Task 2 Flashcards
Who proposed that the PFC is essential for working memory and when?
Goldman-Rakic proposed in 1987 that the prefrontal cortex (PFC) is essential for working memory, referring to the short-term maintenance of task-relevant information
What task do macaque monkeys with dorsal prefrontal lesions fail?
They fail spatial delayed response tasks, which require maintaining spatial information in memory for a few seconds
What activity is observed in cells of the PFC during delay periods?
Many cells in the PFC show sustained firing during delay periods, with different cells coding for different spatial locations
What has research using fMRI shown about sustained activity in the human PFC during spatial memory tasks?
Activity is observed in the posterior PFC (area 8) during delay periods,
similar to monkeys,
but there is less significant activity in more anterior prefrontal areas
Why is it difficult to find sustained activity in area 46 of the human brain during working memory tasks?
The poor sensitivity of fMRI in humans
and the fact that only a small percentage of cells in area 46 show greater delay-related activity when remembering spatial cues compared to a control condition
How did Goldman-Rakic interpret sustained activity in the PFC?
She interpreted it as reflecting the maintenance of sensory items in memory, crucial for performance on delayed response tasks
What factors, besides maintenance of sensory information, can sustained activity reflect?
Sustained activity can reflect response preparation and transformation of sensory input to the response
When does sustained activity occur in area 46 during spatial working memory tasks?
Sustained activity in area 46 occurs only when subjects can prepare their response
What happens during the transformation phase in an oculomotor delayed response task?
Activity in the principal sulcus converts:
from cells representing the cue location
to cells representing the response location during the delay period
How does the lateral PFC relate to task rules during the delay period?
Many cells in the lateral PFC fire differentially according to the specific rule in operation during the delay period
How do reward expectations affect sustained activity in the PFC of monkeys?
Sustained activity during the delay reflects the monkeys’ expectation of rewards, with cells coding for both spatial location and expected reward in the lateral PFC
How does the expectation of high reward influence working memory tasks in humans?
High reward expectation combined with a difficult working memory task leads to interaction between delay-related activity and the expected reward size in the frontal polar cortex
What is the role of the PFC in cognitive control?
The PFC extracts goal-relevant features from experiences and imparts rules to guide thought and action, essential for intelligent behavior
What are task contingencies, and how do they relate to the PFC?
Task contingencies are the logical structures of a task,
prefrontal neurons show tuning for learned associations between cues, actions, and rewards, helping to form ensembles representing these contingencies
What are the behavioral effects of prefrontal cortex damage in humans?
show impaired ability to organize their lives, becoming impulsive and irresponsible
How do people with prefrontal damage perform on the Wisconsin Card Sorting Task?
They can learn the initial sorting rule but struggle to adapt when the rule changes, demonstrating difficulty in switching rules
What does Miller’s model suggest about PFC connections?
The PFC connects to hidden processing units and strengthens associations leading to reward through reward signals, establishing task-relevant neural pathways dynamically
How do reward signals influence PFC activity?
Reward signals from the ventral tegmental area (VTA) influence PFC activity, affecting plasticity and sustaining activity to form associations between events separated in time
What sets working memory apart as a cognitive function?
Working memory retains information over potentially distracting events, unlike other cortical areas whose activity can be easily disrupted by distractors
How does the PFC exert top-down control over other brain systems?
The PFC provides excitatory signals that bias processing in other brain systems towards task-relevant information, similar to selective visual attention
What did studies on monkeys reveal about task-dependent activity in the lateral PFC?
Over half of lateral PFC neurons showed task-dependent activity, coding not just stimuli or actions but their behavioral context
How does the role of the PFC change with task practice?
The PFC plays a key role in task acquisition, but with repeated practice, task-relevant neural pathways are established in other brain systems, making tasks more automatic and less reliant on the PFC
What is the role of the IFJ in attention?
IFJ biases perception in posterior regions through neural synchrony,
Using both top-down goal-directed and bottom-up stimulus-driven attention control
How do VLPFC and DLPFC differ in their roles in rule maintenance?
VLPFC is more involved in the retrieval and maintenance of complex rules,
DLPFC shows less engagement in rule maintenance during delay periods
How does left VLPFC contribute to rule representation and maintenance?
It associates visual cues with appropriate actions, and is sensitive to rule complexity
What role does the frontal polar cortex (FPC) play in rule representation?
The FPC helps elaborate on retrieved rules to guide behavior more effectively, operating on products of the lateral PFC
What regions are involved in maintaining response contingencies during complex rules?
posterior VLPFC,
pre-SMA,
parietal cortices
Are engaged during the maintenance of response contingencies for complex rules
How does experience-dependent plasticity manifest in the PFC?
Neurons in the PFC acquire sensitivity to task-relevant attributes with training, reflecting experience-dependent neural plasticity
Why are predictions important for goal-directed behavior?
They are essential for forming associations and guiding behavior
How does the PFC manage task switching and rule sensitivity?
Task switching activates a network of regions including the medial frontal cortex and ACC, while rule-sensitive regions in the PFC remain engaged regardless of task switching demands
