Matt Wachowiak

Assistant Professor of Biology
and the Department of Biomedical Engineering
Ph.D., University of Florida, 1996

Olfactory coding and synaptic processing, imaging, neurophysiology

My research focuses on how the nervous system encodes and processes information about odors. Odor coding starts with olfactory receptor neurons in the nose, where odor molecules activate specific combinations of receptor neurons. Which receptor neurons are activated depends on the chemical structure and concentration of the odor. We are interested in understanding how the pattern of receptor neuron activity encodes information about an odor as this information is transmitted to the brain, and also how this code is transformed as the information passes through different stages of processing in the brain.

The neural code for an olfactory stimulus involves organized, patterned activity across thousands or millions of neurons. This patterned activity is spatially organized, so that the location of neurons in the brain can encode olfactory information, and also temporally organized, so that the timing of neural activity in the brain can encode olfactory information. We study the relationship between these patterns and an odor stimulus using imaging techniques, which allow us to visualize spatial and temporal patterns of neural activity across an entire brain region.

Because we are also interested in how the code for odors changes from one level to the next, and from one class of neuron to the next, a major goal is to image patterns of activity in populations of specific cell types, but in the intact nervous system. As a first step, we have developed a method that allows us to selectively image patterns of activity in olfactory receptor neurons at the point where they synapse onto their targets in the olfactory bulb. This approach allows us to literally see what the nose tells the brain about odors. So far we have learned that, even at this early stage of the pathway, the code for odors is complex: Odors elicit patterns of input to the bulb that are spatially organized yet distributed across much of the bulb, and which change dramatically with odor concentration. Input to the bulb is also temporally organized, so that spatial patterns can change with time in an odor-specific way.

Research in the lab will focus on understanding more about the coding and processing of odor information. For example, how does the code for odors change as one progresses further into the nervous system? This question can be addressed by selectively imaging activation of second-order neurons in the olfactory bulb and comparing the response patterns to those of the receptor neurons. We can also ask how specific synaptic interactions affect odor coding by characterizing olfactory bulb circuitry in vitro, and then using pharmacological or molecular techniques to alter those interactions in vivo while imaging responses to odor stimulation. Using this approach, we have already learned that receptor neuron input to the brain can be modulated by a presynaptic inhibitory pathway that regulates transmitter release from receptor neurons to neurons in the CNS. Future experiments will ask how this presynaptic inhibition alters how odors are encoded. Finally, because smelling an odor involves an active behavioral process (sniffing), we are also interested in how the neural representation of an odor depends on parameters which are controlled by the animal, such as sniffing frequency and intensity. There is therefore considerable interest in integrating our imaging techniques with behavior, with the goal of understanding how, and at what level, the code for odors is modulated during olfactory-related behavior and learning.

Visit his website at http://people.bu.edu/dmattw for additional information.

Wesson DW, Carey RC, Verhagen JV, Wachowiak M. 2008.Rapid encoding and perception of novel odors in the rat. PLoS Biology. 6:e82

Verhagen JV, Wesson DW, Netoff T, White JA, Wachowiak M 2007. Sniffing controls an adaptive filter of sensory input to the olfactory bulb. Nature Neurosci 10:631-639.

Spors, H., Wachowiak, M., Cohen, L. B., and Friedrich, R. W. 2006. Temporal dynamics and latency patterns of receptor neuron input to the olfactory bulb. J Neurosci/ 26/, 1247-1259.

McGann, J. P., Pirez, N., Gainey, M. A., Muratore, C., Elias, A. S., and Wachowiak, M. 2005. Odorant representations are modulated by intra- but not interglomerular presynaptic inhibition of olfactory sensory neurons. Neuron/ 48/, 1039-1053.

Wachowiak M., Heyward P.M., McGann J.P., Puche A., Shipley M.T. 2005. Inhibition of olfactory receptor neuron input to olfactory bulb glomeruli by suppression of presynaptic calcium influx. J Neurophysiol 94:2700-2712.

Wachowiak M., Denk W., Friedrich R.W. 2004. Functional organization of sensory input to the olfactory bulb glomerulus analyzed by two-photon calcium imaging. Proc Nat Acad Sci USA 101: 9097-9102.

Bozza T., McGann, J.P., Mombaerts P., Wachowiak M. 2004. In vivo imaging of neuronal activity by targeted expression of a genetically encoded probe in the mouse. Neuron 42: 9-21.

Wachowiak M, Cohen LB.J . 2003. Correspondence between odorant-evoked patterns of receptor neuron input and intrinsic optical signals in the mouse olfactory bulb. Neurophysiol. Mar;89(3):1623-39.

Wachowiak M, Cohen LB, Ache BW. 2002. Presynaptic inhibition of olfactory receptor neurons in crustaceans. Microsc Res Tech. Aug 15;58(4):365-75.

Wachowiak M, Cohen LB, Zochowski M. 2002. Distributed and concentration-invariant spatial representations of odorants by receptor neuron input to the turtle olfactory bulb. J Neurophysiol. 87: 1035-1045.

Wachowiak M, Cohen LB. 2001. Representation of odorants by receptor neuron input to the mouse olfactory bulb. Neuron 32:725-737.

Lam Y-W, Cohen LB, Wachowiak M, Zochowski MW. 2000. Odors elicit three different oscillations in the turtle olfactory bulb. J Neurosci 20:749-762.

Wachowiak M, Cohen LB. 1999. Presynaptic inhibition of primary olfactory afferents mediated by different mechanisms in lobster and turtle. J Neurosci 19:8808-8817.

Wachowiak M, Cohen LB. 1998. Presynaptic afferent inhibition of lobster olfactory receptor cells: Reduced action potential propagation into axon terminals. J Neurophysiol 80:1011-1015.