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Home , Lobes of the brain

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Subject PSYCHOLOGY

Paper No and Title Paper No -14: NEUROPSYCHOLOGY

Module No and Title Module No-2: Lobular Organization of the

Module Tag PSY_P14_M2

TABLE OF CONTENTS 1. Learning Outcomes 2. Introduction 3. The two Hemispheres of the 4. Regions of Brain 4.1. The Frontal Cortex/ 4.2. The Parietal Cortex/Lobe 4.3. The Temporal Cortex/Lobe 4.4. The Occipital Cortex/Lobe 4.5. The Brodmann’s Areas 5. Summary

PSYCHOLOGY PAPER No. 14: NEUROPSYCHOLOGY MODULE No. 02: Lobular Organization of the Cerebral Cortex

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1. Learning Outcomes

After studying this module, you will be able to;

 Learn about structure and functions of the spinal cord  Learn about the fissures, sulci and gyri which make up two hemispheres and four cortical regions  Learn what major functions are controlled by the major lobes of the cerebral cortex,  Learn about the organization according to the primary and the secondary areas  Learn about specialized functions in some areas of the cerebral cortex

2. Introduction

The Nervous system may be divided into two major parts. The central nervous system controls the higher order functions, and is the master of what the various parts of the body do. Brain and the spinal cord are included in this. The peripheral nervous system, on the other hand, is made of the spinal and the cranial nerves.

The Spinal Cord

Spinal cord extends from the base of the brain to the lower back. Its thickness is about an adult’s finger. It is about 18 inches in length in adult males. In females, it is about one inch less in length.

Spinal cord collects somato sensory information from the sensory organs and connects it with the motor to reach muscles and glands to perform functions. The spinal cord is specialized for carrying out the simplest motor actions called the reflexes. The sensory messages are received from all the sensory organs and motor responses in the form of reflexes are coordinated within the grey matter of the spinal cord.

The processing of information in the brain takes place at the level of the brain. Brain is the highest information processing centre in the nervous system. It has three main divisions of the nervous system include the , the midbrain, and the hindbrain.

The three main divisions of the nervous system are further divided into telencephalon which consists of cerebral cortex and basal ganglia, diencephalon consisting of the and the hypothalamus, mesencephalon which is the combination of superior and inferior colliculi, metencephalon made up of pons and , and myencephalon which is another name for Medulla oblongata . Amongst the broader divisions of the brain, the fore-brain includes telencephalon and diencephalon, and the functional circuit of the limbic system. The mid brain consists of the functional reticular formation including basal areas, tectum and tegmentum. The hind brain is made of the cerebellum, pons and medulla. The functional structure of the brain stem includes the mid brain, pons, and medulla oblongata. It is also a part of the reticular activating system is referred to together as the brainstem. PSYCHOLOGY PAPER No. 14: NEUROPSYCHOLOGY MODULE No. 02: Lobular Organization of the Cerebral Cortex

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(Fig 1.1 Structure and Function of the two hemispheres)

3. The two Hemispheres of the Brain

The brain is divided into two equal parts via the neuraxix. These two parts are called hemispheres. These two parts are similar to each other as if they were mirror images of each other. They are joined by the thick bundle of fibers called the . This bundle of white matter or the myelinated fibres is the only bridge between the two hemispheres. In spite of looking like two similar halves, they are not totally similar either in terms of function or in terms of anatomy.

The brain controls the body in a contra lateral manner, the right controlling the left and vice versa. More or less similar functions are performed by the two hemispheres for different sides of the body, for example, movements of the right side of body are controlled by the left side of the brain and vice versa. However, they have also specialized to perform different functions. For example, the left brain is more to do with higher cognitive functions like reasoning, logic, mathematics, problem solving and decision making whereas the right side of the brain is more concerned with creative activities, and spatial . The latter is also concerned with comprehension and expression of . PSYCHOLOGY PAPER No. 14: NEUROPSYCHOLOGY MODULE No. 02: Lobular Organization of the Cerebral Cortex

