Journal of Neuroscience, Vol 6, 3297-3308, Copyright © 1986 by Society for Neuroscience
The emergence of tuning in newly generated tuberous electroreceptors
HH Zakon
Tuning curves of afferent electroreceptive fibers in the anterior lateral
line nerve of the weakly electric fish, Sternopygus macrurus, indicate that
the tuberous electroreceptors of each individual are well- tuned to its own
electric organ discharge (EOD) frequency. In order to study how receptor
tuning may develop, new receptor organs were induced to form in
regenerating cheek skin, and their tuning properties were compared with
those of intact receptors from the same fish. At 3 weeks after the onset of
regeneration, new receptors of a given fish were broadly tuned with best
frequencies (BFs) lower than that fish's EOD frequency and the BFs of its
own intact tuberous receptors. Three weeks later, regenerated receptors of
the same fish were indistinguishable from intact receptors in BF, although
tuning curves were occasionally slightly broader than normal. To determine
if the presence of an ongoing electric field is necessary for the genesis
of proper tuning, receptors were allowed to regenerate in fish deprived of
their EODs. At 6 weeks, tuning curves of these receptors also had BFs that
were tuned similarly to intact receptors and to each individual's
characteristic EOD frequency (determined by recordings of the pacemaker
nucleus in the medulla). Thus, as regenerating receptors mature, they
gradually become more sharply tuned and tuned to progressively higher
frequencies until reaching the correct BF, which matches the EOD frequency;
however, tuning to the appropriate EOD frequency occurs without reference
to the ongoing electric field.