TOUCH AND KINESTHESIS 4I3 



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FIG. 17 Lefl: Graphs of the impulse frequency in single afferent neuron innervating the capsule 

 of the knee joint of the cat, as the joint is moved in steps through the 'excitatory angle' for the 

 receptor, in opposite directions. After each small step of the movement the frequency is allowed 

 to reach an adapted rate. The two curves are almost mirror images. [From Skoglund (225).] 



FIG. 18 Right: Graphs of impulse frequencies for eight single neurons innervating slowly adapting re- 

 ceptors in the capsule of the knee joint of the cat. The adapted impulse frequency is plotted against 

 position of the joint in degrees. Solid lines show values for five units in one experiment, dolled lines 

 show those for three units in another. The figure is not fully representative for the distribution of 

 endings which are successively activated during full movement since in general endings which cause 

 maximal adapted discharge rates are more numerous immediately before or at full flexion or full 

 extension than in the intermediate positions of the joint. The sensitive ranges (15 to 30 degrees) are 

 representative of the behavior of most endings. [From Skoglund (aas).] 



located in the pericapsular connective tissue (225). 

 They are innervated by the largest afferents in the 

 articular nerves. 



Central Projection of Joint Afferents 



The evidence that receptors in and about joints 

 do indeed project into the lemniscal system was ob- 

 tained by gross electrode recording of the electrical 



responses evoked in the ventrobasal thalamic complex 

 and the somatic sensory cortex by mechanical stimu- 

 lation of those tissues (182) and by electrical stimula- 

 tion of articular nerves (83, 86). Such experiments 

 indicate that the afferents from bones and joints form 

 together with afferents from cutaneous receptors a 

 common topographic pattern. Knowledge of this 

 projection has been greatly extended by single unit 

 studies. Some single elements in the ventral thalamic 



