The representation of auditory space in the mammalian superior colliculus

The superior colliculus (SC) is involved in orienting responses to sensory stimuli1 and contains detailed sensory and motor maps1–3. The visual and somatosensory maps have been well documented4–15 and are topographic representations of the primary receptor surfaces. However, the formation of an ordered map of auditory space is rather more problematic as it requires either reorganization of monaural information or combination of information from both ears16,17. Nevertheless, such an ordered map has been demonstrated in the midbrain of the barn owl18 and there have been indications that a similar map occurs in mammals7–9,12,13,19–21, although a recent study suggests that this is not the case in the cat22. Here we report briefly the results of our study, showing that auditory space is precisely represented in the deep layers of the guinea pig SC. This map of auditory space resembles the visual map in that cells responding to sounds in the anterior contralateral field are located rostrally, while those responding to sounds in the posterior contralateral field are located in caudal SC.