Abstract
The functional role of the alpha-rhythm which dominates the human electroencephalogram (EEG) is unclear. It has been related to visual processing, attentional selection and object coherence, respectively. Here we tested the interaction of alpha oscillations of the human brain with visual search tasks that differed in their attentional demands (pre-attentive vs. attentive) and also in the necessity to establish object coherence (conjunction vs. single feature). Between pre- and post-assessment elderly subjects received 20 min/d of repetitive transcranial alternating current stimulation (tACS) over the occipital cortex adjusted to their individual alpha frequency over five consecutive days. Compared to sham the entrained alpha oscillations led to a selective, set size independent improvement in the conjunction search task performance but not in the easy or in the hard feature search task. These findings suggest that cortical alpha oscillations play a specific role in establishing object coherence through suppression of distracting objects.
Highlights
The detection of rhythmic electrical potential changes over the human scalp, known as the electroencephalogram (EEG), dates back to the 1920s [1] their role in perceptual and cognitive processes is still not well understood
Three different theories regarding the physiological meaning of the alpha rhythm have been put forward: The first relates alpha oscillations to bottom-up visual processing and perception, the second proposes a correlation between alpha activity and attentional selection, especially inhibition of irrelevant information, and the third suggests a role of alpha synchronization in the integration over distributed neuronal networks in order to create coherent object representations
Post hoc tests revealed that the conjunction search was significantly harder than the easy feature condition but easier to manage than the hard feature condition (p’s < .001)
Summary
The detection of rhythmic electrical potential changes over the human scalp, known as the electroencephalogram (EEG), dates back to the 1920s [1] their role in perceptual and cognitive processes is still not well understood. The most prominent of these EEG fluctuations is the alpha rhythm which emerges most clearly over posterior electrodes during a state of relaxed wakefulness with the eyes closed. To put it three different theories regarding the physiological meaning of the alpha rhythm have been put forward: The first relates alpha oscillations to bottom-up visual processing and perception, the second proposes a correlation between alpha activity and attentional selection, especially inhibition of irrelevant information, and the third suggests a role of alpha synchronization in the integration over distributed neuronal networks in order to create coherent object representations. Much later by the usage of simultaneous EEG and fMRI it was PLOS ONE | DOI:10.1371/journal.pone.0143533 November 25, 2015
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
