International Journal of Neural Systems, Vol. 7, Nos. 4 (1996) 355
© World Scientific Publishing Company
NOISE IN MODELS OF NEUROLOGICAL AND PSYCHIATRIC DISORDERS
NOISE IN MODELS OF NEUROLOGICAL AND PSYCHIATRIC DISORDERS
MANFRED SPITZER<
Department of Psychiatry, University of
Heidelberg, Voss-Str.4, 69115 Heidelberg, Germany
MANFRED NEUMANN
Department of Biology, University of Freiburg,
Schaenzlestr. 3, 79104 Freiburg, Germany
The concept of noise has only recently been applied
to modelling neuropsychiatric disorders. Two examples of such
models are presented.
- A phantom limb is a neurological condition after the
amputation of an extremity. It consists of sensations of the
presence of the lost limb and has been attributed to cortical as
well as non-cortical mechanisms. A neural network model of
phantom limbs is proposed which can parsimoniously account for a
large number of clinical features and recent findings of
cortical map plasticity after deafferentation. In trained
self-organizing feature maps, deafferentation was simulated.
Reorganization is shown to be driven by input noise. According
to the model, the production of input noise by the deafferented
primary sensory neuron drives cortical reorganization in amputees.
No such noise is generated and/or conducted to the cortex in
paraplegics.
- Several clinical features of schizophrenia have been
related to the ratio of signal to noise in neuronal information
processing. In particular, dopamine - which has been implicated
in the causation of schizophrenia for decades - has been
proposed to modulate signal-to-noise ratio. Data are presented
which suggest that schizophrenic thought disorder is the result
of a hypodopaminergic state and concomitant increased effects of
noise in semantic information processing. Possible functions of
noise in the nervous systems are discussed.
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