Cortical Lobes

The most complex thinking abilities are primarily attributable
to the thin layers that cover the two cerebral hemispheres—the

cortex. It is this covering of the brain that makes for the greatest differences

between the intellectual capabilities of humans and other animals. Both

hemispheres are typically divided into four main lobes, the distinct cortical

areas of specialized functioning. There are, however, many differences

among people, not only in the relative size of different lobes but also in how

much cerebral cortex is not directly attributable to any of the four lobes.

The occipital lobe is located at the back of the cerebral cortex. The most

posterior tissue of this lobe is called the striate cortex because of its distinctive

striped appearance. The striate cortex is also called the primary visual

cortex because it is there that most visual information is eventually processed.

Each of the layers of this cortical area is specialized to analyze different

features of visual input. The synthesis of visual information and the interpretation

of that result involve other lobes of the brain. The occipital

lobe also plays the primary role in various aspects of spatial reasoning. Activities

such as spatial orientation, map reading, or knowing what an object will

look like if rotated a certain amount of degrees all depend on this lobe.

Looking down on the top of the brain, a deep groove called the central

sulcus can be seen roughly in the middle of the brain. Between the central

sulcus and the occipital lobe is the parietal lobe. The parietal lobe’s predominate

function is the processing of the bodily sensations: taste, touch, temperature,

pain, and kinesthesia (feedback from muscles and joints). A parietal

band of tissue called the postcentral gyrus that is adjacent to the central

sulcus (posterior and runs parallel to it) contains the somatosensory cortex

in which the surface of the body is represented upside down in a maplike

fashion. Each location along this cortical area corresponds to sensations

from a different body part. Furthermore, the left side of the body is represented

on the right hemisphere and vice versa. Damage to the right parietal

cortex usually leads to sensory neglect of the left side of the body—the

person ignores sensory input from that side. However, damage to the left

parietal cortex causes no or little sensory neglect of the right side of the

body.

The parietal lobe is involved with some aspects of distance sensation. The

posterior parietal lobe plays a role in the visual location of objects and the

bringing together of different types of sensory information, such as coordinating

sight and sound when a person looks at someone who just called his

or her name. Some aspects of the learning of language also engage the operation

of the parietal cortex.

On the sides of each hemisphere, next to the temples of the head, reside

the temporal lobes. The lobes closest to the ears are the primary sites of the

interpretation of sounds. This task is accomplished in the primary auditory

cortex, which is tucked into a groove in each temporal lobe, called a lateral

sulcus. Low-frequency sounds are analyzed on the outer part of this sulcus;

higher-pitched sounds are represented deeper inside this groove. Closely

linked with auditory perception are two other major functions of the temporal

lobe: language and music comprehension. Posterior areas, particularly

Wernicke’s area, play key roles in word understanding and retrieval. More

medial areas are involved in different aspects of music perception, especially

the planum temporale.

The temporal cortex is the primary site of two important visual functions.

Recognition of visual objects is dependent on inferior temporal areas.

These areas of the brain are very active during visual hallucinations. One

area in this location, the fusiformgyrus, is very active during the perception

of faces and complex visual stimuli. A superior temporal area near the conjunction

of the parietal and occipital lobes is essential for reading and writing.

The temporal lobe is in close proximity to, and shares strong connections

with, the limbic system. Thus, it is not surprising that the temporal lobe plays

a significant role in memory and emotions. Damage to the temporal cortex

leads to major deficits in the ability to learn and in maintaining a normal

emotional balance.

The largest cerebral lobe, comprising one-third of the cerebral cortex, is

the frontal lobe. It is involved in the greatest variety of neurological functions.

The frontal lobe consists of several anatomically distinct and functionally

distinguishable areas that can be grouped into three main regions.

Starting at the central sulcus (which divides the parietal and frontal lobes)

and moving toward the anterior limits of the brain, one finds, in order, the

precentral cortex, the premotor cortex, and the prefrontal cortex. Each of

these areas is responsible for different types of activities.

In 1870 German physicians Gustav Fritsch and Eduard Hitzig were the

first to stimulate the brain electrically. They found that stimulating different

regions of the precentral cortex resulted in different parts of the body moving.

Subsequent research identified a “motor map” that represents the body

in a fashion similar to the adjacent and posteriorly located somatosensory

map of the parietal lobe. The precentral cortex, therefore, can be considered

the primary area for the execution of movements.

The premotor cortex is responsible for planning the operations of the

precentral cortex. In other words, the premotor cortex generates the plan

to pick up a pencil, while the precentral cortex directs the arm to do so.

