Differenze nella proiezione somatosensoriale ai due campi citoarchitettonici (aree 6 e 4) della corteccia motrice del Gatto

Cesari, Roberto ; Michelini, Sandro ; Spidalieri, Giuseppe ; Vedovato, Marta

Atti della Accademia nazionale dei Lincei. Rendiconti della Classe di scienze fisiche, matematiche e naturali, Série 8, Tome 62 (1977) no. 6, pp. 859-865

Résumé

The peripheral reactivity of cortical area 6 ($6 \alpha\beta$) of the Cat has been examined, in order to compare its features with those of the peripheral reactivity of area 4 ($4 \gamma$). Peripheral stimulation was actuated by single shocks to the skin applied in sequence by means of several needle-electrodes thrust into standard locations of limbs, trunk, neck and of the whisker region. With conventional electrophysiological techniques, in 19 animals extracellular records from 323 cortical neurones were obtained, 258 of which belonged to area $6 \alpha\beta$ (214 in chloralose-anaesthetized and 44 in locally-anaesthetized preparations) and 65 to area $4 \gamma$ (chloralosed preparations). Only excitatory, all-or-none responses were studied. In chloralosed preparations, the proportion of reactive units appeared to be lower in area 6 (26.6%) than in area 4 (58.5%). In both cortical areas, most reactive neurones (82.5% in area 6; 76.3% in area 4) were endowed with wide PRFs, as judged by reactivity to more than one stimulating electrode. Those neurones exhibiting restricted fields, however, were generally activated by off-focus regions in area 6, and by on-focus regions in area 4. The overwhelming majority of neurones sampled from area 6 appeared to be undrivable by natural stimuli, while as many as 70 % of the units of area 4 reactive to electrical stimulation exhibited physiologically identifiable PRFs. In spite of some exceptions, the responses obtained from area 6 neurones exhibited a lower number of spikes and a mean latency longer than those observed on neurones pertaining to area 4. The peripheral reactivity of area 6 neurones sampled in the absence of chloralose was very low (3 units out of 44) and only present following electrical shocks.