Notes

Mountcastle, Vernon B. "Modality and topographic properties of single neurons of cat's somatic sensory cortex." Journal of neurophysiology 20.4 (1957): 408-434.

The somatic-sensory cortex plays a crucial role in processing peripheral sensory information. Previous studies have demonstrated the topographical organization of this brain area. However, the modality properties and topographical attributes of the somatic-sensory cortex neurons remain unclear. Our study investigates these aspects through an analysis of neuronal activity driven by the deformation of peripheral tissue. In particular, we performed electrophysiological recordings of single-neuron activity in the first somatic-sensory cortex of cats. Such data allowed us to differentiate cells activated by skin stimulation from those activated by deep tissue stimulation. Further, we distinguished the skin-related neurons as driven either by hairs-movements or by pressure upon the skin. These cutaneous subgroups share similar receptive fields but differ significantly in their adaptation properties. Furthermore, we differentiated the neurons related to deep receptors as driven by pressure upon the deep fascia or activated by joint-rotation. The first subgroup shows receptive fields and adaptation properties similar to skin-pressure neurons, while the latter signals the phasic changes and steady position of joints. Perpendicular electrode penetrations of the cortex suggest a vertical grouping of neurons in columns that share the same modality subgroup. In addition, oblique penetrations of the cortex confirmed such organization as we observed consecutive shifts in the modality subgroups of encountered neurons. Hence, our results support the hypothesis of a functional organization of the somatic-sensory cortex. Indeed, these vertical columns of cells could represent an elementary unit of organization capable of input-output activity of considerable complexity without necessarily wide horizontal spread.