Complex information processing systems – such as biochemical, computational, electronic or mechanical – all rely on functional plugins which can implement key elementary operations within integrated chains of actions. In the realm of music production for example, digital and analog plugins or units provide audio signal filters and effects which are essential to the creation of coherent music mixes. To list a few: gates filter out unwanted noise, compressors and limiters homogenize sound intensity and prevent saturation, equalizers filter out certain frequencies, delays control sound timing or provide sequence replay, and reverbs control sound duration. Similar key plugins tailored to spatiotemporal image processing are encountered in the realm of digital photography and videography. The comparison doesn’t stop here and extends to literally all physical and virtual tools designed by humans, as well as to the functional architecture of living systems. Biological plugins exist at all complexity levels – from molecules to integrated behaviors. My research focuses on characterizing the functional plugins provided by simple circuits of neurons in the brain, commonly referred to as neuronal “microcircuits”. Drawing on what we know about information processing at the single neuron level, focusing on microcircuits is a next step towards understanding information processing in complex neuronal networks. Combining electrophysiological, imaging, and genetic methods, I study the structure and function of excitatory and inhibitory neuronal microcircuits, as well as the signaling and integrative properties of the neuronal cells that constitute them. My experimental work focuses on major brain structures involved in sensory processing, information learning, and spatial representation such as the thalamus, cortex, and hippocampus. In past studies, I have shown that di-synaptic inhibitory circuits acting as multi-function plugins can perform powerful, millisecond-precise operations such as: filtering out de-synchronized excitatory synaptic inputs, preserving the temporal information contained in presynaptic spikes, preventing excitatory input saturation, and filtering out or boosting specific input frequencies. These operations are crucial to extracting specific information contained in complex neuronal signals conveyed from the senses or brain centers, and to endowing neurons and circuits with the abilities to detect – hence represent – meaningful information contained in spike series. My research not only aims at deciphering how basic operations performed by microcircuits participate in higher brain functions, but also in which contexts are microcircuits engaged or modulated, as well as how disease alter them and how therapeutic methods can correct them.
