The Journal of Neurophysiology Vol. 83 No. 6 June 2000, pp. 3578-3582
Copyright ©2000 by the American Physiological Society
Onset of Cross-Modal Synthesis in the Neonatal Superior
Colliculus is Gated by the Development of Cortical Influences
M. T.
Wallace and
B. E.
Stein
Department of Neurobiology and Anatomy, Wake Forest University
School of Medicine, Winston-Salem, North Carolina 27157
Wallace, M. T. and
B. E. Stein.
Onset of Cross-Modal Synthesis in the Neonatal Superior
Colliculus is Gated by the Development of Cortical Influences. J. Neurophysiol. 83: 3578-3582, 2000. Many neurons
in the superior colliculus (SC) are able to integrate combinations of
visual, auditory, and somatosensory stimuli, thereby markedly affecting
the vigor of their responses to external stimuli. However, this
capacity for multisensory integration is not inborn. Rather, it appears
comparatively late in postnatal development and is not expressed until
the SC passes through several distinct developmental stages. As shown
here, the final stage in this sequence is one in which a region of
association cortex establishes functional control over the SC, thus
enabling the multisensory integrative capabilities of its target SC
neurons. The first example of this corticotectal input was seen at
postnatal day 28. For any individual SC neuron, the onset of
corticotectal influences appeared to be abrupt. Because this event
occurred at very different times for different SC neurons, a period of 3-4 postnatal months was required before the adult-like condition was
achieved. The protracted postnatal period required for the maturation
of these corticotectal influences corresponded closely with estimates
of the peak period of cortical plasticity, raising the possibility that
the genesis of these corticotectal influences, and hence the onset of
SC multisensory integration, occurs only after the cortex is capable of
exerting experience-dependent control over SC neurons.
