TY  - JOUR
AU  - de Lange, F.P.
AU  - Jensen, O.
AU  - Dehaene, S.
PY  - 2010
UR  - https://hdl.handle.net/2066/115465
AB  - In the last decade, great progress has been made in characterizing the accumulation of neural information during simple unitary perceptual decisions. However, much less is known about how sequentially presented evidence is integrated over time for successful decision making. The aim of this study was to study the mechanisms of sequential decision making in humans. In a magnetoencephalography (MEG) study, we presented healthy volunteers with sequences of centrally presented arrows. Sequence length varied between one and five arrows, and the accumulated directions of the arrows informed the subject about which hand to use for a button press at the end of the sequence (e.g., LRLRR should result in a right-hand press). Mathematical modeling suggested that nonlinear accumulation was the rational strategy for performing this task in the presence of no or little noise, whereas quasilinear accumulation was optimal in the presence of substantial noise. MEG recordings showed a correlate of evidence integration over parietal and central cortex that was inversely related to the amount of accumulated evidence (i.e., when more evidence was accumulated, neural activity for new stimuli was attenuated). This modulation of activity likely reflects a top–down influence on sensory processing, effectively constraining the influence of sensory information on the decision variable over time. The results indicate that, when making decisions on the basis of sequential information, the human nervous system integrates evidence in a nonlinear manner, using the amount of previously accumulated information to constrain the accumulation of additional evidence.
TI  - Accumulation of evidence during sequential decision making: the importance of top-down factors
EP  - 738
SN  - 0270-6474
SP  - 731
JF  - The Journal of Neuroscience
VL  - vol. 30
DO  - https://doi.org/10.1523/JNEUROSCI.4080-09.2010
L1  - https://repository.ubn.ru.nl/bitstream/handle/2066/115465/115465-OA.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/2066/84274
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  - 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  -