Time-course of Posterior Parietal and Occipital Cortex Contribution to Sound Localization

2008 ◽  
Vol 20 (8) ◽  
pp. 1454-1463 ◽  
Author(s):  
Olivier Collignon ◽  
Marco Davare ◽  
Anne G. De Volder ◽  
Colline Poirier ◽  
Etienne Olivier ◽  
...  
Keyword(s):  
Time Course ◽  
Posterior Parietal Cortex ◽  
Space Perception ◽  
Occipital Cortex ◽  
Stimulus Onset ◽  
Spatial Processing ◽  
Auditory Space ◽  
Posterior Parietal ◽  
The Right ◽  
Precise Time

It has been suggested that both the posterior parietal cortex (PPC) and the extrastriate occipital cortex (OC) participate in the spatial processing of sounds. However, the precise time-course of their contribution remains unknown, which is of particular interest, considering that it could give new insights into the mechanisms underlying auditory space perception. To address this issue, we have used event-related transcranial magnetic stimulation (TMS) to induce virtual lesions of either the right PPC or right OC at different delays in subjects performing a sound lateralization task. Our results confirmed that these two areas participate in the spatial processing of sounds. More precisely, we found that TMS applied over the right OC 50 msec after the stimulus onset significantly impaired the localization of sounds presented either to the right or to the left side. Moreover, right PPC virtual lesions induced 100 and 150 msec after sound presentation led to a rightward bias for stimuli delivered on the center and on the left side, reproducing transiently the deficits commonly observed in hemineglect patients. The finding that the right OC is involved in sound processing before the right PPC suggests that the OC exerts a feedforward influence on the PPC during auditory spatial processing.

scholarly journals The Rapid Extraction of Gist—Early Neural Correlates of High-level Visual Processing

2012 ◽  
Vol 24 (2) ◽  
pp. 521-529 ◽  
Author(s):  
Frank Oppermann ◽  
Uwe Hassler ◽  
Jörg D. Jescheniak ◽  
Thomas Gruber
Keyword(s):  
Visual Processing ◽  
Time Course ◽  
Occipital Cortex ◽  
Stimulus Onset ◽  
Gamma Band ◽  
Oscillatory Activity ◽  
Rapid Extraction ◽  
The Right ◽  
High Level ◽  
Individual Objects

The human cognitive system is highly efficient in extracting information from our visual environment. This efficiency is based on acquired knowledge that guides our attention toward relevant events and promotes the recognition of individual objects as they appear in visual scenes. The experience-based representation of such knowledge contains not only information about the individual objects but also about relations between them, such as the typical context in which individual objects co-occur. The present EEG study aimed at exploring the availability of such relational knowledge in the time course of visual scene processing, using oscillatory evoked gamma-band responses as a neural correlate for a currently activated cortical stimulus representation. Participants decided whether two simultaneously presented objects were conceptually coherent (e.g., mouse–cheese) or not (e.g., crown–mushroom). We obtained increased evoked gamma-band responses for coherent scenes compared with incoherent scenes beginning as early as 70 msec after stimulus onset within a distributed cortical network, including the right temporal, the right frontal, and the bilateral occipital cortex. This finding provides empirical evidence for the functional importance of evoked oscillatory activity in high-level vision beyond the visual cortex and, thus, gives new insights into the functional relevance of neuronal interactions. It also indicates the very early availability of experience-based knowledge that might be regarded as a fundamental mechanism for the rapid extraction of the gist of a scene.

Lateralization of the Posterior Parietal Cortex for Internal Monitoring of Self- versus Externally Generated Movements

2007 ◽  
Vol 19 (11) ◽  
pp. 1827-1835 ◽  
Author(s):  
Kenji Ogawa ◽  
Toshio Inui
Keyword(s):  
Parietal Cortex ◽  
Posterior Parietal Cortex ◽  
Brain Activity ◽  
Occipital Cortex ◽  
Clinical Findings ◽  
Visual Occlusion ◽  
Mouse Cursor ◽  
Posterior Parietal ◽  
Human Motor ◽  
The Right

Internal monitoring or state estimation of movements is essential for human motor control to compensate for inherent delays and noise in sensorimotor loops. Two types of internal estimation of movements exist: self-generated movements, and externally generated movements. We used functional magnetic resonance imaging to investigate differences in brain activity for internal monitoring of self- versus externally generated movements during visual occlusion. Participants tracked a sinusoidally moving target with a mouse cursor. On some trials, vision of either target (externally generated) or cursor (self-generated) movement was transiently occluded, during which subjects continued tracking by estimating current position of either the invisible target or cursor on screen. Analysis revealed that both occlusion conditions were associated with increased activity in the presupplementary motor area and decreased activity in the right lateral occipital cortex compared to a control condition with no occlusion. Moreover, the right and left posterior parietal cortex (PPC) showed greater activation during occlusion of target and cursor movements, respectively. This study suggests lateralization of the PPC for internal monitoring of internally versus externally generated movements, fully consistent with previously reported clinical findings.

