behavioral neuroscience exam #2

what sense do we rely on more than any other sense?

vision

why do we know the most about the visual system?

it is a direct pathway

what is sensation?

the physical stimulus from environment to sensory organs to brain

what is perception?

the psychological interpretation of physical stimulus

what is the lens?

flexes and focuses the light onto the retina; has accommodation

what is accommodation?

the process by which the eye's lens changes shape, bends, and flexes to focus near or far objects on the retina

what happens to the lens as you age?

the lens stiffens and it does not flex or focus as well, impairing vision

what is binocular disparity?

the brain takes 2d images and perceives it as 3d; each eyeball has a slightly different image and by comparing the 2, the brain makes a 3d image with depth

what is the pupil?

The hole in the centre where light enters

what is the iris?

the muscle that controls how much light gets into the eye; it is what constricts and dilates the pupil

what is the cornea?

the transparent layer that protects the eye

what is the retina?

inner surface of the eye containing 5 layers of visual receptors, including rods and cones in the last layer

what are cones?

retinal receptors that fire under bright light for fine detail and color (acuity)

what are rods?

retinal receptors that fire under lowlight/dark conditions for movement (specificity)

what happens to the light by the time it reaches the rods and cones?

the image sent to the retina must pass thru 4 layers before it gets to the rods and cones so the light gets distorted and diffuse

what is the fovea?

the concave indentation in the retina where light is not distorted as much and it contains only cones so it has good acuity; fovea is thinner than the rest of the retina

what is a blindspot?

a hole in the visual field where you are not receiving any visual information but our brain fills it in so we cannot see our blindspot

what is the optic chiasm?

the x-shaped structure where visual information gets flipped; L goes to R and R goes to L

how does the brain perceive an image as 3d?

originally, the image put on the retina is upside down and 2d.

- the brain uses intersecting lines to create depth and make the image 3d

- binocular disparity (the brain takes 2d images and perceives it as 3d; each eyeball has a slightly different image and by comparing the 2, the brain makes a 3d image with depth)

- motion gives details; things move faster when they are closer and things move slower when they are farther which also creates depth

What does contralateral mean?

both eyes take in info from the L and R visual fields, but only info from the L visual field gets sent to the right hemisphere and vice versa via the optic chiasm

how many cones do we have?

7 million

how many rods do we have?

120 million

What is phototopic vision?

when cones are firing under bright light; brighter spectrum of colors

what is scotopic vision?

when the rods are firing under lowlight; darker spectrum; night vision

what is the purkinje effect?

as we shift from bright to low light, we detect colors differently; under bright light, we are more sensitive to reds, oranges, etc. under lowlight, we are more sensitive to purples, violets, etc.

why do humans have less cones and more rods than other species?

humans rely on intelligence and conciousness more than vision, which is why humans have less cones --> worse details ---> worse vision; humans need to sense movements more so they have more rods

where are rods primarily found?

peripheral vision

what are saccades?

the jump in between fixation point to fixation point

What is change blindness?

temporary blindness that occurs during saccades (the jump between fixation points)

what is a fixation?

the point your eye jumps to and focuses on

what do our eyes do when we read?

the eye path jumps around, forward and backward, and we do not read every word; we read in 7-9 letter increments

What is inattentional blindness?

failing to see or notice something that is in our visual field because we are not paying attention to it; so you do not perceive it

what is the retina-geniculate-striate pathways?

information from retina to lateral geniculate nuclei to striate pathways

what is the striate cortex?

primary visual cortex located in occipatal lobe

what is the lateral geniculate nuclei?

the thalamus, with 6 layers of cells within it, broken up into M and P pathways

What is the P pathway?

parvocellular: the top 4 layers in the thalamus, deal with fine details and color, get their information from the cones

what is the M pathway?

magnocellular: the bottom 2 layers in the thalamus, deal with movement, get their information from rods

what is retinopic organization?

the entire visual pathway is organized/mapped out based on the retina; where rods and cones fire on the retina, the rest of the information will be processed in the same locations on the lateral geniculate nuclei and striate cortex

how do humans detect edges?

mach bands, contrast enhancement, lateral inhibition

what are mach bands?

brain makes up fake lines/edges when they'e not actually there; the lighter side has more stimulation so a stronger signal, the darker side has less stimulation

what is contrast enhancement?

the neurons on either side of the light and dark shade are firing more and less than they are supposed to, thus enhancing the contrast

what is lateral inhibition?

when a neuron is stimulated, it inhibits all neurons around it in terms of how strong they fire in order to conserve energy; the stronger a neuron is stimulated, the more it will inhibit other neurons; this is what causes contrast enhancement

Describe Hubel and Weisel's work about the receptive fields

they found on-center and off-center cells which are ganglion cells that are round and they help create contrast/determine the edges of objects; they tested a cat's visual field and the neurons only fired when seeing the line/edge of the projector slide

what are on-center cells?

cells that only fire if light hits the center of the cell

what are off-center cells?

cells that only fire if light hits the outside of the cells

what is a simple cortical cell?

rectangular cell in the cortex that works exactly like on and off center cells

what is a complex cortical cell?

a cell in the cortex that is way more complex and does not respond only to on and off cortex

what is columnar organization?

columns in the cortex; each simple cortical cell fires to a different line orientation

what is the pathway between simple and complex cortical cells and on/off center cells?

on/off center --> simple cortical --> complex cortical

what is the component theory (Young 1802)?

if we mix certain colors, we can make more colors, so we must have different receptors in our eyes that mix different waves of light to perceive different colors

what is the opponent processing theory (Hering 1878)?

we must have receptors in the eye that respond to opposite colors; the after image of one color is the opposite

Which theory of color vision is correct?

both; we have B, G, and R cones and when light comes in it stimulates these cones and gives us the perception of other colors

what is color constancy?

