Electrophysiology of the visual system: from neuroscience to human neuropharmacology.

Stimulus-dependent cortical and precortical responses to visual stimulation are substantially unaffected by vigilance shifts and reflect functional characteristics (related to the physical properties of stimulus) of information processing in the CNS. These can be independently activated and selectively affected by drug action; stimulus/response functions allow in experimental conditions a control of spontaneous variability. Chemically specified subsystems of the visual system are identified and a functional (micro)-dissection of cortical and precortical (retinal) circuits is possible based on the effects of pharmacological activation/inactivation, with segregation of components of the evoked response. Practicable hypotheses exist about the functional roles of dopaminergic, GABAergic and cholinergic transmission in the visual system. Comparable responses to stimuli conveying similar information can be obtained with limited inter-species differences from animals and man in experimental conditions varying from in vitro basic research to clinical studies, to the use of neuroactive drugs as test condition in man.