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The covering or the uppermost part of the brain is called the cerebral cortex/. It is here that functions like , imagination, thought, judgment, and decision making occur. The surface of the cerebrum is called the cerebral cortex. Cortex means “bark” and the cerebral cortex surrounds the like the bark of a tree. It is greatly convoluted. The cerebral cortex has six layers of cells. Below them, there are innumerable myelinated neurons. The cortex is heavily convoluted. It includes billions of neurons, with trillions of synapses.The folding of the brain have gyri (singular: gyrus), and sulci (singular: ).i.e., the convolutions and the depressions .The cerebral cortex seems to be divided into various regions because of the presence of gyri and sulci.

4. Regions of Brain

Different regions of the cerebral cortex perform different functions.  The function of seeing or vision is performed by the primary occipital cortex which is separated from the via the calcarine fissure.  The major hearing area is the primary located in the temporal cortex.It is separated from the via the lateral fissure which is a deep ridge in the brain.  The Primary somato-sensory cortex recieves information from body sensations. It is located in the parietal lobe of the brain. The parietal lobe lies beyond the .  The is involved in the control of motor movements, and is located just in front of the primary somatosensory cortex which lies in the frontal lobe of the brain.

Fig 1.2 Structure of Brain, indicating location of different Cortex)

A study of gross anatomical structure or the study of the gross anatomy indicates that cerebral cortex may be divided into four lobes. They are frontal, parietal, temporal, and . In both the hemispheres, this regional classification of the brain may be observed.

PSYCHOLOGY PAPER No. 14: NEUROPSYCHOLOGY MODULE No. 02: Lobular Organization of the Cerebral Cortex

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(Fig 1.3 Lobes of the Cerebral Cortex)

4.1 The Frontal Cortex/Lobe

Located behind the forehead is the frontal lobe. This lobe controls the voluntary movement. Pyramidal and extra pyramidal system for movement originates from here. It is the most important lobe for controlling the traits of personality, and impulse control. In humans, it keeps on developing till about the age of 20 years. So, it is inferred that the cognitive maturity of adulthood is significantly related to the development of this region of the cerebral cortex. . The frontal lobe is found in the brain of mammals. Most of the neurons in this region respond to the neurotransmitter . The dopamine containing neurons are activated when feels rewarded, is paying to a stimulus and is in a state of motivation, doing short term tasks, or doing planning. Dopamine is involved in selection of relevant from the irrelevant information. The Frontal lobe is located behind an organism’s forehead. It is adjacent to the parietal lobe. It is separated from the parietal lobe via the central sulcus. It is also known as the fissure of Rolando. The calcarine fissure separates parietal from the occipital lobe. The lateral or the sylvian fissure divides temporal from the frontal lobe.

PSYCHOLOGY PAPER No. 14: NEUROPSYCHOLOGY MODULE No. 02: Lobular Organization of the Cerebral Cortex

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The frontal cortex can be divided into several regions according to their position in the cortex. They are lateral, polar, orbital (basal or ventral), and medial. They consist of special elevations on the brain tissue. They are pre central gyrus, frontal gyrus, and the middle gyrus.

The pre frontal cortex, which is the most anterior part of the frontal lobe, is involved in complex cognitive processes like reasoning and judgment. These are known as the cognitive processes or the higher order cognitive functions. These processes are called biological intelligence of an individual.

The executive functions of the frontal lobe are controlled by the pre-frontal cortex. The long term are also formed and stored in this part of the brain. Such memories are normally laden and have a direct connection with the limbic system as well. It also contains centres for the control of personality traits, impulse management, ability to delay gratifications etc. The frontal lobe is critical in controlling motor behaviour of the organism. The primary motor areas are located in this lobe. It also contains Broca’s area which controls the production of speech. Neurons in this area also control the movements involved in swallowing..

