Cognitive Neuroscience, the biology of the mind, by M. Gazzaniga (fourth edition) – Summary chapter 12

Cognitive control (executive function) allows us to use our perceptions, knowledge and goals to bias the selection of action and thoughts from a multitude of possibilities. It allows us to override automatic thoughts and behaviour and step out of the realm of habitual responses. It also allows us to plan for the future and troubleshoot problems. Cognitive control is essential for goal-oriented behaviour.

The border between the frontal lobe and the parietal lobe is marked by the central sulcus. The most posterior part of the frontal lobe is the primary motor cortex. The unique cognitive abilities of humans may arise because of the prefrontal cortex and more because of how our brains are connected rather than due to an increase in the number of neurons. The prefrontal cortex is connected with other parts of the brain. The largest input comes from the thalamus. Almost all cortical and subcortical areas influence the prefrontal cortex. The prefrontal cortex consists of the lateral prefrontal cortex, frontal pole, medial frontal cortex and ventromedial prefrontal cortex.

Dysfunction of the prefrontal cortex may result in perseveration, persisting in a response even after being told that it is incorrect. The patient may also be unable to understand the consequences of their actions. The deficits seem to be mild when the lesion is unilateral but severe when the lesion is bilateral. Dysfunction in the frontal cortex leads to a loss of goal-oriented behaviour. Patients show utilization behaviour, behaviour which an extreme dependency on prototypical responses for guiding behaviour.

Goal-oriented actions are based on the assessment of an expected reward or value and the knowledge that there is a causal relationship between the action and the reward. A habit is an action that is no longer under the control of a reward but is stimulus-driven and automatic. Working memory is the transient representation of task-relevant information. It is the temporary maintenance of information, providing an interface between perception, long-term memory and action.

The lateral prefrontal cortex is a major component of working memory. Recency memory refers to the ability to organize and segregate the timing or order of events in memory. There is a breakdown of temporal structure of working memory with frontal lobe lesions. The prefrontal cortex is necessary for working memory but not for associative memory. Cells remain firing while being held in working memory. Prefrontal activation reflects a representation of the task goal and serves as an interface with task-relevant long-term representations in other neural regions.

A key component of fluid intelligence is the ability to maintain focus on task-relevant information in working memory. As dopamine levels increase, learning performance improves, but only to a point. At some level, increasing dopamine levels results in a reduction in performance.

In Petrides’ model of working memory, information held in the posterior cortex is activated, retrieved and maintained by the ventrolateral prefrontal cortex and manipulated in more dorsal regions of the lateral prefrontal cortex.

The frontal pole is essential for integrating the specific contents of mental activity into a general framework. There is a hierarchy in the prefrontal cortex. The simplest tasks are performed in posterior regions. If specific contents have to be integrated into a general framework, then the frontal pole is also recruited. The more challenging a task is for working memory, the further activation extends in the anterior direction.

In the prefrontal cortex, it works as follows: there is a ventral-dorsal gradient organized in terms of maintenance and manipulation. There is an anterior-posterior gradient that varies in abstraction. The more abstract and complex, the more anterior. There is a lateral-medial gradient relate to the degree to which working memory is influenced by information in the environment. The more working memory is influenced by information in the environment, the more lateral.

There are three important components for successfully developing and executing an action plan: identifying the goal and subgoals (1), anticipate consequences (2) and determine what is required to achieve subgoals (3). People with damage to the PFC are unable to monitor and evaluate different subgoals.

Goal-oriented behaviour requires people to select task-relevant information and filter out task-irrelevant behaviour. Working memory includes an attentional component in which an individual’s goals modify the salience of different sources of information. The prefrontal cortex has been conceptualised as a dynamic filtering mechanism.

Functional fixedness refers to thinking in the possible uses of an object and being fixed on the function of an object. Functional fixedness is associated with the prefrontal cortex. It is possible that the late development of the prefrontal cortex assists learning as it can make people more open-minded.

The frontal-eye-field region in the prefrontal cortex is essential for overcoming the tendency to look at novel stimuli. Goal-based control could influence the contents of information processing in two ways: accentuate the attended information (1) and selectively attend by excluding information (2). People with frontal lobe damage suffer from inhibitory control. They find it difficult to inhibit irrelevant information. The task goal, specified by the instruction, can modulate perceptual processing by either amplifying task-relevant information or inhibiting task-irrelevant information. Inhibition is more sensitive to the effects of ageing.

The prefrontal cortex is mostly involved with ignoring irrelevant stimuli but not with attending to relevant stimuli. The inferior frontal cortex is important for inhibiting task-irrelevant information and the dorsal frontal cortex is important for enhancing task-relevant information.

Patients with lesions of the frontal lobe are slow to abort a planned response. This impairment seems to be specific to lesions of the inferior frontal gyrus on the right side. The subthalamic nucleus is important for aborting planned responses, just as the inferior frontal gyrus on the right side.

There are two types of selection processes. Contention scheduling manages schemas for automatic or familiar actions. It is fast and passive. Schemas compete for responses and the winner of the conflict results in the corresponding action to that schema. If there is no winner in the conflict, no schema is triggered enough for a response and the result is no action. Supervisory attentional system can supersede contention scheduling. It is essential for ensuring that behaviour is flexible by allowing us to override automatic behaviour. It is a mechanism for favouring certain schema to emphasize the goals and demands of the situation.

The medial frontal cortex, specifically the anterior cingulate cortex, is involved in the monitoring of goals and actions.

The attentional hierarchy hypothesis states that the medial frontal cortex is part of an attentional hierarchy. It plays a critical role in coordinating activity across attentional systems. This model states that the medial frontal cortex is recruited when attentional demands are high. This model does not specify how the processes occur.

The error detection hypothesis states that the medial frontal cortex is involved in the detection of errors. After an error, a large evoked response sweeps over the prefrontal cortex after the initiation of the movement. This signal is referred to as the error-related negativity (ERN) response.

The response conflict hypothesis states that the medial frontal cortex evaluates response conflicts. If conflict is high, attentional vigilance should be increased.