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Anodal transcranial direct current stimulation over the supramarginal gyrus facilitates pitch memory

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Abstract

Functional neuroimaging studies have shown activation of the supramarginal gyrus during pitch memory tasks. A previous transcranial direct current stimulation study using cathodal stimulation over the left supramarginal gyrus reported a detrimental effect on short-term pitch memory performance, indicating an important role of the supramarginal gyrus in pitch memory. The current study aimed to determine whether pitch memory could be improved following anodal stimulation of the left supramarginal gyrus. The performances of non-musicians on two pitch memory tasks (pitch recognition and recall) and a visual memory control task following anodal or sham transcranial direct current stimulation were compared. The results show that, post-stimulation, the anodal group but not the control group performed significantly better on both pitch memory tasks; performance did not differ on the face memory task. These findings provide strong support for the causal involvement of the left supramarginal gyrus in the pitch memory process, and highlight the potential efficacy of transcranial direct current stimulation as a tool to improve pitch memory.

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... Whereas anodal tDCS leads to a facilitation of neural activity, cathodal tDCS suppresses the cortical excitability under the site of stimulation (Nitsche and Paulus 2000;Cohen Kadosh et al. 2010;Ladeira et al. 2011). Previous tDCS studies have supported the causal involvement of the left SMG in pitch memory recognition by showing a deterioration of performance after cathodal stimulation (Vines et al. 2006) and an improvement of pitch memory on a recognition and recall task (but not visual memory) after anodal stimulation in nonmusicians (Schaal et al. 2013). To date however, there are no tDCS studies of the SMG in trained musicians, so the causal role of the left SMG in superior pitch memory performance remains to be tested. ...
... Therefore, performances on 2 pitch memory tasks (recognition and recall) and a visual control task were investigated following cathodal tDCS over the left SMG, right SMG, or sham stimulation. In line with previous studies, we hypothesized that in nonmusicians, cathodal stimulation over the left SMG would lead to a deterioration of performance on both pitch memory tasks (Vines et al. 2006;Schaal et al. 2013). Regarding the musicians group, 3 outcomes are possible: (1) cathodal stimulation over the left SMG results in deterioration of pitch memory performance, as stronger activation in the left SMG of musicians was found by Ellis et al. 2013, (2) cathodal tDCS over the right SMG would lead to a drop in pitch memory performance, as musicians show more right hemispheric activation for musical memory , or (3) no stimulation effect would be found as musicians activate a more complex neural system for the pitch memory process and can compensate for any stimulation modulations (Schulze, Zysset et al. 2011). ...
... The areas were located using area CP3 for the left and CP4 for the right hemisphere according to the international 10-20 system for electroencephalogram electrode placement, successfully used in previous studies to place the electrodes over the targeted site (Antal et al. 2004, Rogalewski et al. 2004, Vines et al. 2006. CP3 and CP4 are common locations for targeting the SMG on either hemisphere (Mottaghy et al. 2002;Schaal et al. 2013). The reference electrode (5 × 7 cm = 35 cm 2 ) was placed over the contralateral supraorbital area. ...
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For music and language processing, memory for relative pitches is highly important. Functional imaging studies have shown activation of a complex neural system for pitch memory. One region that has been shown to be causally involved in the process for nonmusicians is the supramarginal gyrus (SMG). The present study aims at replicating this finding and at further examining the role of the SMG for pitch memory in musicians. Nonmusicians and musicians received cathodal transcranial direct current stimulation (tDCS) over the left SMG, right SMG, or sham stimulation, while completing a pitch recognition, pitch recall, and visual memory task. Cathodal tDCS over the left SMG led to a significant decrease in performance on both pitch memory tasks in nonmusicians. In musicians, cathodal stimulation over the left SMG had no effect, but stimulation over the right SMG impaired performance on the recognition task only. Furthermore, the results show a more pronounced deterioration effect for longer pitch sequences indicating that the SMG is involved in maintaining higher memory load. No stimulation effect was found in both groups on the visual control task. These findings provide evidence for a causal distinction of the left and right SMG function in musicians and nonmusicians.
... One area that is consistently highlighted across studies is the left supramarginal gyrus (SMG) (Ellis, Bruijn, Norton, Winner, & Schlaug, 2013;Gaab, Gaser, Zaehle, J€ ancke, & Schlaug, 2003). Recently, studies using transcranial direct current stimulation (tDCS) have implied that the left SMG is causally involved in pitch memory processes (Schaal, Williamson, & Banissy, 2013;Vines, Schnider, & Schlaug, 2006). Suppressing left SMG function using cathodal tDCS leads to a deterioration in pitch recognition ability (Vines et al., 2006), while increasing left SMG excitability with anodal tDCS results in a facilitation of pitch memory (Schaal et al., 2013). ...
... Recently, studies using transcranial direct current stimulation (tDCS) have implied that the left SMG is causally involved in pitch memory processes (Schaal, Williamson, & Banissy, 2013;Vines, Schnider, & Schlaug, 2006). Suppressing left SMG function using cathodal tDCS leads to a deterioration in pitch recognition ability (Vines et al., 2006), while increasing left SMG excitability with anodal tDCS results in a facilitation of pitch memory (Schaal et al., 2013). In combination, these studies provide evidence that left SMG activity is important for the output of pitch memory, but the exact role of the left SMG in the pitch memory process remains unknown. ...
... A pitch memory recognition task was created, modeled on the pitch memory span task (Williamson & Stewart, 2010) that was used in one of our previous brain stimulation studies (Schaal et al., 2013). The task parameters were adjusted to match the TMS parameters. ...
... However, also some contrary effects depending on the duration and intensity of the stimulation input have been shown more recently 35 and there is an ongoing discussion about the reliability and efficiency of tDCS protocols depending on a number of trait and state variables 36,37 . With regards to pitch memory, studies using non-invasive brain stimulation methods have consistently revealed a critical role for the left SMG for pitch memory in non-musicians [38][39][40][41] . To date, no brain stimulation studies have been conducted to examine the neural mechanisms of rhythm memory. ...
... More specifically, the aim of this study was to examine the role of the left and right SMG for rhythm and pitch memory. As noted above, prior brain stimulation work has indicated a causal role for the left SMG in pitch memory 38,41 , but whether this region plays a similar role in rhythm memory remains unclear. Previous functional magnetic resonance imaging (fMRI) findings on the role of the SMG in rhythm memory paint a mixed picture: in one study bilateral activation of the SMG was found 13 , in others activation of the right SMG has been reported 9,12,42 , and another study highlighted left hemisphere activation of the SMG 43 . ...
... After stimulation, participants completed a pitch and rhythm span task. Based on previous research 38,40 , an improvement of pitch memory after anodal tDCS over the left SMG was expected. Regarding rhythm memory, an effect of anodal tDCS on memory performance was hypothesised as brain imaging studies show the involvement of the SMG for rhythm memory 12,13,43 , but the lateralisation of the effect is less predictable. ...
