Neural Mechanisms of WM

Question 1

What is WM

Answer 1

acts to bridge temp gaps between perception + action

Question 2

Iconic Memory - sperling

Answer 2

• can briefly attain lots of visual info but it fades very quickly
• ability to remember a string of letters drops As increases durations

Question 3

WM- Baddeley Muiti-component model

Answer 3

• multiple ways to store info on a ST basis
• visual stored in visuo-spatial sketchpad
• Auditory stored in phonological loop
• central executive = memory integration

Question 4

WM Tests

Answer 4

• Digit span
• corsi block = experimenter taps blocks in certain order + asks ppts to copy
• Macaque model - delay saccade (eye movement) task
• Rat Model T Maze
• spatial /verbal span forwards/backwards

Question 5

Frontal lobe lesion - Penfield + Evans

Answer 5

• ppts with frontal lobe lesions struggled with everyday tasks
• linked damage to WM deficits

Question 6

frontal lobe lesions -Shallice + Burgess - 2 task impairement

Answer 6

• frontal lobe lesion patients impaired on both tasks
• six element test: 6 tasks ( route + math problems) in 15 mins
• Multiple Errand test: shopping for several items when constrained by rules

Question 7

Prefrontal cortex + WM - Goldman + Rosvold - Delayed response task - monkeys

Answer 7

• Delayed Response Task
• made PFC lesion in monkeys
• Trained to perform a task where they had to remember which well the food was in
• Blind goes up + asked to indicate where food was located after a delay
• monkey with lesions impaired in ability to remember location across delay

Question 8

Memory cell in PFC - Fuster + Alexander and Miller - Delayed response task

Answer 8

• Fuster+ Alexander - Delayed Response Task
• cells holding onto memory during delay fire
• shows PFC involved in maintaining WM items
• Miller et al > delay activity maintains items in Visual working memory when distracter items are shown
• neurons show preference for certain stimuli + fire harder when present

Question 9

Delay activity in PFC - Sakai et al - study

Answer 9

• Delay activity in Visual WM in human fMRI
• learned Spatial sequence , distractor task then memory test
• Results: delay activity in PFC is higher than baseline activity for correct trials

Question 10

Recency judgement + PFC

Answer 10

• Recency Judgement = which was shown most recently
• PFC is critical for maintaining temporal organisation of WM
• lesions impair recency judgement relative to control + struggle to accurately maintain order of info in WM

Question 10

Functional segregation with PFC memory systems -Sakai

Answer 10

• memory span task : verbal or spatial info remembered in forward (maintenance) or reverse direction (manipulation)
• verbal task increased BOLD (Blood Oxygen Level Dependent ) activity in dorsal PFC
• spatial task - ventral PFC

Question 11

Delay activity in Visual cortex + Distractors - Miller et al - Temporal lobe + PFC

Answer 11

• Temporal lobe: delay activity is abolished by distracting stimuli
• PFC: delay activity is robust to distracting stimuli

Question 12

challenging delay activity theory

Answer 12

• Maintain items in WM in a silent state

Question 13

Fuster - Random gaps in persistent delay activity

Answer 13

• Not all PFC cells show persistent activity

Question 14

Waxing + waning of PFC delay activity

Answer 14

• Brain activity when dual task starts drops off rapidly
• continuous activity isn’t always necessary for successful WM

Question 15

metabolic cost of persistent firing

Answer 15

more efficient for brain to encode info differently so it can preserve energy

Question 16

Bridging activity gaps in silent state - stokes et al - neuron communication

Answer 16

• Neural state can be described as different levels : activity pattern (neuronal firing) , functional connectivity ( neuronal communication)
• can construct memory through remembering conversation between neurons
• Neurons have lower threshold (fire less AP) in functional connectivity level

Question 17

WM in a silent State- stokes et al - cued target detection task

Answer 17

• cued target detection task
• 0-3 non target ( neutral or distractor) distractors then cued target
• Neurons in PFC don’t show continuous firing pattern during delay but monkeys still able to perform task
• High firing when Stimuli present , during delay return to baseline
• Neural stimulus acting as boosting activity

