Hybrid photoacoustic and electrophysiological recording of neurovascular communications in freely-moving rats.

Uncovering the relationships between neural activities and capillary-level hemodynamics such as blood flow and concentration of hemoglobin in the brain plays an important role in the study of animal behaviors and brain disorders. Here, we developed a miniature probe integrating a photoacoustic sensor and micro-electrodes to simultaneously record the dynamics of blood flow and total hemoglobin inside a single capillary and the activities of surrounding neurons with high spatiotemporal resolution in freely-moving rats. In the somatosensory cortex of rats, we observed: 1) early hemodynamic response prior to the changes in local field potential during pentylenetetrazol-induced localized and generalized seizure onsets in both freely-moving and anesthetized rats; and 2) different hemodynamic and neural responses to generalized seizure onsets between freely-moving and anaesthetized rats. These findings suggest that this high-resolution hybrid technique will enable a wide range of new studies of behaviors and brain disorders in small animals.