PSYB55 Lec 1-4

Aggregate field theory

Brain = 1 large, non-specialized thing (any part of brain can perform any function)

→Bc rat lesioning research showed that rats could be fine w/out all parts of their brain

Localization of function

Specific parts of the brain perform specific functions

→Phrenology was in favour of this, although phrenology itself was an incorrect practice

Evidence for localization of function

1. Broca's Area: Broca's aphasia means you can understand but can't speak coherently

2. Jacksonian march: when seizures start in one place (ex. thumb), they would progress in a way consistant w the topographic map of cerebral cortex (ex. up to the index finger, then middle, etc)

3. Montreal Procedure: epilepsy brain mapping to prevent neurosurgeons from removing something that would worsen the life of the epileptic patient

4. Phineas Gage: his orbitofrontal cortex was destroyed, which impaired his personality

5. Patient H.M.: Anterograde amnesia from his bilateral medial temporal resection (removed his hippocampus) bc of his epilepsy → localization of function for memory

6. Callosotomy (resection of corpus callosum): to prevent seizures from spreading from 1 lobe to the other

7. Bad application of localization of function: frontal lobotomy

Techniques in neuropsych

1. Non-human studies: animal lesion studies

2. Structural imagining techniques: CT, sMRI

3. Functional imaging techniques: EEG, fMRI

4. Pertubation studies: TMS, tDCS

5. Human patient studies: stroke, brain trauma survivors

Method of inquiry: Behaviourism

Psych should be an objective science that studies behaviour without reference to mental processes; "seining is believing"

→There was good attention to detail but they overlooked important aspects of learning

→Dark ages of psych: only studied associative learning, conditioning

Method of inquiry: Cognitivism

Broader scope than just behaviour; study of learning and other mental processes

→multitasking: cognitive resources are limited but imp. for functioning well in the world

→variability: there are w/in subject diffs and b/w subjects

→flexibility: cognitive abilities change w use/development and disuse

Method of Inquiry: Introspection (via structuralism)

Breaking down complicated things into smaller parts to better understand something (ex. sadness can be understood by what's happening: tired, sore back, etc)

→requires you to be aware of what's happening

→introspection can't be used to analyse things in the subconscious

Cardiac hypothesis

The heart is the seat of the mind.

→Heart dysfunction leads to cog. impairment (no oxygen = dead brain tissue so they saw a correlation)

→Ancient Egypt kept heart and discarded brain of the dead bc of these beliefs

Brain hypothesis

Brain is the seat of the mind

→Dualism: brain & mind are related but separate entities

→Rationalism: brain is symmetric except for pineal gland which exists in the middle of the brain ∴ it must connect the brain to the soul

→This explained reflexes, which don't need brain orders

Are reflexes greater or inhibited in patients with cut spinal cord

Cut spinal cord = no communication b/w the brain & body → reflex is greater bc of lack of brain's inhibition

→Reflexes are also strong in newborns bc of lack of brain inhibition

Neuron doctrine

The REJECTION OF Golgi's syncytium proposal (the brain was one continuous gelatinous material bc of the role of the synapse)

→Brain develops from the inside-out, w the cortex being made later

Earliest record for dramatic brain injury?

Edwin Smith Papyrus: Treatment of brain swelling after traumatic brain injury

→Hinted at localization of function

Broca's Area

In the left frontal lobe

→Damage: Broca's aphasia = Non-fluent output despite intact comprehension

Wernicke's area

Left temporal lobe

→Damage: Wernicke's aphasia = Impaired comprehension despite fluent output

Montreal Procedure

For epilepsy; Brain mapping using electrocortical stimulation on the brain's surface

→MOTOR/PREMOTOR Movements

→PARIETAL Somatosensory/visual hallucinations

→OCCIPITAL Visual hallucinations

→PREFRONTAL Nothing ('silent cortex')

→TEMPORAL Visual/auditory Hallucinations

Whole memories

Phones Gage

Total ablation of orbitofrontal cortex (OFC);[Variable] impact on emotion, personality

patient H.M.

