Prefrontal Cortex

PREFRONTAL CORTEX OR ORBITOFRONTAL CORTEX

Prefrontal cortex is the anterior part of frontal lobe of cerebral cortex, in front of areas 8 and 44. It occupies the medial, lateral and inferior surfaces and includes orbital gyri, medial frontal gyrus and the anterior portions of superior, middle and inferior frontal gyri. Areas present in prefrontal cortex are 9, 10, 11, 12, 13, 14, 23, 24, 29 and 32. Areas 12, 13, 14, 23, 24, 29 and 32 are in medial surface (Table 152.1). Areas 9, 10 and 11 are in lateral surface.

Connections of Prefrontal Cortex

Afferent fibers

Afferent fibers of prefrontal cortex come from:

1. Dorsomedial nucleus of thalamus

2. Hypothalamus

3. Corpus striatum

4. Amygdala

5. Midbrain.

Areas 23, 24, 29 and 32 receive fibers from anterior nucleus of thalamus. Area 32 receives fibers from suppressor area of precentral cortex also.

Efferent fibers

Efferent fibers are projected to:

1. Thalamus

2. Hypothalamus

3. Tegmentum

4. Caudate nucleus

5. Pons

6. Temporal lobe of cerebral cortex.

Area 13, along with hippocampus, uncus and amygdala sends fibers to mamillary body of hypothalamus

via fornix. This area is concerned with emotional reactions.

Functions of Prefrontal Cortex

Earlier, this area was considered as inexcitable to electrical stimulation. Hence, it was called the silent

area or association area. But, now it is known that the stimulation of this area with low voltage electrical

stimulus causes changes in the activity of digestive, cardiovascular, respiratory and excretory systems and other autonomic functions. It also causes fear. Various functions of prefrontal cortex are:

1. It forms the center for the higher functions like emotion, learning, memory and social behavior.

Short-term memories are registered here.

2. It is the center for planned actions

3. This area is the seat of intelligence; so, it is also called the organ of mind

4. It is responsible for the personality of the individuals

5. Prefrontal cortex is responsible for the various autonomic changes during emotional conditions,

because of its connections with hypothalamus and brainstem.

Effect of Lesion of Prefrontal Cortex

Bilateral lesion or removal of prefrontal cortex in human beings does not cause paralysis. It causes lack of

initiation and loss of mental alertness. Very little or no change occurs in memory, judgment and intelligence.

APPLIED PHYSIOLOGY – FRONTAL

LOBE SYNDROME

Injury or ablation of prefrontal cortex leads to a condition called frontal lobe syndrome.

Features of this syndrome are:

1. Emotional instability: There is lack of restraint, leading to hostility, aggressiveness and restlessness

2. Lack of concentration and lack of fixing attention

3. There is lack of initiation and difficulty in planning any course of action

4. Impairment of recent memory occurs. However, the memory of remote events is not lost.

5. Loss of moral and social sense is common and there is loss of love for family and friends

6. There is failure to realize the seriousness of the condition. The subject has the sense of well-being

and also has flight of ideas.

7. Apart from mental defects, there are some functional abnormalities also:

i. Hyperphagia (increased food intake)

ii. Loss of control over sphincter of the urinary

bladder or rectum

iii. Disturbances in orientation

iv. Slight tremor.