w10 executive functions + w11 anatomy of PFC Flashcards
what are executive functions?
they perform supervisory, regulatory role
modulate activity of other cognitive functions
Support the flexible control of goal-directed behavior.
Arise from a distributed set of brain regions. their primary target is prefrontal cortex
how do we know executive functions have to do with prefrontal cortex?
patients with damage to prefrontal cortex have intackt cognitive abilities but problems with executive functions
taxonomy of executive function
brain regions that support executive control
and how we know them
from lesion studies in dogs and monkeys. in dogs that posterior frontal lobe responsible for movement, in monkeys that prefrontal cortex influenced cognitive performance
Consequences of prefrontal lobe damage
for it to be a problem it has to be bilateral damage
frontal dysexecutive syndrome
people display difficulties managing their daily lives, planning, taking initiative, monitoring goals, completing tasks, having a limited attention span, difficulty interacting with others, lack of insight into the goals and thoughts of others, limited theory of mind
frontal disinhibition syndrome
lack of inhibition: movements that they cannot control without any purpose, might be euphoric or manic, inappropriate sense of humor, fail to respond to social cues, start revealing embarassing personal information, extravert and very out there
initiating rules of behavior
inhibiting inappropriate rules
suppression of unimportant and distracting information. Complementary to the initiation of the new rules. 4 primary forms of inhibition:
- Halting trained or previously valid behaviors
- Preventing interference of irrelevant information
- Restraining socially inappropriate actions
- Removing irrelevant information from working memory
shifting among rules
relating rules
ability to create complex mental models. You present a number of stories to a patient, if she can’t invent a coherent narrative it means she probably has damage to PFC
Experiment: participants were presented with the mismatch (the left and the right figure differ in different ways in the bottom row and in the top row), controls were only presented with one higher-order judgement (only one rule is needed to be found to compare the figures from the top and the bottom rows). the experiment requires integration of several low-order judgements in a higher-order judgement in order to say whether the symbols are the same.
Hierarchical models for executive function
contextual control
matching behavior to context
Example: conflict monitoring tested by the Stroop task
but also dorsomedial prefrontal cortex is involved
Stroop task: conditions
Executive processing in the dorsal anterior cingulate gyrus
Functional organization of the dorsomedial prefrontal cortex
Topographical connections between the medial and lateral prefrontal cortex
complex executive functions result not from the activity of single brain regions but from interactions among regions within larger networks.
- Anterior regions: support functions related to implementing and modifying higher-order abstract goals
- Posterior regions: support executive functions associated with selecting the appropriate motor action
working memory vs executive function
Baddeley model of working memory
3 Capacity-limited memory buffers maintain different representation
Control system: allocates processing resources to memory buffers and performs manipulations
Cowan model of working memory
better supported by evidence
working memory is organised in two embedded levels:
Level 1: activated longterm memory representations. The ones within the squiggly circle. If you don’t rehearse them the activation decays rapidly. The number of the memories in this circle is not fixed. Like what is in buffers in Baddeley’s model, but no separate buffers, just one multimodal memory storage.
Level 2: activate representations that fall within the focus of the executive control. The “iluminated” area. Can only hold 4 items.
delay period activity
the time between the initial activation of information in working memory and the use of this information
Evidence for the role of the lateral prefrontal cortex in working memory
- Activation persists for the entire delay period
- Activation increases as information increases
- Increased activation is associated with better working memory
- Increased activation is associated with less distraction
- Activation increases when the task requires information manipulation
Comparative anatomy of the prefrontal cortex
the relative size of the region is what matters for intelligence, not the absolute size. According to Brodmann in 1912 the bigger the relative size, the better, and humans had the biggest. But now using structural MRI we see that frontal lobe is in humans of a similar proportion as in great apes. So maybe the brain is large relatively to our body size, that’s the trick, not the ratio of neocortex via PFC.