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Functional brain imaging studies and non-invasive brain stimulation methods have shown the importance of the left supramarginal gyrus (SMG) for pitch memory. The extent to which this brain region plays a crucial role in memory for other auditory material remains unclear. Here, we sought to investigate the role of the left and right SMG in pitch and rhythm memory in non-musicians. Anodal or sham transcranial direct current stimulation (tDCS) was applied over the left SMG (Experiment 1) and right SMG (Experiment 2) in two different sessions. In each session participants completed a pitch and rhythm recognition memory task immediately after tDCS. A significant facilitation of pitch memory was revealed when anodal stimulation was applied over the left SMG. No significant effects on pitch memory were found for anodal tDCS over the right SMG or sham condition. For rhythm memory the opposite pattern was found; anodal tDCS over the right SMG led to an improvement in performance, but anodal tDCS over the left SMG had no significant effect. These results highlight a different hemispheric involvement of the SMG in auditory memory processing depending on auditory material that is encoded.
... Most of these studies have tackled the left DLPFC to enhance episodic memory. Moreover, several studies have found modulating effects of parietal cortex tDCS in episodic memory (Jacobson et al., 2012a;Schaal et al., 2013;Jones et al., 2014;Pergolizzi and Chua, 2015;Pisoni et al., 2015). ...
... For prefrontal stimulation of the left DLPFC, the anode electrode was placed over F3 as in Javadi and Walsh. For parietal stimulation, the anode electrode was placed over CP3 as in Schaal et al. (2013) (cf. Mottaghy et al., 2002. ...
... Similar explanations can be discussed in relation to the null-effects of PPC stimulation. For example, Schaal et al. (2013) who found a beneficial effect of PPC tDCS on pitch memory used somewhat higher current strength (i.e., 2 mA). Jones et al. (2014) who found a beneficial effect of PPC tDCS on the California Verbal Learning test (CLVT) stimulated their participants at a somewhat more posterior brain area (P3 electrode). ...
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Boosting memory with transcranial direct current stimulation (tDCS) seems to be an elegant way to optimize learning. Here we tested whether tDCS to the left dorsolateral prefrontal cortex or to the left posterior parietal cortex would boost recognition memory in general and/or particularly for action phrases enacted at study. During study, 48 young adults either read or enacted simple action phrases. Memory for the action phrases was assessed after a retention interval of 45 min and again after 7-days to investigate the long-term consequences of brain stimulation. The results showed a robust enactment effect in both test sessions. Moreover, the decrease in performance was more pronounced for reading than for enacting the phrases at study. However, tDCS did not reveal any effect on subsequent recognition memory performance. We conclude that memory benefits of tDCS are not easily replicated. In contrast, enactment at study reliably boosts subsequent memory.
... Research in the motor domain typically links anodal tDCS to a facilitation of neural activity, whereas cathodal tDCS more likely suppresses the cortical excitability under the site of stimulation (Nitsche & Paulus, 2000). Previous tDCS studies on pitch memory have revealed a causal link between the left supramarginal gyrus and pitch recognition and recall (Vines et al., 2006;Schaal et al., 2013Schaal et al., , 2014b, as well as between Heschl's gyrus and pitch discrimination (Mathys et al., 2010). Thus, we examined the causal involvement of the bilateral PPC for memory for whole melodies. ...
... Even though the majority of tDCS studies link anodal tDCS to a facilitation of cognitive performances (e.g. Ladeira et al., 2011;Javadi & Walsh, 2012;Santiesteban et al., 2012;Schaal et al., 2013), several studies have also reported deterioration of performance after anodal stimulation (Ferrucci et al., 2008;Jones & Berryhill, 2012;Kaminski et al., 2013). A recent tDCS study on an auditory between-channel gap detection task showed a significant decline in performance after anodal stimulation over the left auditory cortex (Heimrath et al., 2014). ...
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Functional brain imaging studies have highlighted the significance of right-lateralized temporal, frontal and parietal brain areas for memory for melodies. The present study investigated the involvement of bilateral posterior parietal cortices (PPC) for the recognition memory of melodies using transcranial direct current stimulation (tDCS). Participants performed a recognition task before and after tDCS. The task included an encoding phase (12 melodies), a retention period, as well as a recognition phase (24 melodies). Experiment 1 revealed that anodal tDCS over the right PPC leads to a deterioration of overall memory performance compared to sham. Experiment 2 confirmed the results of Experiment 1 and further showed that anodal tDCS over the left PPC does not show a modulatory effect on memory task performance, indicating a right lateralization for musical memory. Furthermore, both experiments revealed that the decline in memory for melodies can be traced back to an interference of anodal stimulation on the recollection process (remember judgments) rather than to familiarity judgements. Taken together, this study reveals a causal involvement of the right PPC for memory for melodies and demonstrates a key role for this brain region in the recollection process of the memory task. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
... Looking at tDCS studies investigating the neural basis of pitch memory in non-musicians, the left supramarginal gyrus (SMG) is one area that has received some attention with studies showing that pitch memory was facilitated after anodal stimulation (Schaal et al., 2013. Cathodal stimulation, on the other hand, led to a deterioration of pitch memory performance in healthy non-musicians (Vines et al., 2006;Schaal et al., 2015b). ...
... Looking at the pre-test pitch performances of our sample, it is notable that a group of participants (below median group) displayed fairly poor pitch memory abilities while the above median group displayed pitch memory abilities which match the performance level of healthy non-musicians reported in previous studies (Williamson and Stewart, 2010;Schaal et al., 2013Schaal et al., , 2015bSchaal et al., ,c, 2017. In the above median performers, cathodal tDCS over the right DLPFC selectively led to a significant deterioration of pitch memory supporting neuroimaging studies which have highlighted the activation of the right inferior frontal lobe during pitch memory processes (Zatorre et al., 1994;Gaab et al., 2003;Albouy et al., 2013). ...
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Pitch memory is a resource which is shared by music and language. Neuroimaging studies have shown that the right dorsolateral prefrontal cortex (DLPFC) is activated during pitch memory processes. The present study investigated the causal significance of this brain area for pitch memory in non-musicians by applying cathodal and sham transcranial direct current stimulation (tDCS) over the right DLPFC and examining the impact on offline pitch and visual memory span performances. On the overall sample (N= 22) no significant modulation effect of cathodal stimulation on the pitch span task was found. However, when dividing the sample by means of a median split of pre-test pitch memory abilities into a high and low performing group, a selective effect of significantly impaired pitch memory after cathodal tDCS in good performers was revealed. The visual control task was not affected by the stimulation in either group. The results support previous neuroimaging studies that the right DLPFC is involved in pitch memory processes in non-musicians and highlights the importance of baseline pitch memory abilities for the modulatory effect of tDCS.
