PSYC 304 Midterm 3: Things To Know

which method would choose to study: loss of grey matter in the weeks following a stroke?

CT scans can visualize loss of grey matter well, MRI is another option

which method would choose to study: changes in non-cortical brain activity following a stroke?

fMRI can see how BOLD response in specific regions changes or PET can visualize loss of function

which method would choose to study: cortical activity while running on a treadmill?

EEG - specialized to record electrical activity in motion

which method would choose to study: the external stimuli and situations in which a neuron fires

single-cell recording, extracellular or intracellular single-unit - what goes on outside a neuron or what the neuron’s path look like

which method would choose to study: changes in protein expression following a neurodegenerative disease (ex. Alzheimer’s)

PET - can see specific intensity of proteins in each cortical area

which method would choose to study: the role of the hippocampus in spatial learning and navigation

lesion studies + Morris Water Maze - designed to measure hippocampus’s role in spatial learning

which method would choose to study: changes in decision making and motivation following acute and chronic drug use

event-related fMRI (humans), maze task (rats) - over many trials, follow progression of drug effects

which method would choose to study: how we select words from our vocabulary for speaking?

fMRI - good for identifying specific regions

which method would choose to study: the role of monoamine neurotransmitters in the motivation?

PET - track neurotransmitter systems, selective chemical lesions (6-hydroxydopamine) and reversible lesions (rats)

which method would choose to study: what regions of the motor cortex control what parts of the body?

TMS - lesions can take away function of region temporarily

what are X-Rays good for?

• assessing skull fractures/structural damage

• imaging foreign objects in the brain

• best for bone resolution

what are CT scans good for?

• imagining white matter neurodegenerative (schizo, psychopathy)

• tumour/hemorrhage detection (sensitive to blood/calcification)

• bone injuries

what are MRIs good for?

• soft tissue abnormalities (tumours)

• neurodegenerative diseases

• stroke detection

• detailed brain imaging

what are PETs good for?

• imaging progressing of a drug or neurotransmitter system

• metabolic changes

what are DTIs good for?

• white matter diseases

what are fMRIs good for?

• studying brain activity during tasks in specific brain areas

• brain during resting states

• whole brain studies

what is TMS good for?

• establishing causality

• mapping functional brain activity

• neuroplasticity (rTMS)

• temporal precision

what is ERP good for?

• temporal resolution

• isolation of cognitive components

• changes in behaviour

• responses to certain stimuli

what causes BOLD?

activity in astrocytes due to synaptic transmission signals opening CA channels which causes blood vessels to dilate and release more blood flow in the brain area - why there is a delay in BOLD response after stimulation (takes a bit longer for this process to happen)

default mode network: what brain regions show significant activity during rest?

medial PFC, posterior parietal cortex, hippocampus, lateral temporal cortex

when is paired image subtraction useful?

functional brain imaging - since we want to minimize randomness when determining activity localization

• fMRI

• PET

problems with interpreting fMRI studies

1. spatial averaging: average actually doesn’t represent anyone

2. spatial resolution: million neurons/voxel

3. temporal resolution: delay

4. not necessarily a necessity

5. focus on increases in activity: some areas of brain are more active at rest (rsfcMRI and default mode network)

6. regional hemodynamics: BOLD response varies

7. anxiety and boredom confounds

8. drugs (caffeine, nicotine, medications)

9. anticipatory hemodynamics: BOLD response when we expect a stimulus

10. low between trials (30-40%)

11. statistics (0.05 error rate = high # due to amount of fMRI studies)

how do MRIs work?

1. each hydrogen atom rotates randomly about its axis

2. when placed in a magnetic field, they will align according to their north or south poles

3. a radio frequency pulse knocks atoms out of alignment, but still in same magnetic field - makes them want to relax back to orientation

4. energy that produces magnetic fields is released as atoms try to go back to original orientation

intravenous drug injection

injections into veins through catheters

• drug self-administration studies

• cocaine, heroin

• likely to knock out catheters

intramuscular drug injection

injections into muscles - enters blood stream quickly

• can leave a lot of soreness

subcutaneous drug injection

just under the skin - rats hardly feel it because of their flappy skin

• takes longer to get into bloodstream - ideal for medications that need to be slowly absorbed (insulin)

intraperitoneal drug injection

into abdominal cavity - quickly gets into blood

• most common - rats don’t really feel it

intraventricular drug injections

injections into ventricles

• overcomes blood-brain barrier

• chemotherapy

nissl staining

captures density of neurons

golgi staining

captures individual neurons

optogenetics

controlling and observing activity of neurons using light

• light-sensitive proteins (channelrhodopsins) are inserted into DNA of specific neurons

• fibre optic cable is implanted into brain, targeting area of interest

• light delivered through fibre optic cable

• allows for precise control over specific brain regions, detailed studies of neural circuits

top-down processing

formulate hypothesis of nature of stimulus → select and examine stimulus to check hypothesis → recognize stimulus

bottom-up processing

detect specific features of stimulus → combine specific features into complex forms → recognize stimulus (how we think in class)

how do we determine what system neural information reflection?

• doctrine of specific nerve energies: specialized cells are sensitive to only energies they are fitted for (some exceptions)

• labelled lines theory: specialized cells stay segregated from other types of sensory info

what are the steps of touch processing?

