VISUAL-EVOKED RESPONSES IN THE SALMON TELENCEPHALON CHANGE DURING SMOLT TRANSFORMATION

During smolt transformation. salmon behaviour changes dramatically and the fish are imprinted to their natal stream. This brief episode is a ccompanied by changes in neurochemistry and connectivity of the brain. Comparing visual-evoked potentials, recorded from optic tectum and te lencephalon by glass microcapillaries, we found pronounced differences before and after smolt transformation in the telencephalon. In the fo rebrain of presmolts. only small short-latency responses are present w hereas postsmolts display large long-latency waves with characteristic dynamic properties in addition. These findings suggest changes in the functional role of the tetencephalon during smolt transformation.