The Experts below are selected from a list of 19137 Experts worldwide ranked by ideXlab platform
Neil G Muggleton - One of the best experts on this subject based on the ideXlab platform.
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the Precuneus and visuospatial attention in near and far space a transcranial magnetic stimulation study
Brain Stimulation, 2014Co-Authors: Indra Tri Mahayana, Lili Tcheang, Chiaoyun Chen, Chihung Juan, Neil G MuggletonAbstract:Abstract Background There is a large body of evidence for the involvement of the parietal cortex in orientation and navigation in space. This has been supplemented by investigation of the contribution of a number of subregions using transcranial magnetic stimulation. Objective The role of the Precuneus area, located in the medial plane of posterior parietal cortex (PPC), in visuospatial functions is not well understood. We investigated the contribution of this area using the landmark task. Methods Participants were asked to make forced-choice judgments of which side of prebisected line was longer for near and far viewing conditions (70 and 180 cm, respectively). Online 10 Hz, repetitive transcranial magnetic stimulation (rTMS) was delivered for 500 ms over the right Precuneus, rPPC and vertex (control), in separate blocks of trials. The rPPC stimulation was used as a positive control, having previously resulted in “neglect like” spatial bias effects in a number of studies. Results A no-TMS condition showed a leftward spatial bias (pseudoneglect) for near space judgments but not for far space and was used as the baseline. Precuneus stimulation resulted in rightward spatial bias from the midpoint in near space similar to the rPPC neglect-like effect. No significant effects were seen with vertex stimulation. Conclusion This study shows that Precuneus, like other parietal areas, is involved in visuospatial functions. Further work is required to clarify how the contribution of this area differs from other parietal regions.
Ryan C N Darcy - One of the best experts on this subject based on the ideXlab platform.
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cognitive loading via mental arithmetic modulates effects of blink related oscillations on Precuneus and ventral attention network regions
Human Brain Mapping, 2019Co-Authors: Sujoy Ghosh Hajra, Xiaowei Song, Sam M Doesburg, Teresa P L Cheung, Ryan C N DarcyAbstract:: Blink-related oscillations (BROs) have been linked with environmental monitoring processes associated with blinking, with cortical activations in the bilateral Precuneus. Although BROs have been described under resting and passive fixation conditions, little is known about their characteristics under cognitive loading. To address this, we investigated BRO effects during both mental arithmetic (MA) and passive fixation (PF) tasks using magnetoencephalography (n =20), while maintaining the same sensory environment in both tasks. Our results confirmed the presence of BRO effects in both MA and PF tasks, with similar characteristics including blink-related increase in global field power and blink-related activation of the bilateral Precuneus. In addition, cognitive loading due to MA also modulated BRO effects by decreasing BRO-induced cortical activations in key brain regions including the bilateral anterior Precuneus. Interestingly, blinking during MA-but not PF-activated regions of the ventral attention network (i.e., right supramarginal gyrus and inferior frontal gyrus), suggesting possible recruitment of these areas for blink processing under cognitive loading conditions. Time-frequency analysis revealed a consistent pattern of BRO-related effects in the Precuneus in both tasks, but with task-related functional segregation within the anterior and posterior subregions. Based on these findings, we postulate a potential neurocognitive mechanism for blink processing in the Precuneus. This study is the first investigation of BRO effects under cognitive loading, and our results provide compelling new evidence for the important cognitive implications of blink-related processing in the human brain.
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spontaneous blinks activate the Precuneus characterizing blink related oscillations using magnetoencephalography
Frontiers in Human Neuroscience, 2017Co-Authors: Sujoy Ghosh Hajra, Xiaowei Song, Teresa P L Cheung, Ryan C N DarcyAbstract:Spontaneous blinking occurs 15-20 times per minute. Although blinking has often been associated with its physiological role of corneal lubrication, there is now increasing behavioural evidence suggesting that blinks are also modulated by cognitive processes such as attention and information processing. Recent low-density electroencephalography (EEG) studies have reported so-called blink-related oscillations (BROs) associated with spontaneous blinking at rest. Delta-band (0.5-4Hz) BROs are thought to originate from the Precuneus region involved in environmental monitoring and awareness, with potential clinical utility in evaluation of disorders of consciousness. However, the neural mechanisms of BROs have not been elucidated. Using magnetoencephalography (MEG), we characterized delta-band BROs in 36 healthy individuals while controlling for background brain activity. Results showed that, compared to pre-blink baseline, delta-band BROs resulted in increased global field power (p<0.001) and time-frequency spectral power (p<0.05) at the sensor level, peaking at approximately 250ms post-blink maximum. Source localization showed that spontaneous blinks activated the bilateral Precuneus (p<0.05 FWE), and source activity within the Precuneus was also consistent with sensor-space results. Crucially, these effects were only observed in the blink condition and were absent in the control condition, demonstrating that results were due to spontaneous blinks rather than as part of the inherent brain activity. The current study represents the first MEG examination of BROs. Our findings suggest that spontaneous blinks activate the Precuneus regions consistent with environmental monitoring and awareness, and provide important neuroimaging support for the cognitive role of spontaneous blinks.