Thinking about picking up the pencil, but not doing so, involves more activity

in the premotor cortex than in the precentral cortex. An inferior

premotor area essential for speaking was discovered in 1861 by Paul Broca

and has since been named for him. Broca’s area, usually found only in the
left hemisphere, is responsible for coordinating the various operations necessary

for the production of speech.

The prefrontal cortex is the part of the brain most responsible for a variety

of complex thinking activities, foremost among them being decision

making and abstract reasoning. Damage to the prefrontal cortex often leads

to an impaired ability to make decisions, rendering the person lethargic and

greatly lacking in spontaneous behavior. Numerous aspects of abstract reasoning,

such as planning, organizing, keeping time, and thinking hypothetically,

are also greatly disturbed by injuries to the prefrontal cortex.

Research with patients who have prefrontal disturbances has demonstrated

the important role of this neurological area in personality and social

behavior. Patients with posterior prefrontal damage exhibit many symptoms

of depression: apathy, restlessness, irritability, lack of drive, and lack of ambition.

Anterior abnormalities, particularly in an inferior prefrontal region

called the orbitofrontal area, result in numerous symptoms of psychopathy:

lack of restraint, impulsiveness, egocentricity, lack of responsibility for one’s

actions, and indifference to others’ opinions and rights.

The prefrontal cortex also contributes to the emotional value of decisions,

smell perception, working memory (the current ability to use memory),

and the capacity to concentrate or shift attention. Children correctly

diagnosed with attention-deficit hyperactivity disorder (ADHD) often have

prefrontal abnormalities.

left hemisphere, is responsible for coordinating the various operations necessary

for the production of speech.

The prefrontal cortex is the part of the brain most responsible for a variety

of complex thinking activities, foremost among them being decision

making and abstract reasoning. Damage to the prefrontal cortex often leads

to an impaired ability to make decisions, rendering the person lethargic and

greatly lacking in spontaneous behavior. Numerous aspects of abstract reasoning,

such as planning, organizing, keeping time, and thinking hypothetically,

are also greatly disturbed by injuries to the prefrontal cortex.

Research with patients who have prefrontal disturbances has demonstrated

the important role of this neurological area in personality and social

behavior. Patients with posterior prefrontal damage exhibit many symptoms

of depression: apathy, restlessness, irritability, lack of drive, and lack of ambition.

Anterior abnormalities, particularly in an inferior prefrontal region

called the orbitofrontal area, result in numerous symptoms of psychopathy:

lack of restraint, impulsiveness, egocentricity, lack of responsibility for one’s

actions, and indifference to others’ opinions and rights.

The prefrontal cortex also contributes to the emotional value of decisions,

smell perception, working memory (the current ability to use memory),

and the capacity to concentrate or shift attention. Children correctly

diagnosed with attention-deficit hyperactivity disorder (ADHD) often have

prefrontal abnormalities.
The most complex thinking abilities are primarily attributable

to the thin layers that cover the two cerebral hemispheres—the

cortex. It is this covering of the brain that makes for the greatest differences

between the intellectual capabilities of humans and other animals. Both

hemispheres are typically divided into four main lobes, the distinct cortical

areas of specialized functioning. There are, however, many differences

among people, not only in the relative size of different lobes but also in how

much cerebral cortex is not directly attributable to any of the four lobes.

The occipital lobe is located at the back of the cerebral cortex. The most

posterior tissue of this lobe is called the striate cortex because of its distinctive

striped appearance. The striate cortex is also called the primary visual

cortex because it is there that most visual information is eventually processed.

Each of the layers of this cortical area is specialized to analyze different

features of visual input. The synthesis of visual information and the interpretation

of that result involve other lobes of the brain. The occipital

lobe also plays the primary role in various aspects of spatial reasoning. Activities

such as spatial orientation, map reading, or knowing what an object will

look like if rotated a certain amount of degrees all depend on this lobe.

Looking down on the top of the brain, a deep groove called the central

sulcus can be seen roughly in the middle of the brain. Between the central

sulcus and the occipital lobe is the parietal lobe. The parietal lobe’s predominate

function is the processing of the bodily sensations: taste, touch, temperature,

pain, and kinesthesia (feedback from muscles and joints). A parietal

band of tissue called the postcentral gyrus that is adjacent to the central

sulcus (posterior and runs parallel to it) contains the somatosensory cortex

in which the surface of the body is represented upside down in a maplike

fashion. Each location along this cortical area corresponds to sensations

from a different body part. Furthermore, the left side of the body is represented

on the right hemisphere and vice versa. Damage to the right parietal

cortex usually leads to sensory neglect of the left side of the body—the

person ignores sensory input from that side. However, damage to the left

parietal cortex causes no or little sensory neglect of the right side of the

body.

