A THEORY OF COOPERATIVITY MODULATION IN NEURAL NETWORKS AS AN IMPORTANT PARAMETER OF CNS CATECHOLAMINE FUNCTION AND INDUCTION OF PSYCHOPATHOLOGY

Recent research in computational neuroscience has suggested that psych osis associated with disturbed catecholamine neurotransmission may res ult from disturbances in the gain parameters of neural networks that t here same secondary neurotransmitters are thought to control. We propo se a mathematical model based upon cooperativity theory used in thermo dynamics to explain how the gain parameter that momentarily increases the effect upon the post-synaptic cell of a given weighted connection from the presynaptic cell could be instantiated in the fluctuating ele ctrical conductance of the dendrite of a neuron without requiring exte nsive ion transport or utilization of the ATP energy cycle. More speci fically we propose that catecholamine neurotransmission serves to main tain the dendrite in a cooperative state with regard to changes in ele ctrical conductance due to impulse traffic alone. In this way we suppl y the neuron with an activity driven gain parameter that not only incr eases volume of neuronal output at very low energy cost but that also upscales cooperative effects at the mechanico-chemical level of the de ndrite to the network level itself. An important implication of this m odel is that two extreme states for dendritic electrical conductance w ill occur if cooperativity is lost at the level oi catecholamine deple tion or excess due to drug effects. These are the AND gate effect in w hich dendritic conductance is so low that the neuron requires extensiv e synaptic activity in order to output significantly. We correlate thi s state with negative symptoms in schizophrenia and psychomotor retard ation in depression as well as the rigidity in Parkinsonism. The other extreme is represented by the OR gated dendrite in which conductance is so high that even noisy input to the dendrite will lead to signific ant nerve cell output. We correlate this condition with the positive s ymptoms of schizophrenia, the agitated features the tremors of Parkins onism.