M Serrao1, L Parisi, F Pierelli, P Rossi. 1. Istituto di Clinica delle Malattie Nervose e Mentali, II Clinica Neurologica, Università degli Studi di Roma 'La Sapienza', Viale dell'Università 3000185, Rome, Italy. victor.m@mclink.it
Abstract
OBJECTIVES: To evaluate the contribution of the low-threshold afferents to the production of the cutaneous silent period (CSP) in the upper limbs. METHODS: The CSP was studied in 10 healthy adults and 4 patients with Friedreich's ataxia. The following neurophysiological aspects were studied: (a) relationship between sensory threshold (ST), sensory action potential (SAP) amplitude and CSP parameters; (b) habituation and recovery cycle of the CSP at different stimulus intensities (2xST and 8xST); (c) pattern of responses in distal and proximal muscles at different stimulus intensities (2xST and 8xST). RESULTS: (a) The CSP occurred at low intensities (1xST and 2xST) and increased abruptly between 3.5xST and 4xST (corresponding to the pain threshold). The SAP amplitude was saturated before CSP saturation. In the patients with Friedreich's ataxia, the CSP appeared only at higher stimulus intensities (6xST-8xST). (b) The CSP evoked at 2xST showed a fast habituation and slow recovery cycle whereas the opposite behaviour was found at 8xST. (c) Low-threshold stimuli induced an inhibitory response restricted to the distal muscles. High-intensity stimulation produced an electromyographic suppression, significantly increasing from proximal to distal muscles. CONCLUSIONS: Our findings support the notion that low-threshold afferents participate in the production of the CSP in the upper limbs. The different afferents may activate different central neural networks with separate functional significance.
OBJECTIVES: To evaluate the contribution of the low-threshold afferents to the production of the cutaneous silent period (CSP) in the upper limbs. METHODS: The CSP was studied in 10 healthy adults and 4 patients with Friedreich's ataxia. The following neurophysiological aspects were studied: (a) relationship between sensory threshold (ST), sensory action potential (SAP) amplitude and CSP parameters; (b) habituation and recovery cycle of the CSP at different stimulus intensities (2xST and 8xST); (c) pattern of responses in distal and proximal muscles at different stimulus intensities (2xST and 8xST). RESULTS: (a) The CSP occurred at low intensities (1xST and 2xST) and increased abruptly between 3.5xST and 4xST (corresponding to the pain threshold). The SAP amplitude was saturated before CSP saturation. In the patients with Friedreich's ataxia, the CSP appeared only at higher stimulus intensities (6xST-8xST). (b) The CSP evoked at 2xST showed a fast habituation and slow recovery cycle whereas the opposite behaviour was found at 8xST. (c) Low-threshold stimuli induced an inhibitory response restricted to the distal muscles. High-intensity stimulation produced an electromyographic suppression, significantly increasing from proximal to distal muscles. CONCLUSIONS: Our findings support the notion that low-threshold afferents participate in the production of the CSP in the upper limbs. The different afferents may activate different central neural networks with separate functional significance.
Authors: Markus Kofler; Josep Valls-Solé; Peter Fuhr; Christian Schindler; Barbara R Zaccaria; Leopold Saltuari Journal: Exp Brain Res Date: 2008-04-18 Impact factor: 1.972
Authors: Isabella A Mota; João B Fernandes; Marcio N Cardoso; Xavier Sala-Blanch; Markus Kofler; Josep Valls-Solé Journal: Exp Brain Res Date: 2015-05-30 Impact factor: 1.972