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Systems Neuroscience > Exam 3 > Flashcards

Exam 3 Flashcards

1
Q

3 Phases of memory

A
  1. Acquisition (Encode)
  2. Consolidation (Store)
    • Consolidation can be divided (cellular/system)
  3. Retrieval
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2
Q

Squire (1987) Definition of Learning/Memory

A

“Learning is the process of acquiring new information, while memory refers to the persistence of learning in a state that can be revealed at a later time”
(Squire, 1987)

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3
Q

Hermann Ebbinghaus (1850 - 1909)

A

Forgetting curve w/ nonsense syllables

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4
Q

Edward Thorndike (1874 - 1949)

A

Puzzle boxes where animals learned through stimulus-response associations

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5
Q

Théodule Ribot (1839 - 1916)

A

Ribot’s law of retrograde amnesia:
older memories are more resistant to
disruption
● Habits are lost later than other forms
of memory

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6
Q

William James (1842 - 1910)

A

Idea of neural plasticity

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7
Q

Richard Semon (1859 - 1918)

A

Defined the engram: “the
enduring though primary latent
modifications in the irritable
substance produced by a
stimulus” (Semon & Simon,
1921)

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8
Q

Karl Lashley (1890-1958)

A

Trained rats on mazes
● Lesioned cortex & examined
maze performance
● Concluded that extent not
location of lesion determined
behavioral impairment
● Failed to find the engram

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9
Q

Wilder Penfield (1891- 1976)

A

Mapped brain when performing
surgery on patients with epilepsy
● Stimulating temporal lobes could
prompt memory recall

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10
Q

H.M.

A

● Could not form memories of
experiences (anterograde amnesia)
● Remembered some memories from
his childhood (underwent surgery at
age 27) but lost many memories
(retrograde amnesia)
- Could still learn some tasks

Brenda Milner was caseworker

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11
Q

Which task allowed researchers to reproduce effects similar to HM in NHP?

A

delay non-match to sample (DNMS)

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12
Q

Triple Dissociation Experiments:
1. Win shift - find food, move to different arm.

A

requires an intact hippocampus.
Important for remembering relationships between stimuli

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13
Q

Triple Dissociation Experiments:
2. Conditioned Cue preference task - light arm was paired w/ food. allowed rats to explore paired and unpaired arms

A

requires intact amygdala
remembers info about stimulus-reward contingenceis in absence of response.

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14
Q

Triple Dissociation Experiments:
3. Win-Stay: 4/8 arms were lit. lit arms had food reward. food reward was replaced once after being found

A

requires an intact striatum
required for reinforced stimulus-response associations

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15
Q

Procedural Memories

A

“Knowing How”
studied using instrumental behavior

can divide into action/habit

begins action based but w/ repeated training becomes a habit

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16
Q

Episodic Memory

A

medial temporal lobe is involved

Events in spatiotemporal contexts

Hierarchal processing. has feedforward and feedback projections

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17
Q
A
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18
Q

Procedural Learning (Chuck)

A
  • Motor chunking:
    complex skill acquisition
  • Habitual behaviors:
    stimulus-response associations
  • Goal-directed behaviors:
    action-outcome associations
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19
Q

Components of Basal Ganglia

A
  • Striatum
    – Dorsal Striatum
    – Caudate
    – Putamen
    – Ventral Striatum
    – Nucleus Accumbens
  • Globus Pallidus
    – External / Lateral
    – Internal / Medial
  • Subthalamic Nucleus
  • Substantia Nigra
    – SN pars Reticulata
    – SN pars Compacta
  • Ventral Tegmental Area
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20
Q
A
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21
Q

Dopamine (DA) drive Pathways

A
  • Nigrostriatal pathway
    – SNc to dorsal striatum / CPu
  • Mesolimbic pathway
    – VTA to ventral striatum / NA
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22
Q