Bilateral medial temporal lobe resection for chronic, debilitating epilepsy

→Profound anterograde amnesia despite

relatively intact long-term memory stores

Callostomy

Resection of corpus callosum

→Eliminates cortical cross-hemispheric communication (stops spread of seizures)

What are some specialized subfields of cog. neurosci?

1. Developmental cognitive neuroscience

→ex: development of "theory of mind"

2. Social cognitive neuroscience

→ex: self-monitoring in social situations

3. Cultural cognitive neuroscience

→ex: display rules and emotion regulation

4. Clinical cognitive neuroscience

→ex: neurological basis of hallucinations

5. Rehabilitation neuroscience (CN-angle)

→ex: resumption of speech after Broca's aphasia

Rationalism

•Enlightenment period

•Knowledge is gained t/ reason

•Truth is intellectual, not sensory

•Subjective and ∴ problematic

Experimental psych

Studying the mind by measuring behaviour

→You can use diffs in rxn times to infer diffs in cog. processing

Empiricism

All knowledge comes from sensory experience, the brain began life as a blank slate

→Logical decision-making

→Associationism

What is associationism and how was it discredited?

The aggregate of a person's experience determined the course of mental development

→Close to behaviourism

Language/speech follows grammatical (not probabilistic) rules

→Language rules/grammar are built into our brains and associationism doesn't explain this

What did memory loss after surgery show us?

That there are multiple memory systems; this led to the discovery of working memory

→Signal detection

→Magic number 7±2

Cognition

Process of knowing i.e what arises from awareness, perception and reasoning

Neuroscience

the study of how the nervous system is organized and functions

Cognitive Neuroscience

Psychological testing models to understand how the brain works as an integrated whole = cognitive neuroscience

→Combines many disciplines (biochem, behaviour, etc)

→Study of working memory = phase shift in the understanding of mental illnesses (ex. schizophrenia isn't the result of bad parenting)

Explain decremental conduction and the retina

Weak currents don't usually die out in retinal neutrons bc short 1mm currents can trigger an AP

What is multiple sclerosis?

An autoimmune disease; the immune cells destroy the myelin sheath on axons in the CNS

→Immunosuppressants to slow this process down

chemical transmission

1. Electrical signal (AP) gets to the axon terminal and depolarizes the membrane

2. Depolarization causes V-G Ca2+ channels to open = influx of Ca2+

3. Ca2+ triggers NT-containing vesicles to fuse w the membrane and release the NTs into the synaptic cleft

4. The NTs diffuse across the cleft and bind to specific receptors in the postsynaptic membrane

5. NT binding induces a change in the receptor, which opens specific ion channels

6. This results in an influx of ions leading to either depolarization/excitation (EPSPs) or hyperpolarization/inhibition of the postsynaptic cell (IPSPs)

What are the AA NTs?

aspartate (D), glutamate (E), glycine (G), GABA

What are the biogenic amine NTs?

catecholamines, serotonin, and histamine

→Catecholamines = DA, Epi, NE

Acetylcholine

Is it's own class of NT

What are Neuropeptide NTs? What groups are there?

Larger NTs made of strings of AAs. There are 5 groups:

1. Tachykinins (brain-gut peptides) → substance P (=NT for pain and vasoconstriction)

2. Neurohypophyseal hormones → oxytocin (=mammary functions, bonding & maternal behaviours) and vasopressin (=antidiuretic hormone = ↑renal reabsorption)

3. Hypothalamic releasing hormones → corticotropin-releasing hormone, CRH (=stress response) and somatostatin (=GH inhibitor)

4. Opioid peptides → these NTs bind to opiate receptors. Endorphins and enkephalins bind to reduce the perception of pain (similarly to morphine)

5. Other neuropeptides

Dopamine (DA)

•Produced in: substantia nigra and ventral tegmental area

•Imp. for higher order mental functions such as working memory, holding onto what's important and ignoring distractions

•Movement in the brain (brain controlling body movement)

•Increases the likelihood that you do something that feels good again

•Disturbed [DA] = PD → as it progresses, a person's ability to move decreases until they can't move at all. Due to destruction of the cells in the substantia nigra that produce DA

•Has a role in addiction, and the perpetuation of it

Norepinephrine (NE)

