Chronically monitoring of optogenetic stimulation-induced neural and hemodynamic response

Understanding the link between neuronal activity and cerebral hemodynamics, known as neurovascular coupling (NVC), is critical for studying cerebral vascular dysfunctions. Optogenetics, which involves using light to control electrical activity of opsin-expressing neurons, is an approach to monitor and modulate functions of specific neurons in neuronal networks. Recent studies suggested that optogenetic stimulation induced hemodynamic response could be a good model for studying the mechanism of NVC. The aim of the study is to develop an optogenetic platform for long-term monitoring of the cerebral hemodynamics. An implantable optrode for optical stimulation and neural recording in addition to near-infrared spectroscopy (NIRS) recording have been developed. Through fiber optics, the optogenetic stimulation was introduced into ChR2-positive glutamatergic neuron of primary motor cortex (M1). Neural and hemodynamic responses were evaluated using local field potentials (LFPs) and NIRS recordings. An in-line optical filter was applied to filter off the blue light collected from M1 and to avoid interfering the NIRS measurement. The results showed the classic waveform of evoked hemodynamic response was obtained alongside of LFPs during optogenetic stimulation. Overall, our innovative optogenetic-NIRS interface could provide long-term observation on cerebral hemodynamics during optogenetic modulation.