Enhancement of the somatosensory N140 component during attentional training after stroke

To evaluate the training effect on the N140 component of the somatosensory event related potential in patients suffering from first ever stroke in the middle cerebral artery area and prove the influence, if any, on a component related to spatial attention.

Forty patients were studied. Twenty were enrolled in a daily discrimination training task using an oddball paradigm with cutaneous electrical stimuli. The training period was 3 weeks. Twenty control patients were untrained. Electroencephalographic signals were recorded from scalp electrodes during each training session. In the controls, only two recordings were made, at baseline and after 3 weeks. Disability at the time of admission and discharge were evaluated using the functional independence measure (FIM). Twenty healthy control volunteers were also studied.

During training, event related potentials took the form of a large positive-negative complex over the period 106-160ms after the stimulus, followed by a smaller P300 component. The amplitude of the responses was smaller over the affected hemisphere (P<0.05). In the treatment group, N140 was present in 3 patients from the beginning and in 16 after training. Four of the untrained control patients showed a N140 at baseline, whereas it was seen in only 6 after 3 weeks (Chi-square 8.1; P<0.001).

In stroke patients, training improved the recovery of N140. That potential was prognostic of general outcome since its presence at baseline was correlated with a higher FIM score on discharge.