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2. BRAIN MECHANISMS: NEUROBIOLOGY AND NEUROANATOMY
Fig. 2.4 Structural and functional regions of the cerebral cortex
The cerebral cortex is structurally differentiated into four lobes. The cerebral
cortex can also be differentiated into functionally specialized areas.
Primary motor cortex Central fissure
DORSAL
Primary
somatosensory cortex
Frontal lobe Parietal lobe
Occipital
lobe
ANTERIOR POSTERIOR
Primary
visual cortex
Temporal lobe (mostly hidden
from view)
Primary auditory cortex Cerebellum
(mostly hidden from view)
Source: Reproduced from Carlson, 1988, with permission from the publishers.
cortex is involved in executing this function. Similarly, there is a primary
sensory cortex that receives information from each of these sense organs.
Information from the primary sensory areas goes to sensory association areas
of the cortex, which are involved in perception and memory connected with
the sense organs. Here information from several sense organs can be
combined to form complex perceptions (Fig. 2.5). The cortex is involved in
many aspects of substance dependence, from the primary effects of
psychoactive drugs on sensations and perceptions, to the complex behaviours
and thoughts involved in drug craving and uncontrolled substance use.
Neuroimaging techniques such as positron emission tomography (PET) have
shown changes in areas of the cortex following both short-term and long-
term substance use (see Box 2.1 and Chapter 4 for details).
Beneath the cortex are several other important structures. The basal ganglia
(Fig. 2.6) are structures involved in voluntary motor behaviour and consist
of the caudate, putamen, globus pallidus and amygdala (the amygdala is also
part of the limbic system, and will be discussed in the next section). The
caudate and putamen together are known as the striatum. Just below the
striatum is a key area for substance dependence and motivation, known as
the nucleus accumbens, which is made up of core and shell regions. (Note:
clusters of neurons with similar structure and function make up “nuclei” of
the brain, not to be confused with the nuclei of individual cells). The nucleus
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