By A. Nunez, E. Malmierca
Sensory signs succeed in the cerebral cortex after having made synapses in numerous relay stations alongside the sensory pathway. The stream of sensory details in subcortical relay stations is managed by means of the motion of targeted topographic connections from the neocortex. a number of traces of study point out that the big corticifugal procedure improves ongoing subcortical sensory processing and reorganizes the receptive fields in visible, auditory and somatosensory platforms. In a lot of these sensory platforms cortical neurons mediate either the hugely centred confident suggestions to subcortical neurons with overlapping receptive fields and a frequent inhibition to "non-matching neurons". This cortical suggestions, which has been referred to as "egocentric selection", can play a pivotal position in gating the sensory details that reaches the thalamus and cortex. therefore, corticofugal projections may perhaps give a contribution to selective awareness in view that they increase neuronal responses for attentionally appropriate stimuli and through suppressing sensory responses of distractive stimuli. additionally, corticofugal projections increase oscillatory task so one can synchronize neurons situated within the similar or in several relay stations in an effort to enhance sensory processing. In end, corticofugal pathways accurately regulate sensory transmission during the important frightened process.
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Additional info for Corticofugal Modulation of Sensory Information (Advances in Anatomy, Embryology and Cell Biology)
Krupa et al. (1999) clearly demonstrated that descending corticothalamic glutamatergic projections inﬂuence ascending sensory signals by exerting a dual physiological effect on the thalamic neurons. These effects may include a tonic inhibition, primarily generated by cortically driven excitation of GABAergic neurons located in the thalamic reticular nucleus of the thalamus. Excitation of a topographically related group of thalamic cells and inhibition of adjacent, nontopographically related cells is also seen in the ventral posterior nucleus after focal stimulation of the somatosensory cortex (Rapisarda et al.
First, since the NMDA component increases the amplitude and duration of the corticofugal EPSPs evoked at depolarized membrane potentials, it enhances the possibility Somatosensory System 41 Fig. 10A–C Homosynaptic paired-pulse effects. A Superimposed averages (n = 4) at different paired-pulse intervals show a depression of the second dorsal column EPSP (DC) at delays <50 ms. B Superimposed averages (n = 4) show small facilitation of the second corticofugalEPSP (CF) at delays of 10–30 ms. C Plot of mean EPSP areas of the second EPSP as a function of paired-pulse interval (mean±SEM).
As is shown in Fig. 8D, dorsal column- Somatosensory System 37 Fig. 7 Effect of stimulation of different primary somatosensory cortical areas on tactile gracilis responses. A schematic drawing of the stimulated cortical areas and PSTHs of tactile responses in a representative gracilis neuron are shown. Stimulation cortical electrode in site 1, but not in site 2, had the same RF as the recorded gracilis neuron. 3 ms at 100 Hz for 500 ms) at site 1 facilitated tactile responses. One minute later, equal cortical train stimulation applied at site 2 blocked the tactile response facilitation.