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Behavioral Neuroanatomy 

The brain, and the brain alone, is the source of our pleasures, joys, laughter, and 
amusement, as well as our sorrow, pain, grief, and tears. It is especially the organ we 
use to think and learn, see and hear, to distinguish the ugly from the beautiful, the bad 
from the good, and the pleasant from the unpleasant. The brain is also the seat of 
madness and delirium, of the fears and terrors which assail by night or by day, of 
sleeplessness, awkward mistakes and thoughts that will not come, of pointless 
anxieties, forgetfulness and eccentricities. —Hippocrates 

The human nervous system consists of the central nervous 
system (CNS) and the peripheral nervous system (PNS). The 
CNS contains the brain (cerebral hemispheres, basal ganglia, 
and thalamus); brainstem (pons, medulla, and midbrain); and the 
spinal cord. The PNS consists of somatosensory (afferent) 
neurons, motor (efferent) neurons, and autonomic neurons.  
 

The cerebral cortex 

The area of the brain most closely associated with behavior is 
the cerebral cortex, although subcortical areas are also involved. 
The activity of the cortex can be segregated functionally into 
sensory, motor, and association areas that act together to 
ultimately affect behavior. 
The cortex also can be divided anatomically into frontal, 
temporal, parietal, and occipital lobes, as well as limbic lobes 
that contain the medial parts of the frontal, temporal, and 
parietal lobes.  
 
Frontal lobes 
The frontal lobes have four major subdivisions. The first two, 
the motor strip and the supplemental motor area, are involved in 
motor behavior; the third (Broca's area) in language. The fourth 
division is the prefrontal cortex.

 

Clinically occurring events, 

surgically imposed changes, and neuroimaging studies provide 
evidence for the behavioral and personality functions of the 
prefrontal cortex. The famous case of Phineas Gage, a man who 
received a large prefrontal lobe lesion in an accident in the mid-
nineteenth century, first demonstrated the personality functions 
of the frontal lobes. Although he had remarkably few obvious 
neurological problems, Gage demonstrated a significant 
personality change after his brain lesion healed. A formerly 


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nonaggressive person, Gage showed outbursts of anger after the 
accident. A respectful, energetic, persistent, and organized 
person before his accident, he began to show an inability to 
carry out plans and a lack of self-control and concern for others. 
In a similar way, some patients who have had bilateral 
prefrontal lobotomy, a surgical procedure used in the past to 
treat serious psychiatric illness, retain intellectual functioning 
but show uncharacteristic apathy and lack of goal-directed 
behavior after the surgery. 
Perseveration, engaging in repeated unnecessary behavior and 
thought, disinhibition, and sudden outbursts of temper, as well 
as reinstatement of the infantile sucking ,palmomental and 
rooting reflexes (frontal release signs) are seen in patients with 
prefrontal lobe damage; this is now known as prefrontal lobe 
syndrome. Interestingly, schizophrenia and obsessive-
compulsive disorder (OCD), both of which are characterized by 
personality and affective changes, are associated with decreased 
bilateral prefrontal cortical activity as measured by functional 
magnetic resonance imaging (fMRI) and positron emission 
tomography (PET) . 
Although personality changes are associated with damage to the 
entire prefrontal cortex, clinical and other evidence indicates 
that the three major prefrontal subdivisions”the orbitofrontal 
region, the dorsolateral convexity, and the medial region”have 
specialized behavioral functions. The dorsolateral convexity 
influences behavior and personality and has executive 
responsibilities involving activities like formulating plans, 
maintaining attention and concentration, and changing problem-
solving strategies when needed. The orbitofrontal cortex is a 
center for the biological control of inhibition, emotions, and 
drive states. It is also part of the dopamine-driven reward circuit 
of the brain and is activated in addicts exposed to drug-related 
cues . The medial region has connections to the basal ganglia 
and accessory cortical motor areas and is involved primarily in 
motor activity. Damage to each of these subdivisions results in 
characteristic behavioral abnormalities The emotional-
behavioral functions of the frontal lobes are lateralized. Lesions 


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of the left prefrontal area, both cortical and subcortical, can 
result in depression, whereas lesions of the right are more likely 
to produce manifestations of elevated mood. Similarly, fMRI 
studies reveal that positive mood is associated with activation of 
the left prefrontal cortex and stress with activation of the right 
prefrontal cortex. 
 

Limbic lobe 

Because the neurons within the limbic lobe form circuits that 
play a major role in emotions, the limbic lobe has been called 
the limbic system. Its primary functions are to mediate between 
the hypothalamus and cerebral cortex and to modulate the 
activity of the autonomic nervous system . First described by 
Papez in 1937 and expanded later to include other areas, the 
limbic system or Papez circuit contains the hippocampus, fornix, 
amygdala, septum, part of the thalamus, the cingulate gyrus, and 
related structures . The limbic system also acts on the 
hypothalamus, which in turn influences endocrine control of 
emotions via secretion of hormones. Damage to the limbic lobe, 
particularly the amygdala and hypothalamus, results in 
behavioral abnormalities. Recently, neuroimaging studies 
indicate that, like the prefrontal cortex, the volume of limbic 
structures like the amygdala and hippocampus are reduced in 
patients with schizophrenia. 
 