1. receptor detects touch stimulation

2. stimulation of the receptor stretches the tip of the axon

3. produce a graded potential with an amplitude directly proportional to strength of stimulus, opens gated ion channels in membrane

4. when the receptor potential is big enough, an AP is generated

transduction

turning external energy into nervous system signals

• ionotropic receptors (synaptic transmission)

• metabotropic (GCPRs)

how are different intensities of a stimulus represented in nervous system?

more intense stimuli generate more rapid APs OR more neurons fire parallel to each other

range fractionation

a wide range of intensity values can be coded by a group of cells each of which is a specialist for a particular range of intensities

Meissner’s Corpuscle

light touch - in the dermis, small receptive fields, fast-adapting

Merkel’s discs

fine touch - in dermis, small receptive fields, slow-adapting

Ruffini’s ending

stretch - in the hypodermis, large receptive fields, slow adapting

Pacinian corpuscle

vibration/pressure - hypodermis, large receptive fields, fast-adapting

where are receptor cell bodies located?

dorsal root ganglion

what are skin receptor potentials?

graded potentials at the input layer (opens Na channels through stretch receptors) → APs at cell body

TRPV1

C fibres - binds to spicy foods, capsaicin

• present in itch fibres

TRPM3

A delta fibres - when things get dangerously hot

CMR1

C fibres - binds to menthol

psychogeneic pain management

• placebo - can have some ethical concerns

• hypnosis - unaffected by opiate antagonists

pharmacological pain management

• opiates - block opioid receptors in spinal cord, can have severe side effects

• anti-inflammatory drugs - block prostaglandin at site of injury, side effects

• cannabinoids - act in spinal cord/nociceptor endings, illegal in some places

stimulation pain management

• acupuncture - sometimes affected by opiate antagonists

• TENS - electrical stimulation activating endogenous opiates and blocking pain signals in spinal cord, inhibited by opiate antagonists

surgical pain management

• cut peripheral nerve cord/cut dorsal cord/cord hemisection - create physical break in pain pathway, considerable risk of failure

• frontal lobotomy - irreversible and severely affects behaviour

NSAIDS

non-steroidal anti-inflammatory drugs

• act on COX pathway to reduce production of prostaglandins (reduces pain signals)

what does adaptation mean for the visual system?

we constantly are focusing on the main thing in our environment and not aware of most things in peripheral

• interested in relative values, not absolute

eye to retina path

cornea → lens → virtuous humour → capillaries → retina → axons → photoreceptors

• shows how we have evolved from our aquatic ancestors (as their paths are less messy)

photoreceptors to optic nerve

photoreceptors → bipolar cells → bipolar cells → amacrine cells → ganglion cells → optic nerve

how many rods in the retina?

~120 million

how many cones in the retina?

~ 7 million (most in the fovea)

S-cones

highest absorbance = 420 nm

rod wavelength sensitivity

450 nm

M-cones

highest absorbance = 530 nm

L-cones

highest absorbance = 560 nm

how do dogs see the world?

through dichromatic colour vision - saturation of yellow or bluish-gray

protanopia

loss of long wavelength cones - can’t see red

deuteranopia

loss of medium wavelength cones - can’t see green or red

tritanopia

loss of short wavelength cones - can only see redish and bluish colours

achromatopsia

loss of complete colour vision - usually a CNS issue

lateral inhibition

helps us detect contrast variation (Mach Bands) by inhibiting neighbouring photoreceptors and enhancing the photoreceptor that is being hit by light

• only interest in relative values that contribute to context

• enhances contrast discrimination

• active process

• receptive fields: inhibits light at peripheral in ON-centre cells to specify where the light is hitting

• can mutually inhibit each other because of horizontal cells (opponent processes)

what happens to vision if the left optic nerve is cut?

no visual info is coming through the left eye

what happens if left optic tract is cut?

no info from the right visual field is coming in

what happens if the optic chiasm is cut down the middle?

we lose input from the nasal halves of the retina - lose peripheral vision

what are p-cells/parvocellular layers for?

perception - cones from fovea

what are m-cells/magnocellular layers for?

motion - rods and cones from periphery

what would happen to ocular dominance columns if an eye was blocked at young age?

dominance columns for the covered eye would shrink and grow for eye that is not covered

colour constancy

despite the background colour changing, all objects will remain the same colour to us

Young-Helmoltz trichromatic theory

Every colour we can see is made of a combo of red, green, and blue light - all of them together = white light

• eye contains 3 types of cone cells

• support: colour matching demonstrates that any colour can be matched by mixing red, green, blue

Hering’s opponent process theory

colour vision is based on three opposing colours

• Red vs. Green

• Blue vs. Yellow

• Black vs. White

Vision can only perceive one colour at a time from each pair

• afterimages: staring at a bright red object and then looking at a white surface = green afterimage

are trichromatic theory and opponent process theory mutually exclusive or complementary?

they complement each other

• trichromatic: explains how cones detect light

• opponent-process: explains how brain processes colour

damage to the ventral visual stream

difficulty recognizing what/who things are (agnosia)

• can match bodily movements, but have difficulty recognizing what to do in a task

• some cannot recognize familiar faces (Halle Berry neuron would not work)

damage to the dorsal visual stream

how difficulty with spatial orientation and motor tasks

• can’t sort objects properly

• difficulty with depth perception

non-conscious vision

• still have circadian rhythm

• still can be guided by light to do some photoreceptors attached to RGCs

• can still guess what stimuli is and navigate a room with obstacles

• driven by superior colliculus?