Twelve monkeys, 3 unoperated control animals and 9 with division of various cerebral commissures, were trained on a tactile discrimination task before surgery and retrained post-operatively on the same task with the hand used during original learning. After surgery, the 6 animals with section of the posterior commissural region showed impaired performance on the task learnt pre-operatively, whereas 6 monkeys not having this section were unimpaired. The evaluation of the results points to a non-specific...
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...
Microelectrode recordings from the SII cortical area of chloralose-anaesthetized cats have been performed in order to ascertain the peripheral reactivity of the neurones receiving cortico-cortical projections from the ipsilateral SI area. With glass micropipettes, extracellular records were obtained from 64 cells isolated in the forepaw focus, and each one was tested with stimulation both of its peripheral receptive field (PRF) and of the forepaw region of the SI. Twenty-two such units were endowed...
Intracellular records were obtained from 31 neurones isolated from the first somatosensory cortical projection area of chloralose-anaesthetized cats. These neurones, which are part of a wider sample of 197 cells recorded extracellularly during the same experiments, were all tested with the electrical stimulation of peripheral receptive fields (PRF) and hence classified as somatotopic (contralateral, specific PRF) or non-somatotopic (wide and bilateral PRF). Upon PRF shocks, sequences of EPSP-IPSP...
In 16 chloralose-anaesthetized, curarized cats, extracellular recordings (glass micropipettes) were obtained from 197 SI neurones, and each one was tested with appropriate electrical stimulation both of their cutaneous receptive fields and of contralateral SI, SII, and anterior lateral associative (ALA) cortical areas. The study of peripheral reactivity showed that 97 neurones were endowed with very restricted, contralateral fields (somatotopic units, Group I), whereas 66 had wide fields, often...
The investigation whose preliminary results are reported herewith, was meant to ascertain the functional properties of S neurones receiving callosal projections. Electrophysiological experiments were performed in 9 chloralose-anaesthetized, curarized cats. By means of glass micropipettes the electrical activity from 71 S neurones was recorded. Each neurone has been tested with the stimulation of the peripheral receptive fields in order to classify the neuronal sample in lemniscal (Group I), extralemniscal...
Experiments have been carried out in order to study which ascending spinal pathways are utilized by peripherally-originated impulses and activating callosal fibres. In chloralose-anaesthetized cats stim uli of graded intensities were applied to the superficial (SRN) and deep (DRN) radial nerves. Mass potentials were recorded simultaneously from the cerebral cortex (SI, SII and 3a areas, according to the experiment), from the somesthetic callosal region (SCR) and, on some occasions, from the distal...
Experiments have been carried out in order to study in the first somato-sensory area (SI) the relationships between the topography of callosal neurones and the physiological map of the trunk. Horseradish peroxidase (HRP) was injected into the posterior sygmoid gyrus of one hemisphere of 20 adult cats. On 11 of them, the contralateral homotopic cortex was explored with tungsten microelectrodes on the day after HRP delivery. Neurones retrogradely labelled by HRP (callosal neurones) were grouped within...
The synaptic events, induced by transcallosal afferents in somesthetic cortical neurones were studied with intracellular technique in 21 units (14 belonging to SI and 7 to SII), out of a larger sample whose characteristics of transcallosal as well as peripheral reactivity were determined extracellularly. The recordings were obtained from chloralose-anaesthetized, curarized cats by means of glass micropipettes (2M K-citrate or 2.5 M KCl; 10-50 M in resistance) and DC-, AC-amplifying conventional...
Extending our previous research concerned with the reception of callosal messages by the cortical somatosensory areas of the cat, the present experiments were devoted to studying what kind of somesthetic information is transmitted through the fibers of the corpus callosum (CC). By recording electrical activity through coaxial macroelectrodes and tungsten microelectrodes directly from the CC of chloralose-anaesthetized cats, a set of fibers was identified in the rostral part of this commissure (somesthetic...
Previous results had shown that in the cat subliminal electrical stimulation of the thalamic ventrolateral nucleus (VL) reduces the amplitude of the evoked potentials elicited in the homonymous contralateral nucleus upon somatic peripheral stimulation ("transversal inhibition"), and that the reduction is stronger when muscular rather than cutaneous nerves are activated. In view of the fact that VL responses to both muscular and cutaneous afferents are known to be due to Group II and Group III fibers,...
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