... The improved performance in the C-C condition, which led to significant differences to all other conditions after anodal tDCS, suggests that anodal tDCS over the AC might positively influence the memory process, but only when no background noise is present. Other studies have shown that anodal tDCS over a targeted brain area improves tasks performance (Javadi & Walsh, 2012;Ladeira et al., 2011;Schaal, Williamson, & Banissy, 2013) as it facilitates excitability in the targeted site (Nitsche & Paulus, 2000). This could explain that the C-C condition outperforms all other conditions after anodal tDCS over the AC. ...
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The study investigates how transcranial direct current stimulation (tDCS) over the auditory cortex (AC) modulates memory for melodies under different noise conditions, whilst also considering cumulative disruptive interference effects. Forty-one participants completed a continuous recognition melody task, as well as a visual control task, which included four noise conditions for which noise was either present only during encoding (N-C), only during retrieval (C-N), during both (N-N) or not at all (C-C) and completed the tasks after receiving anodal or sham tDCS over the right AC. The results of the sham session replicate previous findings by revealing that memory for melodies is worse when noise in added to the encoding phase (N-C) whereas the N-N condition shows good performance, highlighting a context effect, and that cumulative disruptive interference is not present in memory for melodies except in the N-C condition. After anodal stimulation the memory pattern differs such as that memory performance is best in the C-C condition and furthermore the cumulative disruptive interference effect in the N-C condition is diminished. In sum, the study highlights the involvement of the right AC for memory for melodies and the results indicate an association of the AC for creating context effects.
... The possibility of non-invasively modulating the activity of the brain using transcranial current brain stimulation (tCS) has been intriguing the researchers in a variety of fields as it allows to improve cognition in various domains (Fregni et al., 2005;Santiesteban et al., 2012;Schaal et al., 2013;Snowball et al., 2013) or treat many human psychiatric conditions (Boggio et al., 2007Rigonatti et al., 2008;Nitsche et al., 2009;Terhune and Cohen Kadosh, 2013). There are a number of tCS techniques available, including, but not limited to, transcranial direct current stimulation (tDCS), transcranial alternating current stimulation (tACS), and transcranial random noise stimulation (tRNS) (for a review on the tCS methods, see: Nitsche et al., 2008;Ruffini et al., 2013). ...
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Transcranial current brain stimulation (tCS) is becoming increasingly popular as a non-pharmacological non-invasive neuromodulatory method that alters cortical excitability by applying weak electrical currents to the scalp via a pair of electrodes. Most applications of this technique have focused on enhancing motor and learning skills, as well as a therapeutic agent in neurological and psychiatric disorders. In these applications, similarly to lesion studies, tCS was used to provide a causal link between a function or behaviour and a specific brain region (e.g., primary motor cortex). Nonetheless, complex cognitive functions are known to rely on functionally connected multitude of brain regions with dynamically changing patterns of information flow rather than on isolated areas, which are most commonly targeted in typical tCS experiments. In this review article, we argue in favour of combining tCS method with other neuroimaging techniques (e.g. fMRI, EEG) and by employing state-of-the-art connectivity data analysis techniques (e.g. graph theory) to obtain a deeper understanding of the underlying spatiotemporal dynamics of functional connectivity patterns and cognitive performance. Finally, we discuss the possibilities of these combined techniques to investigate the neural correlates of human creativity and to enhance creativity.
... Diese Information kann dazu verwendet werden, um sicherstellen zu können, dass sich verschiedene Experimentalgruppen hinsichtlich ihrer musikalischen Ausbildung nicht unterscheiden (z. B. Schaal, Williamson & Banissy, 2013). Über dies hinaus kann bei der Rekrutierung von Versuchspersonen gewährleistet werden, dass die Stichprobe insgesamt ein weites Spektrum an musikalischer Expertise aufweist (z. ...
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The present study introduces the German version of the Gold-MSI inventory, a tool for evaluating self-reported musical abilities and musical expertise. The Gold-MSI is based around the multidimensional construct of Musical Sophistication and builds on the idea that musical expertise cannot only be developed through musical training on an instrument but also through active engagement with music in its many facets. The questionnaire was developed with a very large English sample (Müllensiefen et al., 2014) and comprises musical expertise with five factors as well as the general factor Musical Sophistication. The English Gold-MSI questionnaire was translated into German and evaluated with a German sample (N = 641). Using confirmative factor analysis the underlying factor structure was confirmed. Furthermore, the results show high reliabilities of the five sub-factors as well as the general factor Musical Sophistication (Cronbach’s alpha between .72 and .91.). Additionally, relationships between variables of the socio-economic status and the sub-factors of the Gold-MSI of the German sample are investigated using a structural equation model. The statistical model reveals positive relationships between income and professional status on the one hand and musical training, perceptual abilities and emotional engagement with music on the other hand. The inventory is freely available and is designed to contribute to the refined investigation of musical sophistication and expertise in German speaking countries.
... In the auditory domain, electroencephalography (EEG) measurements demonstrated that anodal tDCS applied over the left temporal cortex increased auditory-evoked potential (AEP) P50 amplitudes (Zaehle et al., 2011), indicating that the stimulation does modulate the functional response of the auditory cortex. At a behavioral level, anodal tDCS showed an enhancing effect and cathodal tDCS has a blocking effect on a pitch memory task when applied over left supramarginal gyrus (Vines et al., 2006;Schaal et al., 2013). Deterioration effects of cathodal tDCS have also been found in a pitch detection task with 2 mA of tDCS over left and right Heschl's gyri (HG), with a stronger effect on the right HG (Mathys et al., 2010), as well as in a pitch matching task with 2 mA of cathodal tDCS over inferior frontal and superior temporal cortical regions . ...
Article
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Transcranial direct current stimulation (tDCS) is attracting increasing interest because of its potential for therapeutic use. While its effects have been investigated mainly with motor and visual tasks, less is known in the auditory domain. Past tDCS studies with auditory tasks demonstrated various behavioral outcomes, possibly due to differences in stimulation parameters, task-induced brain activity, or task measurements used in each study. Further research, using well-validated tasks is therefore required for clarification of behavioral effects of tDCS on the auditory system. Here, we took advantage of findings from a prior functional magnetic resonance imaging study, which demonstrated that the right auditory cortex is modulated during fine-grained pitch learning of microtonal melodic patterns. Targeting the right auditory cortex with tDCS using this same task thus allowed us to test the hypothesis that this region is causally involved in pitch learning. Participants in the current study were trained for 3 days while we measured pitch discrimination thresholds using microtonal melodies on each day using a psychophysical staircase procedure. We administered anodal, cathodal, or sham tDCS to three groups of participants over the right auditory cortex on the second day of training during performance of the task. Both the sham and the cathodal groups showed the expected significant learning effect (decreased pitch threshold) over the 3 days of training; in contrast we observed a blocking effect of anodal tDCS on auditory pitch learning, such that this group showed no significant change in thresholds over the 3 days. The results support a causal role for the right auditory cortex in pitch discrimination learning.
