The Perceptual and Functional Consequences of Parietal Top-Down Modulation on the Visual Cortex

Silvanto, Juha; Muggleton, Neil G.; Lavie, Nilli; Walsh, Vincent

doi:10.1093/cercor/bhn091

Cited by 88 publications

(78 citation statements)

References 28 publications

(27 reference statements)

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“…For instance, a recent study adopted a similar trifocal condition in which TMS was applied concurrently over the left PPC, right PPC, and either left or right visual cortex (V1/V2). The results showed that the increased visual cortical excitability (measured by the percentage of phosphenes induced by TMS) that was observed with unilateral parietal TMS was abolished when TMS was applied over the PPC bilaterally, implying the activation of an inhibitory transcallosal pathway (Silvanto et al, 2009). Interestingly, no hemispheric asymmetry was found.…”

Section: Discussionmentioning

confidence: 88%

“…Neglect occurs as a consequence of an unbalanced system following damage to one of the processors, resulting in a bias toward the ipsilesional hemispace (Kinsbourne, 1977(Kinsbourne, , 1993. Here, we used a trifocal transcranial magnetic stimulation (TMS) method to directly test the hypothesis that the asymmetry of visuospatial functions may be due to an imbalance of interhemispheric interactions between the two parietal cortices (Silvanto et al, 2009). We chose to stimulate a region of the PPC that lies close to the posterior part of the intraparietal sulcus (cIPS) within the inferior parietal lobule (IPL), given that this area is a crucial node of the frontoparietal networks involved in visuospatial attention and neglect (Bisiach et al, 1986;Bowen et al, 1999;Karnath et al, 2002;Mort et al, 2003;Shulman et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

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Asymmetry of Parietal Interhemispheric Connections in Humans

Koch

Cercignani

Bonnı̀

et al. 2011

Journal of Neuroscience

123

110

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Visuospatial abilities are preferentially mediated by the right hemisphere. Although this asymmetry of function is thought to be due to an unbalanced interaction between cerebral hemispheres, the underlying neurophysiological substrate is still largely unknown. Here, using a method of trifocal transcranial magnetic stimulation, we show that the right, but not left, human posterior parietal cortex exerts a strong inhibitory activity over the contralateral homologous area by a short-latency connection. We also clarify, using diffusion-tensor magnetic resonance imaging, that such an interaction is mediated by direct transcallosal projections located in the posterior corpus callosum. We argue that this anatomo-functional network may represent a possible neurophysiological basis for the ongoing functional asymmetry between parietal cortices, and that its damage could contribute to the clinical manifestations of neglect.

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Section: Discussionmentioning

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Asymmetry of Parietal Interhemispheric Connections in Humans

Koch

Cercignani

Bonnı̀

et al. 2011

Journal of Neuroscience

123

110

View full text Add to dashboard Cite

show abstract

“…Applying causal time series analysis to fMRI BOLD data has supported the argument for functional connectivity (e.g., Granger causality analysis) (Bressler et al, 2008), but only direct manipulation of a brain region can provide definitive evidence for a cause and effect relationship. Indeed, the efficacy of using TMS (including in combination with imaging techniques) to show causal influences of one brain region on another has been demonstrated recently where direct stimulation over the FEF and IPS has shown to modify excitability (Silvanto et al, 2006(Silvanto et al, , 2009 as well as the BOLD signal in visual cortex (Ruff et al, 2006(Ruff et al, , 2008. These previous investigations indicate the presence of neural connectivity that may implement the link between attention control areas and their potential effect over perceptual areas.…”

