The effects of early postnatal modification of body shape on the somatosensory-visual organization in mouse superior colliculus.

Different regions of the body of an animal have their own shape and location within visual space. Accordingly, in the superior colliculus there are somatosensory-visual bimodal neurons receiving tactile and visual input from the same region of space. In newborn mice, we changed the position of some body parts within visual space in order to see what happened to the alignment of the somatosensory and visual receptive fields of superior colliculus bimodal neurons. To do this, we modified the shape of the head by displacing the superior vibrissae and the ears, normally in the superior portion of visual space, into the inferior visual space. Analogously, we bent the inferior vibrissae into the superior visual space. At the sixth postnatal week we recorded from somatosensory-visual bimodal neurons of the deep layers of the superior colliculus and found that the tactile and visual receptive fields were aligned. Neurons receiving tactile input from the downward-displaced superior vibrissae and ears showed visual receptive fields in the inferior portion of visual space, whereas neurons receiving input from the upward-displaced inferior vibrissae showed visual receptive fields in the superior visual space. These results show that an experience-dependent interaction between visual and somatosensory inputs occurs during development, and that early exposure to abnormal visual-somatosensory experience modifies the organization of multisensory neurons in the superior colliculus.