

• corticobulbar tract, because it serves the cranial nerves

11. ___ is a flexor muscle; ___ is an extensor muscle.

•  bicep; tricep 

12. Which statement is true?

•  muscles only pull 

13. Which of these pathways is most strongly associated with voluntary movements?

•  lateral pathways 

14. Which of these is not consistent with motor cortex damage?

•  complete inability to use a part of the body 

15. If you are interested in studying movements that occur outside of our conscious awareness, which of these pathways should you start reading about first?

• vendromedial pathways

16. You’re at the doctor and they tap your knee to make sure your leg extends. How many synapses did that reflex involve?

• 1

17. Which of these things occur at the neuromuscular junction:

•  action potential of motor neuron causes acetylcholine release and action potential in muscle fiber 

18. Which of these is not a function of sleep?

• allowing all your neurons to completely stop firing so the brain can rest

19. Say region A and region B mutually inhibit one another. In other words, when region A is active, it sends inhibitory input to region B. And when region B is active, it sends inhibitory input to region A. (This only refers to the connections between these two regions and says nothing about any other inputs that may be involved. Assume region A and region B send the same “amount” of inhibition.) Which of these statements is true? [ select all that apply ]

• There are neural circuits regulating transitions in and out of REM sleep that are wired in this way.

•  Only region A or region B can be active at any given time. They cannot both be active at the same time. 

•  There are neural circuits regulating sleep/wake transitions that are wired in this way. 

20. Which of these are associated with waking EEG activity and/or REM sleep?

•  desynchronized EEG patterns (small amplitude, less visible pattern) 

21. It’s a myth that sleep deprivation is a public health concern. It’s fine to miss a few hours of sleep regularly and can’t possibly cause any problems.

• False

22. What does it mean that sleep is not passive, in terms of what neurons in vIPOA do?

•  sleep is not passive because some neurons have to keep firing in order to keep you asleep 

23. You can tell whether someone is dreaming from their brain activity.

• True

24. In which stage of sleep does muscle paralysis occur?

•  REM sleep 

25. Choose all the statements about orexin/orexinergic neurons that are correct:

• High levels of orexin secretion are associated with alertness/wakefulness (as opposed to sleep)

•  Orexinergic neurons help you stay awake for longer periods of time, rather than flipping between sleep and wakefulness. 

•  Orexinergic neurons respond differently if you’re hungry versus full. 

26. Choose the chemicals or structures that are involved in promoting sleep (when activated, if a structure, or when released, if neurotransmitter/neuromodulator):

•  vIPOA (ventrolateral preoptic area) 

• Adenosine

Module 9 

Emotion

Emotions are increases or decreases in physiological activity that are accompanied by feelings that are characteristic of the emotion 

three systems involved in emotional response: 

1. behavioral – motor system produces appropriate behavior 

Aka part that other people can see

2. autonomic – sympathetic nervous system prepares body for action 

Related to fight or flight response 

3. hormonal – secretion of hormones (NE, epinephrine, cortisol) helps autonomic nervous system

• Anger is associated with elevated heart rate + elevated temperature 

• Sadness is associated with elevated heart rate with no change in temperature 

Amygdala 

• Coordinates emotional responses 

• It does this by influencing the activity of many other brain regions that are responsible for different components of emotional responses 

  • influences activity of anterior cingulate cortex, hypothalamus, septal nuclei, insular cortex, basal ganglia (among others)

• Amygdala is known to be activated by stimuli that have strong emotional content, such as threatnening stimuli, frustrating, fear

  • threatening, frustrating, fear-inducing stimuli → increased activity

• If the amygdala is electrically stimulated, we see fear, anger, or a stress response 

  • stimulation → fear, stress responses, anger

• Amygdala has 3 divisions:

  • Central nucleus

  • Corticomedial nucleus 

  • Basolateral nucleus 

Central nucleus 

• The most important part for emotional responses to aversive stimuli 

• defensive behaviors and predation

• outputs of central nucleus and associated emotional responses

• Amydala can coordinate the startle response

  • For example, someone coming up to you and going “boo,” causing you to jump

• Accomplishes multiple component of emotional responses by projecting to different locations of the brain and sending information to them 

Conditioned emotional response 

• lateral nucleus of amygdala

• Example with conditioning with a rat; rat being in a box with electrocution. When the first rat is electrocuted in box 1 it’s scared, but in box 2 its not. When the second rat is electrocuted + bell ringing in box 1, it’s scared. In box 2, upon hearing the bell ringing, it’s scared. 

