Stimulus-dependent spatial patterns of response in SI cortex

Enda en viktig studie som viser hvordan vibrasjon-stimuli i huden påvirker tilsvarende område i hjernen. Går dypere inn i hva som spesifikt skjer i selve det aktiverte området. Legges til som ekstra referanse.

http://www.biomedcentral.com/1471-2202/6/47

Afferent projections from skin to primary somatosensory cortex (SI) are well known to form a fine map of the body surface in SI. In this map, a skin locus provides afferent input to an extensive cortical region in SI [1,2]. In particular, the direct connectivity between somatosensory thalamus and SI cortex is now recognized to be much more spatially distributed than previously believed (e.g., in primates the ventrobasal thalamic region which receives its input from a single digit projects to an extensive, 20 mm2 sector of SI cortex – [3,4]).

The intrinsic SI excitatory connections link not only neighboring but also widely separated regions of somatosensory cortex[5]. These connections ensure that many members of widely distributed neuronal populations interact extensively within milliseconds after the onset of stimulus-evoked thalamocortical drive. Thus it is not surprising to find that the processing of even a very local skin stimulus is associated with SI activation over several sq. millimeters of cortical area, as revealed, for example, with optical imaging techniques [610].

Together these considerations suggest that the spatial pattern of activity evoked in SI by even the smallest stimuli might be structurally more complex than a typically envisioned basic bell-shaped pattern. A closer inspection of such patterns might reveal certain spatial formations within them with significant functional implications.

Observations of the spatial patterns of SI cortical response within an activated region, such as those evoked by flutter stimulation of the skin, suggest that evoked cortical activity within such a territory is not evenly distributed. Furthermore, the cortical activity patterns change in a manner that appears to be dependent upon stimulus conditions. The observed spatiointensive fractionation on a sub-macrocolumnar scale of the SI response to skin stimulation might be the product of local competitive interactions within the stimulus-activated SI region, and as such can lead to new insights about the functional interactions that take place in the SI cortex.

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