This article throws light upon the four lobes of cerebral cortex. The lobes are: 1. Frontal Lobe/Frontal Cortex 2. Motor Lobe 3. Temporal Lobe 4. Occipital Lobe.
1. Frontal Lobe/Frontal Cortex:
The frontal lobes can be divided into superior, Middle and Inferior gyri, anatomically. However, functionally the frontal lobes may be divided into motor cortex, premotor cortex and prefrontal associational cortex. The frontal cortex is mostly involved in motor behaviour, expressive language, ability to concentrate and attend, reasoning and thinking and orientation to time, place and person.
The prefrontal cortex has also a complex involvement in the evaluation of sensory information. Lesions of the dorsolateral prefrontal cortex produce apathy, indifference, decreased drive to do any work, psychomotor retardation and decreased attention etc.
2. Motor Lobe:
The motor area is located at the end of the frontal lobe and adjacent to the central fissure. It controls the voluntary movements of various parts of the body like leg, arm, face etc. It is technically known as the precentral area (Broadman’s area).
It is located in front of the pre-central area. It controls complex muscular movements of the body. Each hemisphere is connected with the opposite side of the body. If the motor area of the left hemisphere is damaged or destroyed the right limbs are paralyzed and vice versa.
Prefrontal Associational Cortex:
It deals with psychological processes like reasoning and memory. The essential function of these areas is to respond to immediate sense impressions and symbols. Because of these areas we are able to correlate all our present experiences with past experiences and make use of memory and thought processes.
Lesions of the orbit medical frontal cortex lead to withdrawal behaviour, fearful explosiveness, loss of inhibitions mood bring a swing and occasional violent outbursts. Some of the patients appear similar to patients with severe by polar illness.
It lies near the central fissure in the back half of the brain. It has somasthetic area. The major structure of the parietal cortex includes the post central gyrus, superior parietal lobule and inferior parietal lobule. The parietal lobes contain the associational cortices for visual, auditory and tactile input and hence deal with the intellectual processing of sensory information.
Lesions of the dominant parietal lobe lead to Gerstmann’s syndrome, which includes agrapnia, calculation difficulties, right-left disorientation and linger agnosia. A person with a right sided parietal stroke may deny that he has a paralyzed left arm and he may completely ignore the left side of his body like by not washing it while taking bath.
All the bodily sensations are projected in the parietal lobe. If any area of parietal lobe is damaged a person cannot discriminate between a piece of silk cloth and a sand paper. The sensation of wool, pin prick, mud or clay is projected in the parietal cortex.
3. Temporal Lobe:
The lateral aspect of the temporal lobe has three gyri such as superior, middle and inferior. Language, memory and emotions are the primary functions of the temporal cortex. Lesions of the temporal cortex can lead to symptoms like delusions, hallucinations, mood disturbances which by and large resemble those psychiatrics in their research undertakings.
Lesions in the temporal lobe are caused by stroke, trauma, and tumour. Infections in C.N.S. with herpes virus show a particular prediction towards temporal lobes. Bilateral lesions of temporal lobes lead to dementia. Lesions of the dominant temporal lobe lead to euphoria, auditory hallucination, delusions, thought disorders, decreased ability to learn new materials and poor verbal comprehension.
Dysphoria, irritability, cognitive deficiency, decreased visual and musical ability occurs because of lesions of the non- dominant temporal lobe. Damage to the temporal lobe also leads to deafness.
Epilepsy is a major disease characterised by paroxysmal dysfunction of brain tissue. An epileptic focus may be in any cortical area or even sub-cortical nuclei. But epilepsy is included under the temporal cortex because complex partial epilepsy is probably the most relevant of the epilepsies in psychiatry.
Complex partial epilepsy is the most common forms of epilepsy in adults affecting about three in one thousand persons.
4. Occipital Lobe:
Like other lobes, the occipital cortex consists of the superior and inferior occipital gyri as well as the cuneus and the tin lingual gyri. The shape of the occipital cortex is irregular and it is located at the back portion of the brain. It is the seat of visual sensation.
Total destruction of the occipital cortex results in cortical blindness. Other subtle dysfunctions are distortion of images and loss of depth perception. If one part of the occipital lobe is destroyed or there is a lesion the visual field is impaired and the person will not be able to see half of the object.
The retina which is the crucial organ of the eye is connected with it. Hence if one of the optic nerves is damaged either of the eyes will loose its visual ability. Visual hallucination is also found in patients with occipital epilepsy.
Some of these symptoms may be similar to the symptoms of psychiatric patients. Under such circumstances, the psychiatrist may miss the real cause i.e., neurological disorder of the occipital lobe and thus there may be mistaken diagnosis.