TY - JOUR AU - Werf, J. van der AU - Jensen, O. AU - Fries, P. AU - Medendorp, W.P. PY - 2010 UR - https://hdl.handle.net/2066/84274 AB - Although single-unit studies in monkeys have identified effector-related regions in the posterior parietal cortex (PPC) during saccade and reach planning, the degree of effector specificity of corresponding human regions, as established by recordings of the blood oxygen level-dependent signal, is still under debate. Here, we addressed this issue from a different perspective, by studying the neuronal synchronization of the human PPC during both reach and saccade planning. Using magnetoencephalography (MEG), we recorded ongoing brain activity while subjects performed randomly alternating trials of memory-guided reaches or saccades. Additionally, subjects performed a dissociation task requiring them to plan both a memory-guided saccade and reach to locations in opposing visual hemifields. We examined changes in spectral power of the MEG signal during a 1.5 s memory period in relation to target location (left/right) and effector type (eye/hand). The results show direction-selective synchronization in the 70-90 Hz gamma frequency band, originating from the medial aspect of the PPC, when planning a reaching movement. In contrast, activity in a more central portion of the PPC was synchronized in a lower gamma band (50-60 Hz) when planning the direction of a saccade. Both observations were corroborated in the dissociation task. In the lower frequency bands, we observed sustained alpha-band (8-12 Hz) desynchronization in occipitoparietal regions, but in an effector-unspecific manner. These results suggest that distinct modules in the posterior parietal cortex encode movement goals of different effectors by selective gamma-band activity, compatible with the functional organization of monkey PPC. TI - Neuronal synchronization in human posterior parietal cortex during reach planning EP - 1412 SN - 0270-6474 IS - iss. 4 SP - 1402 JF - The Journal of Neuroscience VL - vol. 30 PS - 11 p. DO - https://doi.org/10.1523/JNEUROSCI.3448-09.2010 L1 - https://repository.ubn.ru.nl/bitstream/handle/2066/84274/84274.pdf?sequence=1 ER - TY - JOUR AU - Jensen, O. AU - Mazaheri, A. PY - 2010 UR - https://hdl.handle.net/2066/89275 AB - In order to understand the working brain as a network, it is essential to identify the mechanisms by which information is gated between regions. We here propose that information is gated by inhibiting task-irrelevant regions, thus routing information to task-relevant regions. The functional inhibition is reflected in oscillatory activity in the alpha band (8-13 Hz). From a physiological perspective the alpha activity provides pulsed inhibition reducing the processing capabilities of a given area. Active processing in the engaged areas is reflected by neuronal synchronization in the gamma band (30-100 Hz) accompanied by an alpha band decrease. According to this framework the brain could be studied as a network by investigating cross-frequency interactions between gamma and alpha activity. Specifically the framework predicts that optimal task performance will correlate with alpha activity in task-irrelevant areas. In this review we will discuss the empirical support for this framework. Given that alpha activity is by far the strongest signal recorded by EEG and MEG, we propose that a major part of the electrophysiological activity detected from the working brain reflects gating by inhibition. TI - Shaping functional architecture by oscillatory alpha activity: gating by inhibition. SN - 1662-5161 JF - Frontiers in Human Neuroscience VL - vol. 4 DO - https://doi.org/10.3389/fnhum.2010.00186 L1 - https://repository.ubn.ru.nl/bitstream/handle/2066/89275/89275.pdf?sequence=1 ER - TY - JOUR AU - Mazaheri, A. AU - Jensen, O. PY - 2010 UR - https://hdl.handle.net/2066/89381 AB - The conventional assumption in human cognitive electrophysiology using EEG and MEG is that the presentation of a particular event such as visual or auditory stimuli evokes a "turning on" of additional brain activity that adds to the ongoing background activity. Averaging multiple event-locked trials is thought to result in the cancellation of the seemingly random phased ongoing activity while leaving the evoked response. However, recent work strongly challenges this conventional view and demonstrates that the ongoing activity is not averaged out due to specific non-sinusoidal properties. As a consquence, systematic modulations in ongoing activity can produce slow cortical evoked responses reflecting cognitive processing. In this review we introduce the concept of "rhythmic pulsing" to account for this specific non-sinusoidal property. We will explain how rhythmic pulsing can create slow evoked responses from a physiological perspective. We will also discuss how the notion of rhythmic pulsing provides a unifying framework linking ongoing oscillations, evoked responses and the brain's capacity to process incoming information. TI - Rhythmic pulsing: linking ongoing brain activity with evoked responses. SN - 1662-5161 JF - Frontiers in Human Neuroscience VL - vol. 4 DO - https://doi.org/10.3389/fnhum.2010.00177 L1 - https://repository.ubn.ru.nl/bitstream/handle/2066/89381/89381.pdf?sequence=1 ER - TY - JOUR AU - Werf, J. van der AU - Jensen, O. AU - Fries, P. AU - Medendorp, W.P. PY - 2010 UR - https://hdl.handle.net/2066/84272 TI - Neuronal Synchronization in Human Posterior Parietal Cortex during Reach Planning EP - 1412 SN - 0270-6474 IS - iss. 4 SP - 1402 JF - The Journal of Neuroscience VL - vol. 30 DO - https://doi.org/10.1523/JNEUROSCI.3448-09.2010 L1 - https://repository.ubn.ru.nl/bitstream/handle/2066/84272/84272.pdf?sequence=1 ER -