A SENSORY BRAIN MAP FOR EACH BEHAVIOR

Multiple brain maps are commonly found in virtually every vertebrate s ensory system, Although their functional significance is generally rel atively little understood, they seem to specialize in processing disti nct sensory parameters, Nevertheless, to yield the stimulus features t hat ultimately elicit the adaptive behavior, it appears that informati on streams have to be combined across maps, Results from current lesio n experiments in the electrosensory system, however, suggest an altern ative possibility, Inactivations of different maps of the first-order electrosensory nucleus in electric fish, the electrosensory lateral li ne lobe, resulted in markedly different behavioral deficits, The centr omedial map is both necessary and sufficient for a particular electrol ocation behavior, the jamming avoidance response, whereas it does not affect the communicative response to external electric signals, Conver sely; the lateral map does not affect the jamming avoidance response b ut is necessary and sufficient to evoke communication behavior, Becaus e the premotor pathways controlling the two behaviors in these fish ap pear to be separated as well, this system illustrates that sensory-mot or control of different behaviors can occur in strictly segregated cha nnels from the sensory input of the brain all through to its motor out put, This might reflect an early evolutionary stage where multiplicati on of brain maps can satisfy the demand on processing a wider range of sensory signals ensuing from an enlarged behavioral repertoire, and b ridging across maps is not yet required.