Layer-specific interhemispheric functional connectivity in the somatosensory cortex of rats: resting state electrophysiology and fMRI studies

• DOI: 10.1007/s00429-015-1073-0
• Publication Date: 2015-06-15T09:31:03Z
• Authors: Kwangyeol Baek; Woo Hyun Shim; Jaeseung Jeong; Harsha Radhakrishnan; Bruce R. Rosen; David Boas; Maria Franceschini; Bharat B. Biswal; Young R. Kim
• Keywords: Male; Brain Mapping; Somatosensory Cortex; Magnetic Resonance Imaging; Rats; Rats, Sprague-Dawley; 03 medical and health sciences; 0302 clinical medicine; Chloralose; Touch Perception; Physical Stimulation; Forelimb; Animals; Anesthetics, Intravenous

The spontaneous cerebral hemodynamic fluctuations observed during the resting state have been frequently visualized using functional magnetic resonance imaging (rsfMRI). However, the neuronal populations and neuroelectric characteristics underlying the functional connectivity of cerebrohemodynamic activities are poorly understood. We investigated the characteristics of bi-hemispheric functional connectivity via electrophysiology and rsfMRI in the primary sensory cortex of rats anesthetized by α-chloralose. Unlike the evoked responses, the spontaneous electrophysiological activity was concentrated in the infragranular layers and could be classified into subtypes with distinctive current sources and sinks. Both neuroelectric and rsfMRI signals were interhemispherically correlated in a layer-specific manner, suggesting that there are independent neural inputs to infragranular and granular/supragranular layers. The majority of spontaneous electrophysiological activities were bilaterally paired with delays of up to ~50 ms between each pair. The variable interhemispheric delay implies the involvement of indirect, multi-neural pathways. Our findings demonstrated the diverse activity patterns of layer-specific electrophysiological substrates and suggest the recruitment of multiple, non-specific brain regions in construction of interhemispheric functional connectivity.