Temporal structure of sensory input to the olfactory bulb.

CAREY, R.M.; VERHAGEN, J.V.; WESSON, D.W.; PÍREZ, N.; WACHOWIAK, M.

Tahoe City, California, Estados Unidos

Conferencia; Chemical Senses: Receptors and Circuits; 2009

Keystone Symposia

Sensory inputs to the olfactory bulb (OB), which form the first olfactory representation in the brain, are temporally complex and tightly controlled by sniffing behavior. Here, we have characterized the temporal structure of the olfactory receptor neuron (ORN) inputs in the awake animal for the first time. We use calcium imaging to monitor ORN input to the OB in awake, head-fixed rats performing olfactory discrimination tasks. During low-frequency sniffing behavior, each inhalation of odorant elicits a burst of action potentials with a duration of ~100 ms and a relatively slow mean rise-time of ~90 ms, suggesting a progressive increase in ORN activation as odorant flows through the nasal cavity. These activation patterns are diverse, but odorant-specific, with latencies and rise-times remaining uniform across successive inhalations of the same stimulus. During high-frequency sniffing, the temporal coherence between ORN inputs and the respiratory cycle is strongly reduced. These results suggest that olfactory representations - even among sensory neurons - are strongly shaped by sampling behavior. A critical  question currently being addressed is whether the dynamics of ORN input to the OB can account for the temporal complexity of responses in mitral/tufted cells, the principle output neurons of the OB.