•Produced in the locus coeruleus

•Imp role in memory by helping you pay attention

•Arousal → waking up in the morning, paying attention, etc

•Mental flexibility, trying something new

•Mood

•Disturbed [NE] = Alzheimer's → deterioration of memory, attention, and affect/mood

•Damage in one half of the brain (ex. right), most of the NE goes to the left side of the brain, you can't pay attention/remember anything in the left side of space ∴ NE is imp. for attention = visuospatial neglect. You aren't aware of what you aren't aware of: these patients won't "see" you in their left visual space at all

Serotonin (5-HT)

•Produced in Raphe nucleus (in brain stem), building blocks obtained from diet

•Exp. participants stay in lab over a few days and are free to do whatever they like. They are provided with meals lacking the building block for 5-HT

•They got grouchy and mean and their moods were just gross

•But when they get normal food w 5-HT building blocks, then their mood goes back to normal again (becomes more pleasant)

•1st antidepressants boosted 5-HT to treat major depression

•Low levels of 5-HT are found in many mood disorders and psychotic behaviours (which co-occur w depression quite often)

Acetylcholine (ACh)

•Produced in the basal forebrain (below frontal lobes)

•Processing sensory info

•Paying attention ∴ plays a role in creating memories

•Long- & short-term memories

•Movement in the body (not the brain and spinal cord, but the muscle itself)

•Curare blocks all Ach receptors = you can't move

•Black widow bite = dangerous release of Ach which causes spasms

•Botox paralyzes the muscles to the point they can no longer move via Ach receptors

•[Ach] gets completely destroyed in Alzheimer's disease

•In dementia + Alzheimer's, the basal forebrain is destroyed = 0 Ach

•In Alzheimer's meds that ↑Ach is used to imporove movement

•Ppl use these meds to "be smarter" bc ↑Ach = ↑attention/memory = ↑learning

In electrical transmission, neuronal membranes touch at ____________, which results in the neurons being ___potential

In electrical transmission, neuronal membranes touch at gap junctions, which results in the neutrons being isopotential

→bc of electrotonic conduction, the passive currents are smaller in the postsynaptic neuron than in the presynaptic neuron

→Communication is usually bilateral but rectifying synapses limit current flow in 1 dir'n

Are electric or chemical synapses more plastic?

Chemical synapses are more plastic; that's one disadvantage of electric synapses (gap junctions)

Astrocytes

•Responsable for the BBB: astrocytes make contact w blood vessels of the brain's vasculature at its end feet (structure of astrocyte)

•Imp. for neural development

•Block brain's ability to heal itself

When astrocyte activity is blocked, what happens to neural activity?

When astrocyte activity is blocked, neural activity increases

Microglial cells

Clean up messes, part of immune system in N.S.

What kinds of tracts are there?

1. Association tracts: run from 1 region to another w/in a hemisphere

2. Commissures: association tracts that cross into the other hemisphere

→largest commissure = corpus callosum

3. Projection tracts: run from the cerebral cortex to the deeper subcortical structures & spinal cord

Describe the CSF and it's circulation

CSF is clear containing proteins, glucose, ions (K+, Na+, Cl-)

It flows from the Lateral ventricles → third ventricle → cerebral aqueduct → 4th ventricle → subarachnoid space

→Then it's reabsorbed by the arachnoid villi in the sagittal sinus (large venous system located in b/w the 2 hemispheres on the dorsal surface)

What are the structures of the brainstem?

midbrain (rostral), pons, medulla (caudal)

What does the medulla do?

•Provides sensory/motor innervations to the face, neck, abdomen, throat, tongue, & heart

•Controls respiration, HR, arousal

•The ascending sensory info passes t/ the medulla via that gracile and cuneate nuclei (which continue to synapse in the thalamus for the somatosensory cortex)

•Corticospinal motor axons tightly packed in the pyramidal tract cross here to form the pyramidal decussation which allows for contralateral body movements

What does the pons do?

