Does Interhemispheric Competition Mediate Motion-Induced Blindness? A Transcranial Magnetic Stimulation Study

Perception ◽  
10.1068/p5088 ◽  
2003 ◽  
Vol 32 (11) ◽  
pp. 1328-1338 ◽  
Author(s):  
Agnes P Funk ◽  
John D Pettigrew
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Binocular Rivalry ◽  
Magnetic Stimulation ◽  
Posterior Parietal Cortex ◽  
Right Hemisphere ◽  
Single Pulse ◽  
Underlying Mechanism ◽  
Temporal Properties ◽  
Interhemispheric Competition ◽  
Perceptual Rivalry

Motion-induced blindness (MIB) is a phenomenon, perhaps related to perceptual rivalry, where stationary targets disappear and reappear in a cyclic mode when viewed against a background (mask) of coherent, apparent 3-D motion. Since MIB has recently been shown to share similar temporal properties with binocular rivalry, we probed the appearance–disappearance cycle of MIB using unilateral, single-pulse transcranial magnetic stimulation (TMS)—a manipulation that has previously been shown to influence binocular rivalry. Effects were seen for both hemispheres when the timing of TMS was determined prospectively on the basis of a given subject's appearance–disappearance cycle, so that it occurred on average around 300 ms before the time of perceptual switch. Magnetic stimulation of either hemisphere shortened the time to switch from appearance to disappearance and vice versa. However, TMS of left posterior parietal cortex more selectively shortened the disappearance time of the targets if delivered in phase with the disappearance cycle, but lengthened it if TMS was delivered in the appearance phase after the perceptual switch. Opposite effects were seen in the right hemisphere, although less marked than the left-hemisphere effects. As well as sharing temporal characteristics with binocular rivalry, MIB therefore seems to share a similar underlying mechanism of interhemispheric modulation. Interhemispheric switching may thus provide a common temporal framework for uniting the diverse, multilevel phenomena of perceptual rivalry.

Single-Pulse Transcranial Magnetic Stimulation of Parietal and Prefrontal Areas in a Memory Delay Arm Pointing Task

2003 ◽  
Vol 89 (6) ◽  
pp. 3344-3350 ◽  
Author(s):  
Nikolaos Smyrnis ◽  
Christos Theleritis ◽  
Ioannis Evdokimidis ◽  
Rene M. Müri ◽  
Nikos Karandreas
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Magnetic Stimulation ◽  
Posterior Parietal Cortex ◽  
Right Hemisphere ◽  
Dimensional Space ◽  
Single Pulse ◽  
Pointing Task ◽  
Separate Block ◽  
Posterior Parietal ◽  
Four Blocks

Fifteen healthy volunteers performed a memory-pointing task using their right arm while single-pulse transcranial magnetic stimulation (TMS) above motor threshold was applied over the posterior parietal or prefrontal cortex of the left or right hemisphere in four blocks of trials. The stimulation was randomly delivered at one of three time intervals during the 3-s delay period (early: 300 ms, intermediate: 1,500 ms, late: 2,700 ms). A separate block with no stimulation was used as control. Only early left parietal stimulation resulted in an increase in the variance of movement amplitude but not direction for all targets in two-dimensional space (both hemifields). The results point to the significance of the contralateral posterior parietal cortex early on during the memorization of the target for an upcoming movement. Taking into consideration the limitations of TMS and those imposed by the particular task, the lack of specific effects of prefrontal stimulation provides evidence that these areas might not be involved in the performance of simple memorized arm movements.

scholarly journals The Role of the Parietal Lobe in Visual Extinction Studied with Transcranial Magnetic Stimulation

2009 ◽  
Vol 21 (10) ◽  
pp. 1946-1955 ◽  
Author(s):  
Lorella Battelli ◽  
George A. Alvarez ◽  
Thomas Carlson ◽  
Alvaro Pascual-Leone
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Visual Tracking ◽  
Magnetic Stimulation ◽  
Posterior Parietal Cortex ◽  
Parietal Lobe ◽  
Repetitive Transcranial Magnetic Stimulation ◽  
Visual Fields ◽  
Brain Regions ◽  
Visual Extinction ◽  
Interhemispheric Competition

