Olfaction as an active sense: how sniffing shapes early odor coding

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

Portoroz, Eslovenia

Congreso; 18th European Chemoreception Research Organization Congress; 2008

European Chemoreception Research Organization

We typically think of sensory systems as passively generating faithful representations of external stimuli at initial, low-level stages of the nervous system and then performing increasingly complex transformations of these representations as information propagates to higher levels. Likewise, themodulation of sensory codes during behavior – for example, as a function of behavioral context or attentional state – is typically thought to occur at higher nervous system levels. This talk will discuss recent findings from our laboratory demonstrating that, in the olfactory system, odor representations in the behaving animal can be transformed at low levels – as early as the primarysensory neurons themselves - via a variety of different mechanisms related to the active acquisition of olfactory information. First, changes in odor sampling behavior (i.e. – ‘sniffing’) can dramatically and rapidly alter primary odor representations by changing the strength and temporal structure of sensory input to the olfactory bulb, effectively shaping which features of the olfactorylandscape are emphasized and likely altering how information is processed by the olfactory bulb network. Second, neural substrates exist for presynaptically modulating the strength of sensory input to the bulb as a function of behavioral state. The systems most likely to be involved in this modulation – cholinergic and serotonergic centrifugal inputs to the bulb – are linked to attention and arousal effects in other brain areas. Together, sniffing behavior and presynaptic inhibition have the potential to mediate – or at least contribute to – sensory processing phenomena such as figure-ground separation, intensity-invariance, and context-dependent and attentional modulation of response properties. Thus, even low-level representations of olfactory information are actively shaped in the behaving animal as it samples the olfactory world around it.