Symposium 1

Formation of the neural network for recognition of spatial orientation depends on precise coordination of synaptic integration at different stages of development. Within the vestibular nucleus, the proportion of gravity-related neurons expressing NMDAR or AMPAR subunits changed during postnatal development. Whole-cell patch-clamp experiments further demonstrated developmental change in the contribution of glutamate receptors to miniature- and evoked-excitatory postsynaptic currents: NMDAR predominates in neonates while AMPAR in young adults. Developmental switches in NMDAR subunits were also found. Furthermore, ionotropic glutamate receptors were involved in the conversion of silent synapses to functional ones. The induction of such synaptic events occurred in correlation with the ability of vestibular nuclear neurons to encode spatial orientations. With perinatal blockade of NMDAR in the vestibular nucleus, we documented a postnatal period critical for the orderly establishment of a gravity-related horizontal spatial map in the inferior olive. The impact of such perturbation on motor learning behavior during this critical period of susceptibility will be discussed. Taken together, our results suggest that refinement of the developing vestibular circuitry during a postnatal critical period is crucial for coherent recognition of gravity-related spatial orientations in the mature animal. Acknowledgments: Supported by HK RGC.link_to_subscribed_fulltex