Are recognition deficits following occipital lobe TMS explained by raised detection thresholds?

Kammer, Thomas; Nusseck, Hans-Günther

doi:10.1016/s0028-3932(98)00003-7

Cited by 54 publications

(36 citation statements)

References 16 publications

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“…The rTMS effects we found for briefly presented targets are consistent with other rTMS findings with occipital stimulation in which TMS is only able to disrupt perceptual judgments if the relative duration of presentation is short (e.g., Amassian et al, 1989), stimuli are close to luminance-detection thresholds (Miller, Fendrich, Eliassen, Demirel, & Gazzaniga, 1996) or both (see Kammer & Nusseck, 1998; see also Walsh & Pascual-Leone, 2003, for details of the relationship between stimuli and the temporal duration of TMS effects). In the present study, error rates were affected by rTMS application; however, they were not sensitive to the manipulation of orthographic neighborhood.…”

Section: Discussionsupporting

confidence: 89%

A Magnetic Stimulation Examination of Orthographic Neighborhood Effects in Visual Word Recognition

Lavidor

Walsh

2003

Journal of Cognitive Neuroscience

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Abstract& The split-fovea theory proposes that visual word recognition is mediated by the splitting of the foveal image, with letters to the left of fixation projected to the right hemisphere (RH) and letters to the right of fixation projected to the left hemisphere (LH). We applied repetitive transcranial magnetic stimulation (rTMS) over the left and right occipital cortex during a lexical decision task to investigate the extent to which word recognition processes could be accounted for according to the split-fovea theory. Unilateral rTMS significantly impaired lexical decision latencies to centrally presented words, supporting the suggestion that foveal representation of words is split between the cerebral hemispheres rather than bilateral. Behaviorally, we showed that words that have many orthographic neighbors sharing the same initial letters (''lead neighbors'') facilitated lexical decision more than words with few lead neighbors. This effect did not apply to end neighbors (orthographic neighbors sharing the same final letters). Crucially, rTMS over the RH impaired lead-, but not end-neighborhood facilitation. The results support the split-fovea theory, where the RH has primacy in representing lead neighbors of a written word. &

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Section: Discussionsupporting

confidence: 89%

A Magnetic Stimulation Examination of Orthographic Neighborhood Effects in Visual Word Recognition

Lavidor

Walsh

2003

Journal of Cognitive Neuroscience

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“…TMS disrupts cortical activity only briefly, making it unlikely that any effects observed here may be due to cortical reorganization or long term changes in reading-strategy. Previous TMS studies have demonstrated that there can be raised visual contrast thresholds following stimulation of the occipital pole (Kammer & Nussek, 1998;Paulus et al, 1999). Effects of occipital stimulation on reading have also been reported by Lavidor and Walsh (Lavidor & Walsh, 2004;Lavidor et al, 2003).…”

Section: Experiments 2: Effects Of Tmsmentioning

confidence: 62%

The “Special Effect” of Case Mixing on Word Identification: Neuropsychological and Transcranial Magnetic Stimulation Studies Dissociating Case Mixing from Contrast Reduction

Braet¹,

Humphreys²

2006

Journal of Cognitive Neuroscience

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*We present neuropsychological evidence and evidence from transcranial magnetic stimulation (TMS) with normal readers, that the effects of case mixing and contrast reduction on word identification are qualitatively different. Lesions and TMS applied to the right parietal lobe selectively disrupted the identification of mixed relative to single case stimuli. Bilateral lesions and TMS applied to the occipital cortex selectively disrupted the identification of low contrast words. These data suggest that different visual distortions (case mixing, contrast reduction) exert different effects on reading, modulated by contrasting brain regions. Case mixing is a 'special' distortion, and involves the recruitment of processes that are functionally distinct, and dependent on different regions in the brain, from those required to deal with contrast reduction.

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“…For instance, a train of stimulation (repetitive TMS, rTMS) over the supplementary motor area impaired performance of a complex sequence of finger movements (Gerloff, Corwell, Chen, Hallet, & Cohen, 1997); rTMS over occipital cortex induced scotoma (e.g., Amassian et al, 1998); speech was disrupted by rTMS over the inferior frontal cortex (Pascual-Leone, Gates, & Dhuna, 1991). Single-pulse TMS can also have a disruptive effect when applied at the appropriate time (e.g., for visual perception, Amassian et al, 1998; or manual reaction time [RT], Kammer & Nusseck, 1998). On the other hand, focal TMS can also be used to excite neural pathways: TMS over the primary visual cortex induces phosphenes and TMS over the primary motor cortex evokes motor potentials.…”

Section: Introductionmentioning

confidence: 99%

Transcranial magnetic stimulation of the human frontal eye field facilitates visual awareness

Grosbras

Paus

2003

Eur J of Neuroscience

154

129

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Abstract& When looking at one object, human subjects can shift their attention to another object in their visual field without moving the eyes. Such shifts of attention activate the same brain regions as those involved in the execution of eye movements. Here we investigate the role of one of the main cortical oculomotor area, namely, the frontal eye field (FEF), in shifts of attention. We used transcranial magnetic stimulation (TMS), a technique known to disrupt transiently eyemovements preparation. We hypothesized that if the FEF is a necessary element in the network involved in shifting attention without moving the eyes, then TMS should also disrupt visuospatial attention.For each volunteer, we positioned the TMS coil over the probabilistic anatomical location of the FEF, and we verified that single pulses delayed eye movements. We then applied TMS during a visuospatial attention task. In this task, a central arrow directed shifts of attention and the subject responded by a keypress to a subsequent visual peripheral target without moving the eyes from the central fixation point. In a few trials, the cue was invalid or uninformative, yielding slower responses than when the cue was valid. We delivered single pulses either 53 msec before or 70 msec after target onset.Contrary to our prediction, the main effect of the stimulation was a decrease in reaction time when it was applied 53 msec before target onset. TMS over the left hemisphere facilitated responses to targets in the right hemifield only and for all cueing conditions, whereas TMS over the right hemisphere had a bilateral effect for valid and neutral but not invalid cueing. Thus, TMS interfered with shift of attention only in the case of right hemisphere stimulation: it increased the cost of invalid cueing.Our results suggest that TMS over the FEF facilitates visual detection, and thereby reduces reaction time. This finding provides new insights into the role of the human FEF in processing visual information. The functional asymmetry observed for both facilitation of visual detection and interference with shifts of attention provides further evidence for the dominance of the right hemisphere for those processes. Our results also underline that the disruptive or facilitative effect of TMS over a given region depends upon the behavioral context. &

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Are recognition deficits following occipital lobe TMS explained by raised detection thresholds?

Cited by 54 publications

References 16 publications

A Magnetic Stimulation Examination of Orthographic Neighborhood Effects in Visual Word Recognition

A Magnetic Stimulation Examination of Orthographic Neighborhood Effects in Visual Word Recognition

The “Special Effect” of Case Mixing on Word Identification: Neuropsychological and Transcranial Magnetic Stimulation Studies Dissociating Case Mixing from Contrast Reduction

Transcranial magnetic stimulation of the human frontal eye field facilitates visual awareness

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