The frontal cortex contains an important area involved with the coordination of movements of organs and muscles used in speech production. It is known as the Broca’s speech area. Any damage to this part of the cortex results in aphasia or apraxia. It is Broddman area 44 and 45. It is located on the third frontal gyrus, more developed on the left hemisphere of the brain.

The area in the frontal cortex called the pre central gyrus is also known as the primary motor area. Voluntary movements of the somatic muscles are controlled and coordinated by this area. The major pyramidal and extra-pyramidal systems of the brain which control various kinds of muscular movements originate from here. The lower portions of the primary motor areas are related with the movements of the muscles of the mouth and face. The upper portions in the same region control movements of the lower parts of the body, i.e., legs and feet. Anterior to the primary motor area are the supplementary and the pre motor areas. They are involved with coordinating bilateral movements, sensory motor synergy and the sequencing of movements.

PSYCHOLOGY PAPER No. 14: NEUROPSYCHOLOGY MODULE No. 02: Lobular Organization of the Cerebral Cortex

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(Fig 1.4 the Frontal Lobe)

Total area occuopied by the frontal lobe is the largest. It is the centre for higher cognitive functions, therefore any damage to it may lead to a number of neuro psychological disorders as well. Attention Deficit and Hyperactivity Disorder, several kinds of dementia, motor coordination disorders, and mood disorders have been linked with it

4.2 The Parietal Cortex/Lobe

Next to the frontal lobe, in the post central gyrus region, there is the parietal lobe. It is also known as the somesthetic cortex. It controls sensations of touch, pain, pressure, hot cold, and the kinesthetic perception of movements. It has role to play in spatial perception, three dimensional viewing, map search, reading and writing, and in the manipulation of concrete objects.

Spatial processing is a special feature of the parietal lobe. Recognition of visual symbols is carried out by the in this lobe. The two hemispheres of this cortical region are specialized differently for language functions and the perception of the third dimension. The latter is primarily located in the right hemisphere of the brain.

The parietal lobe contains primary, secondary and association areas. Secondary areas discriminate between stimuli coming from the primary areas while associative areas integrate information from parietal with that coming from other lobes of the brain.

PSYCHOLOGY PAPER No. 14: NEUROPSYCHOLOGY MODULE No. 02: Lobular Organization of the Cerebral Cortex

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All the sensations coming from the soma, that is, the skin and the internal organs are processed in the parietal lobe. The posterior part of the parietal cortex is known to integrate somato sensory information with the visual sensation. This also correlates spatial information with the movements of the body to produce a meaningful action. It also controls eye movements in conjunctions with those of various body parts.

Experimental studies have shown that various regions of the parietal lobe control different orientations in space. Such an organization at the level of the brain produces the right kind of eye movements.

 The ventral parietal cortex receives input from visual, somato-sensory, auditory, and vestibular sensations.  The medial parietal lobe encodes the location of objects with reference to one’s nose.  The anterior regions of the parietal lobe help in the discrimination of shapes, sizes, and other attributes of objects, and in integrating movements accordingly. Grasping and manipulating objects is accomplished through neurons of this area.  Both the left and right parietal cortices play role in self transcendence, the personality traits, and the experience of spirituality.

Damage to the Parietal Lobe may result in disorders related to learning, reading, and writing, movements in a three dimensional context, contra lateral neglect, and inability to do simple calculations. Disorientation with respect to the left or the right side may also occur due to damage to this lobe. The disorder of contra lateral neglect is also related to this.

(Fig 1.5 the Parietal Lobe) PSYCHOLOGY PAPER No. 14: NEUROPSYCHOLOGY MODULE No. 02: Lobular Organization of the Cerebral Cortex

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At the back of the central sulcus, there is the parietal lobe. On the back of this lobe, towards the hind side of the brain, there is occipital lobe. The parieto-occipital sulcus separates it from the occipital lobe, and is separated from the with the lateral fissure in between. The lateral fissure is also known as the sylvian fissure. The , of course, divides the lobe in two hemispheres of the brain. In terms of size, it is the second largest lobe after the frontal lobe of the cerebral cortex.

