The superior colliculus is a small, visual nucleus in the midbrain of all mammals including humans and plays a major role in the control of visual orientation and visual attention. Most of the previous research to understand how it participates in these behaviors has been concerned with specific sensory inputs. However, the superior colliculus also has inputs from other systems not thought to convey specific sensory information, but which can also influence the responses of collicular cells. The most prominent of these is the noradrenergic input which appears to have strong influences upon attention. This research will examine how the noradrenergic input to the superior colliculus modulates information-processing in this nucleus, including: (1) which of the many different types of cells are affected by this neurotransmitter, (2) the membrane and/or ionic events associated with changes in cellular responsiveness, and (3) the circuitry underlying the effects of this neurotransmitter. Very fine electrodes are used to record the activity of neurons in order to assay the effects of norepinephrine on neurons. Other techniques being used combine immunocytochemistry and electron microscopy in order to understand the synaptic organization of inputs to the superior colliculus.