Interhemispheric competition between homologous areas in the human brain is believed to be involved in a wide variety of human behaviors from motor activity to visual perception and particularly attention. For example, patients with lesions in the posterior parietal cortex are unable to selectively track objects in the contralesional side of visual space when targets are simultaneously present in the ipsilesional visual field, a form of visual extinction. Visual extinction may arise due to an imbalance in the normal interhemispheric competition. To directly assess the issue of reciprocal inhibition, we used fMRI to localize those brain regions active during attention-based visual tracking and then applied low-frequency repetitive transcranial magnetic stimulation over identified areas in the left and right intraparietal sulcus to asses the behavioral effects on visual tracking. We induced a severe impairment in visual tracking that was selective for conditions of simultaneous tracking in both visual fields. Our data show that the parietal lobe is essential for visual tracking and that the two hemispheres compete for attentional resources during tracking. Our results provide a neuronal basis for visual extinction in patients with parietal lobe damage.

Hemispheric Asymmetry in Memory-Guided Pointing During Single-Pulse Transcranial Magnetic Stimulation of Human Parietal Cortex

2006 ◽  
Vol 96 (6) ◽  
pp. 3016-3027 ◽  
Author(s):  
Michael Vesia ◽  
Jachin A. Monteon ◽  
Lauren E. Sergio ◽  
J. D. Crawford
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Parietal Cortex ◽  
Magnetic Stimulation ◽  
Hemispheric Asymmetry ◽  
Posterior Parietal Cortex ◽  
Single Pulse ◽  
Pointing Movements ◽  
Posterior Parietal ◽  
The Right ◽  
Stimulation Of

Dorsal posterior parietal cortex (PPC) has been implicated through single-unit recordings, neuroimaging data, and studies of brain-damaged humans in the spatial guidance of reaching and pointing movements. The present study examines the causal effect of single-pulse transcranial magnetic stimulation (TMS) over the left and right dorsal posterior parietal cortex during a memory-guided “reach-to-touch” movement task in six human subjects. Stimulation of the left parietal hemisphere significantly increased endpoint variability, independent of visual field, with no horizontal bias. In contrast, right parietal stimulation did not increase variability, but instead produced a significantly systematic leftward directional shift in pointing (contralateral to stimulation site) in both visual fields. Furthermore, the same lateralized pattern persisted with left-hand movement, suggesting that these aspects of parietal control of pointing movements are spatially fixed. To test whether the right parietal TMS shift occurs in visual or motor coordinates, we trained subjects to point correctly to optically reversed peripheral targets, viewed through a left–right Dove reversing prism. After prism adaptation, the horizontal pointing direction for a given visual target reversed, but the direction of shift during right parietal TMS did not reverse. Taken together, these data suggest that induction of a focal current reveals a hemispheric asymmetry in the early stages of the putative spatial processing in PPC. These results also suggest that a brief TMS pulse modifies the output of the right PPC in motor coordinates downstream from the adapted visuomotor reversal, rather than modifying the upstream visual coordinates of the memory representation.

Effects of single-pulse transcranial magnetic stimulation over the prefrontal and posterior parietal cortices during memory-guided saccades in humans

1996 ◽  
Vol 76 (3) ◽  
pp. 2102-2106 ◽  
Author(s):  
R. M. Muri ◽  
A. I. Vermersch ◽  
S. Rivaud ◽  
B. Gaymard ◽  
C. Pierrot-Deseilligny
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Magnetic Stimulation ◽  
Posterior Parietal Cortex ◽  
Single Pulse ◽  
Occipital Cortex ◽  
Temporal Organization ◽  
Eye Position ◽  
Time Intervals ◽  
Target Presentation ◽  
Posterior Parietal