Giacomo Koch - One of the best experts on this subject based on the ideXlab platform.
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Theta Burst Stimulation of the Precuneus Modulates Resting State Connectivity in the Left Temporal Pole
Brain Topography, 2017Co-Authors: Matteo Mancini, Chiara Mastropasqua, Sonia Bonnì, Viviana Ponzo, Mara Cercignani, Silvia Conforto, Giacomo Koch, Marco BozzaliAbstract:It has been shown that continuous theta burst stimulation (cTBS) over the Precuneus acts on specific memory retrieval abilities. In order to study the neural mechanisms beyond these findings, we combined cTBS and resting-state functional magnetic resonance imaging. Our experimental protocol involved stimulation and sham conditions on a group of healthy subjects, and each condition included a baseline and two follow-up acquisitions (5 and 15 min after baseline) after cTBS. We analysed brain functional connectivity by means of graph theoretical measures, with a specific focus on the network modular structure. Our results showed that cTBS of the Precuneus selectively affects the left temporal pole, decreasing its functional connectivity in the first follow-up. Moreover, we observed a significant increase in the size of the module of the Precuneus in the second follow-up. Such effects were absent in the sham condition. We observed here a modulation of functional connectivity as a result of inhibitory stimulation over the Precuneus. Such a modulation first acts indirectly on the temporal area and then extends the connectivity of the Precuneus itself by a feed-back mechanism. Our current findings extend our previous behavioural observations and increase our understanding of the mechanisms underlying the stimulation of the Precuneus.
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tms evidence for a selective role of the Precuneus in source memory retrieval
Behavioural Brain Research, 2015Co-Authors: Sonia Bonnì, Chiara Mastropasqua, Viviana Ponzo, Marco Bozzali, Domenica Veniero, Carlo Caltagirone, Giacomo KochAbstract:The posteromedial cortex including the Precuneus (PC) is thought to be involved in episodic memory retrieval. Here we used continuous theta burst stimulation (cTBS) to disentangle the role of the Precuneus in the recognition memory process in a sample of healthy subjects. During the encoding phase, subjects were presented with a series of colored pictures. Afterwards, during the retrieval phase, all previously presented items and a sample of new pictures were presented in black, and subjects were asked to indicate whether each item was new or old, and in the latter case to indicate the associated color. cTBS was delivered over PC, posterior parietal cortex (PPC) and vertex before the retrieval phase. The data were analyzed in terms of hits, false alarms, source errors and omissions. cTBS over the Precuneus, but not over the PPC or the vertex, induced a selective decrease in source memory errors, indicating an improvement in context retrieval. All the other accuracy measurements were unchanged. These findings suggest a direct implication of the Precuneus in successful context-dependent retrieval.
Koen V Haak - One of the best experts on this subject based on the ideXlab platform.
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functional connectivity of the Precuneus reflects effectiveness of visual restitution training in chronic hemianopia
bioRxiv, 2020Co-Authors: Hinke N Halbertsma, Joris A Elshout, Douwe P Bergsma, David G Norris, Frans W Cornelissen, Albert V Van Den Berg, Koen V HaakAbstract:Visual field defects in chronic hemianopia can improve through visual restitution training, yet not all patients benefit equally from this long and exhaustive process. Here, we asked if resting-state functional connectivity prior to visual restitution could predict training success. In two training sessions of eight weeks each, 20 patients with chronic hemianopia performed a visual discrimination task by directing spatial attention towards stimuli presented in either hemifield, while suppressing eye movements. We examined two effects: a sensitivity change in the attended (trained) minus the unattended (control) hemifield (i.e., a training-specific improvement), and an overall improvement (i.e., a total change in sensitivity after both sessions). We then identified five visual resting-state networks and evaluated their functional connectivity in relation to both training effects. We found that the functional connectivity strength between the anterior Precuneus and the Occipital Pole Network was positively related to the attention modulated (i.e., training-specific) improvement. No such relationship was found for the overall improvement or for the other visual networks of interest. Our finding suggests that the anterior Precuneus plays a role in training-induced visual field improvements. The resting-state functional connectivity between the anterior Precuneus and the Occipital Pole Network may thus serve as an imaging-based biomarker that quantifies a patient9s potential capacity to direct spatial attention. This may help to identify hemianopia patients that are most likely to benefit from visual restitution training.
