Some anatomical and neurophysiological bases of tactile manual perception

Cutaneous perception and haptic perception can be distinguished by the fact that, in the latter, the motor system is involved in the exploratory activity of the hand which in turn can activate the whole shoulder-arm-hand system. In cutaneous perception, because the corporal segment stimulated is stationary, only the superficial layers of the skin undergo mechanical deformations and are therefore involved in perceptual processing. In haptic perception, the deforma tions of the muscles, joints and tendons resulting from exploratory movements are added to cutaneous perceptions. Haptic perceptual processing is therefore much more complex because it integrates cutaneous and proprioceptive cues and also corrollary dischanges, cf. Chapter 2. The exploratory movements depend on neural circuits that are partly specific. They are intentional (they are aimed at a goal), auto-initiated (they maybe generated internally without external stimulus) and they are generally multi-articular (they activate many corporal segments). Finally, because their speed is relatively slow, they may use the sensory reafferences produced by their execution.

Some selected data concerning the anatomical and neurophysiological bases of cutaneous and haptic perceptions are presented in the two chapters of this Section. In Chapter 2, Gentaz describes some general characteristics of this anatomical and functional organization. Then, in Chapter 3, Gentaz and Badan examine the new insights provided in this domain by the recent data taken from neuropsychology and from functional cerebral imagery methods.

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