Event Details

Peripheral sensory inputs to the brain are generally presumed to be purely "bottom-up," that is, to strictly reflect the external sensory stimulus, but this presumption has rarely been tested experimentally. Recent developments in optical neurophysiology permit the direct observation of neural signals from the nose to the brain's olfactory bulb, where the peripheral inputs from the olfactory nerve converge with projections from other brain regions. This talk will present recent evidence that the synaptic output of the olfactory sensory neurons (the very first cells in the olfactory system) actually reflects a wealth of "top-down" information, including the natural statistics of the olfactory environment, the learned ecological significance of an odor (i.e. whether it predicts a threat), and even the animal's expectations about stimuli in other sensory modalities. These data ultimately suggest that there is no such thing as a purely bottom-up sensory representation in the olfactory brain.