Parietal lobe is also known as the somato sensory cortex. It is located behind the central sulcus. Further it includes an area called the somatosensory cortex, just behind the sulcus separating this lobe from the frontal lobe. The somatosensory cortex can be mapped, with the mouth and face closest to the temples and the legs and feet at the top of the head. Within each hemisphere, the somatosensory cortex represents the skin area on the contra lateral surface of the body.

4.3 The Temporal Cortex/Lobe

Just above the ears of the organism, there is the area called the temporal cortex/lobe. This lobe contains the primary auditory area. It is associated with processing of auditory and also olfactory sensation. It is connected with the parietal and frontal lobes and plays a significant role in sensing of smell and sound, as well as processing of complex stimuli like faces and scenes.

The Temporal lobe is divided into the left temporal lobe and the right temporal lobe. The two together provide a process of communication called lateralization. This allows communication between the left and right temporal lobe, as well as between the occipital, parietal and frontal lobes of the brain. This facilitates the retention of visual memories, facial recognition, sensory input processing, language comprehension, new memory storage, and emotions.

The temporal cortex contains the Wernicke's area which is involved with the comprehension of language. The secondary and the associative areas of this lobe which are involved with the perception of auditory information also contain this area for the processing of the spoken word or language. The temporal cortex also contains other areas called the and the amgydala. Hippocampus is the centre of the formation of short term memories, and amgydala sores the emotion laden long term memories. Thus, temporal lobe plays important role in memory functions.

In the associative areas of the temporal cortex, audio-visual integration takes place. So, a lot of input comes from the visual areas of the brain as well. Such integration allows an organism to comprehend movies, for example, by allowing dialogues and the lip movements to be fused together. Para hippocampal areas and the in this lobe are specifically connected with this function.

The temporal lobe, specifically its medial structure, controls encoding and comprehension of the declarative memory input. It is of the long term memory type. Damage to this area, including that to the hippocampus, can drastically impair memory resulting in retrograde and anterograde amnesia.

PSYCHOLOGY PAPER No. 14: NEUROPSYCHOLOGY MODULE No. 02: Lobular Organization of the Cerebral Cortex

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(Fig 1.6 The Temporal Lobe)

4.4. The Occipital Cortex/ Lobe

At the back of the head is the occipital lobe. At the very rear portions of the occipital lobe is the primary , which receives information from the eyes and specializes, thereby, in the reception of the visual stimulus. The input comes directly from the lateral geniculate nucleus of the thalamus which receives it from the optic nerve. The secondary visual areas help an individual to perceive the given visual stimulus. The associative areas integrate visual information with that coming from other lobes of the brain.

According to function, several areas may be marked on the occipital cortex. Each such area has a specific function for specific visual orientations in the outside world. They are not very clearly separated due to fissures or convolutions.

. The primary visual cortex at the very back of the occipital lobe is labeled V1, and receives input from the optic tract. It has a clear map of visual information that corresponds to the areas of the retina and hence the center of vision is greatly magnified. The individual neurons of V1 are extremely sensitive to particular changes in input from the eyes. V1 has some extra striate regions and they specialize in different visual tasks, such as visuo-spatial processing, color discrimination, and motion perception. . The area V2 is located around V1. It is known as the secondary visual area and has synaptic connections with V1. It provides recognition of the visual input, and helps detect the complex patterns. Perceiving figure out of the background and recognition of contours in the visual input is provided by this area.

PSYCHOLOGY PAPER No. 14: NEUROPSYCHOLOGY MODULE No. 02: Lobular Organization of the Cerebral Cortex

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. The area V3 has projections coming from both areas V1 and V2. Studies have related the perception of depth, and distance with this area. It also integrates vision with the total body movement. It is one of the associative areas of the occipital cortex. . The area V4 is involved with the processes of selective attention . . The area V5 is another region in the visual associative areas. Besides controlling complex pattern recognition, it controls visual processes in relation with complex movements, such as those involved in dancing.

