Neuropsychology: The Executive Brain Flashcards
What are executive functions?
-Needed to optimize performance in situation requiring coordination between cognitive processes
-Supervisory, controlling or meta-cognitive, rather than 1 specific domain (memory, perception, language)
-Linked to distinction between automatic and controlled behavior: controlled behavior requires executive functions (ex: SAS model)
-All linked to prefrontal cortex
Which evidence is there for a link between executive functions and prefrontal cortex?
-Most anterior part of frontal cortex
-Region present in different species: relative size changed due to evolution, in humans much larger than in other animals
-PFC damage: personality changes (no inhibitions)
–>Phineas Gage
What is the case of Phineas Gage?
-Prefrontal cortex damage: left orbitofrontal/ventromedial region and anterior region in prefrontal cortex
-Personality changes: fitful, irreverent, profane, showing little deference, impatient, obstinate, capricious (wispelturig), vacillating (besluiteloos), unable to settle on any of devised plans for future action
What is the anatomy of the prefrontal cortex?
-Lateral surface
-Medial and orbital surface
(image)
What are characteristics of the lateral surface of the prefrontal cortex?
-Receives input: form visual cortex, somatosensory cortex, auditory cortex, multi-motor regions, etc.
-Implicated in cognitive aspects of executive functions
What are characteristic of the medial and orbital surfaces of the prefrontal cortex?
-Connected to medial temporal lobe
-Important for long-term memory and processing emotions: amygdala and hippocampus
-Implicated in emotional/social regulation of behavior
Which Brodman areas are there?
-45, 47, 44
-46, 9
-10
-24, 32 (both dorsal)
-11,12,13,14
What are characteristics of Brodman’s areas 45, 47 and 44?
-Other names: ventro-lateral prefrontal cortex (VLPFC)
-Possible functions in left hemisphere: retrieval and maintenance of semantic and/or linguistic info
-Possible functions in right hemisphere: retrieval and maintenance of visual and/or spatial info
What are characteristics of Brodman’s areas 46 and 9?
-Other names: dorso-lateral prefrontal cortex (DLPFC)
-Possible functions in left hemisphere
–>Selecting possible range of responses and suppressing inappropriate ones
–>Manipulating contents of working memory
-Possible functions in right hemisphere
–>Monitoring and checking of info held in mind, particularly in conditions of uncertainty
–>Vigilance and sustained attention
What are characteristics of Brodman’s area 10?
-Other names
–>Anterior prefrontal cortex
–>Frontal pole
–>Rostral prefrontal cortex
-Possible functions in both hemispheres
–>Multi-tasking
–>Maintaining future intentions/goals whilst currently performing other tasks or sub-goals
What are characteristics of Brodman’s areas 24 and 32?
-Both dorsal
-Other names
–>Anterior cingulate cortex (dorsal)
–>Pre-SMA
-Possible functions in both hemispheres: monitoring in situations of response conflict and error detection
What are characteristics of Brodman’s areas 11, 12, 13 and 14?
-Other names: orbito-frontal cortex
-Possible functions in both hemispheres: executive processing of emotional stimuli
What are characteristics of executive functions in (clinical) practice?
-Working memory
-Task-setting (open-ended) and problem-solving
-Overcoming prepotent or habitual responses
-Task switching
-Multi-tasking
-Planning of (unstructured) activities in daily life
What is working memory?
-Important executive function
-Distinction between 2 working memory processes
–>Maintaining and retrieving info in ventro-lateral prefrontal cortex (VLPFC)
–>Manipulating info in dorso-lateral prefrontal cortex (DLPFC)
What are characteristics of task-setting and problem-solving?
-Related to notions of (fluid) intelligence
-Open-ended task-setting: typical for solving problems: solution not given, participant has to come up with it
-Different tasks
–>Lesions to left prefrontal cortex: clinical symptoms of poor task-setting and problem solving
Which tasks are associated with task-setting and problem solving?
-Tower of London task
-Cognitive estimates
-Cognitive fluency (FAS test)
What is the Tower of London task?
-Associated with task-setting and problem solving
-Nonverbal task
-Generate solution (strategy) to reach end point
-Healthy participants activation in dorsolateral prefrontal cortex
–>Damage in left prefrontal cortex: need more time and moves
(image)
What is the Cognitive Estimates task?
-Associated with task-setting and problem solving
-Verbal task
-Questions of which unlikely to know exact answer, but possible to infer approximate answer by using other relevant knowledge
–>Left prefrontal cortex damage: impaired
What is the Cognitive Fluency task (FAS test)?
-Associated with task-setting and problem solving
-Generate as much words as possible beginning with particular letter in 1min
-Left prefrontal cortex damage: low output, shaky script, break rules (only particular amount of letters)
-Requires strategies on how to generate novel words, select between alternatives, remembering words already said, etc.
What are characteristics of overcoming prepotent or habitual responses?
-Tasks with problem in overcoming habitual responses in patients with prefrontal lesions
-Examples: Stroop Test (concept of inhibition) and Go/No Go Test (concept of inhibition)
What is the Stroop Test?
-Concept of inhibition, overcoming prepotent or habitual responses
-Participants have to name color of word and ignore reading word, which is color itself
–>Functional imaging and lesion studies
-Results: healthy participants can do task with errors, patients with damage in anterior cingulate cortex impaired on task
–>So suggests involvement of anterior cingulate cortex
–>Pre-SMA (supplementary motor area) also seems involved
-Conclusion: word is read in automatic way, generates response conflicts difficult to overcome
What is the Go/No Go Test?
