The demonstration that learning is accompanied by changes in
the effectiveness of connections has led us to a new way of
viewing the relationship between social and biological
processes in the generation of behavior. There is a tendency
in medicine and psychiatry to think that biological determinants
of behavior act on a different level of the mind than do social
and functional determinants. For example, it is still customary
to classify psychiatric illnesses into two major categories:
organic and functional. Organic mental illnesses include the
dementias and the toxic psychoses; functional mental illnesses
include the various depressive syndromes, the schizophrenias,
and the neurotic illnesses. This distinction dates to the
nineteenth century, when neuropathologists examined the
brains of patients coming to autopsy and found gross and
readily demonstrable disturbance in the architecture of the
brain in some psychiatric diseases but not in others.

Diseases that produced anatomical evidenc of brain lesions were called organic; those lacking these features were
called functional.

The data reviewed in this web site show that this distinction is unwarranted. Everyday events - sensory
stimulations, deprivation and learning - have profound biological consequences, causing an effective disruption of
synaptic connections under some circumstances and a reactivation of connections under others. It therefore is
incorrect to imply that certain diseases (organic diseases) affect mentation by producing biological changes in the
brain, whereas other diseases (functional diseases) do not. All mental processes are biological and any alteration
in those processes is organic.

Rather than making the distinction along biological and nonbiological lines, it is more appropriate to ask the
following questions in each type of mental illness: To what degree is this biological process determined by genetic
and developmental factors, to what degree is it determined by a toxic or an infectious agent and to what degree is
it environmentally or socially determined? Even in the most socially determined mental disturbances, the end result
is biological, since it is the activity of the brain that is being modified. Insofar as social intervention, such as
psychotherapy or counseling, works, it must work by acting on the brain, and quite likley on the connections
between nerve cells. Moreover, the absence of demonstrable structural changes does not rule out the possibility
that important changes are nevertheless occurring, although they may be undetectable with available techniques.
To clarify these issues it will be necessary to develop a neuropathology of mental illness that is based on function
as well as on structure. Various imaging techniques such as positron emision tomography and magnetic resonance
imaging, may someday be developed enough to allow the noninvasive exploration of the human brain on a cell-
biological level - the level of resolution that is required to understand the mechanisms of mentation and of mental
disorders.

Cellular studies on synapse development lead one to think of three overlapping ontogenetic stages of synaptic
modifications. The first stage, that of synapse formation, occurs primarily in the developing animal and is under
genetic and developmental control. The second stage, that of validation and fine tuning of newly developed
synapses, occurs during critical early periods of development and requires an appropriate pattern of environmental
stimulation. The third stage, the regulations of the transient and long-term effectiveness of synapses, occurs
throughout later life and is determined by day-to-day experience. One of the implications of this view is that the
potentialities for all behaviors of which humans are capable are built into the brain by genetic and developmental
mechanisms. Environmental factors and learning bring out these latent capabilities by altering the effectiveness of
preexisting pathways, thereby leading to the expression of new patterns of behavior.

It follows from this argument that everything that occurs in the brain - from the most private thoughts to commands
for motor acts - represents organic, or biological, processes. We do not yet have the tools to examine complex
ideas and feelings on the cellular level, but the pace of neurobiological research is quickening, in the not too distant
future we may begin to have a cellular neuropsychology of human mentation and, with it, a new and therapeutically
more efficacious approach to mental illness.

The merger of neurobiology and neuropsychology is filled with promise. We have seen how modern psychology,
whic has shown that the brain stores an internal representation of experiential events, converges with neurobiology,
which has shown that this representation can be understood in terms of individual nerve cells and their
interconnections. From this convergence we have gained a new perspective on perception, learning and memory.
We have also seen that the concept of mentation loses none of its power or its beauty when the experimental
approach is moved from the domain of psychology into the range of molecular biology. On the contrary, the
combined developments in psychology and in neurobiology promise to renew interest in aspects of mentation that
until now have been out of experimental reach. Although the earlier behaviorist psychology was content to explore
observable aspects of behavior, advances in modern cognitive psychology indicate that investigations that fail to
consider internal representations of mental events are inadequate to account for behavior. This recognition of the
importance of internal representations, a conclusion instrinsic to psychoanalytic thought, might have been
discouraging as recently as 15 years ago, when internal mental processes were essentially inaccessible to
experimental analysis. However, subsequent developments in cell and molecular biology have made it feasible to
explore elementary aspects of internal mental processes. Thus, contrary to some expectations, biological analysis is
unlikely to diminish the interest in mentation or to make mentation trivial by reduction, rather, cell and molecular
biology have merely expanded our vision, allowing us to perceive previously unanticipated interrelationships
between biological and psychological phenomena.

The boundary between behavior and biology is arbitrary and changing. It has been imposed not by the natural
contours of the disciplines, but by lack of knowledge. As our knowledge expands, the biological and behavioral
disciplines will merge at certain points and it is at these points of merger that our understanding of mentation will rest
on particularly secure ground. The merger of biology and cognitive psychology is more than a merger of methods
and concepts. Ultimately, the joining of these two disciplines represents the emerging conviction that a coherent and
biologically unified description of mentation is possible.

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