... Polarity-specific tDCS effects have also been demonstrated for the alteration of spectral acoustic processing. Anodal tDCS over the left supramarginal gyrus (SMG) enhanced (Schaal et al., 2013), whereas cathodal tDCS diminished the performance in a pitch memory task (offline effect) (Vines et al., 2006). Thus, the systematic stimulation of the left SMG provides further support for the functional relevance of this cortical area for pitch processing by adding causal evidence to former correlative fMRI data that already associated pitch memory with left SMG processing (Gaab et al., 2003). ...
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Transcranial electrical stimulation (tES) has become a valuable research tool for the investigation of neurophysiological processes underlying human action and cognition. In recent years, striking evidence for the neuromodulatory effects of transcranial direct current stimulation, transcranial alternating current stimulation, and transcranial random noise stimulation has emerged. While the wealth of knowledge has been gained about tES in the motor domain and, to a lesser extent, about its ability to modulate human cognition, surprisingly little is known about its impact on perceptual processing, particularly in the auditory domain. Moreover, while only a few studies systematically investigated the impact of auditory tES, it has already been applied in a large number of clinical trials, leading to a remarkable imbalance between basic and clinical research on auditory tES. Here, we review the state of the art of tES application in the auditory domain focussing on the impact of neuromodulation on acoustic perception and its potential for clinical application in the treatment of auditory related disorders.
... These elements alone could explain the improvements in temporal processing induced in older adults. Indeed, it is possible that tACS perturbs a normal, well-functioning system and leads to a processing deterioration in younger adults, because the neuronal reactivity level is already optimal in this group (Krause et al., 2013;Schaal et al., 2013). Future studies should therefore investigate the effect of tES techniques in older adults with hearing loss and/or impaired auditory processing, to determine if such techniques could have a clinical relevance in audiology. ...
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The effects of transcranial electrical stimulation (tES) approaches have been widely studied for many decades in the motor field, and are well known to have a significant and consistent impact on the rehabilitation of people with motor deficits. Consequently, it can be asked whether tES could also be an effective tool for targeting and modulating plasticity in the sensory field for therapeutic purposes. Specifically, could potentiating sensitivity at the central level with tES help to compensate for sensory loss? The present review examines evidence of the impact of tES on cortical auditory excitability and its corresponding influence on auditory processing, and in particular on hearing rehabilitation. Overall, data strongly suggest that tES approaches can be an effective tool for modulating auditory plasticity. However, its specific impact on auditory processing requires further investigation before it can be considered for therapeutic purposes. Indeed, while it is clear that electrical stimulation has an effect on cortical excitability and overall auditory abilities, the directionality of these effects is puzzling. The knowledge gaps that will need to be filled are discussed.
... Regarding auditory processing, application of tDCS affected performance in a task assessing temporal resolution of auditory processing (Ladeira et al., 2011;Heimrath et al., 2014). Further, tDCS also changed performance in pitch memory (Vines et al., 2006;Schaal et al., 2013), pitch matching , and pitch discrimination (Mathys et al., 2010;Matsushita et al., 2015). In addition to behavioral performance, tDCS effects on electrophysiological changes for auditory discrimination were investigated using Mismatch Negativity (MMN). ...
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Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique to change cortical excitability. Its effects are shown for cognitive processing, and behavior in the motor and perceptual domains. However, evidence of tDCS effects in the perceptual domain particularly for auditory processing is rare. Therefore, and in the context of disturbances in auditory processing in psychiatric populations, e.g., in patients with auditory verbal hallucinations, we aimed to investigate the potential modulatory effect of tDCS on the excitability of left posterior temporal cortex in detail. We included 24 healthy participants in a crossover design, applying sham and anodal stimulation in two measurement sessions 1 week apart. Electroencephalography (EEG) was recorded while participants listened to tones before, during, and after stimulation. Amplitudes and latencies of P50, N100, and P200 auditory-evoked potentials (AEP) were compared between anodal and sham stimulation, and between time points before, during, and after tDCS. In contrast to previous studies, results demonstrate no significant differences between stimulation types or time points for any of the investigated AEP amplitudes or latencies. Furthermore, a topographical analysis did not show any topographical differences during peak time periods of the investigated AEP for stimulation types and time points besides a habituation effect. Thus, our results suggest that tDCS modulation of excitability of the left posterior temporal cortex, targeting the auditory cortex, does not have any effect on AEP. This is particularly interesting in the context of tDCS as a potential treatment for changed electrophysiological parameters and symptoms of psychiatric diseases, e.g., lower N100 or auditory verbal hallucinations in schizophrenia.
... In one study, suppressing the left supramarginal gyrus function using cathodal transcranial direct current stimulation led to a deterioration in pitch recognition ability (16). In another study of rTMS in 27 healthy participants, the left supramarginal gyrus was involved in the retention phase of pitch memory (17). ...
... rhythm, melody). The present results are however consistent with those of brain stimulation studies, showing a causal role in pitch memory for the left but not the right supramarginal gyrus 43,44,53 . Further, θ-frequency stimulation to the left intraparietal sulcus has been shown to boost performance for mental manipulation of melodies 38 . ...
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Recent magnetoencephalography (MEG) studies have established that sensorimotor brain rhythms are strongly modulated during mental imagery of musical beat and rhythm, suggesting that motor regions of the brain are important for temporal aspects of musical imagery. The present study examined whether these rhythms also play a role in non-temporal aspects of musical imagery including musical pitch. Brain function was measured with MEG from 19 healthy adults while they performed a validated musical pitch imagery task and two non-imagery control tasks with identical temporal characteristics. A 4-dipole source model probed activity in bilateral auditory and sensorimotor cortices. Significantly greater β-band modulation was found during imagery compared to control tasks of auditory perception and mental arithmetic. Imagery-induced β-modulation showed no significant differences between auditory and sensorimotor regions, which may reflect a tightly coordinated mode of communication between these areas. Directed connectivity analysis in the θ-band revealed that the left sensorimotor region drove left auditory region during imagery onset. These results add to the growing evidence that motor regions of the brain are involved in the top-down generation of musical imagery, and that imagery-like processes may be involved in musical perception.
... Interestingly, a few studies using repetitive TMS (rTMS) or transcranial direct stimulation (tDCS) have shown that the left SMG is involved in the storage of non-verbal information. These studies show that left SMG stimulation is detrimental when applied during the interval between the irst and second tone sequences during a pitch memory task but not when applied during the presentation of the irst sequence (Schaal et al. 2013(Schaal et al. , 2015aVines et al. 2006). The authors interpreted these indings as indicating that the left SMG is involved in the maintenance of pitch information, which suggests that the phonological store holds non-verbal auditory information in transient storage. ...
