Abstract
In the cerebro-cerebellar system of anthropoid apes and humans, the cerebellum seems able to contribute not only to motor skills but also to mental and language skills. Anatomical evidence suggests that in these species the cerebellum can function at two different hierarchical levels. At a lower level, the cerebellum can supply signals to the frontal motor areas for effecting the manipulation of muscles. At a higher level, the cerebellum can supply signals to some prefrontal areas for effecting the manipulation of symbols. At both levels, the cerebellum can function in essentially the same way: when incoming information is processed repeatedly in the neural loops in which the cerebellum is embedded, the cerebellum can learn to generate new sequences of signals, which constitute new programs for carrying out learned procedures. If cerebellar programs are used in the frontal motor areas (area 4 and are 6), motor manipulations can be effected rapidly and skillfully. Similarly, if cerebellar programs are used in some prefrontal areas (e.g., area 8 and the inferior frontal convolution), mental and language manipulations could be effected rapidly and skillfully. The cerebellum, in its contributions to these mental and language functions, as in its contributions to motor function, could serve as an adaptive mechanism whose signals enable the frontal cortex to execute learned procedures optimally. In the absence of such cerebellar signals, the frontal cortex would have to perform these procedures less rapidly and fluently. Modern testing techniques can reveal such a subtle difference in performance. These techniques are therefore now being used to test human subjects, in an attempt to validate or refute this broadened concept of cerebellar function. If the new concept is validated, it can provide powerful explanations for some unresolved mysteries about the human brain.
Sommario
Nel sistema cerebro-cerebellare delle scimmie antropoidi e degli uomini, il cervelletto sembra in grado di contribuire non soltanto all’abilità motoria, ma anche alle attività mentali e del linguaggio. I dati anatomici sembrano dimostrare che in queste specie il cervelletto può funzionare a 2 livelli gerarchici differenziati. Al livello inferiore, il cervelletto può inviare segnali alle aree motorie frontali, per effettuare il comando dei muscoli. A livello superiore, il cervelletto può inviare segnali ad alcune aree prefrontali, per attivare i simboli. Ai 2 livelli, il cervelletto può funzionare nella medesima maniera. Quando l’informazione in arrivo è fissata ripetutamente nei circuiti neurali cerebellari, il cervelletto può imparare a produrre nuove sequenze di segnali, che costituiscono nuovi programmi per realizzare le procedure apprese. Se i programmi cerebellari sono usati nelle aree motorie frontali 4 e 6, si verificano azioni motorie rapide ed abili; e similarmente, se i programmi cerebellari sono usati in alcune aree frontali, come l’area 8 e la circonvoluzione frontale inferiore, operazioni mentali e di linguaggio possono essere realizzate rapidamente ed abilmente. Il cervelletto, col suo contributo a queste funzioni mentali e del linguaggio o nell’azione motoria, può riuscire come un meccanismo adattativo, i cui segnali permettono alla corteccia frontale di eseguire in modo ottimale le procedure apprese. In assenza di questi segnali cerebellari, la corteccia frontale eseguirebbe queste procedure in modo meno fluente. Nuove tecniche di valutazione confermano queste differenze di performance. Perciò queste tecniche vengono adottate per testare soggetti umani, nel tentativo di confermare o rifiutare questo concetto più allargato delle funzioni cerebrali. Se questi nuovi concetti saranno convalidati, ne conseguirà la possibilità di avere spiegazioni su alcuni non risolti misteri del cervello umano.
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Leiner, H.C., Leiner, A.L. & Dow, R.S. Cerebro-cerebellar learning loops in apes and humans. Ital J Neuro Sci 8, 423–436 (1987). https://doi.org/10.1007/BF02334599
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DOI: https://doi.org/10.1007/BF02334599