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2. BRAIN MECHANISMS: NEUROBIOLOGY AND NEUROANATOMY

Another region relevant to the neuroscience of dependence is the limbic
system (Fig. 2.7). This is an interconnected series of structures that are
important in relation to emotion, motivation and learning. The limbic system
plays a vital role in the development of dependence, and interacts with the
cortex and nucleus accumbens. Important structures of the limbic system
are the hippocampus, which plays an important role in memory, and the
amygdala, which is critical in emotional regulation. All of these areas receive
sensory information from other brain areas to help coordinate the
appropriate emotional and behavioural response to external stimuli.

The neuron

Communication in the brain takes place between nerve cells or neurons.
Psychoactive substances alter many aspects of communication between
neurons, as will be discussed below. Neurons are highly specialized cells that
exist in many shapes, sizes and varieties. However, they share the following
basic structural regions: cell body or soma, dendrites, axon, and terminal
buttons (Fig. 2.8) (Carlson, 1988).

Fig. 2.7 Major structures of the limbic system

Right cingulate gyrus Left cingulate gyrus
Longitudinal fissure

Left fornix Left thalamus

Septum Left hippocampus
Olfactory bulb

Medulla

Hypothalamus
Mammillary body

Left amygdala

Source: Reproduced from Pinel, 1990, with permission from the publishers.

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