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It has been proposed that the maintenance of phonological information in verbal working memory (vWM) is carried by a domain-specific short-term storage center—the phonological loop—which is composed of a phonological store and an articulatory rehearsal system. Several brain regions including the left posterior inferior frontal gyrus (pIFG) and anterior supramarginal gyri (aSMG) are thought to support these processes. However, recent behavioral evidence suggests that verbal and non-verbal auditory information may be processed as part of a unique domain general short-term storage center instead of through specialized subsystems such as the phonological loop. In the current study, we used a single-pulse transcranial magnetic stimulation (TMS)-delayed priming paradigm with speech (syllables) and acoustically complex non-speech sounds (bird songs) to examine whether the pIFG and aSMG are involved in the processing of verbal information or, alternatively, in the processing of any complex auditory information. Our results demonstrate that TMS delivered to both regions had an effect on performance for speech and non-speech stimuli, but the nature of the effect was different. That is, priming was reduced for the speech sounds because TMS facilitated the detection of different but not identical stimuli, and accuracy was decreased for non-speech sounds. Since TMS interfered with both speech and non-speech sounds, these findings support the existence of an auditory short-term storage center located within the dorsal auditory stream.
... They gave written consent before taking part to the experiment. The whole procedure was carried out in accordance with the principles of the The active electrode (5 x 5 cm) was placed over C4/P4 site of the 10-20 EEG system, corresponding to the right SMG [17], and the reference electrode (5 x 9.5 cm) was placed over the left shoulder. ...
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Neural populations in the supramarginal gyrus (SMG) of the right hemisphere have been shown to be involved in processing the subjective experience of time, particularly because of their selectivity to specific temporal durations. To directly investigate this relationship, we applied high-frequency transcranial Random Noise Stimulation (hf-tRNS) on the right SMG during a duration judgment task: 24 participants were required to judge the duration of a test visual stimulus (350, 450, 550, 650 ms) as shorter or longer than the duration of a reference auditory stimulus (500 ms). In half of the trials this procedure was preceded by a visual adaptation paradigm, used as a tool to manipulate the subjective experience of time: for 12 participants the adaptor was shorter than the test (250 ms), and for 12 participants it was longer than the test (750 ms). All participants performed an online hf-tRNS session and a sham control session. For each participant and for each condition, the Point of Subjective Equality (PSE) was calculated and results revealed an expected negative aftereffect in the group exposed to a longer adaptor. Moreover, hf-tRNS modulated participants’ performance with respect to sham, confirming the involvement of the right SMG in temporal experience. Importantly, only in the group exposed to the longer adaptor, PSE values were higher during stimulation than during sham, only after the adaptation procedure (no difference emerged in trials without adaptation). This pattern of results confirms recent neuroimaging findings, and adds a direct evidence of the causal role of this area in subjective time experience.
... While cathodal tDCS when applied to particular regions of the brain or nodes of a network has been shown to cause a dysfunction, anodal tDCS and 35 Hz transcranial Alternating Current Stimulation (tACS) if applied in the same manner has been used to improve short-term memory function for pitched information (Schaal et al., 2013(Schaal et al., , 2015a. To establish the causality of each major node in the neural network, and to test the hemispheric laterality of pitch production functioning, the current study aimed to disrupt the functions of STG and IFG-cortical regions in the hypothesized pitch production network-on either hemisphere and then to observe effects of the modulated functions of each of these candidate regions in a pitch matching task. ...
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Previous studies have shown that transcranial direct current stimulation (tDCS) can affect performance by decreasing regional excitability in a brain region that contributes to the task of interest. To our knowledge, no research to date has found both enhancing and diminishing effects on performance, depending upon which polarity of current is applied. The supramarginal gyrus (SMG) is an ideal brain region for testing tDCS effects because it is easy to identify using the 10-20 EEG coordinate system, and results of neuroimaging studies have implicated the left SMG in short-term memory for phonological and non-phonological sounds. In the present study, we found that applying tDCS to the left SMG affected pitch memory in a manner that depended upon the polarity of stimulation: cathodal tDCS had a negative impact on performance while anodal tDCS had a positive impact. These effects were significantly different from sham stimulation, which did not influence performance; they were also specific to the left hemisphere (no effect was found when applying cathodal stimulation to the right SMG) and were unique to pitch memory as opposed to memory for visual shapes. Our results provide further evidence that the left SMG is a nodal point for short-term auditory storage and demonstrate the potential of tDCS to influence cognitive performance, and to causally examine hypotheses derived from neuroimaging studies.
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The study introduces a rhythm memory task and compares performance of musicians and non-musicians. The rhythm span task with increasing and decreasing sequence length according to the participants’ performance, measures the individual memory capacity for musical rhythms. Results show that musicians perform significantly better on the rhythm span task indicating that memory capacity for rhythms is superior after many years of formal musical training. Additionally performance correlates positively with an established pitch span task (Williamson & Stewart, 2010) as well as the five dimensions of the Gold-MSI self-report questionnaire (Müllensiefen et al., 2014) evaluating musical sophistication.
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The limits of human visual short-term memory (VSTM) have been well documented, and recent neuroscientific studies suggest that VSTM performance is associated with activity in the posterior parietal cortex. Here we show that artificially elevating parietal activity via positively charged electric current through the skull can rapidly and effortlessly improve people's VSTM performance. This artificial improvement, however, comes with an interesting twist: it interacts with people's natural VSTM capability such that low performers who tend to remember less information benefitted from the stimulation, whereas high performers did not. This behavioral dichotomy is explained by event-related potentials around the parietal regions: low performers showed increased waveforms in N2pc and contralateral delay activity (CDA), which implies improvement in attention deployment and memory access in the current paradigm, respectively. Interestingly, these components are found during the presentation of the test array instead of the retention interval, from the parietal sites ipsilateral to the target location, thus suggesting that transcranial direct current stimulation (tDCS) was mainly improving one's ability to suppress no-change distractors located on the irrelevant side of the display during the comparison stage. The high performers, however, did not benefit from tDCS as they showed equally large waveforms in N2pc and CDA, or SPCN (sustained parietal contralateral negativity), before and after the stimulation such that electrical stimulation could not help any further, which also accurately accounts for our behavioral observations. Together, these results suggest that there is indeed a fixed upper limit in VSTM, but the low performers can benefit from neurostimulation to reach that maximum via enhanced comparison processes, and such behavioral improvement can be directly quantified and visualized by the magnitude of its associated electrophysiological waveforms.
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Given the polarity dependent effects of transcranial direct current stimulation (tDCS) in facilitating or inhibiting neuronal processing, and tDCS effects on pitch perception, we tested the effects of tDCS on temporal aspects of auditory processing. We aimed to change baseline activity of the auditory cortex using tDCS as to modulate temporal aspects of auditory processing in healthy subjects without hearing impairment. Eleven subjects received 2mA bilateral anodal, cathodal and sham tDCS over auditory cortex in a randomized and counterbalanced order. Subjects were evaluated by the Random Gap Detection Test (RGDT), a test measuring temporal processing abilities in the auditory domain, before and during the stimulation. Statistical analysis revealed a significant interaction effect of time vs. tDCS condition for 4000 Hz and for clicks. Post-hoc tests showed significant differences according to stimulation polarity on RGDT performance: anodal improved 22.5% and cathodal decreased 54.5% subjects' performance, as compared to baseline. For clicks, anodal also increased performance in 29.4% when compared to baseline. tDCS presented polarity-dependent effects on the activity of the auditory cortex, which results in a positive or negative impact in a temporal resolution task performance. These results encourage further studies exploring tDCS in central auditory processing disorders.
