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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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          Chapter_2                23                              19.1.2004, 11:27
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