Cognitive Control, Executive Control, and Frontal Lobe Functions

Transcription

1 Cognitive Control, Executive Control, and Frontal Lobe Functions Anatomy of Cognitive Control Cognitive Control Goal-Oriented Behavior Involves prefrontal cortex (PFC) Highly advanced and evolved in humans Anatomy of Cognitive Control Anatomy of macaque monkey PFC 1

2 Anatomy of Cognitive Control Subdivisions of prefrontal cortex (PFC) Lateral prefrontal cortex (LPFC) Frontal polar region (FP) Orbitofrontal cortex (OFC) Medial frontal cortex (MFC) Interconnections between motor, perceptual, limbic regions, basal ganglia, thalamus, and cerebellum Dopamine system is also important Ventral tegmental area Anatomy of Cognitive Control Lesions to PFC can Result in Cognitive Control Deficits Response perseveration problems Continue a behavior, even when incorrect Disregard of social conventions Schallice & Burgess (1991) Utilization behavior Francios Lhermitte Patients with PFC damage may engage in prototypical usage behaviors of objects Goal-Oriented Behavior is initiated based on expected rewards/outcomes Habits are more stimulus driven and automatic Requires working memory Maintenance of information Needed is not all actions are stimulus-driven PFC Necessary for Working Memory, not Associative Memory LPFC integrates perceptual information with stored representations LPFC lesions are associated with working memory deficits only 2

3 Delayed-Response Task Assessment of memory Must continue to represent location (a) Must form association between ford and signal (b) LPFC lesions lead to deficits in a, not b Human patients with LPFC lesions show similar deficits in recency memory, but not recognition memory Working Memory System Requires: Mechanism for accessing stored information Mechanism for keeping information active PFC neurons show sustained activity during delayed-response LPFC Neurons Show Task-Specific Selectivity Rao et al. (1997) trained macaque on a working memory task LPFC cells identified as: what cells where cells what-where cells 3

4 LPFC Neurons Show Task-Specific Selectivity what cells where cells what-where cells LPFC Likely Integrates Goal Information with the Activation and Maintenance of Long Term Knowledge LPFC Shows Increased BOLD Response During Encoding and Maintenance Delayed response-task Remember 1-4 faces (4 sec.) 6-sec. delay, before probe Task demands increased activity Maintenance activity higher in LPFC than in FFA 4

5 Sub-regions of PFC Some sensitive to contents of working memory Others sensitive to processing requirements of working memory One hypothesis Ventrolateral PFC (VLPFC) Activation and retrieval Dorsolateral PFC (DLPFC) Manipulation and integration Examining Dissociation of VLPFC and DLPFC Functions Working memory task with Forward instructions required maintenance Backward instructions required maintenance and manipulation Examining Dissociation of VLPFC and DLPFC Functions VLPFC active for all tasks DLPFC more active for backward tasks Hence VLPFC for activation and retrieval DLPFC for manipulation and integration BOLD Signal Change (%) VLPFC DLPFC 5

6 Hierarchical Organization of PFC Prefrontal activation increases along the posterior anterior gradient as task requirements become more complex Stimulus-response task Contextual task Task instruction variation Hierarchical Organization of PFC Along Three Axes? Dorsal Medial Anterior Maintenance Manipulation Ventral Posterior Lateral Planning and Executing Goals Requires PFC Action hierarchy PFC lesions impede goal planning Anterior-posterior gradient (abstraction) PFC Badre & D Esposito (2007) Subjects complete tested tasks As abstraction of goal increases, BOLD activation becomes more anterior 6

7 Badre & D Esposito (2007) Badre & D Esposito (2007) Premotor area (A) sensitive to all four tasks Anterior premotor cortex (B) sensitive to feature, dimension, and context tasks IFS (C) sensitive to dimension and context tasks FP region (D) sensitive to only context task 7

8 Retrieving and Selecting Task(Goal)-Relevant Information LTM representations are passed into working memory Attention highlights relevant components PFC may act as a dynamic filter Early PET Studies on Language Semantic generation tasks (give noun, provide associate) Increase in activation in inferior frontal gyrus May reflect dynamic filtering of information from LTM Thompson-Schill et al. (1997; 1998) Noun-verb generation task Varied demands of the filtering process If IFG is involved with dynamic filtering, should see more activation for highfiltering condition 8

9 Thompson-Schill et al. (1997; 1998) Higher activity in the highfiltering condition are in red Lesion overlap in patients who had difficulty in the high-filtering condition. Colors indicate the percentage of patients with damage in the highlighted regions PFC is Involved with Performance in Task-Switching Task changed every few trials Switching cost External stimulus can remind subject of goal/task Task Switch Task Switch PFC Lesions Are Associated with Larger Switching Costs Type of cue is critical Color cues requires additional, abstract information 9

10 PFC Lesions Associated With Deficits in goal planning Improved performance when task requires atypical solution Dunker s matchbox problem Functional fixedness Matchstick math Modified Wisconsin Card Sorting Task Match target to one of four objects in periphery Match can be on basis of color, form, or number During Wisconsin Card Sorting Increased activation bilaterally in IFC Follows goal/dimension shift Peaks at about 7 seconds 10

11 Must Attend to Goal-Relevant Information and Inhibit Goal-Irrelevant Information E.g., Stroop Task (BLUE) Frontal lobe dysfunction is associated with loss of inhibitory control Knight and Grabowecky (1995) Controls vs. patients with lesions in temporal, parietal, or frontal cortices Present tones, no response required Dissociation (in ERPs) of enhancement and inhibition Knight and Grabowecky (1995) Parietal lesions: No difference in A1 ERPs Temporoparietal lesions: Attenuated A1 ERPs Frontal lesions: Enhanced A1 ERPs Knight and Grabowecky (1995) Attention modulates this loss of control Normals: Typical larger N1 to attended stimuli PFC lesions: Difference is mostly absent Difference is near-absent in contralesional ear 11

12 Task Goals Modulate Cortical Activity in Object-Sensitive Regions Druzgal & D Esposito (2003) presented faces and scenes for a memory test Monitored PPA and FFA activity Druzgal & D Esposito (2003) Enhancement in PPA and FFA to selective stimulus congruent with task Suppression in PPA and FFA to selective stimulus incongruent with task 12