Question 18

WM as a dynamic process

Answer 18

• Info held in WM changes over time
• During encoding task-relevant Stimuli are represented as highly dynamic activity
• Maintenance is a stable, low energy State
• retrieval brings it back to an active state of task relevant neurons

Question 19

Interaction between WM+ attention

Answer 19

• Attention as a gate keeper inter WM
• Attention can select which items go into WM + which to prioritise
• WM as an Attentional template
• wM holds attentional template
• WM content biases attention

Question 20

Attentional selection into WM- Sperling - letter study

Answer 20

• WM has limited capacity
• Partial report task: Cue shown after letter array telling pprs which letters to report
• Vigel et al - attended items can be selectively stored in WM

Question 21

Attentional selection Within WM - Murray et al - retro cue + trials

Answer 21

• Attention works within WM to improve performance
• All WM items decay over time
• Retro cue slows down decay
• WM can be modulated during maintenance
• long trial - cue reduces comp among other items
• short trial- cue enables remembering of a forgotten item

Question 22

WM automatically biases attention - Soto et al - dual task

Answer 22

• Dual Task : store cue item, find target in search array, report if item is same as cue
• Attention in search task is auto drawn to WM contents
• poor performance in search for a target not in WM

Question 23

Anatomy behind cog control- 2 systems + goals

Answer 23

• set of psychological processes that enable US to use our perceptions + knowledge to bias actions + thoughts
• cog control is necessary to meet goals
• Develop a plan that uses personal experiences
• monitor action to stay on target + attain goals
• 2 prefrontal control systems : lateral PFC , orbitofrontal cortex + frontal pole supporting goal-oriented beh medial FC for guiding + monitoring ben

Question 24

cog control deficits

Answer 24

- Frontal lobe lesions - patient May persist in a response even once being told its incorrect (preservation beh) - patient may be apathetic, distractible, impulsive, unable to Plan or make decisions

Question 25

lesions + cog control deficits

Answer 25

- Shallice + Burgess -> + took 3 patients with frontal lobe lesions to a shopping centre + assigned each a list - obtaining all the items was a real problem - 1 failed as store didn't have favourite brand, 1 wandered outside + 1 failed to pay for an item

Question 26

Drug addiction + cog control

Answer 26

- Goldstein + Volkow - one model of drug addiction suggests disruption of PFC underlies characteristic of inability to stop destructive ben

Question 27

Goal-oriented Beh

Answer 27

- Based or assessment of expected reward + knowledge - Action-outcome relationship - Habitual actions = actions no longer under control of reward but is stimulus driven

Question 28

PFC is necessary for WM- monkey study

Answer 28

- in spatial memory test 0 monkeys observe food in 1 well + curtain lowered after delay must choose correct well - Demands monkey to continue to retain location of unseen food - monkeys with PFC lesions do poorly

Question 29

LPFC + WM

Answer 29

- LPFC actively reflects representation of task goal - functional image studies support this: delayed -response tasK found BOLD response in LPFC began to rise during encoding + response maintained across delay LP+C is critical for WM sustains representation of task goal

Question 30

Organisational principles of PFC

Answer 30

.- Anterior-posterior gradient across PFC follows a hierarchy : simple WM tasks limited to posterior regions + challenging tastes extend anterior - Demonstrates how o goal-riented ben can require integration of multiple pieces of info

Question 31

WM representations in PFC

Answer 31

- cells in PFC maintain WM - through sustained firing - Miller-> some cells maintained memory specificity After distracting items indicating potential distracter-resistant wM

Question 32

WM basis for preparatory attention

Answer 32

- WM important for maintaining relevant info determining focus of attention - Desimone + Duncan -> WM representations could Constitute top-down bias - Soto et al found WM representations are sufficient for biasing visual processing

Question 33

Dynamic Population coding

Answer 33

- Info content peaks during most dynamic phase of trajectory - Dynamic changes in population coding could reflect remapping from cue representation to anticipated target representation - stimulus processing is associated with complex spatiotemporal trajectory - Buonomano + Maas argue complex population dynamics could result from evolution of state- dependent processing that is determined by cascading interaction between past + current input - Hidden states can be used to maintain info in WM