A sealed cranial window system for simultaneous recording of blood flow, and electrical and optical signals in the rat barrel cortex

We have developed a new sealed cranial window technique which allows the ma nipulation of simultaneously and independently multiple sensor probes, such as a glass microelectrode and a laser-Doppler probe. possible. Furthermore , normal intracranial pressure (4 mmHg) can be maintained throughout the cr aniectomy and the experiment. Using this technique, we have measured the ne uronal activity and local cerebral blood flow together with the intrinsic o ptical properties in the rat barrel cortex during mechanical stimulation of the whiskers. The onset of the field response recorded by an extracellular electrode in the principal barrel columns occurred about 8 ms from the beg inning of stimulation. These responses were well correlated with the whiske r displacements (3 Hz, 2 s). The local cerebral blood flow, measured by las er-Doppler flowmetry, started to increase about 0.5 s after the first field response, peaked at about 1.7 s, and then gradually waned. A similar time- course of changes in the local blood volume was observed by simultaneous in trinsic optical imaging at the hemoglobin-isosbestic wavelength (570 nm). T hese results suggest that our technique would be useful for assessing the m echanism underlying neurovascular coupling under physiological conditions i n vivo. (C) 2000 Elsevier Science B.V. All rights reserved.