Electrosensory systems in fish

A close integration of behavioral, neurophysiological, and neuroanatomical approaches has guided research on the neural basis of electrosensation and the generation of behaviors associated with this modality. By postulating neuronal implementaions of specific computations in sensory information processing, behavioral studies have been curcial in focusing studies at the neuronal level onto behaviorally relevant structural and functional aspects. Physiological and anatomical studies have analyzed (a) neural networks underlying the distributed processing of sensory information, (b) the role of descending recurrent pathways and eference copy mechanisms for the filtering of incoming information, c) the significance of multiple topographic representations for sensory information processing, and d) the modulation of sensory and motor structures through various transmitters and receptor subtypes. Developmental studies have explored the significance of steroid hormones for the tuning of electroreceptors to the frequency of an endogenous neuronal oscillator which drives the electric current pulses necessary for their stimulation. Embryological studies have revealed that the development of mechanoreceptors and electroreceptors in the fish's skin is induced by the innervation of primary afferent nerve fibers which are specific with regard to their central connections as well as with regard to the type of receptor induced in the periphery.