Temporal Lobe

TEMPORAL LOBE

Temporal lobe of cerebral cortex includes three functional areas :

A. Primary auditory area

B. Secondary auditory area or auditopsychic area

C. Area for equilibrium.

PRIMARY AUDITORY AREA

Primary auditory area includes:

1. Area 41

2. Area 42

3. Wernicke area.

Areas 41 and 42 are situated in anterior transverse gyrus and lateral surface of superior temporal gyrus.

Wernicke area is in upper part of superior temporal gyrus posterior to areas 41 and 42.

Connections of Primary Auditory Area

Afferent connections

Primary auditory are receives afferent fibers from:

1. Medial geniculate body via auditory radiation

2. Pulvinar of thalamus.

Efferent connections

This area sends efferent fibers to:

1. Medial geniculate body

2. Pulvinar.

Functions of Primary Auditory Area

Primary auditory area is concerned with perception of auditory impulses, analysis of pitch and determination of intensity and source of sound. Areas 41 and 42 are concerned only with the perception

of auditory sensation (sound). Wernicke area is responsible for the interpretation of auditory sensation.

It carries out this function with the help of secondary auditory area (area 22). Wernicke area is also

responsible for understanding the auditory information about any word and sending the information to Broca area.

SECONDARY AUDITORY AREA

Secondary auditory area occupies the superior temporal gyrus. It is also called or auditopsychic area or auditory association area. It includes area 22. This area is concerned with interpretation of auditory sensation along with Wernicke area. It is also concerned with storage of memories of spoken words.

AREA FOR EQUILIBRIUM

Area for equilibrium is in the posterior part of superior temporal gyrus. It is concerned with the maintenance of equilibrium of the body. Stimulation of this area causes dizziness, swaying, falling and feeling of rotation.

TEMPORAL LOBE SYNDROME

Temporal lobe syndrome is otherwise known as Kluver- Bucy syndrome. It is observed in animals, particularly monkeys after the bilateral ablation of temporal lobe along with amygdala and uncus. It occurs in human beings during bilateral lesions of these structures.

Manifestations of this syndrome are:

1. Aphasia

2. Auditory disturbances such as frequent attacks of tinnitus, auditory hallucinations with sounds

like buzzing, ringing or humming. Tinnitus means noise in the ear. Hallucination means feeling of a

particular type of sensation without any stimulus.

3. Disturbances in smell and taste sensations

4. Dreamy states: The patients are not aware of their own activities and have the feeling of unreality

5. Visual hallucinations associated with hemianopia.

OCCIPITAL LOBE

Occipital lobe is called the visual cortex.

AREAS OF VISUAL CORTEX

Occipital lobe consists of three functional areas:

1. Primary visual area (area 17)

2. Secondary visual area or visuopsychic area (area 18)

3. Occipital eye field (area 19).

Connections of Occipital Lobe

Occipital lobe receives afferent fibers from lateral geni culate body. It sends efferent fibers to superior

colliculus and lateral geniculate body.

Functions of Occipital Lobe

1. Primary visual area (area 17) is concerned with perception of visual sensation

2. Secondary visual area (area 18) is concerned with interpretation of visual sensation and storage of

memories of visual symbols

3. Occipital eye field (area 19) is concerned with reflex movement of eyeballs. It is also concerned with

associated movements of eyeballs while following a moving object.

APPLIED PHYSIOLOGY

Lesion in the upper or lower part of visual cortex results

in hemianopia. Bilateral lesion leads to total blindness.

 

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