Contingent negative variation in dementia

The Contingent Negative Variation (CNV) is a slow DC shift seen over the scalp during states of anticipation. The present investigation is an attempt to study the differences in the CNV between patients with dementia and the normal controls. The sample consisted of 8 patients with dementia, of which 4 had cortical atrophy and 4 had subcortical atrophy and 8 age and gender-matched normal subjects. CNV and auditory evoked potentials (AEP) were recorded on a Biologic Topographic Mapping System. Results indicated that in normals a typical topographic distribution of early and late components of CNV show greater amplitudes in the anterior and central electrodes. Of the 8 dementia patients, 4 patients with subcortical atrophy and 2 with cortical atrophy showed only early component. All the patients showed the N1 component and there was no significant difference in the latency compared with the normal controls. However, significant amplitude reduction was noticed in the patients.