RESUMO
Blink reflex-related areas in the human cerebellum were studied using [15O]H2O PET in eight healthy subjects. Eyeblinks were evoked by airpuff stimulation and recorded via surface electrodes. PET analysis revealed a cerebellar increase of regional cerebral blood flow in vermal lobule VI and a small ipsilateral paravermal extension in the eyeblink condition compared to rest. This activation partly overlapped with areas found in recent fMRI and animal studies investigating the cerebellar involvement in control of the unconditioned and acquisition of the conditioned eyeblink response. In conclusion, vermal lobule VI extending to ipsilateral paravermal areas appears to be involved in control of the unconditioned eyeblink response.
Assuntos
Piscadela/fisiologia , Córtex Cerebelar/fisiologia , Tomografia Computadorizada de Emissão/métodos , Adulto , Mapeamento Encefálico , Córtex Cerebelar/anatomia & histologia , Córtex Cerebelar/diagnóstico por imagem , Eletromiografia/instrumentação , Eletromiografia/métodos , Feminino , Humanos , Imageamento por Ressonância Magnética/instrumentação , Imageamento por Ressonância Magnética/métodos , Masculino , Isótopos de Oxigênio/farmacocinética , Estimulação Física , Fluxo Sanguíneo Regional , Tomografia Computadorizada de Emissão/instrumentaçãoRESUMO
Numerous studies have shown that the cerebellum is involved in classical conditioning of specific aversive reactions. Only few studies, however, have examined the exact localization of cerebellar areas involved in the control of unconditioned reflex responses. The present study investigated cerebellar areas, which are activated during eliciting of the limb flexion reflex in healthy controls using [15O]H2O PET. Limb flexion reflex related areas were found in vermal lobules III-VI with the local maximum in vermal lobule V. Areas of activation were more widespread compared to a voluntary foot movement and a sensory foot stimulation condition. Limb flexion reflex areas probably reflect efferent reflex modulation as well as sensory inputs from the stimulus itself and/or the reflex response.
Assuntos
Cerebelo/anatomia & histologia , Cerebelo/fisiologia , Extremidades/inervação , Movimento/fisiologia , Vias Neurais/anatomia & histologia , Vias Neurais/fisiologia , Adulto , Mapeamento Encefálico , Cerebelo/diagnóstico por imagem , Circulação Cerebrovascular/fisiologia , Eletromiografia , Extremidades/fisiologia , Retroalimentação/fisiologia , Feminino , Lateralidade Funcional/fisiologia , Humanos , Masculino , Mecanorreceptores/fisiologia , Contração Muscular/fisiologia , Rede Nervosa/anatomia & histologia , Rede Nervosa/diagnóstico por imagem , Rede Nervosa/fisiologia , Condução Nervosa/fisiologia , Vias Neurais/diagnóstico por imagem , Reflexo/fisiologia , Sensação/fisiologia , Nervo Tibial/fisiologia , Tomografia Computadorizada de Emissão , Volição/fisiologiaRESUMO
Fear-conditioned potentiation of the startle response was used to study the role of the cerebellum in associative learning of non-specific aversive reactions in healthy human subjects using PET. Prior PET scanning initially neutral light stimuli were paired with painful electric shocks (fear-conditioning phase). Four PET-scans each were performed with presentation of acoustic startle stimuli (T), fear-conditioned light stimuli (L) or acoustic stimuli paired with light (LT, potentation phase). As a measure of fear-conditioning subtraction of condition T from LT revealed an increase of regional cerebellar blood flow (rCBF) in the left cerebellar hemisphere. Subtraction of condition L from LT, as a measure of fear-conditioned potentiation, revealed an increase of rCBF in the medial cerebellum. Different parts of the cerebellum appear to be involved in this form of motor associative learning.
