Information processing in the olfactory system.

Problems solved by the olfactory system are generally similar to those solved by other sensory systems such as vision or audition. Our research on olfaction is targeted to reveal the general principles and the neural circuitry involved in the encoding of sensory information in the brain. In collaboration with experimentalists, we construct detailed biophysical models of insect and vertebrate olfactory systems to study odor encoding, processing and learning. This study offers the promise of insight into a successful and perhaps optimal biological algorithm for processing complex information.



Using the structure of inhibitory networks to unravel mechanisms of spatiotemporal patterning

Neuronal networks exhibit a rich dynamical repertoire, a consequence of both the intrinsic properties of neurons and the structure of the network. It has been hypothesized that inhibitory interneurons corral principal neurons into transiently synchronous ensembles that encode sensory information and sub-serve behavior. How does the structure of the inhibitory network facilitate such spatiotemporal patterning? We established a relationship between an important structural property of a network, its colorings, and the dynamics it constrains. Using a model of the insect antennal lobe we show that our description allows the explicit identification of the groups of inhibitory interneurons that switch, during odor stimulation, between activity and quiescence in a coordinated manner determined by features of the network structure. This description optimally matches the perspective of the downstream neurons looking for synchrony in ensembles of pre-synaptic cells and allows a low-dimensional description of seemingly complex high-dimensional network activity.


Dynamic and distributed memory in olfaction

Early olfactory processing is fundamentally similar in animals as different as mammals and insects. Because of this similarity there have been very significant advances in understanding of sensory encoding by primary sensory cells the olfactory epitheliums of these animals. Yet a similar understanding of how sensory information is transformed across the few first synapses in the brain remains elusive. The primary objective of our research is to understand how early processing in the brain transforms sensory input about odors, and how this transformation is modified by associative and nonassociative plasticity.  We are testing a hypothesis that olfactory memory is distributed across two main levels of the odor processing, the antennal lobe and the mushroom body, and both areas play critical roles in supervised and unsupervised odor learning.


Role of oscillations and synchrony in olfactory coding

Despite years of studies, the question how olfactory information is represented in the brain remains open. The long-term goal of our research is to reveal intrinsic and synaptic mechanisms that are involved in encoding olfactory information. It has been known for some time that odor stimulation leads to synchronized firing in populations of olfactory neurons – neuronal oscillations. While the basic mechanisms of oscillations in neuronal circuits have been described before, the nature of the “transient” synchronization of olfactory neurons (manifested by groups of neurons being transiently synchronized together in odor specific matter) remained unknown. We develop detailed models of the insect olfactory system to reveal synaptic mechanisms that explains transient synchronization of olfactory neurons to understand fundamental mechanisms that underlie how olfactory signals are encoded at the subsequent levels of olfactory processing.