• The learning through this sort of conditioning is learned through the lateral nucleus of the amygdala 

  • This part of the amygdala communicates with the central nucleus 

Amygdala lesions/damange 

• When damaged, there’s fewer:

  • fear responses 

  • conditioned emotional responses

  • Effects of emotion on memory 

  • Reduced sympathetic/autonomic nervous system activation 

  • Fewer stress hormones 

  • Less of long term consequences of stress hormones, like ulcers

Ventromedial PFC (vmPFC) orbitofrontal cortex

• Part of the brain responsible for adulting 

  • Everytime you wanted to say smth mean, but bit your tongue or did your work/responsibilities instead of playing around, it’s bc of this part of the brain

• We see developmental changes in this region into the early 20s at least and potentially even longer 

• It has a big role on impulse control 

• Has a role in regulating emotions + helps produce the appropriate emotional behavioral responses 

• It communicates with the amygdala, ofc 

  • It sends axons to the amygdala and the amygdala sends axons back. This is called being reciprocally connected 

• Plays an important role in the extinction of conditioned fear responses 

Extinction of conditioned emotional responses

• Going back to the rat: the conditioned response can be removed! Hip hip hooray for the rat! 

  • If the rat is kept in the same room it was afraid of (the safe one) with the bell ringing, the rat will stop being afraid 

  • extinction = inhibition (not erasure) of previous emotional response 

  • inhibition courtesy of vmPFC 

  • Context-specific

• Emotional memories are very easy to learn + it’s very easy fo these memories to be retained for a very long time 

• When we stop acting like those fear memories want us to act, it’s not bc we forgot the fear memories, it’s bc we learned something different that sort of overrides them when we can manage to get the ventromedial prefrontal cortex engage. That original fear learning is not gone. 

vmPFC lesions

• People with ventromedial prefrontal cortex damage like Phineas Gage have trouble regulating their emotions 

• This difficulty in regulating how they feel seems to be linked with their difficulties and behaving appropriately 

• People report emotional instability, irritability, low tolerance for frustration, etc.

  • This is associated with those overt behaviorial responses that are not so appropriate 

• People with this dmg also make bad decisions 

  • They KNOW what the right decision IS, but tend to still make bad decisions for themselves 

• In summary; 

  • emotional dysregulation 

  • poor impulse control 

  • poor decision making 

• Phineas Gage 

  • responsible, hardworking → irresponsible 

  • mild-mannered → couldn’t control temper, swore, drank a lot

Anterior cingulate cortex (ACC)

• Mediates people’s experience of pain; not the sensation of pain, but the experience of it 

• ACC mediates a lot of emotional experience in general 

  • It collects feedback from our behavioral responses + our autonomic and hormonal responses. This feedback forms our feelings of emotion. 

  • Involved in our emotional responses to pain and our anticipation of pain, including pain that’s directed at others potential pain

• ACC differs among individuals; for example, one guy can have it larger and the other smaller 

  • Research suggests that people who have a larger ACC may also have higher levels of the personality trait harm avoidance, meaning they might go out of their way to avoid experiencing any sort of painful or difficult 

• ACC in general: attention, cognitive processing, emotion, consciousness(??)

Aggression 

• In animals, there are 2 types of aggressive behaviors: defensive attacks and predatory behavior.

• Attack behaviors involve a high level of sympathetic autonomic nervous system activity, predatory behaviors do not. Predatory behaviors are like business as usual 

• amygdala+hypothalamus control activity of brain stem circuits associated with species-typical behaviors 

  • aggressive behaviors via PAG 

  • stimulate PAG → defensive attack, predation 

• amygdala+hypothalamus also involved in human aggression

• PFC restrains 

  • reduced PFC function in impulsive murderers; antisocial personality disorder…

testosterone & aggression 

• • CONTEXT MATTERS.

• • sometimes,

• ↑testosterone → ↑aggression.

• • sometimes,

• ↑testosterone → ↓aggression.

• • sometimes,

• ↑testosterone → ↓aggression in some and

• ↑testosterone → ↓aggression in others

• Basically, testosterone in itself does not cause aggression. It CAN cause aggression in some people, but not all. 

• If you give someone testosterone in a social situation where aggressive behavior will help them to achieve higher status, then they may act more aggressive. 

