Caratteristiche funzionali dei nuclei talamici di relais somatico dopo lesioni corticali croniche

Bava, Antonio ; Fadiga, Ettore ; Manzoni, Tullio

Atti della Accademia nazionale dei Lincei. Rendiconti della Classe di scienze fisiche, matematiche e naturali, Série 8, Tome 40 (1966) no. 6, pp. 1109-1116.

Résumé

Chronic experiments were performed on cats operated for ablation of their cortical somatic (S1 and S2) and motor areas. After allowing convenient time for retrograde degeneration of thalamo-cortical relay cells (TCR), the excitatory responses to central and peripheral stimulations were recorded (extracellular microelectrodes) from 133 units of n. ventralis posterolateralis (VPL). Under these conditions, a substantial proportion of VPL residual population was seen to react to stimulation of contralateral homonymous nucleus and (when still reached by peripheral impulses) of widespread cutaneous fields, thus exhibiting clear extralemniscal properties. This pattern of reactivity strongly diverges from the typical “lemniscal” pattern exhibited by VPL units of neuraxially intact or acute decorticate cats, as well as of cats with chronic lesions of lateral columns of the cord, whilst it is similar in many aspects to that previously observed after chronic lesions of the dorsal columns. Since TCR degeneration must disrupt the recurrent inhibition exerted postsynaptically by interneurons impinged upon by collaterals of TCR axons, the appearance of extralemniscal properties might be related to the suppression of inhibiting channels. To some extent the results of the present experiments might be compared with those yielded by cats in which lesions of the dorsal columns have impaired afferent inhibition.