[Associated EMG responses in Alzheimer's disease and in healthy subjects].
OBJECTIVE
Recently, the appearance of associated EMG responses in patients with probable Alzheimer s disease (AD) have been reported during the performance of cue stimuli recognition tasks using an oddball model. We present our work with AD patients and on the possibility of obtaining these responses in normal subjects by modifying the conditions under which the exploration is carried out.


METHODS
We review 38 cases of probable AD, mild and moderate in intensity, in which we explored reaction time by bilateral EMG recording in the extensor muscles of the hand. The same exploration was performed in 20 healthy subjects in basal conditions and again while a simple mathematical task was being performed.


RESULTS
In two of the 38 cases, both of moderate intensity, we observed associated EMG responses. On varying the conditions of exploration, 12 of the 20 normal subjects presented associated EMG responses.


CONCLUSIONS
Associated EMG responses are a neurophysiological phenomenon that can be observed in some patients with AD. In normal subjects, it is possible to trigger the appearance of associated EMG responses by reducing their capacity to concentrate on the task to be performed. During the performance of unilateral motor tasks, inhibition pathways are activated physiologically to prevent the mirror contraction of contralateral muscles, which can be affected by the lowered capacity to pay attention.
Fernández-Lastra
A
A
Servicio de Neurofisiología Clínica, Complexo Hospitalario Xeral-Calde, Lugo, 27004, España. aflastra@hotmail.com
Molares-Rodríguez
M
M
Penzol-Díaz
J
J
D000328:Adult; D000544:Alzheimer Disease / Q000175:diagnosis / Q000503:physiopathology*; D001288:Attention / Q000502:physiology; D004576:Electromyography; D006225:Hand; D006801:Humans; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology; D011930:Reaction Time