•Sensory & motor nuclei (face/mouth)

•Visuomotor nuclei (eye movements)

•Superior olive (auditory info)

•REM sleep

Limbic system

A band above the corpus callosum consisting of:

The cingulate gyrus (hypothalamus, anterior thalamic nuclei, hippocampus) and the amygdala

Basal ganglia

Integrates sensory & motor context w reward info for the motor/prefrontal cortex to make decisions

→Includes the substantia nigra

Functions of the human cortical surface

1st: enable more cortical surface to be packed into the skull

2nd: brings neurons into closer 3-D relationships to one another

3rd: brings nearby regions closer together

Ischemic stroke

a type of stroke that occurs when the flow of blood to the brain is blocked

→Lack of oxygen to tissue in any part of body = stroke

corticospinal tract

A.k.a. pyramidal tract

→motor tract

→switches in the medulla/brainstem (that's why we have contralateral control over our body)

Name of a bundle of axons in the CNS and PNS

In the CNS it's a tract, in the PNS it's a nerve

Dermatomes

Mapping of nerves b/w spinal cord & body

Frontal lobe

Mostly speech production (Broca's area), movement (motor cortex), and higher order cognition

Parietal lobe

Mostly touch (touch cortex) and attention (external & when thinking to yourself)

Temporal lobe

Mostly memory, understanding language, hearing

Association cortex

Most common kind of cortex in our brain; has most complex complications when damaged bc it's responsible for multiple things

→Whereas primary sensory/motor cortex is responsible for mainly one thing

→The frontal & temporal lobes are mostly association cortex

Limbic system function (and what brain parts perform these functions?)

Emotion & memory

→Hippocampus for memory formation

→Amygdala for emotion processing

What sense doesn't synapse onto the thalamus?

Smell

Thalamus

Sensory relay station and imp. for consciousness

What wraps around the thalamus and what is it important for?

Basal ganglia wraps around the thalamus and is imp. for motor control and automatic behaviours

→role in PD, HD (overactive, loss of control), Terret's syndrome

Name 2 motor tracts

Crus cerebri & red nucleus

Perlaqueductal gray matter

Gates pain

→Can block pain when it's beneficial to survive but when it's no longer needed you feel the pain again

→ex. "Runner's high"

Cerebellum

Evolutionarily old (common across many species). Despite this, it is imp. for:

→motor coordination: tongue/mouth muscles for speech

→Memory & higher order cognition

What happens when you damage the pons?

Locked-in syndrome bc the brain can no longer communicate w the body

Pons

Bridges cerebellum to cerebral cortex

→how to play a sport, ride a bike, etc.

→hand-eye coordination

What is the toughest, most outer layer of the meninges?

The dura mater

What are the ventricles for?

Buoyancy & metabolism

→continuous w the CSF of the spinal cord

→Test for brain health in the spinal cord (CSF should always be clear)

lumber puncture

AKA spinal tap; obtains CSF to show health of the brain

3 arteries to know for the Circle of Willis

1. Middle cerebral artery

2. Anterior cerebral artery

3. Posterior cerebral artery

Middle cerebral artery

→Most common for strokes

→Covers lateral cerebral cortex

→Affected in Broca's & Wernicke's aphasia

anterior cerebral artery

→Covers medial frontal & parietal cerebral cortex

→Stroke here results in you acting like Phineas Gage

Posterior cerebral artery

→Covers occipital lobe & parts of temporal lobe

Neurophysiology uses in higher primates

1. Single-cell recordings

2. Lesion studies

single cell recording

Electrode inserted to neuron (ex. in occipital lobe), then you display something in the visual field and observe the neuron's response

→Cell is only responsive when stimulus is in receptive field (ex. upper right corner)

→Method is useful for understanding the neuron's properties

→But this doesn't give the big picture (just 1 in 80 billion neurons)

→Good for mapping visual & auditory processing

Coding value

Your "option 1" neuron & "option 2" neurons are flexible and change according to your preferences so that your option 1 neuron always activates when you see your #1 preference

What are the 3 stages of a working memory experiment?

1. Cue

2. Delay → high activity in prefrontal cortex

3. Response

Lesion studies

→Discovered connections b/w the parietal lobe & visual areas; the link b/w what you see and how you interact w it using your motor system

What happens when you impair the parietal system?

You can't use vision to guide action anymore

What happens when the amygdala is damaged?

In animals, they try to fornicate w animals of other species and they can't identify objects visually so they'll put objects in their mouths to figure it out via taste/touch

Why isn't stroke in humans a good method of study?

