TOUCH AND KINESTHESIS 



415 



The thesis that the sense of position and movements 

 of the joints is dependent upon joint receptors them- 

 selves fits well the clinical observations. However, we 

 shall not discuss here the extensive clinical and psycho- 

 physical data available on this subject; we refer the 

 interested reader to a series of articles by Goldscheider 

 collected in a book (99). His careful work and his clear 

 recognition of the joints as the source for kinesthetic 

 sensations are unfortunately usually forgotten or dis- 

 regarded in modern physiological texts perhaps 

 because he was satisfied to treat these sensations within 

 the concept of 'muscle sense' (^Muskelsinn). 



Projections of Deij) Receptors Other Than in Joints 



Studies of the modality properties of individual 

 neurons of the lemniscal system at thalamic and 

 cortical levels have shown a class of cells whose 

 peripheral receptive fields lie in deep fascia (181; 

 and Mountcastle, V. B. & J. E. Rose, unpublished 

 observations). These fields are of similar shape and 

 size as those for neurons driven from the skin (see fig. 

 7). The units are driven by very light mechanical 

 stimuli to the fascia, and the threshold for activity is 

 so low that even a very small displacement of the 

 overlying skin may evoke their discharge. They may 

 also be driven by pressure changes occurring in the 

 deep fascial compartments when the enclosed muscles 

 contract. It is reasonable to assume that this cla.ss of 

 neurons functions in the overall sense of touch-pres- 

 sure, for they respond to all but the very weakest of 

 stimuli impinging upon the skin overlying their own 

 fascial receptive fields. 



Other neurons of this class are activated by direct 

 pressure upon the periosteum. What role they may 

 play in kinesthesis or some other aspect of deep sensi- 

 bility is unknown. 



FUNCTIONAL ORG.^NIZ.^TION OF FIRST SOMATIC 

 CORTICAL FIELD 



One of the central problems of neurophysiology at 

 the present time is to understand the functional 

 mechanisms of any given region of the cerebral cortex. 

 Investigators proceed on the premise that if they can 

 determine the patterns of neural activity entering a 

 cortical region, the modifications of those patterns 

 occurring across intracortical synaptic relays ('inte- 

 grative action') and the spatial and temporal patterns 

 of output from the region, they will then be able to 

 reconstruct with some insight the way in which the 

 particular cortical region operates. In the past few 



years much effort has been expended to study the 

 response properties of single cells in the first somatic 

 field, the way these cells are activated from the thala- 

 mus, the relations of the unitary discharges to the 

 evoked slow cortical wave on the surface of the cortex 

 and in its depths and the relation of single cell dis- 

 charges to the cortical EEG (13, 14, 157-159), matters 

 recently reviewed by Albe-Fe.ssard (7). Recently 

 Mountcastle (181) has suggested on the basis of his 

 studies that a vertical group of cells extending across 

 all the cellular layers acts, as it were, as a functional 

 cortical unit. Three observations are the reasons for 

 this suggestion, a) The neurons of such a vertical 

 group are all related to the same, or nearly the same, 

 peripheral receptive field. This observation establishes 

 also that the topographical pattern present on the 

 surface of the cortex extends throughout its depth. 

 6) The neurons of such a vertical group belong as a 

 rule to the same modality group, i.e. they are acti- 

 vated by the same type of peripheral stimulus. This 

 implies that a small group of thalamocortical fibers 

 entering the cortex is activated by a single mode of 

 peripheral stimulation and in turn activates a narrow 

 vertical column of cortical cells. All cells of such a 

 vertical column disrharge on the average at more or 

 less the same latency to a brief peripheral stimulus. 

 The discharges are thus grouped within the time limits 

 of a few milliseconds into an initial firing pattern. This 

 observation is based, however, only upon the first 

 response of cortical cells, the latency of which is 

 known to be sensitive to various parameters of the 

 peripheral stimulus. 



The possibility that a vertical column of cells tends 

 to behave as a functional unit appears acceptable 

 anatomically both from the cytoarchitectural point of 

 view and as regards the connections of such a vertical 

 column as seen in the Golgi material (162). The sub- 

 pial dicing experiments of several cortical fields (226, 

 227) could also be interpreted to imply that a complex 

 cortical activity is still possible as long as the cortical 

 organization in depth is preserved. 



It is, of course, not implied by these observations 

 that the cortex is organized into sets of isolated, 

 vertically oriented tissue prisms. It appears, however, 

 that at least for the incoming activity a columnar 

 vertical organization is of special significance. 



SPINOTHALAMIC SYSTEM 



In comparison to our knowledge of the lemniscal 

 system, that pertaining to the tactile activity of the 



