Age-Related Task Sensitivity of Frontal EEG Entropy During Encoding Predicts Retrieval

Abstract

Age-related declines in memory may be due in part to changes in the complexity of neural activity in the aging brain. Electrophysiological entropy provides an accessible measure of the complexity of ongoing neural activity. In the current study, we calculated the permutation entropy of the electroencephalogram (EEG) during encoding of relevant (to be learned) and irrelevant (to be ignored) stimuli by younger adults, older adults, and older cognitively declined adults. EEG entropy was differentially sensitive to task requirements across groups, with younger and older controls exhibiting greater control of encoding-related activity than older declined participants. Task sensitivity of frontal EEG during encoding predicted later retrieval, in line with previous evidence that cognitive decline is associated with reduced ability to self-initiate encoding-related processes.

The effects of cardiorespiratory fitness and acute aerobic exercise on executive functioning and EEG entropy in adolescents

“…What the current study adds is the suggestion that levels of physical fitness may also alter brain dynamics in left frontal areas, with lower entropy possibly reflecting higher levels of efficiency in terms of information processing, or the requirements for higher levels of adaptive system uncertainty in the context of executive functioning tasks. Previous studies have shown that task-sensitivity of entropy is associated with poorer cognitive performance when younger and older adults are compared (O’Hora et al, 2013 ). Specifically, the reduction of EEG entropy from more disordered to less disordered in line with task demands predicted later retrieval.…”

“…Importantly, recent research suggests that EEG entropy may be sensitive to cognitive demands and can be used to predict group differences in cognitive performance (Hogan et al, 2012 ; O’Hora et al, 2013 ). For example, O’Hora et al ( 2013 ) found that task sensitivity of frontal EEG during encoding predicted later retrieval in a sample of younger and older adults, with reduced task sensitivity of frontal EEG observed in older adults with cognitive decline. However, no study to date has examined if fitness levels or acute bouts of aerobic exercise influence the entropy of the EEG in response to cognitive demands, or whether fitness levels interact with acute exercise in this context.…”

States and traits of neural irregularity in the age-varying human brain

“…A desirable measure of neural irregularity should not only predict differences in encoding and perceptual decisions between identical stimuli (in terms of a neural state), but also track changes in the degree of irregularity that come with older age (in terms of a neural trait) 2 . The most promising measures in this respect, offering sufficient resolution in time and space, derive from information theory: Entropy measures have been used extensively to research epileptic seizures 12 , 13 or vigilance states 14 and cognitive processes in the EEG 15 . They offer an intuitive way of quantifying neural irregularity since with increasing versus decreasing irregularity of the EEG signal, entropy of the EEG will increase versus decrease, respectively.…”

States and traits of neural irregularity in the age-varying human brain

“…Information-theoretic measures on the other hand have been used extensively to research epileptic seizures (Nicolaou and Georgiou, 2012;Dickten et al, 2016) or vigilance states (Bruzzo et al, 2008;Nicolaou and Georgiou, 2011) and cognitive processes in the EEG (O'Hora et al, 2013).…”