1. We used single-pulse transcranial magnetic stimulation (TMS) to explore the temporal organization of the cortical control of memory-guided saccades in eight humans. The posterior parietal cortex (PPC) or the dorsolateral prefrontal cortex (DPFC), which are both known to be involved in the control of such saccades, were stimulated on the right side at different time intervals after the presentation of a flashed lateral visual target. The memorization delay was 2,000 ms. Single pulses were applied at 160, 260, and 360 ms after the flashed target, during the period of 700 and 1,500 ms, and finally at 2,100 ms, i.e., 100 ms after the extinguishing of the central fixation point. The effects of TMS were evaluated by calculating the percentage of error in amplitude (PEA) and latency of memory-guided saccades. The PEA was determined for the primary saccade (motor aspect) and the final eye position, i.e., after the end saccade (mnemonic aspect). Stimulation over the occipital cortex at the same time intervals served as control experiments. 2. After PPC stimulation, a significant increase in the PEA of the primary saccade and final eye position existed for contralateral saccades, compared with the PEA without stimulation, when stimulation was applied 260 ms after target presentation, but not at other time intervals. There was no significant effect on ipsilateral saccades. Latency was significantly increased bilaterally when stimulation was performed 2,100 ms after target presentation. 3. After prefrontal stimulation, a significant increase in the PEA of the primary saccade and final eye position existed for contralateral saccades, when stimulation was applied between 700 and 1,500 ms after target presentation, but not at other time intervals. There was no significant effect on ipsilateral saccades. Latency was not affected by prefrontal TMS at any stimulation times. 4. Occipital stimulation resulted in no significant effect on the PEA and latency of ipsilateral or contralateral saccades, in particular including the application at 260 ms after target presentation or during the memorization phase. 5. From these results it may be concluded that the observed effects of TMS on saccade accuracy were specific to the stimulated region and specific to the stimulation time. The PPC seems to be involved in the preparation of saccade amplitude, during the early phase of the paradigm, i.e., the sensorimotor processing period, whereas the DPFC could play a role during the later phase of the paradigm, i.e., the memorization period. Therefore in humans these results support the experimental findings suggesting that sensorimotor integration is controlled by the PPC and spatial memory by the DPFC. Furthermore, our results suggest that the PPC, although not the DPFC, plays a role in saccade triggering.

scholarly journals Motor disability in patients with multiple sclerosis: transcranial magnetic stimulation study

2020 ◽  
Vol 56 (1) ◽  
Author(s):  
Anssam Bassem Mohy ◽  
Aqeel Kareem Hatem ◽  
Hussein Ghani Kadoori ◽  
Farqad Bader Hamdan
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Lower Limb ◽  
Magnetic Stimulation ◽  
Motor Evoked Potential ◽  
Invasive Procedure ◽  
Single Pulse ◽  
Lower Limbs ◽  
Control Group ◽  
Conduction Time ◽  
Motor Disability

Abstract Background Transcranial magnetic stimulation (TMS) is a non-invasive procedure used in a small targeted region of the brain via electromagnetic induction and used diagnostically to measure the connection between the central nervous system (CNS) and skeletal muscle to evaluate the damage that occurs in MS. Objectives The study aims to investigate whether single-pulse TMS measures differ between patients with MS and healthy controls and to consider if these measures are associated with clinical disability. Patients and methods Single-pulse TMS was performed in 26 patients with MS who hand an Expanded Disability Status Scale (EDSS) score between 0 and 9.5 and in 26 normal subjects. Different TMS parameters from upper and lower limbs were investigated. Results TMS disclosed no difference in all MEP parameters between the right and left side of the upper and lower limbs in patients with MS and controls. In all patients, TMS parameters were different from the control group. Upper limb central motor conduction time (CMCT) was prolonged in MS patients with pyramidal signs. Upper and lower limb CMCT and CMCT-f wave (CMCT-f) were prolonged in patients with ataxia. Moreover, CMCT and CMCT-f were prolonged in MS patients with EDSS of 5–9.5 as compared to those with a score of 0–4.5. EDSS correlated with upper and lower limb cortical latency (CL), CMCT, and CMCT-f whereas motor evoked potential (MEP) amplitude not. Conclusion TMS yields objective data to evaluate clinical disability and its parameters correlated well with EDSS.

