Electrophysiological experiments of microelectrode recording were performed in the parietal operculum and post-central gyrus of 3 Java monkeys (Macacus Irus) previously submitted to horseradish peroxidase (HRP) injections (5-8; $0.5 \mu l$ each) in the parietal operculum of the contralateral side. The aim was to ascertain as to whether the regions of the first and second somatosensory areas (SI and SII) containing HRP labelled callosal neurones receive sensory projections from hand receptive fields (RFs). Microelectrode recording started 16-20 hours after HRP injections and was carried out with animals curarized and artificially ventilated with $N_{2} O—O_{2}$ and halothane. Data concerning HRP experiments have been already reported (this volume, ref. 10). In the parietal operculum, 12 penetrations were performed and the RFs stimulation was tested on 95 single neurones and 88 multineuronal foci. In the course of 6 penetrations performed in the post-central gyrus, the RFs stimulation was tested on 30 single neurones and on 35 multineuronal foci. In the parietal operculum wide regions were explored, belonging to area SII, which contained neurones responding to stimulation of the contralateral hand. In the post-central gyrus the region explored corresponded to the hand representation zone of area SI. On comparing the RFs data with the distribution of HRP labelled neurones, it resulted that cortical regions of both area SI and SII containing neurones responsive to contralateral hand stimulation also contained callosal neurones.
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Con il contributo del Ministero per i Beni e le Attività Culturali