Lateralization of responses to vibrissal stimulation: connectivity and information integration in the rat sensory-motor cortex assessed with fMRI.

Rats move their whiskers or vibrissae to gain sensory information about the world surrounding them. A single whisker can work as an independent detector but normal whisking involves the use of several vibrissae in a bilateral fashion. Here we used blood oxygen level dependent (BOLD) contrast to acquire functional magnetic resonance images (fMRI) of the rat brain activity during uni- and bilateral whisker stimulations with different timing schemes under Isoflurane anesthesia. Experiments were performed to assess the integration of bilateral information produced by normal whisking behavior. First, we showed that it was possible to obtain BOLD whisker activations using Isoflurane harmless for the animals and thus allowing for future repetitive/longitudinal studies. Second, we obtained different BOLD activation patterns depending on the number of stimulated whiskers and timing of the stimulation scheme. Third, we found lateralization of BOLD activations in the somatosensory-motor cortex. It manifested itself in considerably larger activations in the right hemisphere during equal bilateral whisker stimulation. Fourth, we found Granger Causality Analysis (GCA) to be a useful tool in information integration analysis, as it reproduced the stimulus specific Cross-correlation Analysis results. Both analyses showed that the amount of whiskers stimulated and the timing of stimulation lead to specific dynamic connectivity patterns. Finally, by adding directionality information GCA revealed meaningful lateralization of information processing in the rat whisker system consistent with the observed BOLD activation patterns.