• If you give someone testosterone in in a social situation where they can gain higher social status by acting prosocially, or not aggressively, then giving them testosterone makes them act LESS aggressively and more socially 

• Testosterone is more about achieving higher social status rather than acting aggressively 

• We cant say that the hormone caused the result, because sometimes the result causes the hormone (to be produced)

Serotonin & risky behavior 

• Serotonin does inhibit aggressive behavior in some cases 

  • Decreasing serotonin makes aggressive attacks more likely 

• ↑5HT → ↓aggression

•  ↑5HT → ↓risky behavior 

• many 5HT projections to vmPFC, PFC in general 

• Serotonin inhibits risky behavior in general 

“One thing that's clear, though, is you're not going to get anywhere if you think there's going to be the brain region or the hormone or the gene or the childhood experience or the evolutionary mechanism that explains everything. Instead, every bit of behavior has multiple levels of causality.” - Robert Sapolsky

Communicating emotions

• how? 

  • postural changes 

  • facial expressions 

  • non-verbal sounds

• why? 

  • what are they going to do next???? 

  • “inferring mental state”

Basic emotions

• anger, fear, sadness, disgust, surprise, happiness

• easily & quickly identified from an individual’s face alone

• automatic occurrence, involuntary, rapid onset & typically rapid dissipation of emotion itself & accompanying autonomic system & endocrine activity 

• Cross-cultural

Complex / ‘social“ emotions

• e.g. grief, regret jealousy, awe, pride, shame, guilt, embarassment 

• more variable across cultures 

• slower, more difficult, to recognize

  • sometimes need more information than face, like posture

lateralization & emotion

• visual areas (including fusiform gyrus – faces), and auditory areas (including speech processing) 

• right hemisphere is dominant for recognition and expression of emotion

  • right hemisphere lesions → impaired visual and auditory recognition of emotion 

  • right hemisphere lesions → deficit in facial and voice expression

  • left half of face more expressive than right

amygdala & emotion recognition 

• amygdala lesion 

  • ↓ emotion recognition from faces & bodies (posture), especially fear 

  • preserved emotion recognition from tone of voice 

  • why? 

  • affective blindsight - refers to a form of blindness that’s relevant for emotions 

    • For example, they cannot see the person but they can still tell what emotion they’re feeling 

Feeling & perceiving disgust

• insula – location of primary gustatory cortex (taste)

• Insula is involved in taste, but a lot of other things as well such as interoception 

  • Interoception is a word for how we’re feeling 

  • It combines information about gut-feelings which includes feelings from your visceral organs as well as information about proprioception, temperature, etc 

• Anterior insula also plays a role in disgust. This area that perceives and feels disgust is near the primary gustatory cortex 

• When someone sees someone else experiencing disgust, they also recruit this anterior insula 

• This area of the brain comes into play when;

  • We taste something bad

  • We see something that makes us feel disgusted 

  • We see someone else who’s making facial expressions as though they were disgusted 

Expressing emotions

• Expressing emotions is automatic and involuntary 

• It’s hard to fake expressing emotions, and no one is really good at it

  • Yes, people who can fake emotions exist BUT it’s rare. Not a lotta people have it 

• Method acting exists bc people arent that good at faking emotions they’re not currently feeling 

• Smiling with the mouth can be done, but smiling with the eyes is difficult, near impossible to do. The only way to smile w the eyes is to actually smile

• Smiling only with the mouth and not the eyes is called a social smile 

• Volitional facial paresis

  • People have damage to the primary motor cortex aka M1 or it’s outputs or the axons that project down to the motor neurons in the spinal cord 

  • When people suffer from this type of damage, they cannot move their facial muscles voluntarily. So even if you tell them to make a facial emotion, they’re unable to do so. 

• Emotional facial paresis

  • Damage to the insula, white matter fibers in the frontal lobes, or damage to parts of the thalamus. 

  • People can voluntarily move their muscles, but can’t express genuine emotion with same muscles

Feedback from emotional expressions

• People that are told to make a face that is associated with a certain emotion [eg telling them to scrunch up their eyebrows, frown] causes them to actually have the physiological changes that are associated with said emotion.

  • For example, angry. This emotion is associated with scrunching up your eyebrows, your nose, frowning and when someone is angry, their hearrate increases and their temperature as well. When told to ‘scrunch your eyebrows,’ people would experience the physiological symptoms of anger without them feeling that emotion.

  • People have also reported that after making the face, they’d actually start feeling the emotion afterward

• Getting botox to reduce your wrinkles can also influence your experience of emotions as well 

• People who get botox in the corrugator muscle report less negative moods 

• Reduced in amygdala activity 

  • botox → ↓frown → ↓ negative emotions, ↓ amygdala activity

Feeling your feelings 

•  James-Lange theory:

  • sensory feedback → feelings

• Common sense theory; ‘im shaking because im afraid.’

• James-lange theory; ‘im afraid because im shaking.’