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functional connectivity of the Precuneus reflects effectiveness of visual restitution training in chronic hemianopia
NeuroImage: Clinical, 2020Co-Authors: Hinke N Halbertsma, Joris A Elshout, Douwe P Bergsma, David G Norris, Frans W Cornelissen, Albert V Van Den Berg, Koen V HaakAbstract:Abstract Visual field defects in chronic hemianopia can improve through visual restitution training, yet not all patients benefit equally from this long and exhaustive procedure. Here, we asked if resting-state functional connectivity prior to visual restitution could predict training success. In two training sessions of eight weeks each, 20 patients with chronic hemianopia performed a visual discrimination task by directing spatial selective attention towards stimuli presented in either hemifield, while suppressing eye movements. We examined two effects: a sensitivity change in the attended (trained) minus the unattended (control) hemifield (i.e., a training-specific improvement), and an overall improvement (i.e., a total change in sensitivity after both sessions). We then identified five visual resting-state networks and evaluated their functional connectivity in relation to both training effects. We found that the functional connectivity strength between the anterior Precuneus and the Occipital Pole Network was positively related to the attention modulated (i.e., training-specific) improvement. No such relationship was found for the overall improvement or for the other visual networks of interest. Our finding suggests that the anterior Precuneus plays a role in attention-modulated visual field improvements. The resting-state functional connectivity between the anterior Precuneus and the Occipital Pole Network may thus serve as an imaging-based biomarker that quantifies a patient's potential capacity to direct spatial attention. This may help to identify hemianopia patients that are most likely to benefit from visual restitution training.
Hidenao Fukuyama - One of the best experts on this subject based on the ideXlab platform.
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functional relevance of the Precuneus in verbal politeness
Neuroscience Research, 2015Co-Authors: Aoi Ashizuka, Tatsuya Mima, Nobukatsu Sawamoto, Naoya Oishi, Genichi Sugihara, Ryosaku Kawada, Hidehiko Takahashi, Toshiya Murai, Hidenao FukuyamaAbstract:Abstract Non-competitive and non-threatening aspects of social hierarchy, such as politeness, are universal among human cultures, and might have evolved from ritualized submission in primates; however, these behaviors have rarely been studied. Honorific language is a type of polite linguistic communication that plays an important role in human social interactions ranging from everyday conversation to international diplomacy. Here, functional magnetic resonance imaging (fMRI) revealed selective Precuneus activation during a verbal politeness judgment task, but not other linguistic-judgment or social-status recognition tasks. The magnitude of the activation was correlated with the task performance. Functional suppression of the activation using cathodal transcranial direct-current stimulation reduced performance in the politeness task. These results suggest that the Precuneus is an essential hub of the verbal politeness judgment.
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Activation of the Precuneus is related to reduced reaction time in serial reaction time tasks
Neuroscience Research, 2005Co-Authors: Kenichi Oishi, Keiichiro Toma, Epifanio Bagarinao, Kayako Matsuo, Toshiharu Nakai, Kazuo Chihara, Hidenao FukuyamaAbstract:Multiple brain areas are activated during serial reaction time (RT) tasks (SRTTs), but the part of the brain that facilitates reductions in RT remains unclear. The present study attempted to determine the brain region contributing most to improved RTs during explicit SRTTs. Subjects comprised 18 healthy volunteers who were instructed to press one of four buttons corresponding to visual stimuli as quickly as possible and with minimal errors during functional MRI. Stimuli were presented either in random order (control condition) or in a repeated six-item sequence (learning condition). Conventional analysis contrasting learning and control conditions revealed activation in the prefrontal-parietal area, which shifted to motor area. Subjects with high RT reduction showed more prominent activation in the Precuneus than subjects with low RT reduction. Intra-subject correlation analysis revealed that time course of Precuneus activation was unrelated to time-course of RT reduction. However, inter-subject correlation analysis revealed that RT changes correlate only with Precuneus activation, meaning that subjects showing more prominent RT reduction revealed more prominent activation of the Precuneus, which is known to play critical roles in controlling finger movements with reference to buffered memory.
