L1-7

Question 1

Sensory dermatome refers to

Answer 1

map of areas on the body where sensory info is carried along each of the 31 cranial nerves

Question 2

describe the 6 layers of the neocortex from outside in

Answer 2

1. axons and dendrites, few cell bodies
2. densely packed stellate cells, a few small pyramidal cells
3. loosely packed stellate cells, intermediate sized pyramidal cells
4. bands of densely packed stellate cells, no pyramidal cells
5. few loosely packed stellate cells, very large pyramidal cells
6. loosely packed stellate cells, pyramidal cells of var sizes

Question 3

what do Intrinsically Photosensitive Retinal Ganglion Cells (ipRGC) do?

Answer 3

• light senseitive retinal ganglion cells
• most sensitive to blue light
• bottom half of retina (top half of visual field)
• connect through to SCN for entraining circadian rhythms

Question 4

what is lateral inhibition, in context of shaded rectangles

Answer 4

• excited neurons inhibit surrounding neurons
• opponent process
• darker/less intense surround = less inhibition = perceive as brighter
• for grey rectangle inside white or black background, perceive as lighter against black background

Question 5

explain opponent process theory of colour vision

Answer 5

• colour vision controlled by activity of 2 opponent systems - blue-yellow and red-green
• Competition between the cones makes the different colours
• adaptation of particular colour receptors favours opponent receptors –> afterimage

Question 6

simple cells (V1)

Answer 6

• Respond best to elongated bars or edges
• Are orientation selective.
• Have separate ON and OFF subregions
• Can be monocular or binocular (some respond only to one eye, some to info from both

Question 7

COMPLEX CELLS (V1)

Answer 7

• don’t have off region to the side
• moving in same orientation → still fires
• orientation selective
• Have spatially homogeneous receptive fields (no separate ON/OFF subregions).
• Nearly all binocular.

Question 8

cortical magnification

Answer 8

lots more of visual cortex devoted to info straight in front, compared to peripheral

Question 9

Collumnar arcitecture of V1

Answer 9

columns of brain tissue responding to shape in different spatial location - systematically mapped

Question 10

describe how auditory info gets from ear to cortex

Answer 10

cochlea → brainstem → midbrain (inferior colliculus - own sounds are filtered out here eg breathing, chewing) → medial Geniculate Nucleus of Thalamus - forebrain → auditory cortex

Question 11

Why tonotopic mapping?

Answer 11

• Reduces axon length? —> Sounds close in frequency are processed together
• Facilitates processing (lateral inhibition)
• Allows sounds to be encoded on the basis of time/frequency changes
• Scene analysis – frequency separation relates to objects in the environment
  
  • lower sounds = big predator

Question 12

Top down processing in visual vs auditory

Answer 12

Most (66%) connectivity is top down in auditory, compared to ~6% in visual cortex
Why? = language

Question 13

insert L4 stuff here

Question 14

Hebb’s model for memory

Answer 14

• cell assemblies/distributed processes
• A unique pattern of activity in millions of cells corresponding to each experience

Question 15

short term memory (under Hebb’s theory)

Answer 15

circuit feeds back on itself to say active = reverberating
20 sec

Question 16

long term memory (under Hebb’s theory)

Answer 16

connections would be strengthened so easier to reactivate circuit, needs a cue

Question 17

recall memory (under Hebb’s theory)

Answer 17

Recall = reactivation of an assembly (network) of neurons, due to different synaptic strength,
- The reactivation is a partial match to the original experience

Question 18

Strengthening (under Hebb’s theory)

Answer 18

when the postsynaptic and the presynaptic cell fire together → connection between them is strengthened

Question 19

object perception

Answer 19

= hierarchy of parallel pathways to construct an image
- memory will be stored across these different regions in the brain

Question 20

object perception - how does info not get confused?

Answer 20

• coordinated TIMING of firing patterns
• Cells firing in synchrony form cell assemblies that collectively represent a given object at a moment in time
• firing at different rates

Question 21

patient HM

Answer 21

• temporal lobotomy
• severe anterograde amnesia (new mems)
• also retrograde amnesia for 2 years pre surgery
• procedural memory intact

Question 22

Patient R. B.

Answer 22

• ischemic episode after open heart surgery
• subtle damage in hippocampus
• resulted in selective, marked anterograde amnesia and very minor retrograde amnesia

Question 23

Patient N.A.

Answer 23

• Damage to the mediodorsal thalamus and mammillary bodies
• connected to hippocampus by fornix
  = anterograde amnesia

Question 24

Wernicke-Korsakoff Syndrome cause and symptoms

Answer 24

• caused by lack of thiamine, due to poor diet
• prevalent in chronic drinker
• impaired memory, paried association, story recall

Question 25

importance of hippocampus for memory, consolidated and not (explanation for anterograde and retrograde amnesia)

Answer 25

• Without hippocampus → can’t remember because no relay system to link different brain areas
• until consolidated → can remember without needing hippocampus because links established between areas without needing hippocampus

Question 26

egocentric vs allocentric

Answer 26

• egocentric = things relative to yourself
• allocentric = relative to other things in external world

hippocampus largely allosteric deficit

Question 27

Hippocampus in london taxi drivers

Answer 27

• anterior hippocampus = smaller
• posterior = bigger

Compared to bus drivers bc bus = repetitive route

Question 28

Place cells

Answer 28

• cell firing localised to specific location
• each cell represents a different place
• for any location there are some hippocampal cells firing → can be incorporated into memories
• may underlie the ‘where’ of episodic memory

Question 29

how to test difference between chronological and subjective time

Answer 29

asking how long the task took [time estimation],
or to hold down a button for given time [time production]

Question 30

time perception with THC, and conclusion

Answer 30

increased time estimation, decreased time production
= perception of time given by neurological condition

Question 31

chroneostatsis with quick eye movement

Answer 31

chroneostatsis = the stopping of time
- when visual system makes rapid movement (saccade) → surpresses the imput until you refixate again
- nervous system fills in the gap retrospectively → hand of clock seems to sit stationary for a short second

Question 32

Scalar Expectancy Theory (SET)

Answer 32

• pacemaker/internal clock
• when an event starts → switch on → pulses accumulate → stored in short term memory → compared to memory (specifically the ratio)

Question 33

what is the ‘pacemaker’?

Answer 33

• a loop of cell activation
• can tag event to this

Question 34

internal pacemaker is sped up during recall - implications?

Answer 34

Time estimation – duration experienced as longer
Interval reproduction – duration shorter
e.g. THC, life-threatening situation

Question 35

Ramping

Answer 35

• stimulus getting bigger as you get closer to a reward or something
• This would be observed as individual cells firing during a specific part of an interval

Question 36

Timing cells in hippocampus

Answer 36

• cells fire after a particular time period
  
  • like place cells but within time
• damage to hippocampus → skewed time recall
• also inability to organise time events

Question 37

Why do some memories endure?

Answer 37

• we remember what is meaningful, emotional and novel
• emotional content is really important
  
  • e.g. geographically further away from world trade centre = less memory of 9/11 events

Question 38

adrenaline

Answer 38

• fight or flight
• released from adrenal cortex (hypothalamic–pituitary–adrenal (HPA) axis)
• doesn’t cross the BBB well - influences the brain via activation of the vagus nerve

Question 39

Cortisol

Answer 39

• HPA axia
• slower stress hormone