scholarly journals Top-down control of visual cortex by the frontal eye fields through oscillatory realignment

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Domenica Veniero ◽  
Joachim Gross ◽  
Stephanie Morand ◽  
Felix Duecker ◽  
Alexander T. Sack ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Transcranial Magnetic Stimulation ◽  
Visual Perception ◽  
Magnetic Stimulation ◽  
Single Pulse ◽  
Frontal Eye Fields ◽  
Phase Reset ◽  
Top Down ◽  
Visual Areas ◽  
Beta Frequency

AbstractVoluntary allocation of visual attention is controlled by top-down signals generated within the Frontal Eye Fields (FEFs) that can change the excitability of lower-level visual areas. However, the mechanism through which this control is achieved remains elusive. Here, we emulated the generation of an attentional signal using single-pulse transcranial magnetic stimulation to activate the FEFs and tracked its consequences over the visual cortex. First, we documented changes to brain oscillations using electroencephalography and found evidence for a phase reset over occipital sites at beta frequency. We then probed for perceptual consequences of this top-down triggered phase reset and assessed its anatomical specificity. We show that FEF activation leads to cyclic modulation of visual perception and extrastriate but not primary visual cortex excitability, again at beta frequency. We conclude that top-down signals originating in FEF causally shape visual cortex activity and perception through mechanisms of oscillatory realignment.

scholarly journals Single-Pulse Transcranial Magnetic Stimulation-Evoked Potential Amplitudes and Latencies in the Motor and Dorsolateral Prefrontal Cortex among Young, Older Healthy Participants, and Schizophrenia Patients

2021 ◽  
Vol 11 (1) ◽  
pp. 54
Author(s):  
Yoshihiro Noda ◽  
Mera S. Barr ◽  
Reza Zomorrodi ◽  
Robin F. H. Cash ◽  
Pantelis Lioumis ◽  
...  
Keyword(s):  
Prefrontal Cortex ◽  
Transcranial Magnetic Stimulation ◽  
Magnetic Stimulation ◽  
Dorsolateral Prefrontal Cortex ◽  
Evoked Potential ◽  
Single Pulse ◽  
Signal Propagation ◽  
Lower Amplitude ◽  
Dorsolateral Prefrontal ◽  
The Right

Background: The combination of transcranial magnetic stimulation (TMS) with electroencephalography (EEG) allows for non-invasive investigation of cortical response and connectivity in human cortex. This study aimed to examine the amplitudes and latencies of each TMS-evoked potential (TEP) component induced by single-pulse TMS (spTMS) to the left motor (M1) and dorsolateral prefrontal cortex (DLPFC) among healthy young participants (YNG), older participants (OLD), and patients with schizophrenia (SCZ). Methods: We compared the spatiotemporal characteristics of TEPs induced by spTMS among the groups. Results: Compared to YNG, M1-spTMS induced lower amplitudes of N45 and P180 in OLD and a lower amplitude of P180 in SCZ, whereas the DLPFC-spTMS induced a lower N45 in OLD. Further, OLD demonstrated latency delays in P60 after M1-spTMS and in N45-P60 over the right central region after left DLPFC-spTMS, whereas SCZ demonstrated latency delays in N45-P60 over the midline and right central regions after DLPFC-spTMS. Conclusions: These findings suggest that inhibitory and excitatory mechanisms mediating TEPs may be altered in OLD and SCZ. The amplitude and latency changes of TEPs with spTMS may reflect underlying neurophysiological changes in OLD and SCZ, respectively. The spTMS administered to M1 and the DLPFC can probe cortical functions by examining TEPs. Thus, TMS-EEG can be used to study changes in cortical connectivity and signal propagation from healthy to pathological brains.

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