It is believed that visual perception occurs largely based on interactions of nerve cells, or neurons, in the visual cortex of the brain. The visual cortex itself is a structure composed of several layers of different classes on neurons. These classes are distinguished by the shape of the cells, their connections, their response to particular patterns of light stimulation or motion or color, and by the chemicals called neurotransmitters that the neurons secrete at their functional connections, called synapses. Two important neurotransmitters of a group called mono-amines are known as NE (norepinephrine) and 5-HT (5-hydroxy- tryptamine). The pathways for neurons in the brain to the cells they innervate are fairly well known for both these compounds, and monoamines are known to modulate activity in several neural systems. The equipment provided will allow a new approach to understanding modulation of cortical activity. The study is a preliminary effort to determine at the level of single cells in the well-described layers of the primate visual cortex, how information processing is modulated by the similarly layered and specifically connected neurons secreting monoamines. Highly controlled visual stimuli will be used to excite visual cortical cells, and when the responses are characterized, highly localized pharmacological applications of monoamines will be made by microelectrode. Changes in visual properties attributable to the monoamines which are specific to a cell class, lamina, or cortical area may be described in terms of their potential significance for perception and behavior. This work will have impact on psychology of arousal and attention, as well as on visual and sensory neuroscience, and provide a novel bridge between these communities.
