Basic NeuroscienceSensory and cognitive neurophysiology in rats, Part 1: Controlled tactile stimulation and micro-ECoG recordings in freely moving animals

•High-density micro-ECoG over the whole rat somatosensory system.•A novel co-registration mof anatomical and functional brain surface data.•A head-mounted device provides controlled tactile stimulation to the rat's snout.

BackgroundWe have developed a setup for rats that allows for controlled sensory input to an animal engaged in a task while recording both electrophysiological signals and behavioral output.New methodWe record electrophysiological signals using a novel high-density micro-electrocorticography (micro-ECoG) grid that covers almost the whole somatosensory system. We dealt with the well-known difficulty that the rat uses its whisker system in an active (motor-controlled) way to explore its environment by designing a head-mounted device that stimulates the rat's snout in a way unaffected by whisker movements.ResultsWe replicate the spatial specificity of early evoked responses in somatosensory and auditory cortex. In a companion paper (Cognitive Neurophysiology in Rats, Part 2: Validation and Demonstration) we validate our setup and show for the first time that the ECoG can be used to record evoked responses in a signal that reflects neural output (spiking activity).Comparison with existing methodsCompared with high-density wire recordings, micro-ECoG offers a much more stable signal without readjustments, and a much better scalability. Compared with head-fixed preparations, our head-mounted stimulator allows to stay closer to the rat's natural way of collecting sensory information.ConclusionsFor perceptual and cognitive research, our setup provides a unique combination of possibilities that cannot be achieved in other setups for rodents.