Eeg Markers for Cognitive Decline in Elderly Subjects With Subjective Memory Complaints

Abstract

New treatments for Alzheimer's disease require early detection of cognitive decline. Most studies seeking to identify markers of early cognitive decline have focused on a limited number of measures. We sought to establish the profile of brain function measures which best define early neuropsychological decline. We compared subjects with subjective memory complaints to normative controls on a wide range of EEG derived measures, including a new measure of event-related spatio-temporal waves and biophysical modeling, which derives anatomical and physiological parameters based on subject's EEG measurements. Measures that distinguished the groups were then related to cognitive performance on a variety of learning and executive function tasks. The EEG measures include standard power measures, peak alpha frequency, EEG desynchronization to eyes-opening, and global phase synchrony. The most prominent differences in subjective memory complaint subjects were elevated alpha power and an increased number of spatio-temporal wave events. Higher alpha power and changes in wave activity related most strongly to a decline in verbal memory performance in subjects with subjective memory complaints, and also declines in maze performance and working memory reaction time. Interestingly, higher alpha power and wave activity were correlated with improved performance in reverse digit span in the subjective memory complaint group. The modeling results suggest that differences in the subjective memory complaint subjects were due to a decrease in cortical and thalamic inhibitory gains and slowed dendritic time-constants. The complementary profile that emerges from the variety of measures and analyses points to a nonlinear progression in electrophysiological changes from early neuropsychological decline to late-stage dementia, and electrophysiological changes in subjective memory complaint that vary in their relationships to a range of memory-related tasks.

Alpha band disruption in the AD-continuum starts in the Subjective Cognitive Decline stage: a MEG study

“…As above mentioned, those neuroimaging studies reporting brain alterations in SCD have mostly reported AD-like pathology or changes in a similar direction but to a lesser extent to those exhibited by AD patients. However, to the best of our knowledge the only study to date reporting resting state power spectral analysis in SCD reported an increase in alpha power both in eyes open and eyes closed condition with respect to controls without cognitive concerns28. The authors suggested a nonlinear evolution from healthy controls to AD.…”

Measurement of phase gradients in the EEG

“…Patterns of spatio-temporal wave activity, measured in scalp EEG, showed specificity across a number of clinical groups: attention deficit/hyperactivity disorder, first episode psychosis and Alzheimer's disease. Phase gradient measures have also been used to predict cognitive decline in elderly subjects with subjective memory complaints (Alexander et al, 2006). relative phases by s did not alter the types or number of factors found.…”

Brain Structure and Function Correlates of General and Social Cognition

“…Research has also identified structural, neurophysiological and neuropsychological markers that are associated with conditions such as schizophrenia, mild cognitive impairment, Alzheimer's disease and Attention Deficit Disorder [3,10,38,43,104]. These markers alone show a low level of specificity but when combined using an integrative approach and multiple measures from a large test battery tapping into structural, neurophysiological and neuropsychological domains, the specificity between disorders can be significantly increased [34].…”

“…This methodology has been frequently published in articles in is this current volume and the following references [3,17,40,48,100]. A summary of the measures is provided below.…”