scholarly journals Effects of rTMS Conditioning over the Fronto-parietal Network on Motor versus Visual Attention

2007 ◽  
Vol 19 (3) ◽  
pp. 513-524 ◽  
Author(s):  
Elisabeth Rounis ◽  
Kielan Yarrow ◽  
John C. Rothwell
Keyword(s):  
Visual Attention ◽  
Parietal Cortex ◽  
Posterior Parietal Cortex ◽  
Right Hemisphere ◽  
Repetitive Transcranial Magnetic Stimulation ◽  
Motor Preparation ◽  
Attention Task ◽  
Spatial Orienting ◽  
Left Dlpfc ◽  
The Right

Many studies have shown that visuospatial orienting attention depends on a network of frontal and parietal areas in the right hemisphere. Rushworth et al. [Rushworth, M. F., Krams, M., & Passingham, R. E. The attentional role of the left parietal cortex: The distinct lateralization and localization of motor attention in the human brain. Journal of Cognitive Neuroscience, 13, 698–710, 2001] have recently provided evidence for a left-lateralized network of parietal areas involved in motor attention. Using two variants of a cued reaction time (RT) task, we set out to investigate whether high-frequency repetitive transcranial magnetic stimulation (rTMS; 5 Hz) delivered “off-line” in a virtual lesion paradigm over the right or left dorsolateral prefrontal cortex (DLPFC) or the posterior parietal cortex (PPC) would affect performance in a motor versus a visual attention task. Although rTMS over the DLPFC on either side did not affect RT performance on a spatial orienting task, it did lead to an increase in the RTs of invalidly cued trials in a motor attention task when delivered to the left DLPFC. The opposite effect was found when rTMS was delivered to the PPC: In this case, conditioning the right PPC led to increased RTs in invalidly cued trials located in the left hemispace, in the spatial orienting task. rTMS over the PPC on either side did not affect performance in the motor attention task. This double dissociation was evident in the first 10 min after rTMS conditioning. These results enhance our understanding of the networks associated with attention. They provide evidence of a role for the left DLPFC in the mechanisms of motor preparation, and confirm Mesulam's original proposal for a right PPC dominance in spatial attention [Mesulam, M. M. A cortical network for directed attention and unilateral neglect. Annals of Neurology, 10, 309–325, 1981].

scholarly journals Paired-Pulse Parietal-Motor Stimulation Differentially Modulates Corticospinal Excitability across Hemispheres When Combined with Prism Adaptation

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Selene Schintu ◽  
Elisa Martín-Arévalo ◽  
Michael Vesia ◽  
Yves Rossetti ◽  
Romeo Salemme ◽  
...  
Keyword(s):  
Left Hemisphere ◽  
Posterior Parietal Cortex ◽  
Right Hemisphere ◽  
Motor Evoked Potentials ◽  
Repetitive Transcranial Magnetic Stimulation ◽  
Prism Adaptation ◽  
Healthy Individuals ◽  
Paired Pulse ◽  
Posterior Parietal ◽  
The Right

Rightward prism adaptation ameliorates neglect symptoms while leftward prism adaptation (LPA) induces neglect-like biases in healthy individuals. Similarly, inhibitory repetitive transcranial magnetic stimulation (rTMS) on the right posterior parietal cortex (PPC) induces neglect-like behavior, whereas on the left PPC it ameliorates neglect symptoms and normalizes hyperexcitability of left hemisphere parietal-motor (PPC-M1) connectivity. Based on this analogy we hypothesized that LPA increases PPC-M1 excitability in the left hemisphere and decreases it in the right one. In an attempt to shed some light on the mechanisms underlying LPA’s effects on cognition, we investigated this hypothesis in healthy individuals measuring PPC-M1 excitability with dual-site paired-pulse TMS (ppTMS). We found a left hemisphere increase and a right hemisphere decrease in the amplitude of motor evoked potentials elicited by paired as well as single pulses on M1. While this could indicate that LPA biases interhemispheric connectivity, it contradicts previous evidence that M1-only MEPs are unchanged after LPA. A control experiment showed that input-output curves were not affected by LPAper se. We conclude that LPA combined with ppTMS on PPC-M1 differentially alters the excitability of the left and right M1.

scholarly journals Asymmetries in numerical density of pyramidal neurons in the fifth layer of the human posterior parietal cortex

2012 ◽  
Vol 69 (8) ◽  
pp. 681-685
Author(s):  
Natasa Djukic-Macut ◽  
Slobodan Malobabic ◽  
Natalija Stefanovic ◽  
Predrag Mandic ◽  
Tatjana Filipovic ◽  
...  
Keyword(s):  
Parietal Cortex ◽  
Posterior Parietal Cortex ◽  
Pyramidal Neurons ◽  
Right Hemisphere ◽  
Numerical Density ◽  
Group I ◽  
Posterior Parietal ◽  
Left And Right ◽  
Layer V ◽  
The Right

Background/Aim. Both superior parietal lobule (SPL) of dorsolateral hemispheric surface and precuneus (PEC) of medial surface are the parts of posterior parietal cortex. The aim of this study was to determine the numerical density (NV) of pyramidal neurons in the layer V of SPL and PEC and their potential differences. Methods. From 20 (40 hemispheres) formaline fixed human brains (both sexes; 27- 65 years) tissue blocks from SPL and PEC from the left and right hemisphere were used. According to their size the brains were divided into two groups, the group I with the larger left (15 brains) and the group II with the larger right hemisphere (5 brains). Serial Nissl sections (5 ?m) of the left and right SPL and PEC were used for stereological estimation of NV of the layer V pyramidal neurons. Results. NV of pyramidal neurons in the layer V in the left SPL of brains with larger left hemispheres was significantly higher than in the left SPL of brains with larger right hemisphere. Comparing sides in brains with larger left hemisphere, the left SPL had higher NV than the right one, and then the left PEC, and the right SPL had significantly higher NV than the right PEC. Comparing sides in brains with the larger right hemisphere, the left SPL had significantly higher NV than left PEC, but the right SPL had significantly higher NV than left SPL and the right PEC. Conclusion. Generally, there is an inverse relationship of NV between the medial and lateral areas of the human posterior parietal cortex. The obtained values were different between the brains with larger left and right hemispheres, as well as between the SPL and PEC. In all the comparisons the left SPL had the highest values of NV of pyramidal neurons in the layer V (4771.80 mm-3), except in brains with the larger right hemisphere.