Dopamine (DA) Drive Effect

A

Striatal DA modulates all thalamo-cortical loop classes
DA up-regulates D1-MSNs;
DA down-regulates D2-MSNs;
Both increase activity level
For action selection circuits to modulate behavior in both directions, they maintain a baseline DA level that only varies slightly and slowly: Tonic Dopamine

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23
Q

Phasic Dopamine

A
  • Unexpected reward triggers
    release by SNc & VTA
    – measured indirectly via cyclic
    voltammetry in striatum
  • Intrinsic reward for
    unconditioned stimulus
    – actual reward (food, sex)
  • Extrinsic reward for
    conditioned stimulus
    – neutral stimulus associated with
    an intrinsic reward (bell, $$$)
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24
Q

Reinforcement
Learning

A
  • Phasic DA feels great!
    – strengthens striatal synapses
    associated with selected action
  • Repeat a situation many times
    – Positive cues & correct responses
    reinforced with reward
    – Over time reinforced stimulus or
    response plan triggers phasic DA
  • Drugs of abuse associated with
    increased phasic DA drive
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25
Q

Stimulus-Response
Learning

A

Mediated by sensorimotor loops
through Dorsal-Lateral Striatum
(or Putamen)
* Motor chunking and
sensorimotor sequencing
* Learned responses are
egocentric, habitual. E.g.,
– always turn left at first intersection
– keep pressing food lever, even after
it has stopped working
* Once habit is formed, DLS lesion
does not make it go away

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26
Q

Action-Outcome
Learning

A
  • Mediated by associative loops
    through Dorsal-Medial Striatum
    (or Caudate)
  • Goal-Directed and/or problem-
    solving strategies, e.g.,
    – Reinforcement learning: Phasic DA
    strengthens strategy selection, e.g.,
     orienting at intersection to go north
     finding water-maze platform in a
    new position every trial
  • If A-O behavior is over trained,
    it may drift into S-R behavior
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27
Q

Reversal Learning

A
  • Goal-oriented learning: DMS
    – breaking a habit is, in many cases,
    an A-O riented learning task
  • Once a habit has formed, via
    DLS-mediated S-R learning,
    DMS-mediated A-O learning is
    necessary to reverse the habit
    – A-O processing readily enables
    learning despite probabilistic
    rewards and/or punishments
  • General: higher-level brain
    loops reshape the activity of
    lower-level brain loops
28
Q

Implicit Memory Summary

A

Dopamine sourced from SNc & VTA to striatum
Targets essentially all action selection loops

Tonic dopamine maintains baseline activity level

Phasic dopamine associated with unexpected reward
Strengthens synaptic pathways of selected action

Sensorimotor Learning: DLS, Stimulus-Response
Reinforcement drives habituation, egocentric

Associative Learning: DMS, Action-Outcome
Reinforcement drives cognitive learning
& more strategic problem-solving approaches

Reversal Learning: DMS A-O necessary to unlearn DLS S-R

29
Q
A
30
Q

O’Keefe and Dostrovsky (1971)

A

Hippocampal place cells. This is allosteric representation (meaning more abstract and based on animal’s relative position)

31
Q

Remapping

A

Global remapping
– all cells fires in different place in different context

Partial remapping
– some cells map differently in different context

rate remapping
– remapping is based on firing rate and not physical location of firing

32
Q

Hippocampal replay

A

non-local coding during awake stopping periods

33
Q

Dopamine regulation of D1- and D2- MSNs

A

DA upregulates D1-MSNs. increases activity and motivates action selection

DA down regulates D2-MSNs. decreases inhibition

Both increase activity level that lead to action selection.

34
Q
A

-expansion/divergence of inputs
-feedback and lateral inhibition
-sparse connectivity between inputs to
dentate granule cells

35
Q

Entorhinal Cortex to Dentate gyrus connectivity?

A

Feedforward w/ expansion of 1:5

36
Q

What is the evidence for pattern separation in DG?

A
37
Q

CA3 anatomy

A
38
Q

CA3 encoding

A
39
Q

CA3 Retrieval

A
40
Q

Auto-associative CA3 circuit leads to what kind of network?

