Representations of odors in the early olfactory pathway
Friday 21 October 2011
to 11:00 at
Benjamin Auffarth (KTH/CSC/CB)
The organization of representations in the brain has been observed to locally reflect subspaces of inputs that are relevant to behavioral or perceptual feature combinations, such as in areas receptive to lower and higher-order features in the visual system. For the perception of smells, this analysis is not as straightforward, because the physical metric is unclear, however some studies reported local zones for several combinations of physical properties on the olfactory bulb level at the level of secondary neurons and before at the synapse level between first-order and secondary neurons. In a systematic study of representations of odors on a dataset of activity-related images comprising over 300 odors and covering the whole spatial array of the first synaptic level in the olfactory system, we found continuous spatial representations for several physical properties and we tried to compare them by their relevance to spatial activations. In a second study, we grouped odors together by perceptual categories, such as floral and fruity and others, and again found continuous spatial zones. Furthermore, we found that distances between spatial representations were related to perceptual differences in humans as reported in literature. In a third study, we modeled axon convergence from olfactory receptor neurons to the olfactory bulb. Sensory neurons were stimulated by a set of biologically-relevant odors, which were described by a set of properties that varied with activation at the olfactory bulb. We found that spatial relationships between representational zones correlated with perceptual differences. Together, these results could suggest organizational principles of representations at the olfactory bulb level.