ABDUCENS NERVE RESPONSES OF THE FROG DURING HORIZONTAL LINEAR ACCELERATION - DATA AND MODEL

Abducens nerve responses of frogs were evoked by sinusoidal oscillatio ns on a horizontal linear sled. The depth of modulation of these respo nses and their phases depended on the orientation of the head with res pect to the direction of linear acceleration. Longitudinal acceleratio n evoked abducens responses that consisted of two discharge maxima per stimulus cycle. At consecutively more oblique head orientations, one of these two discharge maxima increased and the other decreased. Trans verse accelerations evoked abducens responses that consisted of only o ne discharge maximum per stimulus cycle. Removal of the labyrinthine o rgans on one side abolished these responses in the contralateral abduc ens nerve but did not affect the responses in the ipsilateral abducens nerve. The latter result indicates that the responses in each abducen s nerve originate from hair cells on the contralateral utricle. The ex perimentally determined modulation and phase values and their dependen ce on the orientation angle of the acceleration vector were used to ch aracterize a functional cluster of hair cells located medially with re spect to the striola in a fanlike sector on the utricle ('lateral rect us fan'). Parameters of this fan were used to develop a model that sat isfactorily simulates the recorded abducens responses. This model pred icts a majority of afferents with excitatory and a few afferents with inhibitory contributions to the abducens nerve responses. The phasic r esponse components of about 90% of these afferents are larger than the ir tonic response components.