scholarly journals Saccades, attentional orienting and disengagement: the effects of anodal tDCS over right posterior parietal cortex (PPC) and frontal eye field (FEF)

2021 ◽  
Author(s):  
Lorenzo Diana ◽  
Patrick Pilastro ◽  
Edoardo N. Aiello ◽  
Aleksandra K. Eberhard-Moscicka ◽  
René M. Müri ◽  
...  
Keyword(s):  
Parietal Cortex ◽  
Posterior Parietal Cortex ◽  
Right Hemisphere ◽  
Reaction Times ◽  
Gap Effect ◽  
Frontal Eye Field ◽  
Attentional Orienting ◽  
Eye Field ◽  
Posterior Parietal ◽  
The Right

ABSTRACTIn the present work, we applied anodal transcranial direct current stimulation (tDCS) over the posterior parietal cortex (PPC) and frontal eye field (FEF) of the right hemisphere in healthy subjects to modulate attentional orienting and disengagement in a gap-overlap task. Both stimulations led to bilateral improvements in saccadic reaction times (SRTs), with larger effects for gap trials. However, analyses showed that the gap effect was not affected by tDCS. Importantly, we observed significant effects of baseline performance that may mediate side- and task-specific effects of brain stimulation.

scholarly journals Lesions to right posterior parietal cortex impair visual depth perception from disparity but not motion cues

2016 ◽  
Vol 371 (1697) ◽  
pp. 20150263 ◽  
Author(s):  
Aidan P. Murphy ◽  
David A. Leopold ◽  
Glyn W. Humphreys ◽  
Andrew E. Welchman
Keyword(s):  
Parietal Cortex ◽  
Depth Perception ◽  
Posterior Parietal Cortex ◽  
Right Hemisphere ◽  
3D Structure ◽  
Three Dimensional ◽  
Stimulus Presentation ◽  
Visual Depth ◽  
Posterior Parietal ◽  
The Right

The posterior parietal cortex (PPC) is understood to be active when observers perceive three-dimensional (3D) structure. However, it is not clear how central this activity is in the construction of 3D spatial representations. Here, we examine whether PPC is essential for two aspects of visual depth perception by testing patients with lesions affecting this region. First, we measured subjects' ability to discriminate depth structure in various 3D surfaces and objects using binocular disparity. Patients with lesions to right PPC ( N = 3) exhibited marked perceptual deficits on these tasks, whereas those with left hemisphere lesions ( N = 2) were able to reliably discriminate depth as accurately as control subjects. Second, we presented an ambiguous 3D stimulus defined by structure from motion to determine whether PPC lesions influence the rate of bistable perceptual alternations. Patients' percept durations for the 3D stimulus were generally within a normal range, although the two patients with bilateral PPC lesions showed the fastest perceptual alternation rates in our sample. Intermittent stimulus presentation reduced the reversal rate similarly across subjects. Together, the results suggest that PPC plays a causal role in both inferring and maintaining the perception of 3D structure with stereopsis supported primarily by the right hemisphere, but do not lend support to the view that PPC is a critical contributor to bistable perceptual alternations. This article is part of the themed issue ‘Vision in our three-dimensional world’.

scholarly journals Decreased Visual Attention Further from the Perceived Direction of Gaze for Equidistant Retinal Targets

2011 ◽  
Vol 23 (3) ◽  
pp. 661-669 ◽  
Author(s):  
Daniela Balslev ◽  
Emma Gowen ◽  
R. Chris Miall
Keyword(s):  
Visual Attention ◽  
Visual Processing ◽  
Repetitive Transcranial Magnetic Stimulation ◽  
Eye Position ◽  
Eye Muscle ◽  
Visual Hemifield ◽  
Proprioceptive Signal ◽  
Visual Targets ◽  
Attention Systems ◽  
The Right

The oculomotor and spatial attention systems are interconnected. Whereas a link between motor commands and spatial shifts in visual attention is demonstrated, it is still unknown whether the recently discovered proprioceptive signal in somatosensory cortex impacts on visual attention, too. This study investigated whether visual targets near the perceived direction of gaze are detected more accurately than targets further away, despite the equal eccentricity of their retinal projections. We dissociated real and perceived eye position using left somatosensory repetitive transcranial magnetic stimulation (rTMS), which decreases cortical processing of eye muscle proprioceptive inflow and produces an underestimation of the rotation of the right eye. Participants detected near-threshold visual targets presented in the left or right visual hemifield at equal distance from fixation. We have previously shown that when the right eye is rotated to the left of the parasagittal plane, TMS produces an underestimation of this rotation, shifting perceived eye position to the right. Here we found that, in this condition, TMS also decreased target detection in the left visual hemifield and increased it in the right. This effect depended on the direction of rotation of the right eye. When the right eye was rotated rightward and TMS, we assume, shifted perceived gaze direction in opposite direction, leftward, visual accuracy decreased now in the right hemifield. We suggest that the proprioceptive eye position signal modulates the spatial distribution of visual processing resources, producing “pseudo-neglect” for objects located far relative to near the perceived direction of gaze.

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