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NEUROSCIENCE OF PSYCHOACTIVE SUBSTANCE USE AND DEPENDENCE

functions – concerning, for example, water balance, body temperature and
reproductive hormones – as well as for responding to changes in these
functions. The hypothalamus also secretes hormones that travel to the nearby
posterior lobe of the pituitary gland. The thalamus functions as a relay station
for sensory and motor information going to and from the cortex to other areas
of the brain and body.
The telencephalon of the forebrain is the most highly developed area of
the brain, and is composed of two cerebral hemispheres separated by the
longitudinal fissure (Fig. 2.3). The outermost layer of the brain is the cortex,
which is made up of layers of nerve cells or neurons, and has a highly folded
organization that increases its surface area and the number of neurons that
it contains. Beneath the cortex run millions of axons that interconnect the
neurons and allow the different areas of the brain to communicate and to
coordinate behaviour.
Each hemisphere of the brain is divided into four lobes: frontal, parietal,
temporal, and occipital (Fig. 2.3). Different areas of the cortex are specialized
for different functions (Fig. 2.4). The motor association cortex, for example,
is involved in coordinating movements of the body, and the primary motor

Fig. 2.3 Cerebral hemispheres
The telencephalon is composed of two cerebral hemisphere separated
by the medial longitudinal fissure. Each hemisphere is subdivided into
four lobes: frontal, parietal, occipital, and temporal.

Central sulcus Frontal
Frontal
Parietal Parietal
Occipital Occipital

Lateral
fissure
LATERAL Temporal MEDIAL Temporal

Longitudinal Frontal
fissure
Central
sulcus
Parietal
Temporal

DORSAL Occipital VENTRAL
Source: Reproduced from Kolb & Whishaw, 1996, with permission from the publishers.

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Chapter_2 22 19.1.2004, 11:27