Organizzazione topografica delle proiezioni talamocorticali alla zona di rappresentazione del tronco dell'area somestesica prima del Gatto

Barbaresi, Paolo   ; Conti, Fiorenzo   ; Manzoni, Tullio

Atti della Accademia nazionale dei Lincei. Rendiconti della Classe di scienze fisiche, matematiche e naturali, Série 8, Tome 75 (1983) no. 5, pp. 238-244

Résumé

The topography of the thalamic projections to the trunk representation zone of the first somatosensory area (SI) was studied in the cat by performing experiments of retrograde neuronal tracing. Single injections of horseradish peroxidase or fluorescent tracers (Evans Blue, Nuclear Yellow, Fast Blue) in area SI resulted in retrograde labelling of cell aggregates in the dorsal region of the nucleus ventralis postero-lateralis (VPL) intervening between the lateral (VPLl) and medial (VPLm) subnucleus. The aggregates of labelled cells were elongated rostrocaudally in VPL but were narrow in the dorsoventral and mediolateral extent. In separate experiments, physiologically defined sites of the trunk zone, corresponding to the representation of the dorsal midline, lateral trunk and ventral midline, were injected with different fluorescent markers. The three sites were located in rostrocaudal sequence in the medial part of area SI and corresponded, in the order, to the cytoarchitectonie fields 3b, 1, 2. In these animals three different cell aggregates were labelled, orderly located in topographically distinct regions of VPL trunk zone. According to these results, adjacent cortical foci disposed in rostrocaudal sequence in area SI receive thalamic projections from adjacent neuronal aggregates located in lateromedial sequence in VPL. Each aggregate had a focal projection to a single cortical region since no double-labelled cells were found in VPL.

Bibliographie

[1] Adams J.C. (1977) - Technical considerations on the use of horseradish peroxidase as a neuronal marker, «Neuroscience», 2, 141-145.

[2] Bentivoglio M., Kuypers H.G.J.M. e Catsman-Berrevoets C.E. (1980) - Retrograde neuronal labelling by means of bisbenzimide and nuclear yellow (Hoechst S 769121). Measures to prevent diffusion of the tracers out of retrogradely labelled neurones. «Neurosci. Letters», 18, 19-24.

[3] Barbaresi P., Conti F. e Manzoni T. - Ricerche elettrofisiologiche sulla rappresentazione del tronco nel talamo del Gatto, «Atti Acc. Naz. Lincei Cl. Sc. Fis. Mat. e Nat.», in stampa.

[4] Berlucchi G. (1972) - Anatomical and physiological aspects of visual functions of corpus callosum. «Brain Res.», 37, 371-392.

[5] Berlucchi G. (1981) - Recent advances in the analysis of the neural substrate of interhemispheric communication. In Pompeiano O. e Ajmone-Marsan C. (Eds), Brain mechanisms and perceptual awareness, Raven Press, New York, 133-152.

[6] Caminiti R., Innocenti G.M. e Manzoni T. (1979) - The anatomical substrate of callosal messages from SI and SII in the cat. «Exp. Brain Res.», 35, 295-314.

[7] Donaldson L., Hand P.J. e Morrison A.R. (1975) - Cortico-thalamic relationships in the rat, «Exp. Neurol.», 47, 448-458.

[8] Jones E.G. e Powell T.P.S. (1968) - The commissural connexions of the somatic sensory cortex in the cat, «J. Anat.», 103, 433-455.

[9] Kaas J.H. (1983) - What, if anything, is SI? Organization of first somatosensory cortex, «Physiol. Rev.», 63, 206-231.

[10] Kuypers H.G.J.M., Bentivoglio M., Catsman-Berrevoets C.E. e Bharos A.T. (1980) - Double retrograde neuronal labeling through divergent axon collaterals, using two fluorescent tracers with the same excitation wavelength which label different features of the cell, «Exp. Brain Res.», 40, 383-392.

[11] Landry P. e Deschenes M. (1981) - Intracortical arborizations and receptive fields of identified ventrobasal thalamo-cortical afferents to the primary somatic sensory cortex of the cat, «J. Comp. Neurol.», 199, 345-371.

[12] Manzoni T., Barbaresi P., Bellardinelli E. e Caminiti R. (1980) - Callosal projections from the two body midlines, «Exp. Brain Res.», 39, 1-9.

[13] Mckenna T.M., Whitsel B.L., Dreyer D.A. e Metz C.B. (1981) - Organization of the cat anterior parietal cortex: relations among cytoarchitecture, single neuron functional properties and interhemispheric connectivity, «J. Neurophysiol.», 45, 667-697.

[14] Rinvik E. (1968) - A re-evaluation of the citoarchitectonic of the ventral nuclear complex of the cat's thalamus on the basis of cortico-thalamic connections, «Brain Res.», 8, 237-254.