La corteza cerebral modula la transmisión cutánea a través de los núcleos de los cordones posteriores

Abstract

The mechanisms used by the cerebral cortex to modulate the cutaneous information at prethalamic level have been scarcely studied. This article reviews experimental evidence leading to a better understanding of this issue at the level of the cuneate nucleus (Burdach nucleus). The primary afferents and the corticocuneate fibers make synaptic contact with cuneothalamic neurons and with inhibitory interneurons in the middle cuneate nucleus. By stimulating the skin at different places while recording the cuneothalamic intracellular activity in anaesthetized animals with the cortex intact, with the cortex pharmacologically inactivated, or in absence of a cerebral cortex it was possible to ascertain the functional role of the corticocuneate fibers. The primary afferents activated by stimulating a particular zone of the skin induce monosynaptic excitation on a group of cuneothalamic cells at the same time at which inhibit, through intranuclear interneurons, neighboring cuneothalamic cells with unmatched receptive fields. Similarly, the corticocuneate cells receiving information from the stimulated skin further increase the excitation of the cuneothalamic neurons with matched receptive fields while inhibiting others with unmatched fields. The cortex exaggerates an excited center surrounded by an inhibited periphery thus increasing the tactile discrimination both spatially and temporally which is essential for exploratory and manipulative purposes.