Spectral signature of spatial updating across eye-movements
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1
Radboud University Nijmegen, Donders Institute for Brain, Cognition and Behaviour, Netherlands
It has been shown that extrastriate and parietal areas encode spatial working memories in dynamic, gaze-centered maps, with each eye movement causing an internal updating of these representations. We have applied magnetoencephalography (MEG) to investigate the role of alpha (~10 Hz) and gamma (>40 Hz) band oscillations in the storage and updating of briefly flashed saccade goals. In the experiments, subjects had to remember the location of a visual goal, briefly presented to the left or right relative to a central fixation point. After a delay of 2 s., the central fixation point jumped to a new location, immediately followed by the subject’s gaze. Then, after a second delay, subjects made a saccade to the remembered goal location. We examined changes in spectral power during the two delay periods, excluding error trials based on EOG eye tracking, and removing ocular artifacts using ICA. We used spatial filtering (beamforming) techniques to locate the sources of our effects. After presentation of the goal target, we found a strong increase of gamma band (40-100 Hz) power in contralateral occipito-parietal areas. This gamma band power was sustained in a more narrow frequency band (~50-60 Hz) during the first delay period in extrastriate areas only. The alpha band showed a strong increase of power over ipsilateral occipital areas, which decreased over the course of the first delay period. After the change of fixation point, i.e., during the second delay period, power increased in 70-100 Hz gamma band, (70-100 Hz) depending on the remembered location of the goal relative to the new fixation point, with a stronger gamma band synchronizing in the posterior parietal cortex contralateral to the upcoming saccade direction. Similarly, the alpha power remained biased to the ipsilateral hemisphere when the remembered goal remained at the same side of the fixation point, but switched to the other hemisphere when the goal location reversed sides relative to the new fixation point. The dynamic synchronization of the alpha band during spatial updating is consistent with an eye-centered mechanism, disengaging the hemisphere that does not encode the saccade goal before and after updating. The neuronal synchronization in the gamma band seems to reflect an updated eye-centered goal representation of the upcoming saccade in the posterior parietal cortex.
Conference:
Biomag 2010 - 17th International Conference on Biomagnetism , Dubrovnik, Croatia, 28 Mar - 1 Apr, 2010.
Presentation Type:
Poster Presentation
Topic:
Sensory Processing and Functional Connectivity
Citation:
Der Werf
JV,
Buchholz
VN,
Jensen
O and
Medendorp
PW
(2010). Spectral signature of spatial updating across eye-movements.
Front. Neurosci.
Conference Abstract:
Biomag 2010 - 17th International Conference on Biomagnetism .
doi: 10.3389/conf.fnins.2010.06.00207
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Received:
30 Mar 2010;
Published Online:
30 Mar 2010.
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Correspondence:
Jurrian V Der Werf, Radboud University Nijmegen, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, Netherlands, j.vanderwerf@donders.ru.nl