depending on the source of the light, the amount of light reflecting off an object will be different; but our perceptual system perceives it as the same color regardless of the source of light

What is the retinex theory (Land 1977)?

even though the source of light changes, the efficiency at which an object reflects light remains the same

what is a scotoma?

blind spot

what is blindsight?

the ability to respond to visual stimuli without consciously perceiving them

the sensorimotor system uses parallel processing. what does this mean?

every area works together and communicates at the same time

what does it mean for the sensorimotor system to be functionally segregated?

each area specializes in processing certain types of info and works together

the sensorimotor system is a feedback loop. what does this mean?

motor output is guided by sensory input

how does learning change the nature and locus of sensorimotor control?

at first we are consciously aware of our actions, such as driving or walking, but as we practice, it becomes automatic. Learning an action to the point of automaticity allows for efficiency as it frees up higher order loci of sensorimotor control, so we can designate more energy to complex things.

can automaticity be taken over?

yes

what is an action slip?

sensorimotor programs are primed by environmental things (ex. turning on a light switch if the light is already on)

what is the pathway of the sensorimotor system?

starting in the brain and come out through the brainstem to the skeletal muscles

what is the posterior parietal association cortex?

parietal lobe where the integration of sensory information and objects in space

describe apraxia.

difficulty in initiating voluntary movements, problems with planning of motor coordination; usually caused by damage to left parietal lobe; affects fine motor skills more severely but also can affect gross motor skills; actions may be able to be done with automaticity but often struggles when the action is controlled; ex. stuttering

what is the egocentric left?

damage to right side of the parietal lobe causes an attentional deficiency to one half of the body, usually the left side

what is object-based neglect?

the only thing one cannot see is one particular object in their visual field

damage to the dorsolateral prefrontal association cortex causes what?

damage causes problems interacting with external world and stimuli ex. catching things/reaching for things

what does the supplementary motor area deal with?

sensory input

What does the premotor cortex do?

visual information

how many areas of the secondary motor cortex are there?

we used to think there were 2, now we identify 7, but we do not know exactly where the boundaries of each area are

what are the 7 areas of the secondary motor cortex?

- supplementary motor area and presupplementary motor area

- dorsal premotor area and ventral premotor area

- 3 cingulate motor areas

what happens if you damage your primary motor cortex?

damage to the area can cause difficulty with smoothness, speed, and accuracy of movements; one may also develop asterognosia (cannot determine objects with eyes closed)

what does it mean for the primary motor cortex to be somatotopically organized?

it is organized according to the body

describe the motor homunculus.

face and hands are even bigger than in the somatosensory; ears are hella small

describe the cerebellum in regards to the sensorimotor system.

it deals with learning and storage of sensory motor programs (muscle memory); it is 10% the size of the brain but contains 1/2 of all neurons; damage to the cerebellum causes very severe deficits; also involved in learning cognitive programs (learning patterns/repetition)

describe the basal ganglia in regards to the sensorimotor system.

associated with voluntary motor movements; deals with learning of sensorimotor and cognitive programs, such as stimulus-response relationships

which direction do descending motor pathways go?

toward the external world

describe the dorsolateral region of the descending motor pathways.

it projects into the distal parts of the arms and legs; the dorsolateral corticospinal tract is a direct pathway dealing with lower leg muscles. the dorsolateral corticorubrospinal tract is an indirect pathway dealing with distal areas such as hands, feet, wrists

describe the ventromedial region of the descending motor pathways.

deals with proximal areas such as shoulders, thighs. ventromedial corticospinal tract is a direct pathway and the ventromedial cortico-brainstem-spinal tract is the indirect pathway

what does the ventromedial cortico-brainstem-spinal tract contain?

1) tectum: inferior and superior colliculi that deal with processing auditory and visual info

2) vestibular nucleus: balance

3) reticular formation: in the brainstem and in this pathway it deals with species specific movements such as walking and climbing

4) motor nuclei of cranial nerves that control the face

what is the stretch reflex?

sudden impact on muscle that helps guide motor output. ex. knee jerk reaction

what is the withdrawal reflex?

when you do something painful and you automatically send a signal to stop the action, bypassing the brain ex. moving hand off of a hot stove

what is reciprocal innervation?

as antagonistic muscles work, one works a lot and one works to a lesser degree in order to guide movement smoothly

what is recurrent collateral inhibition?

when a motor neuron fires, it immediately shifts responsibility next time to a motor neuron around it to avoid fatigue and overwork

What do ligaments connect?

bone to bone

what do tendons connect?

bone to muscle

what is a motor unit?

the smallest unit of motor activity that contains a single motor neuron and all the muscle fibers that it innervates (touches)

what is a motor pool?

all motor units that innervate a single muscle

what is a fast twitch muscle?

consumes more oxygen because it contracts quickly and fatigues quickly

what is a slow twitch muscle?

consumes less oxygen because it does not fire as quickly or strongly and does not fatigue as quickly

what is a flexor?

a muscle that bends a joint; ex. bicep

what is an extensor?

muscle that straightens a joint; ex. tricep

what are synergistic muscles?

muscles that work together for a joint movement; ex. the 2 muscles that make the bicep

what are antagonistic muscles?

muscles that oppose each other/do opposite jobs; ex. biceps vs. triceps

what is an isometric contraction?

muscle contracts but does not change length or actually move anything; ex. plank

what is a dynamic contraction?

This term refers to any muscle action that produces joint movement. ex. bicep curl

what causes a muscle to contract?

nerves firing electric current to fibers

what are golgi tendon organs?

located where bone and muscle connects; they send info to the brain about the amount of stretch that is occurring and cause the muscle to go lax so that it protects the muscle from injury

what are muscle spindles?

Sensory receptors within muscles