The Detailed Morphology of the Cortical Terminals of the Thalamocortical Fibres from the Ventromedial Nucleus in the Rat
Iontophoretic injections of the Phaseolus Vulgaris leucoagglutinin (PhAL) in the region of the ventromedial thalamic nucleus of the rat resulted in a complete “Golgi-like” filling of small groups of neurones. The gross distribution of the terminals across the surface of the cortex confirms earlier studies with other tracing methods. The detail available in the PhAL material suggests a rather more restricted domain of influence for individual cells. Some terminal axons were limited to a small area in the motor cortex with boutons in both deeper and surface layers. Other terminals ran for several millimeters, parallel to the surface and immediately below it. In related electrophysiological experiments two groups of ventromedial cells were encountered. One group was antidromically activated by threshold stimulation only in a small area of cortex. Another was characterised by activation from several points on the cortical surface along a strip with a maximum width of 0.5mm but which could be as long as the exposed area of cortex.
KeywordsCortical Surface Cortical Stimulation Ventromedial Nucleus Camera Lucida Drawing Iontophoretic Injection
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