Background Decreased amplitudes and prolonged latencies of cortical somatosensory evoked potentials have been described in mildly affected HD and in assymptomatic genetic carriers. It has been postulated that, due to cognitive impairment, awareness of stimuli is impaired contributing to the neurophysiological findings.

Objetives We have examined temporal awareness using the Libet’s method (Libet et al., 1983) while recording Long Latency Evoked Potentials (LLEPs). We hypothesised awareness of the stimuli would be preserved in spite of altered LLEPs in HD.

Methods We recorded LLEPs to contact heat and electrical stimuli while subjects were looking at the Libet’s clock to assess the time of subjective perception of the stimulus. We measured reaction time, quantitative sensory testing, the sudomotor skin response and silent periods too during sustained voluntary contraction.

Conclusions Patients with HD had significantly reduced amplitudes and persistence of LLEPs as well as prolonged simple reaction times to the stimuli. However, awareness of the stimuli was not impaired and QST, SSR and silent periods showed no significant alterations regarding control subjects.

Conscious awareness of a stimulus is not altered in HD at early stages of the disease. The alterations of the evoked potentials could therefore be a reflex of the loss of stimulus salience, probably related to striatal degeneration which also impairs the ability to react towards a highly salient stimuli. Normal awareness may even compensate for these alterations making the subject functional for daily living.