Development of single-cell binaural interaction in the inferior colliculus of the rat

The importance of early binaural stimulation for the expression of binaural interaction in the rat inferior colliculus was investigated following monaural or binaural sound deprivation. Stimulus deprivation was achieved by unilateral or bilateral ligation of the external auditory meatuses of rats at ten days or one month of age. At three months of age the ligatures were removed, and responses of single units in the inferior colliculus were recorded while click stimuli were presented binaurally. Interaural intensity differences were varied over a range of 40 dB in 10-dB steps. Those rats monaurally deprived from ten days of age showed a marked loss of binaural interaction as manifested in an absence of ipsilateral inhibition of unit activity. Animals monaurally deprived from one month of age, or those binaurally deprived from ten days or one month, exhibited normal binaural interaction. The results indicate that the development of binaural interaction at the inferior colliculus of the rat is dependent on symmetrical binaural stimulation during the first postnatal month in the rat.