Feedback Training of EEG Gamma Band Oscillations Improves Object Processing

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Introduction

The binding-by-synchrony hypothesis assumes that neural object coding in the visual cortex is associated with oscillatory modulation of cell firing in the gamma frequency range between 30 and 50 Hz. Studies have shown that attention can enhance the gamma band activity, accordingly indicating a possible manipulation of the gamma band by a Biofeedback approach. Our aim was to investigate a voluntary influence of participants on their gamma band power within several sessions of Biofeedback training. We were further interested in exploring the impact of trained gamma power over the visual cortex on object perception and recognition.

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Methods

We used an EEG based Biofeedback method based on an online estimation of the gamma band power over the occipital cortex (electrodes PO7/PO8). With a latency of 1 second this signal was displayed back to the participant as vertically moving bars and the participant was instructed to move the bars upwards. A trial consisted of a Disengaged Period for the measurement of a baseline value of gamma band power and the position of the bars of the following Feedback Period represented the percent change

Results

Participants showed a clear increment in the ability of voluntarily increasing the gamma band power with each session. The power within the gamma band increased over sessions and was larger during the feedback training compared to baseline recordings between the training sessions. The resulting topography showed that the increase of the gamma power was limited to the visual cortex and was not a general increase of gamma band power of the whole head (Figure 2A). A frequency distribution showed

Conclusions

Our results of Biofeedback training demonstrated that the participants clearly learned to increase the power of the gamma band over the visual cortex. Within a few training sessions, participants gained a voluntary influence on the oscillatory state and showed a clear increase of gamma power mainly in the trained electrodes PO7 and PO8. In addition, we showed that an increase of gamma band activity over the visual cortex can improve object detection and encoding accompanied by a greater

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