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Around 20% of the population exhibits moderate to severe numerical disabilities [1-3], and a further percentage loses its numerical competence during the lifespan as a result of stroke or degenerative diseases [4]. In this work, we investigated the feasibility of using noninvasive stimulation to the parietal lobe during numerical learning to selectively improve numerical abilities. We used transcranial direct current stimulation (TDCS), a method that can selectively inhibit or excitate neuronal populations by modulating GABAergic (anodal stimulation) and glutamatergic (cathodal stimulation) activity [5, 6]. We trained subjects for 6 days with artificial numerical symbols, during which we applied concurrent TDCS to the parietal lobes. The polarity of the brain stimulation specifically enhanced or impaired the acquisition of automatic number processing and the mapping of number into space, both important indices of numerical proficiency [7-9]. The improvement was still present 6 months after the training. Control tasks revealed that the effect of brain stimulation was specific to the representation of artificial numerical symbols. The specificity and longevity of TDCS on numerical abilities establishes TDCS as a realistic tool for intervention in cases of atypical numerical development or loss of numerical abilities because of stroke or degenerative illnesses.
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Congenital amusia is a disorder that affects the perception and production of music. While amusia has been associated with deficits in pitch discrimination, several reports suggest that memory deficits also play a role. The present study investigated short-term memory span for pitch-based and verbal information in 14 individuals with amusia and matched controls. Analogous adaptive-tracking procedures were used to generate tone and digit spans using stimuli that exceeded psychophysically measured pitch perception thresholds. Individuals with amusia had significantly smaller tone spans, whereas their digits spans were a similar size to those of controls. An automated operation span task was used to determine working memory capacity. Working memory deficits were seen in only a small subgroup of individuals with amusia. These findings support the existence of a pitch-specific component within short-term memory and suggest that congenital amusia is more than a disorder of fine-grained pitch discrimination.
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In the classic neurological model of language, the human inferior parietal lobule (IPL) plays an important role in visual word recognition. The region is both functionally and structurally heterogeneous, however, suggesting that subregions of IPL may differentially contribute to reading. The two main sub-divisions are the supramarginal (SMG) and angular gyri, which have been hypothesized to contribute preferentially to phonological and semantic aspects of word processing, respectively. Here we used single-pulse transcranial magnetic stimulation (TMS) to investigate the functional specificity and timing of SMG involvement in reading. Participants performed two reading tasks that focused attention on either the phonological or semantic relation between two simultaneously presented words. A third task focused attention on the visual relation between pairs of consonant letter strings to control for basic input and output characteristics of the paradigm using non-linguistic stimuli. TMS to SMG was delivered on every trial at 120, 180, 240 or 300 msec post-stimulus onset. Stimulation at 180 msec produced a reliable facilitation of reaction times for both the phonological and semantic tasks, but not for the control visual task. These findings demonstrate that SMG contributes to reading regardless of the specific task demands, and suggests this may be due to automatically computing the sound of a word even when the task does not explicitly require it.
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The neural correlates of music perception were studied by measuring cerebral blood flow (CBF) changes with positron emission tomography (PET). Twelve volunteers were scanned using the bolus water method under four separate conditions: (1) listening to a sequence of noise bursts, (2) listening to unfamiliar tonal melodies, (3) comparing the pitch of the first two notes of the same set of melodies, and (4) comparing the pitch of the first and last notes of the melodies. The latter two conditions were designed to investigate short-term pitch retention under low or high memory load, respectively. Subtraction of the obtained PET images, superimposed on matched MRI scans, provides anatomical localization of CBF changes associated with specific cognitive functions. Listening to melodies, relative to acoustically matched noise sequences, resulted in CBF increases in the right superior temporal and right occipital cortices. Pitch judgments of the first two notes of each melody, relative to passive listening to the same stimuli, resulted in right frontal-lobe activation. Analysis of the high memory load condition relative to passive listening revealed the participation of a number of cortical and subcortical regions, notably in the right frontal and right temporal lobes, as well as in parietal and insular cortex. Both pitch judgment conditions also revealed CBF decreases within the left primary auditory cortex. We conclude that specialized neural systems in the right superior temporal cortex participate in perceptual analysis of melodies; pitch comparisons are effected via a neural network that includes right prefrontal cortex, but active retention of pitch involves the interaction of right temporal and frontal cortices.
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In this paper we demonstrate in the intact human the possibility of a non-invasive modulation of motor cortex excitability by the application of weak direct current through the scalp. Excitability changes of up to 40 %, revealed by transcranial magnetic stimulation, were accomplished and lasted for several minutes after the end of current stimulation. Excitation could be achieved selectively by anodal stimulation, and inhibition by cathodal stimulation. By varying the current intensity and duration, the strength and duration of the after-effects could be controlled. The effects were probably induced by modification of membrane polarisation. Functional alterations related to post-tetanic potentiation, short-term potentiation and processes similar to postexcitatory central inhibition are the likely candidates for the excitability changes after the end of stimulation. Transcranial electrical stimulation using weak current may thus be a promising tool to modulate cerebral excitability in a non-invasive, painless, reversible, selective and focal way.
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The primary aim of this study was to determine the extent to which human MT+/V5, an extrastriate visual area known to mediate motion processing, is involved in visuomotor coordination. To pursue this we increased or decreased the excitability of MT+/V5, primary motor, and primary visual cortex by the application of 7 min of anodal and cathodal transcranial direct current stimulation (tDCS) in healthy human subjects while they were performing a visuomotor tracking task involving hand movements. The percentage of correct tracking movements increased specifically during and immediately after cathodal stimulation, which decreases cortical excitability, only when V5 was stimulated. None of the other stimulation conditions affected visuomotor performance. We propose that the improvement in performance caused by cathodal tDCS of V5 is due to a focusing effect on to the complex motion perception conditions involved in this task. This hypothesis was proven by additional experiments: Testing simple and complex motion perception in dot kinetograms, we found that a diminution in excitability induced by cathodal stimulation improved the subject's perception of the direction of the coherent motion only if this was presented among random dots (complex motion perception), and worsened it if only one motion direction was presented (simple movement perception). Our data suggest that area V5 is critically involved in complex motion perception and identification processes important for visuomotor coordination. The results also raise the possibility of the usefulness of tDCS in rehabilitation strategies for neurological patients with visuomotor disorders.