With damage to the primary visual area, a complete loss of visual sensation or total blindness will result. It may also cause blind spots in the visual field depending on the extent of damage. The impairment of secondary and associative areas can result in a condition known as agnosia, an inability to comprehend or perceive /recognize the visual input, a condition known as agnosia. Anomia, a problem with naming of the seen image may also result in such a condition.

Damage or lesions in the occipital lobe have been related with visual hallucinations. If the associative areas of all the three sensory regions, i.e., occipital, parietal, and temporal lobes are lesioned, color agnosia, inability to differentiate between colors, movement agnosia, inability to follow movements, and agraphia., i.e., inability to comprehend the written word may be the result. Damage to the primary motor areas could lead to a "hole" in the vision called scotoma. Some people with scotoma can still partially react to stimuli, and thus, they are said to have the blind sight.

(Fig 1.7 the Occipital Lobe)

PSYCHOLOGY PAPER No. 14: NEUROPSYCHOLOGY MODULE No. 02: Lobular Organization of the Cerebral Cortex

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The occipital lobe is the smallest of four lobes in the cerebral cortex. It is located in the rearmost portion of the skull. The lobe is located under the occipital bone, and is therefore called the occipital cortex. The lobes rest on the tentorium cerebelli, a process of dura mater that separates the cerebrum from the cerebellum. They are structurally isolated in their respective cerebral hemispheres by the separation of the cerebral fissure. At the front edge of the occipital are several lateral , which are separated by .

The occipital aspects along the inside face of each hemisphere are divided by the . Above the medial, Y-shaped sulcus lies the , and the area below the sulcus is the

4.5. Brodmann’s Areas

(Fig 1.7 The Brodmann’s Areas)

PSYCHOLOGY PAPER No. 14: NEUROPSYCHOLOGY MODULE No. 02: Lobular Organization of the Cerebral Cortex

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Brodmann studied the function of several regions on the cerebral cortex. He numbered each area as he described its function in detail He delineated 52 such areas. They are known as the Brodmann areas. According to him, Area 4 is located in the frontal cortex, and was named as the primary motor area as it controls voluntary movements of all the skeletal muscles. Area 6, and 8 are also located in the frontal cortex. Area 8 facilitates eye movements. It was found that it is also involved in visual reflexes, and pupil dilation and constriction. In the frontal cortex, Areas 9, 10, and 11 were found to be concerned with cognitive processes like reasoning and judgment which may be called executive functions. Concerned with spoken language, Areas 44 and 45, Broca's area, were also delineated. Important areas in the Parietal Lobe, which play role in somatosensory processes, are areas 3, 2, and 1. Other functionally important areas were Areas 5, 7, and 40 in this lobe. Area 39 is the angular gyrus, involved with integration with other slobes sensory input with the somesthetic sensations. Temporal lobe contains area 41 as the primary auditory area. Area 42 was involved in the detection and recognition of speech. Areas 21 and 22 are known as the Wernicke's area involved with language comprehension. In the Occipital Lobe, Area 17 is the primary visual area. Areas 18 and 19 are the secondary visual (association) areas where visual processing occurs.

Areas of the lobes that are not specialized are called association cortex. Besides connecting the various sensory and motor cortices, this is also believed to be where our thought processes occur and many of our memories are ultimately stored

5. Summary

 There are four prominent lobes of the brain. Each lobe consists of primary secondary) and association areas.  The Frontal Lobe is specialized for logical thinking, problem-solving, decision making, reasoning and other higher order cognitive functions. It is also the highest centre controlling motor behaviour .It also has some role to in speech.  The parietal cortex is somato-sensory. It mediates the of touch, temperature, pressure, pain , spatio-manipulable activities, learning of second language etc.  Temporal cortex involves sense of hearing and the vestibular or equilibrium..  Occipital Cortex is involved with of complex and integrated visual stimuli.

PSYCHOLOGY PAPER No. 14: NEUROPSYCHOLOGY MODULE No. 02: Lobular Organization of the Cerebral Cortex