Baptiste GIRIN

DOES RESPIRATORY RYTHMS PACES BRAIN ACTIVITY?

Cerebral rhythms are known to be involved in numerous functions. Particularly, they could allow brain areas to communicate over long distances. To be efficient, inter-area communication requires the different brain rhythms to be synchronized between areas.

We hypothesize that respiratory rhythm could act as a central clock for cerebral rhythms. If our hypothesis is true, one can expect neuronal activity to be influenced by respiration in a large brain network. This is what we wanted to explore in our study. We have recorded respiration and neuronal activity in different brain areas in the freely-moving rat during different vigilance states. Local field potentials were recorded in six brain areas: olfactory bulb, anterior piriform cortex, CA1 and dentate gyrus of hippocampus, S1 in primary somesthetic cortex and V1 in the visual cortex.

Analyses allowed us to show that: 1) respiration parameters (frequencies and amplitude) are significantly different during the different vigilance states, 2) a respiration-related modulation appears synchronizing the different structures only during periods of quiet wakening, when respiration rhythm is around 2 Hz, 3) Gamma oscillations are respiration-modulated in all brain structures only when olfactory structures are themselves strongly impacted.

These preliminary results reveal a respiratory modulation in a wide cerebral network in the rat. In this condition, respiratory rhythm could serve as a common reference for communication between different brain networks.