Time- and Task-Dependent Non-Neural Effects of Real and Sham TMS

Duecker, Felix; Graaf, Tom A. de; Jacobs, Christianne; Sack, Alexander T.

doi:10.1371/journal.pone.0073813

Cited by 53 publications

(44 citation statements)

References 18 publications

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“…Audible ‘clicks’ from a TMS machine can have differential attentional cuing effects when presented at different time points [44], and thus have the potential to influence behavior differently early versus late during a memory delay. Because sham TMS has no neural effects, we collected a total of 320 sham trials (160 per pulse timing) for each participant to investigate possible effects of pulse timing.…”

Section: Resultsmentioning

confidence: 99%

“…A TMS coil (real or sham) was placed over either the left or the right dorsal part of early visual cortex (V1/V2). Sham TMS was used to control for attentional biasing effects that can arise from “clicking” sounds at different points in time [44]. For half of our participants, a single session consisted of 4 blocks of 80 working memory trials per block, of which three blocks involved triple-pulse TMS stimulation at 10 Hz, and one block involved triple-pulse sham stimulation at 10 Hz.…”

Section: Methodsmentioning

confidence: 99%

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The impact of early visual cortex transcranial magnetic stimulation on visual working memory precision and guess rate

et al. 2017

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Neuroimaging studies have demonstrated that activity patterns in early visual areas predict stimulus properties actively maintained in visual working memory. Yet, the mechanisms by which such information is represented remain largely unknown. In this study, observers remembered the orientations of 4 briefly presented gratings, one in each quadrant of the visual field. A 10Hz Transcranial Magnetic Stimulation (TMS) triplet was applied directly at stimulus offset, or midway through a 2-second delay, targeting early visual cortex corresponding retinotopically to a sample item in the lower hemifield. Memory for one of the four gratings was probed at random, and participants reported this orientation via method of adjustment. Recall errors were smaller when the visual field location targeted by TMS overlapped with that of the cued memory item, compared to errors for stimuli probed diagonally to TMS. This implied topographic storage of orientation information, and a memory-enhancing effect at the targeted location. Furthermore, early pulses impaired performance at all four locations, compared to late pulses. Next, response errors were fit empirically using a mixture model to characterize memory precision and guess rates. Memory was more precise for items proximal to the pulse location, irrespective of pulse timing. Guesses were more probable with early TMS pulses, regardless of stimulus location. Thus, while TMS administered at the offset of the stimulus array might disrupt early-phase consolidation in a non-topographic manner, TMS also boosts the precise representation of an item at its targeted retinotopic location, possibly by increasing attentional resources or by injecting a beneficial amount of noise.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

The impact of early visual cortex transcranial magnetic stimulation on visual working memory precision and guess rate

et al. 2017

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“…This was highly beneficial as this meant that the comparisons of our four experimental conditions involved the exact same TMS stimulation. This optimal control could have not been achieved by using either sham or vertex stimulation, alternative procedures commonly used in TMS research [8, 19, 40] to mimic the TMS coil click but that do not control for all TMS-associated peripheral sensations. Moreover, given that TMS was close to the inter-hemispheric fissure, the noise it produced could not be responsible for the observed effects, as it would not have induced differential effects for the target and distractor that were presented in separate hemifields.…”

Section: Discussionmentioning

confidence: 99%

Attention Reorients Periodically

2016

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SUMMARY Reorienting of voluntary attention enables the processing of stimuli at previously unattended locations. Although studies have identified a ventral fronto-parietal network underlying attention [1, 2], little is known about whether and how early visual areas are involved in involuntary [3, 4] and even less in voluntary [5] reorienting, and their temporal dynamics are unknown. We used transcranial magnetic stimulation (TMS) over the occipital cortex to interfere with attentional reorienting and study its role and temporal dynamics in this process. Human observers performed an orientation discrimination task, with either valid or invalid attention cueing, across a range of stimulus contrasts. Valid cueing induced a behavioral response gain increase, higher asymptotic performance for attended than unattended locations. During subsequent TMS sessions, observers performed the same task, with high stimulus contrast. Based on phosphene mapping, TMS double pulses were applied at one of various delays to a consistent brain location in retinotopic areas (V1/V2), corresponding to the evoked signal of the target or distractor, in a valid or invalid trial. Thus, the stimulation was identical for the four experimental conditions (valid/invalid cue condition × target/distractor-stimulated). TMS modulation of the target and distractor were both periodic (5 Hz, theta) and out of phase with respect to each other in invalid trials only, when attention had to be disengaged from the distractor and reoriented to the target location. Reorientation of voluntary attention periodically involves V1/V2 at the theta frequency. These results suggest that TMS probes theta phase-reset by attentional reorienting and help link periodic sampling in time and attention reorienting in space.

