Abstract
BackgroundPrestimulus EEG alpha activity in humans has been considered to reflect ongoing top-down preparation for the performance of subsequent tasks. Since theta oscillations may be related to poststimulus top-down processing, we investigated whether prestimulus EEG theta activity also reflects top-down cognitive preparation for a stimulus.ResultsWe recorded EEG data from 15 healthy controls performing a color and shape discrimination task, and used the wavelet transformation to investigate the time course and power of oscillatory activity in the signals. We observed a relationship between both anterior theta and posterior alpha power in the prestimulus period and the type of subsequent task.ConclusionsSince task-differences were reflected in both theta and alpha activities prior to stimulus onset, both prestimulus theta (particularly around the anterior region) and prestimulus alpha (particularly around the posterior region) activities may reflect prestimulus top-down preparation for the performance of subsequent tasks.
Highlights
Prestimulus EEG alpha activity in humans has been considered to reflect ongoing top-down preparation for the performance of subsequent tasks
For the accuracy of the task-performance, we found a strong 'task' effect (F(1,14) = 15.0, p < 0.005), indicating that the color task performance showed significantly higher accuracy than the shape task performance
We observed that the anterior regions of interest (ROIs) showed significantly higher prestimulus total theta power than the posterior ROI (F(1,14) = 10.0, p < 0.01; anterior ROI: 10.2 μV2, posterior ROI: 3.5 μV2; cf
Summary
Prestimulus EEG alpha activity in humans has been considered to reflect ongoing top-down preparation for the performance of subsequent tasks. Since theta oscillations may be related to poststimulus top-down processing, we investigated whether prestimulus EEG theta activity reflects top-down cognitive preparation for a stimulus. A cognitive intention (e.g. expectation, mental readiness, active redirection of attention), embedded in a top-down process, may precede an event or stimulus. Bottom-up sensory processing is guided by such top-down processing as a specific reallocation of attention relevant to the type of stimulus to follow or task to be performed. In this way, top-down intentional processing can increase the speed and efficiency of perceptual identification
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