The parietal lobe is involved with some aspects of distance sensation. The

posterior parietal lobe plays a role in the visual location of objects and the

bringing together of different types of sensory information, such as coordinating

sight and sound when a person looks at someone who just called his

or her name. Some aspects of the learning of language also engage the operation

of the parietal cortex.

On the sides of each hemisphere, next to the temples of the head, reside

the temporal lobes. The lobes closest to the ears are the primary sites of the

interpretation of sounds. This task is accomplished in the primary auditory

cortex, which is tucked into a groove in each temporal lobe, called a lateral

sulcus. Low-frequency sounds are analyzed on the outer part of this sulcus;

higher-pitched sounds are represented deeper inside this groove. Closely

linked with auditory perception are two other major functions of the temporal

lobe: language and music comprehension. Posterior areas, particularly

Wernicke’s area, play key roles in word understanding and retrieval. More

medial areas are involved in different aspects of music perception, especially

the planum temporale.

The temporal cortex is the primary site of two important visual functions.

Recognition of visual objects is dependent on inferior temporal areas.

These areas of the brain are very active during visual hallucinations. One

area in this location, the fusiformgyrus, is very active during the perception

of faces and complex visual stimuli. A superior temporal area near the conjunction

of the parietal and occipital lobes is essential for reading and writing.

The temporal lobe is in close proximity to, and shares strong connections

with, the limbic system. Thus, it is not surprising that the temporal lobe plays

a significant role in memory and emotions. Damage to the temporal cortex

leads to major deficits in the ability to learn and in maintaining a normal

emotional balance.

The largest cerebral lobe, comprising one-third of the cerebral cortex, is

the frontal lobe. It is involved in the greatest variety of neurological functions.

The frontal lobe consists of several anatomically distinct and functionally

distinguishable areas that can be grouped into three main regions.

Starting at the central sulcus (which divides the parietal and frontal lobes)

and moving toward the anterior limits of the brain, one finds, in order, the

precentral cortex, the premotor cortex, and the prefrontal cortex. Each of

these areas is responsible for different types of activities.

In 1870 German physicians Gustav Fritsch and Eduard Hitzig were the

first to stimulate the brain electrically. They found that stimulating different

regions of the precentral cortex resulted in different parts of the body moving.

Subsequent research identified a “motor map” that represents the body

in a fashion similar to the adjacent and posteriorly located somatosensory

map of the parietal lobe. The precentral cortex, therefore, can be considered

the primary area for the execution of movements.

The premotor cortex is responsible for planning the operations of the

precentral cortex. In other words, the premotor cortex generates the plan

to pick up a pencil, while the precentral cortex directs the arm to do so.

Thinking about picking up the pencil, but not doing so, involves more activity

in the premotor cortex than in the precentral cortex. An inferior

premotor area essential for speaking was discovered in 1861 by Paul Broca

and has since been named for him. Broca’s area, usually found only in the

left hemisphere, is responsible for coordinating the various operations necessary

for the production of speech.

The prefrontal cortex is the part of the brain most responsible for a variety

of complex thinking activities, foremost among them being decision

making and abstract reasoning. Damage to the prefrontal cortex often leads

to an impaired ability to make decisions, rendering the person lethargic and

greatly lacking in spontaneous behavior. Numerous aspects of abstract reasoning,

such as planning, organizing, keeping time, and thinking hypothetically,

are also greatly disturbed by injuries to the prefrontal cortex.

Research with patients who have prefrontal disturbances has demonstrated

the important role of this neurological area in personality and social

behavior. Patients with posterior prefrontal damage exhibit many symptoms

of depression: apathy, restlessness, irritability, lack of drive, and lack of ambition.

Anterior abnormalities, particularly in an inferior prefrontal region

called the orbitofrontal area, result in numerous symptoms of psychopathy:

lack of restraint, impulsiveness, egocentricity, lack of responsibility for one’s

actions, and indifference to others’ opinions and rights.

The prefrontal cortex also contributes to the emotional value of decisions,

smell perception, working memory (the current ability to use memory),

and the capacity to concentrate or shift attention. Children correctly

diagnosed with attention-deficit hyperactivity disorder (ADHD) often have

prefrontal abnormalities.