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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.

Original publication

DOI

10.1523/JNEUROSCI.3448-09.2010

Type

Journal article

Journal

J Neurosci

Publication Date

27/01/2010

Volume

30

Pages

1402 - 1412

Keywords

Adult, Arm, Brain Mapping, Cognition, Cortical Synchronization, Evoked Potentials, Executive Function, Female, Hand Strength, Humans, Magnetoencephalography, Male, Motion Perception, Movement, Muscle, Skeletal, Nerve Net, Neurons, Neuropsychological Tests, Orientation, Parietal Lobe, Photic Stimulation, Psychomotor Performance, Saccades, Space Perception, Visual Fields