-Concept of inhibition, overcoming prepotent or habitual responses
-Participants presented fast with series of stimuli and have to respond to most of stimuli (go-trials) but not to other stimuli (no-go-trials)
-Results: healthy participants can do task with errors, patients with damage in anterior cingulate cortex and pre-SMA (supplementary motor area) impaired on task
–>So these regions are involved in inhibition
-Conclusion: response usually not inhibited when no-go presented
What are characteristics of task switching?
-There are tasks with problem in task switching in patients with prefrontal lesions
-Needing ability to discard previous schema and establishing new one
-More simple studies developed: isolating different aspects of switch, used more in healthy participants (rather than patients), switch cost (related to suppressing/inhibiting old task, greater when switching from hard to easy (ex: 2nd language to 1st, colour naming to word naming in Stroop))
-Importance of lateral PFC and medial surface PFC (anterior cingulate and pre-SMA (supplementary motor area))
-Example: Wisconsin Card Sorting Test (WCST)
What is the Wisconsin Card Sorting Test (WCST)?
-Task switching task: requires rule inference and unpredictable switches
-Participant presented with 4 cards and have to link given card with presented cards according to similarity
-Feedback given after card is sorted and rules can be changed over course test
-Results: patients with PFC damage impaired on task
-Conclusion: requires rule inference and unpredictable switches
What are characteristics of multi-tasking?
-Carrying out several tasks in succession
-Complex form of task-switching: constantly switching between tasks
-Requires task switching and maintaining future goals while current goals are dealt with
-Lesions to PFC: poor multi-tasking
-Example: Six Elements Task
What is the Six Elements Task?
-3 sub-tasks, each divided in 2 parts, all in 15 minutes: verbal dictation, picture naming and arithmetic problems
-Participants receive rules about task execution: each task attempted at least once and some tasks should be finished first and some tasks have to be performed next, etc.
-Results: patients with PFC damage impaired on task
What are characteristics of planning of (unstructured) activities in daily life?
-Patients with prefrontal lesions also have difficulties with planning activities in daily life
-Example: Birmingham Cognitive Screen Test
What is the Birmingham Cognitive Screen Test?
-Planning of (unstructured) activities
-Patient receives instructions to make torch work and gets several tools: necessary or irrelevant
-Results: patient does relatively well on easy task, but slower than expected in coming up with actual action
What kind of organization is there of executive functions?
-Emotional vs cognitive control
-Multiple-demand network
-Posterior vs anterior lateral PFC
-Left vs right lateral PFC
-Anterior cingulate vs lateral PFC
What brain regions are involved in emotional vs cognitive control as organization of executive functions?
-Orbitofrontal and ventromedial PFC: control of affective or reward-related stimuli
–>Lesion: acquired sociopathy (anto-social personality disorder)
-Lateral PFC: control of purely cognitive stimuli
–>Lesion: dysexecutive syndrome
(image)
What is acquired sociopathy or anti-social personality disorder?
-Lesions in orbitofrontal and ventromedial prefrontal cortex
-Unable to control social behavior, irresponsible, unreliable behavior, no long-lasting commitments, egocentrism, impulsivity
What is the multiple-demand network as an organization of executive functions?
-Tests of executive function and fluid intelligence (ex: Ravens matrices) uses same brain regions (“multiple demand network)
–>Regions: lateral prefrontal cortex, anterior cingulate cortex, intraparietal sulcus
-Prefrontal cortex damage: impairs performance on both measures, but NOT on crystallized intelligence (ex: WAIS)
(image)
What are characteristics of organization of executive functions in terms of posterior vs anterior lateral prefrontal cortex?
-Anterior lateral PFC: involved when multiple tasks need to be coordinated
-Posterior lateral PFC: involved in complicated tasks with single goal
(image)
What are characteristics of organization of executive functions in terms of left vs right lateral prefrontal cortex?
-Left lateral PFC: involved in task-setting
–>Tower of London, open-ended (standard) version of Wisconsin Card Sorting Test
–>Task switching: much slower to switch
-Right lateral PFC: involved in task monitoring and sustained attention
–>Predictable version of Wisconsin Card Sorting Test impaired
–>Task-switching: more likely to revert to previous rule
What are characteristics of organization of executive functions in terms of anterior cingulate vs lateral prefrontal cortex?
-(Dorsal) anterior cingulate cortex: detection of errors and detection of response conflict (ex: potential errors)
-Evidence in monkey studies
What evidence for the role of the anterior cingulate cortex is found in monkeys?
-Monkeys with lesions in anterior cingulate cortex don’t trouble shoot after making error (error+1 trial worse than correct+1)
-Might be source of error potential: error-related negativity
-fMRI: activity greatest on error trial, but lateral prefrontal cortex greatest on error+1 trial
-Suggests anterior cingulate cortex detects, but doesn’t correct errors
What summary of the organization of executive functions is there?
-Converging evidence to suggest that prefrontal cortex is not single source of “executive control” over brain
-Generally accepted division between functions of orbital and lateral surface
-Growing consensus over anterior vs posterior functions
-Less consensus over left-right functional differences and differences between anterior cingulate cortex and lateral prefrontal cortex