Bc strokes affect large parts of the brain so it's hard to draw conclusions as to what part caused what injury/disorder

CT (computerized axial tomography)

→Structural analyses

→ Diff. tissue absorb radiation at diff. rates

→Imp. for emergency med (cancer, tear in knee, etc)

→Problem: exposure to radiation

sMRI (structural magnetic resonance imaging)

→Structural analyses

→Solves radiation problem

→Gives image of part of body

1. Patient placed in strong magnet

2. Protons in body align w magnetic field

3. Radio-frequency pulse knocks protons out of alignment (in the fluid they go far, in the skull they don't get knocked much)

4. These protons give off resonance

→More clear than CT

→Problem: can't use with any kind of metal (ferrous material) in body

→Also, they're really expensive

What is a voxel?

Like a pixel but for MRI; so the brain image will be made up of voxels

→Imp. for how size of regions relates to disorders

→ex. smaller hippocampus is correlated w more severe experience of PTSD

Lesion overlap technique

Using sMRI on many ppl with the same impairment then overlapping all the pictures and colour-coating which areas are most commonly damaged in these patients

Diffusion Tensor Imaging (DTI)

Structural analyses using MRI scanner:

1. in MRI scanner you're jostled around

2. Where the water moves unidirectionally in the brain is measured → moves more freely in white matter so you'd observe that there's axons where there's a lot of movement

Doesn't detect anything in ventricles bc H20 doesn't move unidirectionally there

What can diffusion tensor imaging (DTI) be used to study?

•Longitudinal fascicles (anterior to posterior length of brain) can be visualized

•Map tracts to understand neurodevelopment & disfunction

•Concussions

•Multiple sclerosis and how myelinated axons have changed

Fractional anisotropy

Which way H20 is moving best; measured using DTI (diffusion tensor imaging)

→water moves easiest along side myelinated axons

Electroencephalography (EEG)

Recording the electrical activity of the brain via electrodes on the scalp; more electrodes = more recording channels

→good temporal resolution

→BAD spatial resolution

→Functional analyses

How can EEG be used for seizures?

EEG tells us when the seizure begins based on the recording channel that spikes first → then you look at the corresponding electrode and will know the general area of the seizure

→Helps to localize where you should be looking

How is EEG used for cognition?

For emotion regulation you put the EEG cap on the subject and show them a video that makes them certain kind of emotional

→Repeat this w subject 50x (remember imp. of multiple trials)

→this would be mapping

Event-related potentials (ERP)

For a sentence that makes sense, the brain responds normally; when the subject hears a sentence that doesn't make sense, then you see a diff. ERP or graph

→EEG

Electrocorticography (ECoG)

Electrodes placed directly on the brain to determine precise regions of particular neural activity

→To determine if an imp. brain area will be affected during neural surgery (before the surgery happens)

→There are no pain receptors in the brain so patients are awake for this

→Basically EEG on the brain

→Functional

Positron Emission Tomography (PET)

Functional analyses to track blood flow

1. Inject radioactive molecule w high affinity for what you're studying (ex. DA, glucose, etc) into bloodstream

2. The subject performs mental tasks while their head is in the machine; during this, the radioactive molecule collides w the thing it has high affinity for

→Ex. you'd see the diff. blood flow for which parts of the brain engage in verbs vs. nouns

→Problem: radiation

Ex. of PET used for AD

PiB (radioactive chemical) interacts w beta-amyloid plaques

→Controls show no PiB interactions whereas AD patients show high PiB interactions

→This identified plaques in AD patients in vivo

→You can track the progression of the disease: more PiB interactions = more plaques

Ex. of PET used for PD

Looking at interactions with DA

Functional magnetic resonance imaging (fMRI)

Neurovascular coupling: looking at changes of blood flow = changes of neural activity

→Oxygenated & unoxygenated blog have diff. dipole moments (magnetic) bc of hemoglobin

→BOLD = blood oxygenation level dependent

→Good spatial resolution

→Bad temporal resolution bc blood flow

→Solves problem of PET radiation

→Correlational method

Will the left temporal lobe have a high or low BOLD while I speak?

A high BOLD signal bc oxygenated blood will rush there since that area will be active