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“…Similarly, magnetic stimulations delivered with the coil in various tilted positions demonstrated that none of the sham positions tested were ideal sham due to the possibility of slight cortical activation as measured by the integrated voltage recorded with intracranial electrodes (Lisanby et al, 2001) and due to a lesser scalp sensation (Loo et al, 2000). Furthermore, the 90° coil tilting and the shield equipped coils that reduce the effective magnetic field by approximately 80% fail to evoke somatosensory sensation perceived with the active TMS (Duecker et al, 2013). To reproduce click sound and somatosensory sensations, new sham coils have been manufactured, looking alike active coils but equipped with a magnetic shield resulting in a delivered magnetic field of only 10% compared to active coils (Sommer et al, 2006).…”

Section: Therapeutic Procedures In Dystoniamentioning

confidence: 99%

Contribution of TMS and rTMS in the Understanding of the Pathophysiology and in the Treatment of Dystonia

Lozeron

Poujois

Richard

et al. 2016

Front. Neural Circuits

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Dystonias represent a heterogeneous group of movement disorders responsible for sustained muscle contraction, abnormal postures, and muscle twists. It can affect focal or segmental body parts or be generalized. Primary dystonia is the most common form of dystonia but it can also be secondary to metabolic or structural dysfunction, the consequence of a drug’s side-effect or of genetic origin. The pathophysiology is still not elucidated. Based on lesion studies, dystonia has been regarded as a pure motor dysfunction of the basal ganglia loop. However, basal ganglia lesions do not consistently produce dystonia and lesions outside basal ganglia can lead to dystonia; mild sensory abnormalities have been reported in the dystonic limb and imaging studies have shown involvement of multiple other brain regions including the cerebellum and the cerebral motor, premotor and sensorimotor cortices. Transcranial magnetic stimulation (TMS) is a non-invasive technique of brain stimulation with a magnetic field applied over the cortex allowing investigation of cortical excitability. Hyperexcitability of contralateral motor cortex has been suggested to be the trigger of focal dystonia. High or low frequency repetitive TMS (rTMS) can induce excitatory or inhibitory lasting effects beyond the time of stimulation and protocols have been developed having either a positive or a negative effect on cortical excitability and associated with prevention of cell death, γ-aminobutyric acid (GABA) interneurons mediated inhibition and brain-derived neurotrophic factor modulation. rTMS studies as a therapeutic strategy of dystonia have been conducted to modulate the cerebral areas involved in the disease. Especially, when applied on the contralateral (pre)-motor cortex or supplementary motor area of brains of small cohorts of dystonic patients, rTMS has shown a beneficial transient clinical effect in association with restrained motor cortex excitability. TMS is currently a valuable tool to improve our understanding of the pathophysiology of dystonia but large controlled studies using sham stimulation are still necessary to delineate the place of rTMS in the therapeutic strategy of dystonia. In this review, we will focus successively on the use of TMS as a tool to better understand pathophysiology, and the use of rTMS as a therapeutic strategy.

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Time- and Task-Dependent Non-Neural Effects of Real and Sham TMS

Cited by 53 publications

References 18 publications

The impact of early visual cortex transcranial magnetic stimulation on visual working memory precision and guess rate

The impact of early visual cortex transcranial magnetic stimulation on visual working memory precision and guess rate

Attention Reorients Periodically

Contribution of TMS and rTMS in the Understanding of the Pathophysiology and in the Treatment of Dystonia

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