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Emilie SyedEffect of sensory stimulation in rat barrel cortex, dorso-lateral striatum and on cortico-striatal functional connectivity

Abstract :

The striatum integrates sensory and motor information to enable action selection and behavioral reinforcement.
There is a large topographical projection from the rat barrel cortex to widely distributed areas of the striatum. The response of the striatum to sensory stimuli at a network level is, however, not comprehensively understood. We used a 10Hz/100ms air puff, allowing un-damped movement of multiple whiskers, to look at functional connectivity in contralateral cortex and striatum in response to sensory stimulation. Simultaneous recordings of cortical and striatal local field potentials (LFPs) were made under isoflurane anaesthesia in 15 male Brown Norway rats. Four electrodes were placed in barrel cortex while the dorsolateral striatum was mapped with 500µm-spaced micro-electrodes spanning the left striatum medio-laterally and moved both dorso-ventrally and rostro-caudally with 500µm steps. This resulted in a maximum of 315 striatal positions per animal. Significant event-related responses were found to be unevenly distributed throughout the dorso-lateral striatum in ~50% of recorded positions. In the frequency domain during the stimulation period, only ~5% of recorded positions displayed significant total power increases in the LFP, especially at 10-20Hz, and ~3% showed significant induced LFP power, mostly above 20Hz. Analysis of cortico-striatal imaginary coherence indicated stimulus induced changes in functional connectivity. This was further investigated using phase locking indices. About 10% of striatal recordings showed a significant phase-locking of spontaneous LFP activity with one given cortical recording, but no increase in phase-locking during stimulation. In addition, a small minority of cortico-striatal LFP pairs showed a significant increase in phase-locking in response to the stimulus. In conclusion, sparsely distributed neuronal ensembles within dorso-lateral striatum respond to vibrissae stimulation and their functional connectivity to cell populations in barrel cortex may be reflected in spontaneous and stimulus induced phase locking.

Supported by EU grants IST-2000-28127 (AMOUSE), IST-2005-27268 (POP), by BMBF-MOS and by the Volkswagen Foundation.

Selected publications

Mahmoud M. Iravani, Emilie Syed, Michael J. Jackson, Louisa C. Johnston, Lance A. Smith, Peter Jenner (2005), A modified MPTP treatment regime produces reproducible partial nigrostriatal lesions in common marmosets, European Journal of Neuroscience 21 (4), 841–854. 

Thomas Boraud