Effects of early binocular enucleation on auditory and somatosensory coding in the superior colliculus of the rat

The present study aimed at investigating the effects of early visual deprivation (bilateral neonatal enucleation) on auditory and somatosensory coding in the polysensory deep layers of the superior colliculus of the rat. The proportion of cells responding to auditory and somatosensory stimulation and the receptive field properties of single neurons were assessed in both normal and enucleated rats. As expected, in enucleated rats there was a drastic increase in the number of unresponsive units and visual responses could no longer be evoked. Most importantly, the proportion of cells that responded to auditory stimulation was drastically reduced. However, the few cells that remained responsive to auditory stimulation were well tuned to noise stimuli presented in both azimuth and elevation, principally in the contralateral hemifield. Enucleation also increased the proportion of cells responding to somatosensory stimulation, particularly to the vibrissae. Implications in terms of neural plasticity and functionality are discussed.