Phineas Gage Case Study: Frontal Lobe Function

Phineas Gage survived a severe head trauma, but his behavioral changes were significant.
He became fitful, irreverent, and indulged in profanity, showing little respect for others.
His friends and acquaintances said he was "no longer Gage" due to the radical change in his mind.

The frontal lobes were once considered "the silent lobes" due to the lack of understanding of their functions.
The concept of executive control is closely linked to the function of the frontal lobes.
Not all functions of the frontal lobes fall under executive control, and not all executive control functions are subserved by the frontal lobes.

The prefrontal cortex has expanded over mammalian and primate evolution.
The prefrontal cortex accounts for 29% of the total cortex in humans, compared to 17% in chimpanzees, 11.5% in macaques, and 3.5% in cats.

The prefrontal cortex plays a central role in forming goals and objectives and devising a plan to attain them.
It selects the cognitive skills needed to implement the plans, coordinates those skills, and applies them in the correct order.
The prefrontal cortex is responsible for evaluating actions as success or failure relative to intentions.

The prefrontal cortex can be defined using Brodmann area maps, which are based on the types of neurons and connections found within each area.
The prefrontal cortex is comprised of Brodmann areas 8, 9, 10, 11, 12, 13, 44, 45, 46, and 47.
The prefrontal cortex is directly connected to every distinct functional unit of the brain.

Two broad types of cognitive operations linked to the frontal lobe executive system are:
- Guiding behavior by internal representations (formulating plans and guiding behavior according to those plans).
- Switching gears when something unexpected happens (mental flexibility).
Mental flexibility is the capacity to respond rapidly to unanticipated environmental contingencies.
The frontal lobe executive system is closely associated with the development of social maturity.

Four broad types of cognitive operations linked to the executive systems in the frontal lobes have been extensively investigated using neuroimaging techniques:
- Attention and perception
- Working memory
- Executive function
- Motor control
Neuroimaging studies have shown that the prefrontal cortex is intricately involved in many cognitive and executive processes.
Attention and perception processes activate different brain regions, including the visual cortex and the fusiform face area.

Working memory is the ability to keep something in mind for a limited time.
Working memory is closely associated with the voluntary attention systems.
In working memory tasks, sensory regions in the occipital (for visual memory) and the temporal (for verbal memory) remain activated throughout the experimental trial.

Executive functions like planning and executing complex behaviors have been studied using the Tower of London task.
This task activates regions in the dorsolateral prefrontal cortex (DLPFC).
The anterior cingulate cortex (ACC) is another brain region involved in executive function, serving as an inhibitory effect on the frontal lobes.

The frontal lobes are highly vulnerable to damage.
Damage to different parts of the frontal lobes produces distinct, clinically different syndromes.
The most common syndromes are dorsolateral and orbitofrontal syndromes.

Dorsolateral syndrome is characterized by:
- Perseverative behavior
- Field-dependent behavior
- Mental rigidity
Orbitofrontal syndrome is characterized by:
- Emotional instability
- Impulsivity
- Disinhibition### Frontal Lobe Dysfunction
Orbitofrontal syndrome is characterized by behavioral and emotional disinhibition, with patients experiencing intense emotions, poor impulse control, and lack of concern for social norms.
Patients with orbitofrontal syndrome have impaired ability to inhibit the urge for instant gratification, leading to impulsive behavior.

Frontal lobe damage can occur in various disorders, including schizophrenia, Tourette's syndrome, and Attention Deficit (Hyperactivity) Disorder (ADHD).
These disorders can lead to prefrontal dysfunction, even without direct damage to the frontal lobes.

Attentional functions are influenced by the frontal lobes, as well as an "attentional loop" involving frontal, brainstem, and posterior cortex.
Damage to the prefrontal cortex or its pathways can result in attentional impairment, leading to attention deficit disorders.

The frontal lobe is dedicated to the representation and production of action at all levels of biological complexity.
The neuronal substrates for action production and representation are identical.
The frontal lobe is organized hierarchically, with simpler actions in the orbitofrontal and motor cortex, and more complex and abstract actions in the lateral prefrontal cortex.

Frontal lobe functions are organized hierarchically, with simpler functions serving more global functions.
A brain schematic shows an anterior-posterior organization based on the level of abstraction of action.

Executive functions have become a focus of increasing research after being overlooked for many decades.
Two approaches to understanding executive functions are the Modular View and the Gradient View.
The Modular View fractionates executive functions along sensory modalities, linguistic and non-linguistic distinctions, and object versus spatial distinctions.
The Gradient View suggests that the functional organization of heteromodal association cortices is interactive and distributed, rather than modular.