Final Report Summary - NEUROCHEMS (From neurons to behavior: analysis of the mechanisms underlying sensory coding and plasticity in chemical senses)
This research project proposed to study the cellular and network mechanisms controlling sensory perception. In particular, we aimed to precise how sensory stimuli are coded by brain networks and how these representations may be influenced by experience or modulatory brain centers. In order to address these general questions, we proposed to study olfaction as model sensory system. The olfactory system is central to the behavior of rodents (animal models that we study), is highly plastic and largely modulated by the neuromodulatory brain centers. This system has a relatively simple organization (only two synapses from sensory neurons to the cortex…), integrates cues and drive specific behavior. We used a combination of genetic, electrophysiological, imaging and behavioral methods to study how odor information is processed in the central nervous system as it moves from the periphery to higher areas of the brain. During the course of this project, we could show that:
- Some of our work represents a significant step forward in understanding the origin of some functional brain imaging signals and our data provide crucial information about different physiological correlates of neuronal activity that can be monitored by large-scale non-invasive functional imaging techniques.
- Some of work proposes to revise the current view about olfactory processing in rodents: dense coding is used in the olfactory bulb for natural odorants at their native concentrations whereas the odor code becomes sparser at lower concentration.
- Some of our work shows that odor representation does not just include a response during the presence of the stimulus but also after odor cessation – an odor afterimage generated internally in the brain. It shows that afterimages are common to all sensory systems, and may reflect that afterimages are useful for sensory processing, either as a form of short-term memory, or to help shape networks for learning
- Some of our work shows that odorant perception is causally linked to changes of ensemble network activity which involve the interplay between excitatory and inhibitory neurons of the olfactory bulb.
- Some of our work identified a novel population of olfactory bulb neurons ideally positioned to control the transfer of odorant information from sensory neurons to cortex while being under the control of both bottom-up and top-down inputs including neuromodulatory centers.
- Some of our work reports the existence of a novel form of plasticity mediated by associative learning in the olfactory system. This experience-dependent plasticity occurs surprisingly early in the pathway.
- Some of our work represents a significant step forward in understanding the origin of some functional brain imaging signals and our data provide crucial information about different physiological correlates of neuronal activity that can be monitored by large-scale non-invasive functional imaging techniques.
- Some of work proposes to revise the current view about olfactory processing in rodents: dense coding is used in the olfactory bulb for natural odorants at their native concentrations whereas the odor code becomes sparser at lower concentration.
- Some of our work shows that odor representation does not just include a response during the presence of the stimulus but also after odor cessation – an odor afterimage generated internally in the brain. It shows that afterimages are common to all sensory systems, and may reflect that afterimages are useful for sensory processing, either as a form of short-term memory, or to help shape networks for learning
- Some of our work shows that odorant perception is causally linked to changes of ensemble network activity which involve the interplay between excitatory and inhibitory neurons of the olfactory bulb.
- Some of our work identified a novel population of olfactory bulb neurons ideally positioned to control the transfer of odorant information from sensory neurons to cortex while being under the control of both bottom-up and top-down inputs including neuromodulatory centers.
- Some of our work reports the existence of a novel form of plasticity mediated by associative learning in the olfactory system. This experience-dependent plasticity occurs surprisingly early in the pathway.