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PSYC 325 > locating memories > Flashcards

locating memories Flashcards

1
Q

wayfinding

A

is the set of cognitive processes required to get from here to there

how do we navigate?

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2
Q

egocentric

A

object positions are framed in relation to the self (“I”)

spatial reference frames

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3
Q

allocentric

A

spatial reference frame

object (including self) positions are framed in relation to external objects

absolute: unchanging
intrinsic: depends on orientation of the reference object ie/ right/left

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4
Q

categorical wayfinding

A

technique

qualitative or nominal relationships (general terms)

ie/ above/below, in/on

affect valence biases object spatial memory (good-up; bad-down)

sense of division of things

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5
Q

coordinate wayfinding

A

technique

quantitative or metric relationships (specific)

ie/ 4.67m NW, 3 times this far

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6
Q

categorical wayfinding brain area

A

spatial perception is lateralized to the left cerebral hemisphere

left parietal lesion patients make more categorical errors

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7
Q

coordinate wayfinding brain area

A

spatial perception is lateralized to the right cerebral hemisphere

posterior parietal cortex

right parietal lesion patients make more coordinate errors

actual distances between objects

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8
Q

place cells

A

receive input from many grid cells and code for specific places

located in dentate gyrus

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9
Q

grid cells

A

receive multimodal input and respond to distinct spatial frequencies

located in entorhinal cortex

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10
Q

time cells

A

are sensitive to intervals between key events

located in both dentate gyrus and entorhinal cortex

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11
Q

Parts of the hippocampal index theory

A

Formation
Recognition
Recall
Memory Failure

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12
Q

formation

A

experience is represented in many cortical regions and stored in hippocampus by LTP as an index n

not a memory but a pointer

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13
Q

recognition

A

similar stimuli activate the index, which triggers cortical and subcortical associations of an engram

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14
Q

recall

A

a sufficient subset of stimuli activate enough of the index to then activate the whole index and engram

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15
Q

memory failure

A

insufficient subset of information to reactivate an index

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16
Q

episodic memory formation

A

hippocampus is blind to modality; does not itself discriminate visual, auditory, somatic, olfactory, or other sensory-specific information
- intrinsic theta oscillations (~8Hz), with gamma bursts in each cycle
- the sequence with each gamma burst involves place cells for recently past, current, and upcoming places

one theory proposes that the hippocampus is a general sequence generator for memory
- the “index” is a sequence, not a mere reference to a cell assembly

17
Q

dorsal stream contribution

A

the dorsal stream supports spatial awareness with three output pathways:

  1. Prefrontal Pathway
    - spatial working memory
  2. Premotor pathway
    - visually guided action
    - dissociable from purely perceptional or cognitive estimates of distance
  3. medial temporal cortex
    - spatial navigation, wayfinding
18
Q

inferior parietal lobule (IPL)

A

region of association cortex in the right hemisphere specialized for tracking distances

19
Q

what is the rIPL specialized for

A

spatial distances
temporal distances (intervals)
social distances

parts of rIPL do not discriminate between distance type

20
Q

what are the three egocentric layers of space

A

personal
peripersonal
extrapersonal

cultural and individual variation exist in average comfortable social distances

21
Q

personal

A

within ones body

22
Q

peripersonal

A

within reach

can be adjusted, ue/ when driving

23
Q

extrapersonal

A

beyond reach

24
Q

where are memories located

A

episodic memories must encode a location, but the memory itself must also be stored somewhere

engrams are not stored as discrete packets of info in a specific location in the brain

rather, memories are stored as distributed networks of neurons whose connections have been mutually strengthened by encoding and consolidation (everything that contributes to the experience)

25
Q

memory storage: structure of engrams

A

when an axon of cell A is near enough to excite a cell B and repeatedly or persistently take part in firing it, some growth processes or metabolic change rakes place in one or both cells such that A’s efficiency, as one of the cells firing B, is increased

cells that fire together wire together

26
Q

techniques for studying engram location have evolved

A

A. Large cortical ablation
B. small cortical ablation
C. stereotaxic surgery (BLA)
- basolateral amygdala
D. stereotaxic surgery

27
Q

how to identify engram neurons?

A

cell must be active during learning

cell must be active during test

when activated they can generate the engram behaviour

when inhibited they prevent (or reduce) the engram behaviour

28
Q

immediate early genes

A

genes whose protein products are present after cell activation

tagged (co-expressed) with fluorescent protein to measure it

problem: it degrades in minutes

29
Q

TetTag mouse

A

engineered so FOS promotes the expression of Tetracycline-transactivator (ttTA) system

tTA promotes reporter gene LAC

30
Q

Detecting Cell Activity

A

Temporal control over the expression of LAC offers longer tracking of cell activity

A. DOX (doxycycline) - inhibits LAC production is an antibiotic that blocks LAC expression when consumed
- Remove DOX, LAC is expressed

B. Fear conditioning with no DOX causes expression of LAC
- add DOX during retrieval
- detect coincidence of LAC and ZIF

C. LAC and ZIF found more often in cells active in animals who froze more after fear conditioning
- sign of both encoding and retrieval

31
Q

Optogenetics

A

DOX prevents expression of ChR2 (light sensitive receptor)

After being fear condition in Context B, mice froze to blue light applied to dentate gyrus in Context A, even on DOX

32
Q

How are engram cells chosen

A

Experiment:
1. There is a difference between fear retention based on training-test interval

A. short intervals (10s) are remembered much less than longer intertrial intervals (8m)
B. CREB infusion “restores” fear memory trace for 10s intervals

  1. engram cells targeted to die cause the the erasure of the conditioned memory
    A. CREB can be overexpressed by injecting it into neurons
    B. CREB overexpression leads to likely selection as engram cell
    C. Neurotoxin (diptheria) targets and kills cells that overexpress CREB
    D. Animals that overexpress CREB and treated with diptheria fail to remember
33
Q

How does CREB help a neuron

A

does it up-regulate genes that are involved in consolidation?
- It does but thats not why

CREB changes the intrinsic excitability
- lowers firing thresholds, making it more likely to join hebbian cell assembly

PSYC 325 (5 decks)

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