The basal ganglia 

The basal ganglia are a group of nuclei that receive information 
from the entire cerebral cortex and project it to the frontal lobes 
via the thalamus. There are four structural components of the 
basal ganglia: 

• 

Striatum (containing the caudate nucleus and the putamen) 

• 

Pallidum (also called the globus pallidus) 

• 

Substantia nigra 

• 

Subthalamic nucleus 

The basal ganglia function to translate the desire to execute 
movement into actual movement. Conditions causing damage to 
its nuclei can result in neuropsychiatric illnesses with motor 


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symptoms. For example, over activity of the striatum or damage 
to the substantia nigra results in Parkinson's-like symptoms like 
the inability to initiate movement (bradykinesia). Underactivity 
of the striatum and shrinking of the caudate nucleus are 
associated with the symptoms of Huntington's disease. Damage 
to the caudate is associated also with Tourette's syndrome, 
whereas lesions of the pallidum and subthalamic nucleus result 
in conditions characterized by sudden, uncontrolled limb 
movements (hemi….?) 
 
Hemispheric specialization 
The left side of the brain controls the right side of the body. 
Because approximately 90% of the population preferentially 
uses the right hand, the left hemisphere of the brain is referred to 
as the dominant hemisphere. Communication between the 
cerebral hemispheres occurs via structures including the corpus 
callosum, anterior commissure, hippocampal commissure, and 
habenular commissure.  
Because the left hemisphere is associated with language 
function, damage to this hemisphere results in impairment of 
skills such as speech, writing, and reading in almost all right-
handed people and in most left-handed people. The right, or 
nondominant hemisphere, is associated primarily with 
perception and also with spatial relations, body image, 
recognition of faces and music, puzzle-solving, map-reading, 
and musical and artistic ability. Damage to the right hemisphere 
has motor sequelae and indirect effects on behavior but does not 
usually affect intelligence or personality directly. 
There are sex differences in functional organization of the brain. 
For example, women generally have a larger corpus callosum 
and anterior commissure and appear to have better 
interhemispheric communication than men. When doing a 
verbal task, women typically use both hemispheres, whereas 
men show activation of only one hemisphere. The better-
developed right hemispheres of men may in part explain the 
consistently documented male advantage in executing spatial 
tasks 


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Consciousness, coma, and brain death 

The thalamus and reticular formation, a network of neurons in 
the brainstem, are the brain regions most closely involved in 
arousal and consciousness. In contrast to cortical lesions 
(particularly left-sided lesions), which must be extensive to 
cause loss of consciousness, relatively small, localized lesions of 
either of these structures, particularly the reticular formation, 
can cause profound loss of consciousness or coma, nonsleep loss 
of consciousness that extends for a prolonged period. Similarly, 
lesions that disrupt connections between the brainstem and 
thalamus can result in coma.  
A patient in a profound coma has no conscious cognitive 
function. If this condition is not reversible, the person is said to 
be in a persistent vegetative state. Whether to maintain a person 
who is in this state on life support is an important ethical issue 
in medicine  

TABLE  Neuropsychiatric Anatomy: Function and Dysfunction 

REGION/DIVISION MAJOR FUNCTIONS 

EFFECTS OF LESION ON 

BEHAVIOR 

Frontal lobes 
Dorsolateral 
convexity 

Planning for future action 
(executive functions) 

• 

Decreased motivation, 
concentration and attention  

• 

Disorientation  

• 

Mood disturbances 

Orbitofrontal cortex  Control over biological 

drives 

• 

Disinhibition and 
inappropriate behavior  

• 

Poor judgment  

• 

Lack of inhibition or remorse 
(pseudopsychopathic 
behavior) 

Medial cortex 

Control of movement 

• 

Apathy  

• 

Decreased spontaneous 
movement (akinesia)  

• 

Gait disturbances  

• 

Incontinence 

Temporal lobes 

• 

Memory  

• 

Learning  

• 

Emotion  

• 

Impaired memory  

• 

Psychomotor seizures  

• 

Changes in aggressive 
behavior  


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• 

Auditory 
processing 

• 

Inability to understand 
language (i.e., Wernicke's 
aphasia [left-side lesions]) 

LIMBIC LOBES 
Hippocampus 

• 

Memory storage 

• 

Poor new learning 

Amygdala 

• 

Coordination of 
emotional states, 
particularly anger 
and aggression, 
with somatic 
responses 

• 

Klأuer-Bucy syndrome 
(decreased aggression, 
increased sexuality, 
hyperorality)  

• 

Decreased conditioned fear 
response  

• 

Inability to recognize facial 
and vocal expressions of 
anger in others 

Parietal lobes 

• 

Somatic sensation 
and body image 

• 

Impaired IQ  

• 

Impaired processing of visual-
spatial information, (i.e., 
cannot copy a simple line 
drawing or a clock face 
correctly [right-sided lesions])  

• 

Gerstmann's syndrome (i.e., 
cannot name fingers, write, 
tell left from right, or do 
simple math, and impaired 
processing of verbal 
information [left-sided 
lesions]) 

Occipital lobes 

• 

Vision 

• 

Visual hallucinations and 
illusions  

• 

Inability to identify 
camouflaged objects  

• 

Blindness 

 

 
 
 




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