The Role of Central Monoaminergic Systems in Arousal and Selective Attention

The work described here is part of an ongoing set of studies aimed at characterizing the physiological actions and anatomical organization of the monoaminergic projection systems to the rat cerebral cortex. The underlying theme of this work is that the endogenous monoamines, norepinephrine NE and serotonin 5-HT, serve to modulate central neuronal responsiveness to afferent synaptic inputs and by so doing participate in the cognitive process of selective attention. Individual studies conducted during the period of support have investigated 1 the effects of NE and 5-HT on postsynaptic membrane responses of cortical neurons layers IIIII and V to threshold and subthreshold level stimulation of synaptic input pathways, 2 the effects of NE and 5-HT on receptive field and tuning properties of rat and cat visual cortical neurons, 3 the distribution of locus coeruleus and dorsal raphe neurons that project to principal relay sites along the visual and somatosensory pathways in rat, and 4 the actions of cocaine on response properties of central neurons. Overall, these data provide further support for the contention that the diffusely distributed monoamine systems of the mammalian brain may enhance the performance of target neuronal circuits as a function of changing behavioral conditions.