Transfer callosale d'impulsi profondi di diversa origine recettoriale

Manzoni, Tullio ; Michelini, Sandro ; Spidalieri, Giuseppe

Atti della Accademia nazionale dei Lincei. Rendiconti della Classe di scienze fisiche, matematiche e naturali, Série 8, Tome 58 (1975) no. 4, pp. 656-661

Résumé

Experiments have been carried out in order to ascertain the peripheral origin of Group I-III deep afferent fibres, previously shown to project to the somesthetic region of the corpus callosum (SCR). In chloralose-anaesthetized cats some forelimb nerves and nerve branches (muscular branch of the deep radial nerve supplying the extensor carpi radialis, ECR; distal part of the same nerve containing also the branches to the interosseous membrane and carpal joints, NRP-D; muscular branch of the median nerve distributing to the palmaris longus, flexor carpi radialis and I-III flexor digitorum profundus, MN1; muscular branch of the same nerve for the IV-V flexor digitorum profundus and pronator quadratus, MN2; interosseus nerve, Int-MN) have been isolated and stimulated. Mass potentials were recorded (and averaged on-line with a multichannel analyzer) simultaneously from the dorsal root (C7-C8), from the surface of the contralateral post-central dimple area (3a) and, with concentric bipolar electrodes, from fibres of the SCR. Upon stimulation of the three muscular branches ECR, MN1 and MN2 with strength provoking full activation of Group I afferents and additional engagement of those of Group II, no responses could be detected in the whole rostro—caudal extent of the SCR. In order to obtain callosal mass potentials upon stimulation of such nerves, it was necessary to increase the stimulus strength at or above the threshold for Group III fibres. The same callosal foci unresponsive to Group I and II muscular volleys exhibited clear-cut responses to pure Group I and/or Group II afferent volleys elicited through D-DRN and int-MN. From these results it might be inferred that the callosal transfer of deep information is significantly present only if it originates from extramuscular receptors (such as those in joints or interosseus membranes), or from non-fusal muscular terminals.