Regions with different evoked frequency band responses during early-stage visual processing distinguish mild Alzheimer dementia from mild cognitive impairment and normal aging.

Although diagnostic procedures have been developed for detection of mild cognitive impairment (MCI) and mild Alzheimer dementia (AD), more valid noninvasive tools are needed. In this work, we apply a procedure based on the evidences that different evoked frequency band responses may emerge from different sources during early-stage visual processing in a mental state-specific manner, while subjects were passively viewing a visual stimulus. In this case, spatial differences should arise across mental conditions such as mild Alzheimer dementia, mild cognitive impairment, and normal aging. With the use of EEG source image we found three different neural patterns in aged individuals: (1) left hippocampus and midbrain in mild AD, (2) left lateral orbitofrontal gyrus, left nucleus accumbens, caudate nucleus, thalamus, posterior cinguli, right precuneous, right superior parietal lobe in MCI, and (3) right lateral-medial orbitofrontal gyrus, caudate nucleus, thalamus, right lateral occipitotemporal gyrus in elderly controls. Although preliminary, these results show remarkably robust differences that distinguish between an age-matched control group, a group with MCI, and a group with mild AD. Because the method applied in this work differentiates among clinical entities with varying severity of cognitive decline, it may eventually serve as an electrophysiological marker in the early detection of neurodegeneration.