Klarsfeld, A. | bioRxiv Science

bioRxiv2022

EEG-neurofeedback for promoting neuromodulation in the elderly: evidence from a double-blind study

BackgroundElectroencephalography (EEG) is a non-invasive method that records the brain signals with time resolution in the millisecond range, thereby allowing the monitoring of subjects mental states in real time. Using appropriate biomarkers extracted from these EEG signals and presenting them back in a neurofeedback loop can foster neural compensation mechanisms by teaching subjects to modulate their brain activity. Over the last decades, several neural biomarkers of aging have been described, with growing evidence suggesting that neuromodulation may have an important role in regulating brain activity in the elderly. Methods and objectivesWe used three neural biomarkers of aging, namely the Peak Alpha Frequency, the Gamma-band synchronization, and the Theta/Beta ratio, in the framework of an EEG-based brain-computer interface, with two main objectives: 1) to test whether healthy elderly people with subjective memory complaints may learn to modulate their brain activity through EEG-neurofeedback training in a double-blind, placebo-controlled study; and 2) whether that neuromodulation may have a positive impact on subjects cognition. ResultsA significant self-modulation of two neural biomarkers that usually decline with age was observed exclusively in the group of subjects who underwent the EEG-neurofeedback training, in clear contrast with the subjects who received the sham feedback. This neuromodulation did not have a direct effect on subjects cognitive abilities, as measured by neuropsychological tests pre-versus post-training, probably because all the subjects accurately performed these tests already at study entry (i.e., pre-training). ConclusionThe results of this double-blind study are in line with one of the main criteria for successful neuromodulation, thus encouraging research on EEG-neurofeedback as a promising non-pharmacological intervention for promoting self-regulation of brain activity with a view to improve cognitive aging.

neuroscience↗

bioRxiv2022

Why Are Alzheimer's Disease Patients Unaware of their Memory Deficits?

Anosognosia, or the lack of awareness of ones own impairment, is frequent for memory deficits in patients with Alzheimers disease (AD). Although often related to frontal dysfunctions, the neural mechanisms of anosognosia remain largely unknown. We hypothesized that anosognosia in AD may result from a failure in the error-monitoring system, thus preventing patients from being aware of and learning from their own errors. We therefore investigated the event-related potentials evoked by erroneous responses during a memory task in two groups of amyloid positive individuals who had only subjective memory complaints at study entry: 1) those who progressed to AD; and 2) those who remained cognitively normal after five years of follow-up. Our findings revealed direct evidence of a failure in the error-monitoring system at early stages of AD, suggesting that it may be the critical neural substrate of anosognosia in this neurodegenerative disorder.

neuroscience↗