Timing Spatial Conflict within the Parietal Cortex: A TMS Study

2011 ◽  
Vol 23 (12) ◽  
pp. 3998-4007 ◽  
Author(s):  
Sami Schiff ◽  
Lara Bardi ◽  
Demis Basso ◽  
Daniela Mapelli
Keyword(s):  
Parietal Cortex ◽  
Visual Information ◽  
Motor Response ◽  
Time Course ◽  
Posterior Parietal Cortex ◽  
Simon Task ◽  
Single Pulse ◽  
Stimulus Onset ◽  
Parietal Lobes ◽  
The Right

Orienting and motor attention are known to recruit different regions within right and left parietal lobes. However, the time course and the role played by these modules when visual information competes for different motor response are still unknown. To deal with this issue, single-pulse TMS was applied over the angular (AG) and the supramarginal (SMG) gyri of both hemispheres at several time intervals during the execution of a Simon task. Suppression of the conflict between stimulus and response positions (i.e., the Simon effect) was found when TMS pulse was applied 130 msec after stimulus onset over the right AG and after 160 msec when applied over the left AG and SMG. Interestingly, only stimulation of the left SMG suppressed the asymmetry in conflict magnitude between left- and right-hand responses, usually observed in the Simon task. The present data show that orienting attention and motor attention processes are temporally, functionally, and spatially separated in the posterior parietal cortex, and both contribute to prime motor response during spatial conflict.

scholarly journals Systematic Underreproduction of Time Is Independent of Judgment Certainty

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Martin Riemer ◽  
Darren Rhodes ◽  
Thomas Wolbers
Keyword(s):  
Magnetic Stimulation ◽  
Posterior Parietal Cortex ◽  
Judgment Bias ◽  
Time Discrimination ◽  
Temporal Intervals ◽  
Neuronal Processes ◽  
Posterior Parietal ◽  
Temporal Stimuli ◽  
The Right ◽  
Temporal Judgments

We recently proposed that systematic underreproduction of time is caused by a general judgment bias towards earlier responses, instead of reflecting a genuine misperception of temporal intervals. Here we tested whether this bias can be explained by the uncertainty associated with temporal judgments. We applied transcranial magnetic stimulation (TMS) to inhibit neuronal processes in the right posterior parietal cortex (PPC) and tested its effects on time discrimination and reproduction tasks. The results show increased certainty for discriminative time judgments after PPC inhibition. They suggest that the right PPC plays an inhibitory role for time perception, possibly by mediating the multisensory integration between temporal stimuli and other quantities. Importantly, this increased judgment certainty had no influence on the degree of temporal underreproduction. We conclude that the systematic underreproduction of time is not caused by uncertainty for temporal judgments.

scholarly journals Attentional bias to threat and gray mater volume morphology in high anxious individuals

2020 ◽  
Author(s):  
Joshua M. Carlson ◽  
Lin Fang
Keyword(s):  
Attentional Bias ◽  
Parietal Cortex ◽  
Gray Matter ◽  
Posterior Parietal Cortex ◽  
Gray Matter Volume ◽  
Anterior Cingulate ◽  
Brain Morphology ◽  
Matter Volume ◽  
Posterior Parietal ◽  
The Right

AbstractIn a sample of highly anxious individuals, the relationship between gray matter volume brain morphology and attentional bias to threat was assessed. Participants performed a dot-probe task of attentional bias to threat and gray matter volume was acquired from whole brain structural T1-weighted MRI scans. The results replicate previous findings in unselected samples that elevated attentional bias to threat is linked to greater gray matter volume in the anterior cingulate cortex, middle frontal gyrus, and striatum. In addition, we provide novel evidence that elevated attentional bias to threat is associated with greater gray matter volume in the right posterior parietal cortex, cerebellum, and other distributed regions. Lastly, exploratory analyses provide initial evidence that distinct sub-regions of the right posterior parietal cortex may contribute to attentional bias in a sex-specific manner. Our results illuminate how differences in gray matter volume morphology relate to attentional bias to threat in anxious individuals. This knowledge could inform neurocognitive models of anxiety-related attentional bias to threat and targets of neuroplasticity in anxiety interventions such as attention bias modification.

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.

Interhemispheric EEG asymmetries during unilateral bright-light exposure and subsequent sleep in humans

2008 ◽  
Vol 294 (3) ◽  
pp. R1053-R1060 ◽  
Author(s):  
Christian Cajochen ◽  
Rosalba Di Biase ◽  
Makoto Imai
Keyword(s):  
Visual Cortex ◽  
Time Course ◽  
Visual Stimulation ◽  
Light Exposure ◽  
Bright Light ◽  
Occipital Cortex ◽  
Alpha Activity ◽  
Hemispheric Dominance ◽  
Eeg Activity ◽  
The Right

We tested whether evening exposure to unilateral photic stimulation has repercussions on interhemispheric EEG asymmetries during wakefulness and later sleep. Because light exerts an alerting response in humans, which correlates with a decrease in waking EEG theta/alpha-activity and a reduction in sleep EEG delta activity, we hypothesized that EEG activity in these frequency bands show interhemispheric asymmetries after unilateral bright light (1,500 lux) exposure. A 2-h hemi-field light exposure acutely suppressed occipital EEG alpha activity in the ipsilateral hemisphere activated by light. Subjects felt more alert during bright light than dim light, an effect that was significantly more pronounced during activation of the right than the left visual cortex. During subsequent sleep, occipital EEG activity in the delta and theta range was significantly reduced after activation of the right visual cortex but not after stimulation of the left visual cortex. Furthermore, hemivisual field light exposure was able to shift the left predominance in occipital spindle EEG activity toward the stimulated hemisphere. Time course analysis revealed that this spindle shift remained significant during the first two sleep cycles. Our results reflect rather a hemispheric asymmetry in the alerting action of light than a use-dependent recovery function of sleep in response to the visual stimulation during prior waking. However, the observed shift in the spindle hemispheric dominance in the occipital cortex may still represent subtle local use-dependent recovery functions during sleep in a frequency range different from the delta range.

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