Understanding how nerve cells are wired together into functional circuits is essential to understanding how the brain works. Traditional anatomical techniques can reveal the structure of neuronal circuits. However, determining which nerve cells actually communicate with one another in a complex circuit is more challenging. Recent advances in genetics have ushered in a new age of functional circuit mapping. We can genetically ‘tag’ specific populations of neurons in the intact mouse brain with a light-activated channel, allowing us to selectively activate spatially-defined subsets of neurons with light. Using this photostimulation-based approach, we plan to map the strengths of local circuit connections in the olfactory bulb, a part of the brain that processes sensory information about smell. We use the olfactory system because it is well-characterized, genetically tractable, and functionally important to the animal. The research described here will allow us to address fundamental questions about sensory processing that were previously not possible to address using traditional techniques. Future work will focus on how the activation of specific circuits using light elicits or influences odor perception. The ‘optogenetic’ approach described here can also be further exploited to study other parts of the mammalian brain.
Thomas Bozza, Ph.D.