13 Cognitive Control Man cannot live without selfcontrol

13 Cognitive Control Man cannot live without self-control – Isaac Bashevis Singer 1

Cognitive control I Cognitive control is The ability of our thoughts and actions to rise above mere reactions to the immediate environment and be proactive. To anticipate possible futures and to coordinate and direct thought and action to them (goal-directed behavior). a hallmark of intelligent behavior. The prefrontal cortex (PFC), seems to play a central role in cognition. It is the cortical area that reaches the greatest relative size in the human brain and is thus thought to be the neural instantiation of the mental qualities that we think of as “intelligent. ” 2

Cognitive control II The cognitive control system must also have the ability to select which sensory, memory, and motor processes are activated at a given moment. → Attention The neural system for cognitive control must have The infrastructure and mechanisms for selecting goal-relevant, and suppressing goal-irrelevant, processes throughout the cerebral cortex. A way to deal with the gaps in time that are inevitable with goal-directed behaviors. The ability to keep goal-relevant information online and available for processing is called working memory. 3

Cognitive control III Finally, and perhaps most importantly, the cognitive control system must be highly plastic and flexible. Virtually all voluntary, goal-directed behaviors are acquired by experience, and given that humans and other primates are capable of rapid learning of new volitional behaviors, the cognitive control system must have an equal capacity for rapid learning. Goal-directed behaviors can also be temporarily interrupted and resumed at ease. One might temporarily divert oneself from wine shopping, for example, to pick up some cheese. By contrast, automatic behaviors are characterized by their rigidity. 4

Areas of the frontal lobe. The prefrontal cortex includes all of the areas in front of the primary and secondary motor areas 5

The PFC occupies a far greater proportion of the human cerebral cortex than in other animals, suggesting that it might contribute to those elusive cognitive capacities that separate humans from animals. 6

Anatomy and organization of the prefrontal cortex 7

PFC: the silent cortex Unlike electrical stimulation of more posterior regions that produce hallucinations or motoric responses, stimulation of the PFC produces no obvious effect. This led it to be termed silent cortex. PFC damage has remarkably little overt effect; patients can perceive and move, there is little impairment in their memory, and they can appear remarkably normal in casual conversation. 8

Distinguishing between stored knowledge and activated information • We have unbounded capacity in long-term memory, but very limited ability to keep information active is severely limited • Early work on memory emphasized that short-term memory was to assist in the translation of newly acquired information into a format for longer-term storage. • More recently work has reconceptualized the function role of a different form of short-term memory -- the working memory. • Working memory system has been suggested as the processes that represent the current contents of cognition. • Patricia Goldman-Rakic has called working memory the “blackboard of the mind. ” 9

Prefrontal cortex is necessary for working memory but not associative memory 10

• A working memory / recognition memory task requires monkeys to pick a previously unselected object • Monkeys with lesions that encompassed areas 46 and 9 of the DLPFC had selectively impaired working memories. • In a control experiment, monkeys received frontal lesions in the vicinity of areas 6 and 8. These animals performed well in both versions of the task. 11

• Children younger than 1 year are unable to accomplish a similar working memory task. • The child acts as though the object is “out of sight, out of mind. ” • The ability to succeed in this type of tasks parallels the development of the frontal lobes. 12

Physiological correlates of working memory • In the working memory tasks, it is not enough for a stimulus to be recognized; subjects need to retain a record of its relevance • To conditions for working memory system: First, it should have a mechanism to access stored information; second: there should be a way to keep the information active Prefrontal neurons can show sustained activity during delayed-response tasks 13

The sustained activity could reflect either sensory information related to the cue or movement information related to the behavioral response. Both are found in the PFC, each with different temporal characteristics. PFC delay activity has been shown to convey a wide range of behaviorally relevant cues: objects, colors, sounds, the frequency of a vibration to the hand, and forthcoming eye and arm movements. 14

Earl Miller conducted a series of experiments to determine the specificity of prefrontal neurons Two possibilities: • Prefrontal neurons simply provide a generic signal that supports representation in other cortical areas • Prefrontal neurons code specific stimulus features 15

Firing profile of a neuron that shows a preference for one object over another during the “what” delay 16