A

Stable (fixed-point) attractor network

41
Q

Where in the brain are grid cells found?

A

Medial entrorhinal Cortex

42
Q

How does grid cell location in MEC relate to shape of grid?

A

Spatial periodicity of grid cells changes along the DV axis of MEC. (dorsal has points closer together)

43
Q

what circuit motif allows grid cell formation?

A

structured lateral inhibition

44
Q

How do we get from grid cells to place cells?

A

feedforward linear integration

45
Q

Little Albert Fear Conditioning Experiment

A

Paired adversie sound w/ white rat. Baby generalized fearful response to anything white/fluffy

46
Q

Delayed Stimulus Pairing

A
47
Q

Trace Stimulus Pairing

A
48
Q

Simultaneous Stimulus Pairing

A
49
Q

Backward Stimulus Pairing

A
50
Q

In a fear acquisition curve, what controls the asymptote and rate of acquisition?

A

Asymptote: Controlled by strength of stimulus/intensity of US (gamma)
Rate: controlled by saliency of CS (alpha)

51
Q

Fear Circuit ( a brief overview)

A
52
Q

Modality specific retrograde amnesia

A

either 1, 7, 14, or 28 days after fear conditioning, the hippocampus was lesioned. then 7 days after lesion fear conditioning was tested. animals lesioned 1 day later didn’t exhibit context fear, but did 28 days later. All animals did have tone fear conditioning

53
Q

Consolidation

A
54
Q

What brain region stores remote contextual memories?

A

ACC
anterior cingulate cortex.

although CA1 does seem to remain important for recall…

55
Q

Fear Extinction Curve

A
56
Q

FEAR RENEWAL:

A

Fear Recovers due to a shift out of the extinction context
This reveals that extinction is new learning that competes with the original fear memory
The context disambiguates the meaning of the cue

57
Q

SPONTANEOUS RECOVERY:

A

Fear recovers after extinction due to an increase in time (“incubation”)

58
Q

REINSTATEMENT :

A

Fear recovers after extinction due to re-exposure to the shock

59
Q

Basal ganglia does what kind of memory?

A

non-declarative

60
Q

Basal Ganglia: movement

A

selects particular movement

triggers, initiation, terminates

scales amplitude, speed, force

61
Q

Basal Ganglia: motivation

A

drives ideation/cognitive focus

modulates emotional response

slows impulses or obsessions, compulsions and addictions

62
Q

What type of transmission do MSNs do?

A

GABAergic

63
Q

Action selection via disinhibition (Direct pathway)

A

1) Striatal afferents activate normally quiet D1 MSNs (Striatal afferents are excitatory D1-MSNs are inhibitory)

2) D1-MSNs then inhibit SNr and GPi which are usually active (they are GABAergic and wash thalamus in GABA)

3) silenced output neurons stop inhibiting a select pathway in thalamus and selects that action

64
Q

Action Inhibition via disinhibition (Indirect Pathway)

A

1) cortex activates normally unactive D2-MSNs
2) D2-MSNs broadly inhibit typically active GABAergic GPe cells
3) GPe broadly inhibits GPi and SNr
4) GPi/SNr inhibits thalamus. (GPe cells that disinhibited GPi/SNr lead to pathways of increased inhibition in thalamus)

GPe also inhibits STN. STN is excitatory and stimulates GPi/SNr. So inhibited STN leads to less excitatory drive. So when GPe inhibition is turned off by D2-MSNs, STN stimulates GPi/SNr more which leads to increased inhibition of thalamus

65
Q

action inhibition w/ STN

A
66
Q

Center-Surround

A

Direct pathway
– focal action selection

Indirect Pathway
– diffuse action suppression

Together: center-surround detection.

67
Q

Center Surround NHP

A

NHPs trained on value of glyphs.

Saccade preferentially to high value glyphs

During fixation, glyph value in RF drives rate change:
– correlated in caudate
– anticorrelated in SNr

Systems Neuroscience (5 decks)

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