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Transcranial DC stimulation (tDCS) induces stimulation polarity-dependent neuroplastic excitability shifts in the human brain. Because it accomplishes long-lasting effects and its application is simple, it is used increasingly. However, one drawback is its low focality, caused by 1) the large stimulation electrode and 2) the functionally effective reference electrode, which is also situated on the scalp. We aimed to increase the focality of tDCS, which might improve the interpretation of the functional effects of stimulation because it will restrict its effects to more clearly defined cortical areas. Moreover, it will avoid unwanted reversed effects of tDCS under the reference electrode, which is of special importance in clinical settings, when a homogeneous shift of cortical excitability is needed. Because current density (current strength/electrode size) determines the efficacy of tDCS, increased focality should be accomplished by 1) reducing stimulation electrode size, but keeping current density constant; or 2) increasing reference electrode size under constant current strength. We tested these hypotheses for motor cortex tDCS. The results show that reducing the size of the motor cortex DC-stimulation electrode focalized the respective tDCS-induced excitability changes. Increasing the size of the frontopolar reference electrode rendered stimulation over this cortex functionally inefficient, but did not compromise the tDCS-generated motor cortical excitability shifts. Thus tDCS-generated modulations of cortical excitability can be focused by reducing the size of the stimulation electrode and by increasing the size of the reference electrode. For future applications of tDCS, such paradigms may help to achieve more selective tDCS effects.
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The neural correlates of music perception were studied by measuring cerebral blood flow (CBF) changes with positron emission tomography (PET). Twelve volunteers were scanned using the bolus water method under four separate conditions: (1) listening to a sequence of noise bursts, (2) listening to unfamiliar tonal melodies, (3) comparing the pitch of the first two notes of the same set of melodies, and (4) comparing the pitch of the first and last notes of the melodies. The latter two conditions were designed to investigate short-term pitch retention under low or high memory load, respectively. Subtraction of the obtained PET images, superimposed on matched MRI scans, provides anatomical localization of CBF changes associated with specific cognitive functions. Listening to melodies, relative to acoustically matched noise sequences, resulted in CBF increases in the right superior temporal and right occipital cortices. Pitch judgments of the first two notes of each melody, relative to passive listening to the same stimuli, resulted in right frontal-lobe activation. Analysis of the high memory load condition relative to passive listening revealed the participation of a number of cortical and subcortical regions, notably in the right frontal and right temporal lobes, as well as in parietal and insular cortex. Both pitch judgment conditions also revealed CBF decreases within the left primary auditory cortex. We conclude that specialized neural systems in the right superior temporal cortex participate in perceptual analysis of melodies; pitch comparisons are effected via a neural network that includes right prefrontal cortex, but active retention of pitch involves the interaction of right temporal and frontal cortices.
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Language-music comparative studies have highlighted the potential for shared resources or neural overlap in auditory short-term memory. However, there is a lack of behavioral methodologies for comparing verbal and musical serial recall. We developed a visual grid response that allowed both musicians and nonmusicians to perform serial recall of letter and tone sequences. The new method was used to compare the phonological similarity effect with the impact of an operationalized musical equivalent-pitch proximity. Over the course of three experiments, we found that short-term memory for tones had several similarities to verbal memory, including limited capacity and a significant effect of pitch proximity in nonmusicians. Despite being vulnerable to phonological similarity when recalling letters, however, musicians showed no effect of pitch proximity, a result that we suggest might reflect strategy differences. Overall, the findings support a limited degree of correspondence in the way that verbal and musical sounds are processed in auditory short-term memory.
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We examined memory for pitch in congenital amusia in two tasks. In one task, we varied the pitch distance between the target and comparison tone from 4 to 9 semitones and inserted either a silence or 6 interpolated tones between the tones to be compared. In a second task, we manipulated the number of pitches to be retained in sequences of length 1, 3, or 5. Amusics' sensitivity to pitch distance was exacerbated by the presence of interpolated tones, and amusics' performance was more strongly affected by the number of pitches to maintain in memory than controls. A pitch perception deficit could not account for the pitch memory deficit of amusics.
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To evaluate the role of the sub-cortical white matter and cortical areas of the supramarginal gyrus in short-term memory impairment (shortened digit or letter span) and repetition difficulty, four patients with conduction aphasia and impaired short-term memory and two patients with only short-term memory impairment were given digit span, letter span, speech audiometry and dichotic listening tests. The results showed that in most of the patients letter span was inferior to digit span and that bilateral ear suppression in the dichotic listening test was observed in two patients with a lesion in the inferior part of the supramarginal gyrus, suggesting that what was affected was phonological information and that the supramarginal gyrus was the storage site. The overlapped lesion of conduction aphasia patients with short-term memory impairment was the periventricular white matter at the upper to middle part of the trigone, while patients with only short-term memory impairment had a lesion in the inferior supramarginal gyrus in common. Thus, damage to the periventricular white matter at the trigone may yield the phonemic paraphasia characteristic of conduction aphasia, while damage to the inferior part of the supramarginal gyrus may result in the impairment of short-term memory. We believe that as a part of the mechanisms of short-term memory and repetition, phonological information is processed in the primary auditory cortex and goes through the periventricular white matter to the inferior part of the supramarginal gyrus and is temporarily stored there.
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The authors show that in the human transcranial direct current stimulation is able to induce sustained cortical excitability elevations. As revealed by transcranial magnetic stimulation, motor cortical excitability increased approximately 150% above baseline for up to 90 minutes after the end of stimulation. The feasibility of inducing long-lasting excitability modulations in a noninvasive, painless, and reversible way makes this technique a potentially valuable tool in neuroplasticity modulation.
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Verbal working memory has been attributed to a left-dominant neuronal network, including parietal, temporal and prefrontal cortical areas. The current study was designed to evaluate the contribution of these brain regions to verbal working memory processes and to assess possible hemispheric asymmetry. The effect of repetitive transcranial stimulation (rTMS) on performance in a verbal working memory task both during, and after an rTMS train (110% of individual motor threshold, 4 Hz) over nine different scalp locations was studied [bilateral middle frontal gyrus (MFG), bilateral supramarginal gyrus (SMG), bilateral inferior parietal cortex (IP) and three different midline control sites]. Significant performance deterioration was observed during rTMS over the left and right MFG and left and right IP. There was no consistent interference effect across subjects over the left or right SMG and the three different midline control sites. The interference effect with the given stimulation parameters did not last beyond the rTMS train itself. The data provide evidence for a symmetrical, bilateral parieto-frontal verbal working memory network. The data are discussed with respect to the competing ideas of a parieto-frontal central executive network vs. a network that processes the inherent semantic and object features of the visually presented verbal stimuli in parallel.
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It is often proposed that prefrontal cortex is important in organization and control of working memory contents. In some cases, effective reorganization can decrease task difficulty, implying a dissociation between frontal activity and basic memory demand. In a spatial working memory task, we studied the improvement of performance that occurs when materials can be reorganized into higher level groups or chunks. Structured sequences, encouraging reorganization and chunking, were compared with unstructured sequences. Though structured sequences were easier to remember, event-related functional magnetic resonance imaging (fMRI) showed increased activation of lateral frontal cortex, in particular during memory encoding. The results show that, even when memory demand decreases, organization of working memory contents into higher level chunks is associated with increased prefrontal activity.