Firing profile of a neuron that shows a preference for one location (“where” neuron) There also “what-where” neurons! 17

The selectivity of PFC neurons are task specific • In these studies, the cell activity is dependent on the monkey’s using that information to obtain a response • If the animal is required simply to passively view the stimuli, the response of these cells is minimal and the persistent activity during the delay period is absent. • If the task conditions change, the same cell become responsive to a new set of stimuli But, maybe these activities represent a mechanism for maintaining motor responses? • The activity of these cells is modified by past experience. • Fewer sustained responses are observed in an untrained animal 18

Two hypotheses of the role of PFC: • PFC maintains working memory as well as stores long-term memory • PFC are a temporary repository for representations accessed from other neural sites PFC is connected intimately with post-sensory regions of the temporal and parietal cortices 19

• PFC response sensitive to working memory demand • Lower FFA response during delay period • FFA leads PFC during encoding • PFC leads FFA during retrieval 20

Three components are essential for successfully executing an action plan: 1. One must identify the goal the develop subgoals 2. In choosing among goals, consequences must be anticipated 3. One must determine what is required to achieve the subgoals • Failure to achieve a goal can happen in many ways • The failures of goal-oriented behavior in patients with prefrontal lesions can be traced to many potential sources • They often provide unreasonable solutions • They demonstrate a certain inflexibility in their decision making 21

• Cognitive control provides the interface through which goals influence behavior • Complex actions require that we maintain our current goal • Focusing on the information that is relevant to achieving that goal • Ignoring irrelevant information • Shift from on subgoal to another in a coordinated manner 22

Dynamic filtering mechanism Working memory is more than passive sustaining of representations; it requires an attentional component in which the subject’s goals modify the salience of sources of information 23

Inhibitory control of sensory responses Evoked potentials reveal filtering deficits in patients with lesions in the lateral prefrontal cortex. 24

Humans with Frontal Damage Are Disinhibited The patients are unable to inhibit sorting by the previous rule. This inability to ignore irrelevant stimuli and the actions they trigger has led PFC patients to be described as stimulusbound, and the disruption of the patient’s ability to think and plan has been termed goal neglect Wisconsin Card Sorting Task 25

Humans with Frontal Damage Have Difficulty in Planning Prefrontal patients have a great deal of difficulty planning and organizing their lives. Wilder Penfield, a neurosurgeon during the mid-twentieth century described the case of his sister, on whom he operated to remove a large frontal tumor. Prior to the surgery she had been an excellent cook, and though her basic culinary skills remained subsequent to the operation, she seemed unable to organize her behavior so that all the elements of the meal were ready simultaneously. The Tower of London Test → requires the patient to think several moves in advance Patients with prefrontal damage are greatly impaired at this task, making many more moves than necessary to reach the fi nal goal position. 26

Thinking outside the (match) box Functional fixedness 27

Top-down control may also involve the amplification of task-relevant information 28

The task goal, specified by the instruction, can modulate perceptual processing by either amplifying task-relevant information or inhibiting taskirrelevant information. However, the data do not reveal if this modulation is the result of prefrontal activation 29

In an extension of the study comparing healthy elders and young people, researchers found: • Older subjects showed only an enhancement effect • They did not show the suppression effect in either FFA or PPA. • The result suggests that enhancement and suppression involve different neural mechanisms • Aging disproportionately affect prefrontal function 30

The medial frontal cortex as a monitoring system • ACC was assumed to be a component of the limbic system, helping to modulate autonomic responses during painful or threatening situations. • The medial frontal cortex, especially the anterior cingulate cortex (ACC) is now recognized as a critical component of a monitoring system. • Medial frontal cortex is engaged whenever a task becomes more difficult • Activation of ACC increases when the subjects make mistakes 31

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Interactions between the medial and lateral frontal cortex to facilitate goaloriented behavior. 33

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Disinhibition in behavioral control One of the most striking features of prefrontal patients is their disinhibition and lack of behavioral control. The patients are often impulsive, quick to anger, and prone to making rude and childish remarks. An example of disinhibition is utilization behavior. During a medical examination, a patient with PFC damage will pick up and use items that have been left on the doctor’s desk. The ability of disinhibition can be tested using the Stroop test 35