Microelectrode recordings (glass micropipettes filled with 2.5 M KCl) from the two subdivisions of the motor cortex (area $4\gamma$ and $6\alpha\beta$, [5]) of chloralose-anaesthetized, curarized cats have been performed in order to characterize the response properties of the neurones receiving projections from the n. ventralis lateralis (VL). Extracellular unitary activity was obtained from 345 cells (226 from area 6 and 119 from area 4). Each one was tested for the effects of the electrical stimulation of the dorsal and ventral portions of VL (dVL and vVL). Only 3.1% of area 6 neurones and 3.3% of area 4 neurones were activated by dVL; 25.2% and 23.5% by vVL; 31.8% and 51.3% by stimulation of both. Response patterns were similar for units of the two areas and most latencies ranged between 1 and 8 msec. More detailed analysis of these data showed that the mean latencies of the responses to vVL-shocks were significantly longer in area 6 than in area 4. On the other hand, in area 4 the longest latencies were measured upon stimulation of dVL. These results, in comparison with anatomical studies showing that dVL sends projections mainly to area 6 and vVL mainly to area 4, suggest the possibility that the influence of dVL on area 4, as well as that of vVL on area 6, be exerted in part over cortico-cortical relays between the two subdivisions of motor cortex.
Referenze Bibliografiche
[1] P. ANGAUT (1973) - Bases anatomo-fonctionelles des interrelations cerebello-cerebrales, «J. Physiol. (Paris)», 67, 53A.
[2] H. ASANUMA, J. FERNANDEZ, M. E. SCHEIBEL e A. B. SCHEIBEL (1974) - Characteristics of projections from the nucleus ventralis lateralis to the motor cortex in the cat: an anatomical and physiological study, «Exp. Brain Res.», 20, 315.
[3] R. CESARI, S. MICHELINI, G. SPIDALIERI e M. VEDOVATO (1977) - Differential afferent organization of cytoarchitectonie sub-divisions of cat motor cortex. Peripheral and cerebellar reactivities of neurones identified in area 6 $\alpha\beta$, «Arch. Ital. Biol.», 115, 386.
[4] J. F. DORMONT e J. MASSION (1970) - Duality of cortical control on ventrolateral thalamic activity, «Exp. Brain Res.», 10, 205.
[5] R. HASSLER e K. MUHS-CLEMENT (1964) - Architektonischer aufbau der sensomotorischen und parietalen cortex der katze, «J. Hirnforsch.», 6, 377.
[6] E. G. JONES e T. P. S. POWELL (1968) - The ipsilateral cortical connections of the somatic sensory areas in the cat, «Brain Res.», 9, 71.
[7] K. KAWAMURA e K. OTANI (1970) - Corticocortical fiber connections in the cat cerebrum: the frontal region, «J. Comp. Neurol.», 139, 423.
[8] J. MASSION (1973) - Intervention de voies cerebello-corticales et cortico-cerebelleuses dans l'organization et la regulation du mouvement, «J. Physiol (Paris)», 67, 117A.
[9] A. NIEOULLON e L. RISPAL-PADEL (1976) - Somatopic localization in cat motor cortex, «Brain Res.», 105, 405.
[10] E. RINVIK (1972) - Organization of thalamic connections from motor and somatosensory cortical areas in the cat. In Frigyesi T. L., Rinvik E. e Yahr M. D. (Eds.), Corticothalamic projections and sensorimotor activities, Raven Press, New York, pp. 57-90.
[11] L. RISPAL-PADEL e A. GRANCETTO (1977) - The cerebello-thalamocortical pathway. Topographical investigation at the unitary level in the cat, «Exp. Brain Res.», 28, 101.
[12] L. RISPAL-PADEL e L. LATREILLE (1974) - The organization of projections from the cerebellar nuclei to the contralateral motor cortex in the cat, «Exp. Brain Res.», 19, 36.
[13] L. RISPAL-PADEL e J. MASSION (1970) - Relations between the ventrolateral nucleus and the motor cortex in the cat, «Exp. Brain Res.», 10, 331.
[14] L. RISPAL-PADEL e J. MASSION e A. GRANCETTO (1973) - Relations between the ventrolateral thalamic nucleus and motor cortex and their possible role in the central organization of motor control, «Brain Res.», 60, 1.
[15] H. SAKATA, T. ISHIJIMA e Y. TOYODA (1966) - Single unit studies on ventrolateral nucleus of the thalamus in cats: its relation to the cerebellum, motor cortex and basal ganglia, «Jap. J. Physiol.», 16, 42.
[16] M. STERIADE, V. APOSTOL e G. OAKSON (1971) - Control of unitary activities in cerebellothalamic pathway during wakefulness and synchronized sleep, «J. Neurophysiol.», 34, 389
[17] M. STERIADE, P. WYZINSKYI e V. APOSTOL (1972) - Corticofugal projections governing rhythmic thalamic activity. In Frigyesi T. L., Rinvik E. e Yahr M. D. (Eds.), Corticothalamic projections and sensorimotor activities, Raven Press, New York, pp. 221-272.
[18] P. L. STRICK (1973) - Light microscopic analysis of the cortical projection of the thalamic ventrolateral nucleus in the cat, «Brain Res.», 55, 1.
[19] M. UNO, M. YOSHIDA e I. HIROTA (1970)- The mode of cerebellothalamic relay transmission investigated with intracellular recording from cells of the ventrolateral nucleus of cat's thalamus, «Exp. Brain Res.», 10, 121.
[20] M. VEDOVATO (1978) - Identification of afferent connections to cortical area 6a of the cat by means of retrograde horseradish peroxidase transport, «Neuroscience Letters» in corso di stampa.
Con il contributo del Ministero per i Beni e le Attività Culturali