Section: Discussionmentioning

confidence: 94%

Ignoring the Elephant in the Room: A Neural Circuit to Downregulate Salience

Mevorach¹,

Hodsoll

Allen³

et al. 2010

J. Neurosci.

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How do we ignore stimuli that are salient but irrelevant when our task is to select a lower salient stimulus? Since bottom-up processes favor high saliency, detection of a low-salient target in the presence of highly salient distractors requires top-down attentional guidance. Previous studies have demonstrated that top-down attention can modulate perceptual processing and also that the control of attention is driven by frontoparietal regions. However, to date, there is no direct evidence on the cause and effect relationship between control regions and perceptual processing. Here, we report the first evidence demonstrating a neural circuit for the downregulation of salient distractors when a low-salient target is selected, combining brain imaging using functional magnetic resonance imaging with brain stimulation by transcranial magnetic stimulation. Using these combined techniques, we were able to identify a cause and effect relationship in the suppression of saliency, based on an interaction between the left intraparietal sulcus (IPS) and a region implicated in visual processing in our task (the left occipital pole). In particular, low-salient stimuli were selected by the left IPS suppressing early visual areas that would otherwise respond to a high-saliency distractor in the task. Apart from providing a first documentation of the neural circuit supporting selection by saliency, these data can be critical for understanding the underlying causes of problems in ignoring irrelevant salience that are found in both acquired and neurodevelopmental disorders (e.g., attention deficit/hyperactivity disorder or autism).

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“…Previous research has shown that using conditioning pulses over distant areas such as the motion sensitive area MT (Pascual-Leone and Walsh 2001), parietal cortex (Silvanto et al 2009), or frontal eye fields (Silvanto et al 2006) can affect the propensity of a subsequent pulse over the occipital cortex to elicit phosphenes. Other research has reported remote effects of TMS outside of the visual cortex (Hampson and Hoffman 2010;Ruff et al 2009).…”

Section: Discussionmentioning

confidence: 99%

Continuous theta burst transcranial magnetic stimulation reduces resting state connectivity between visual areas

Rahnev

Kok

Munneke

et al. 2013

Journal of Neurophysiology

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Research to date has focused on the effect of cTBS on the target area, but less is known about its effects on the resting state functional connectivity between different brain regions. We investigated this issue by applying cTBS to the occipital cortex and probing its influence in retinotopically defined regions in early visual cortex using functional MRI. We found that occipital cTBS reliably decreased the resting state functional connectivity (i.e., the correlation of spontaneous activity) between regions of the early visual cortex. In the context of a perceptual task, such an effect could mean that cTBS affects the strength of the perceptual signal, its variability, or both. We investigated this issue in a second experiment in which subjects performed a perceptual discrimination task and indicated their level of certainty on each trial. The results showed that occipital cTBS decreased both subjects' accuracy and confidence. Signal detection modeling suggested that these impairments resulted primarily from a decreased strength of the perceptual signal, with a nonsignificant trend of a decrease in signal variability. We discuss the implications of these experiments for understanding the mechanisms by which cTBS influences brain activity and perceptual processes. cTBS; fMRI; visual cortex; perception; resting state connectivity; signal detection theory REPETITIVE TRANSCRANIAL MAGNETIC stimulation is a popular technique used to transiently affect neural activity in a noninvasive manner. One recently developed variant of repetitive transcranial magnetic stimulation (TMS), continuous theta burst stimulation (cTBS;Huang et al. 2005), has shown promise because of its rapid application (Ͻ1 min), its ability to produce behavioral effects for up to 1 h after stimulation, and its connection to known neuronal mechanisms, such as long-term potentiation and depression (LTD). Indeed, research has shown that cTBS reduces motor cortical excitability in a manner consistent with LTD effects (Allen et al. 2007;Di Lazzaro et al. 2005Gentner et al. 2008;Huang et al. 2005Huang et al. , 2007.When applied to the occipital cortex, cTBS has been found to increase phosphene thresholds (PTs), such that higher stimulation intensity is needed to produce conscious visual experience (Franca et al. 2006). One possibility is that such an increase in PTs is, at least in part, due to decreased connectivity between areas in the early visual cortex, which would make the Here we tested for this possibility by investigating the resting state connectivity between retinotopically defined regions in the early visual cortex after occipital application of cTBS. We identified areas V1, V2, and V3 as three separate regions of interest (ROIs) and found that cTBS decreased the resting state functional connectivity between each pair of regions. In separate analyses, we separated the left and right hemisphere of each of these areas and observed that cTBS decreased the inter-and intrahemispheric resting state connectivity between these retinotopically defined re...

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The Perceptual and Functional Consequences of Parietal Top-Down Modulation on the Visual Cortex

Cited by 88 publications

References 28 publications

Asymmetry of Parietal Interhemispheric Connections in Humans

Asymmetry of Parietal Interhemispheric Connections in Humans

Ignoring the Elephant in the Room: A Neural Circuit to Downregulate Salience

Continuous theta burst transcranial magnetic stimulation reduces resting state connectivity between visual areas

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