Texture detection and discrimination by the whisker/barrel-cortex system in awake behaving rats

Robert A. Jenks, Tim Warren, Loren M. Frank, and Garrett B. Stanley
Division of Engineering and Applied Sciences
Harvard University

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Many rodents actively sense the environment using an extensive whisker system on the snout, which has a large somatotopic representation in primary somatosensory cortex. Although many studies have investigated this system in anesthetized rats, there has a been a growing recognition of the importance of making electrophysiological recordings in a awake behaving animals. We have demonstrated the ability to make multiple (6) simultaneous single unit extracellular and multiple (8) field potential recordings from the barrel region of primary somatosensory cortex in awake, freely behaving adult female Long-Evans rats. In our pilot study, the rats were trained to run on a linear track for a chocolate reward. Part of the track was textured, and part was open. At one end, we presented various textures for the rats to whisk. Preliminary results show that using only the trial-averaged spike rate of single units, we were able to distinguish between the presence or absence of texture. Further work will employ a behavioral paradigm that requires the rat to make a choice after a whisker-based discrimination between different textures. We hope to use spike and EEG recordings to determine whether the behavioral discrimination can also be made neurometrically, and to what degree the fidelity of the discrimination depends on the attentional state of the animal. Supported by the Whitaker Foundation, grant RG-01-0087