It is now widely recognised that biological psychiatry is rapidly
coming into its own. For over the last three decades dramatic
advances in this young discipline have been made, all of which
attest to the staying power of the experimental method. Those who
made this revolution in knowledge happen are a breed of
investigators availing themselves of the tools of molecular
biology, pharmacology, genetics, and perhaps, above all, the
technology of neuroimaging. The introduction of the
interdisciplinary method of approach to the study of
psychopathology had made it very clear that neuroimaging, as a set
of techniques, is unique in that it is gradually providing us with
evidence supporting Kraepelin's original view that mental illness
is closely associated with abnormal changes in the brain.
Broadly speaking, there are presently two structural techniques in
neuroimaging - computed tomography and magnetic resonance imaging
(MRI) - and three functional techniques - single photon emission
tomography (SPECT), positron emission tomography and magnetic
resonance imaging (fMRI). Through PET technology, for example, we
have learned that, in early brain development, the primitive areas,
mostly the brain stem and thalamus, are the first to show high
activity in an infant. This is followed by the development of
cortical areas by year one. Between the ages of four to 10, the
cortex is almost twice as active in the child as in the adult. This
information alerts us to what might happen in the way of trauma in
abused children, especially those under the age of three. Child
abuse increases the risk of physical changes, not only in the
stress systems, but also in brain development (Glaser and
Weissman). In addition to the difficult problem of post-traumatic
stress disorder (PTSD), we have to take into account the
possibility of other types of mental illness as the consequences of
child abuse. These include depression, eating disorders, and drug
and alcohol problems.
The combination of PET and fMRI represents a more remarkable
example of the power of neuroimaging since the two have made it
feasible to map accurately in vitro identifiable cortical fields,
or networks. In a landmark NIH investigation of human cortical
reorganization (plasticity), persuasive evidence was brought
forward showing that the process of learning as a motor task
involves a specific network of neurons. These neurons occur in the
cortical field that is responsible for that particular task. Such
findings are important partly because they provide evidence
supporting the current notion that labor in the cortex is divided
among ensembles of specialized neurons that cooperate in the
performance of complex tasks. Cooperation, then, in this, sense
implies crosstalk among ensembles and that signals are both
processed and retransmitted to neighbouring ensembles. To
understand the workings of these ensembles, much better spatial and
temporal resolution in functional brain mapping is required. This
can be achieved with an NMR instrument whose magnet is 4.1 Tesla or
more.
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