TOLERANCE TO SOUND INTENSITY OF BINAURAL COINCIDENCE DETECTION IN THENUCLEUS LAMINARIS OF THE OWL

Neurons of the owl's nucleus laminaris serve as coincidence detectors for measurement of interaural time difference. The discharge rate of n ucleus laminaris neurons for both monaural and binaural stimulation in creased with sound intensity until they reached an asymptote, Intense sounds affected neither the ratio between binaural and monaural respon ses nor the interaural time difference for which nucleus laminaris neu rons were selective. Theoretical analysis showed that high afferent di scharge rates cause coincidence detectors with only excitatory input t o lose their selectivity for interaural time difference when coinciden ce of impulses from the same side becomes as likely as that of impulse s from the two sides. We hypothesize that inhibitory input whose stren gth increases with sound intensity protects nucleus laminaris neurons from losing their sensitivity to interaural time difference with inten se sounds.