The effect of sound direction on frequency tuning in mouse inferior collicular neurons

This study examined the effect of sound direction on frequency tuning of inferior collicular (IC) neurons of mice under free field stimulation conditions. Fewer than 20% of IC neurons studied were spontaneously active. Discharge patterns can be described as phasic on responders, phasic on-off responders, off responders, choppers and tonic responders. The frequency tuning curves (FTCs) of IC neurons can be described as narrow, intermediate or broad. Although sound direction typically had little effect on most best frequencies (BFs), sharpness of FTCs increased as sound direction changed from contralateral angles to ipsilateral angles. Sound delivered from the upper and lower portions of the frontal auditory space also appeared to produce sharper frequency tuning than from the front. Possible mechanisms underlying this direction dependent frequency tuning are discussed.