Interactions of layer one with specific thalamocortical activity in somatosensory cortex: An in vitro optical imaging study

LEZNIK, E, URBANO, FJ, & LLINÁS, RR.

San Diego, USA.

Congreso; 31st Annual Meeting of the Society for Neuroscience.; 2001

Spatiotemporal interactions between superficial and specific thalamocortical connections were studied using optical imaging of voltage-sensitive dye signals combined with field potentials and intracellular recordings. Optical recordings were implemented in thalamocortical slices (400-450 m thick) from 1-3 weeks old mice that were stained with a voltage-sensitive dye RH795. Fluorescent activity was recorded using a CCD camera (Fujix HRDeltaron 1700), 128x128 pixels of spatial resolution and 0.6 msec of temporal resolution. Specific thalamic nucleus and layer 1 were stimulated with either single pulses or high frequency trains of stimuli using concentric bipolar electrodes. A radial cut across deep layers (from layer 2/3 to white matter) was made to limit layer 1 activation to a well-defined band of activity in the most superficial cortical layers. Stimulating electrodes were positioned on opposed sites of the cut so that only the spread of activity from layer 1 was able to interact with the specific thalamic stimulation. Optical and electrophysiological recordings from different cortical layers were implemented following this paradigm. Repetitive stimulation in the gamma band frequency facilitated electrophysiological and optical responses and produced lateral spatial restriction when activating layer 1. Similar findings were obtained with specific thalamic nucleus stimuli. The simultaneous activation of layer 1 and specific thalamocortical inputs induced summation of activity, recorded optically and electrophysiologically. These results support the idea that specific and unspecific systems can work in a coincidence detection mode. Supported by: NIH-NINDS NS13742