We investigated somatosensory evoked potentials (SEPs) habituation in 29 patients with mild dementia, grouped according to clinical, neuropsychological, and neuroimaging features.
We recorded median-nerve SEPs in 15 AD-type and 14 VD-type, mild dementia, and 15 controls. We measured N20-P25 amplitudes from 3 blocks of 200 sweeps, and assessed amplitude of block 1, and habituation from amplitude changes between the 3 sequential blocks.
ANOVA showed a main effect of factor group (F = 3.43 p = 0.042). AD-type patients, had normal block1 SEP amplitudes, but abnormal habituation (p = 0.036). VD-type patients had normal SEP amplitudes and habituation (p = 0.58).
SEP habituation is altered in AD-type dementia suggesting hyperresponsivity of the somatosensory cortex. This abnormality is not found in patients with VD-type mild dementia, which manifest normal synaptic function to repetitive stimulation. Further investigation is deserved to see whether abnormal SEP habituation may represent a neurophysiological marker of degenerative dementia.