Repetitive Transcranial Magnetic Stimulation Effects on Language Function Depend on the Stimulation Parameters

Abstract

In previous studies it has been shown that picture-naming latencies can be facilitated with both suprathreshold single and repetitive transcranial magnetic stimulation (TMS/rTMS) over Wernicke's area. The aim of this study was to investigate whether low-frequency rTMS (1 Hz) or high-frequency rTMS (20 Hz) at subthreshold intensities is also capable of influencing picture naming. In 16 healthy right-hand male subjects, trains of 1 Hz or 20 Hz were applied over either Wernicke's area, Broca's area, or the primary visual cortex. The subjects had to name 20 black-and-white line drawings, which were shown immediately after rTMS and again 2 minutes later. Naming latency could be facilitated only immediately after Wernicke's area stimulation at a frequency of 20 Hz and at an intensity of 55% of the maximal stimulator output, which was more than the motor threshold. All other stimulation procedures failed to influence naming latencies. These results indicate that language functions can be facilitated in healthy subjects only by high-frequency rTMS with intensities at or above the motor threshold.

Potentiation of Gamma Oscillatory Activity through Repetitive Transcranial Magnetic Stimulation of the Dorsolateral Prefrontal Cortex

“…High-frequency rTMS has been shown to improve cognitive performance (Little et al, 2000;Sparing et al, 2001;Martis et al, 2003;O'Connor et al, 2005), however, the underlying mechanisms have not been investigated. We contend that a possible explanation is through its effects on GABAergic inhibitory neurotransmission critical in both the generation and synchronization of oscillatory activity (Whittington et al, 1995;Wang and Buzsaki, 1996;Bartos et al, 2007).…”

“…For example, high-frequency rTMS has been shown to improve language functions in healthy individuals (Sparing et al, 2001), as well as to improve different aspects of memory in major depressive disorder patients (Little et al, 2000;Martis et al, 2003;O'Connor et al, 2005). In addition, rTMS on the motor cortex has been shown to enhance GABA-mediated inhibitory neurotransmission in healthy individualsFthat is, Daskalakis et al (2006) reported a lengthening of the cortical silent period (CSP), a measure reflective of GABA Bmediated inhibitory neurotransmission (Ziemann et al, 1996) with increased stimulation frequency, which was maximal at 20 Hz (Daskalakis et al, 2006).…”

Impact of low frequency transcranial magnetic stimulation on event-related brain potentials

“…However, several studies did not report any modification after 1 Hz rTMS on either motor or cognitive functions. Although naming latency is facilitated only immediately after Wernicke's area stimulation at a frequency of 20 Hz, trains of 1 Hz failed to influence naming latencies (Sparing et al, 2001), and single session of 1 Hz TMS over the right or the left prefrontal areas did not interfere with neuropsychological functioning in normal volunteers (Koren et al, 2001). Furthermore, 1 Hz rTMS used continuously for 2 min of right or left prefrontal cortex did not modify P300 latency whereas 20 Hz rTMS applied in three trains of 5 s duration of left prefrontal cortex reduced significantly P300 latency (Evers et al, 2001).…”

Combined noninvasive language mapping by navigated transcranial magnetic stimulation and functional MRI and its comparison with direct cortical stimulation

“…22,33,35,52,53,77 Furthermore, repetitive navigated TMS (rTMS) and nonnavigated TMS are able to localize cortical language function. 18,19,40,48,69,80 Its clinical applicability and correlation to DCS during awake surgery have repeatedly been shown as well. 36,37,51,68,75 Although rTMS language mapping has already experienced some improvement, 40 the standard for preoperative, noninvasive language mapping remains functional MRI (fMRI).…”