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Auditory functional magnetic resonance imaging tasks are challenging since the MR scanner noise can interfere with the auditory stimulation. To avoid this interference a sparse temporal sampling method with a long repetition time (TR = 17 s) was used to explore the functional anatomy of pitch memory. Eighteen right-handed subjects listened to a sequence of sine-wave tones (4.6 s total duration) and were asked to make a decision (depending on a visual prompt) whether the last or second to last tone was the same or different as the first tone. An alternating button press condition served as a control. Sets of 24 axial slices were acquired with a variable delay time (between 0 and 6 s) between the end of the auditory stimulation and the MR acquisition. Individual imaging time points were combined into three clusters (0-2, 3-4, and 5-6 s after the end of the auditory stimulation) for the analysis. The analysis showed a dynamic activation pattern over time which involved the superior temporal gyrus, supramarginal gyrus, posterior dorsolateral frontal regions, superior parietal regions, and dorsolateral cerebellar regions bilaterally as well as the left inferior frontal gyrus. By regressing the performance score in the pitch memory task with task-related MR signal changes, the supramarginal gyrus (left>right) and the dorsolateral cerebellum (lobules V and VI, left>right) were significantly correlated with good task performance. The SMG and the dorsolateral cerebellum may play a critical role in short-term storage of pitch information and the continuous pitch discrimination necessary for performing this pitch memory task.
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The concept of working memory proposes that a dedicated system maintains and stores information in the short term, and that this system underlies human thought processes. Current views of working memory involve a central executive and two storage systems: the phonological loop and the visuospatial sketchpad. Although this basic model was first proposed 30 years ago, it has continued to develop and to stimulate research and debate. The model and the most recent results are reviewed in this article.
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The excitability of the cerebral cortex can be modulated by various transcranial stimulation techniques. Transcranial direct current stimulation (tDCS) offers the advantage of portable equipment and could, therefore, be used for ambulatory modulation of brain excitability. However, modulation of cortical excitability by tDCS has so far mostly been shown by indirect measures. Therefore, we examined whether tDCS has a direct behavioral/perceptional effect. We compared tactile discrimination of vibratory stimuli to the left ring finger prior to, during and after tDCS applied for 7 min at 1-mA current intensity in 13 subjects. Stimulation was pseudorandomized into cathodal, anodal and sham conditions in a within-subject design. The active electrode was placed over the corresponding somatosensory cortex at C4 according to the 10-20 EEG system and the reference electrode at the forehead above the contralateral orbita. Cathodal stimulation compared with sham induced a prolonged decrease of tactile discrimination, while anodal and sham stimulation did not. Thus, cortical processing can be modulated in a behaviorally/perceptually meaningful way by weak transcranial current stimulation applied through portable technology. This finding offers a new perspective for the treatment of conditions characterized by alterations of cortical excitability.
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Brain polarization in the form of transcranial direct current stimulation (tDCS), which influences motor function and learning processes, has been proposed as an adjuvant strategy to enhance training effects in Neurorehabilitation. Proper testing in Neurorehabilitation requires double-blind sham-controlled study designs. Here, we evaluated the effects of tDCS and sham stimulation (SHAM) on healthy subjects and stroke patients' self-report measures of attention, fatigue, duration of elicited sensations and discomfort. tDCS or SHAM was in all cases applied over the motor cortex. Attention, fatigue, and discomfort were self rated by study participants using visual analog scales. Duration of perceived sensations and the ability to distinguish tDCS from Sham sessions were determined. Investigators questioning the patients were blind to the intervention type. tDCS and SHAM elicited comparably minimal discomfort and duration of sensations in the absence of differences in attention or fatigue, and could not be distinguished from SHAM by study participants nor investigators. Successful blinding of subjects and investigators and ease of application simultaneously with training protocols supports the feasibility of using tDCS in double-blind, sham-controlled randomized trials in clinical Neurorehabilitation. tDCS could evolve into a useful tool, in addition to TMS, to modulate cortical activity in Neurorehabilitation.
Article
Functional activation patterns of an auditory working memory task were examined prior to and after 5 days of training (1 h/day). A control group with no training was scanned twice at the same intervals to assess test-retest effects. Based on behavioral improvement scores, the training group (n = 14) was divided into "Strong-Learners (SL)" and "Weak-Learners (WL)". No significant functional or structural brain differences were seen between the SL and WL groups prior to training. Imaging contrasts comparing post- with pre-training sessions showed a significant signal increase in the left Heschl's gyrus (HG) as well as in the left posterior superior temporal and supramarginal gyrus for the SL group, while the WL group showed significant signal increases in the left HG and anterior insular cortex as well as in a lingual-orbitofrontal-parahippocampal network. The test-retest analysis in the control group revealed only minimal signal increases in a right dorsolateral prefrontal region. A random effects analysis comparing the SL group with the WL group using the post- and pre-training contrast images showed increased activation only in the left supramarginal gyrus but not in HG. The importance of HG in pitch discrimination has been established in previous studies. The pitch memory component differentiated our task from a straight pitch discrimination task. It is most likely that the activation of the SMG reflects its importance in the short-term storage of auditory material, and it was this activation that best differentiated between subjects' levels of performance.
Article
Neuroimaging studies have implicated the left supramarginal gyrus in short-term auditory memory processing, including memory for pitch. The present study investigated the causal role of the left supramarginal gyrus in short-term pitch memory by comparing the effects of cathodal transcranial direct current stimulation when applied over the left or right supramarginal gyrus with sham transcranial direct current stimulation. Only cathodal transcranial direct current stimulation over the left supramarginal gyrus had a detrimental effect on short-term pitch-memory performance in 11 adult participants. These results provide support for the important role of the left supramarginal gyrus in short-term memory for pitch information, and they further demonstrate the potential of transcranial direct current stimulation to modulate the functional contribution of a brain area to a particular cognitive process.
Article
This study investigates the functional architecture of working memory (WM) for verbal and tonal information during rehearsal and articulatory suppression. Participants were presented with strings of four sung syllables with the task to remember either the pitches (tonal information) or the syllables (verbal information). Rehearsal of verbal, as well as of tonal information activated a network comprising ventrolateral premotor cortex (encroaching Broca's area), dorsal premotor cortex, the planum temporale, inferior parietal lobe, the anterior insula, subcortical structures (basal ganglia and thalamus), as well as the cerebellum. The topography of activations was virtually identical for the rehearsal of syllables and pitches, showing a remarkable overlap of the WM components for the rehearsal of verbal and tonal information. When the WM task was performed under articulatory suppression, activations in those areas decreased, while additional activations arose in anterior prefrontal areas. These prefrontal areas might contain additional storage components of verbal and tonal WM that are activated when auditory information cannot be rehearsed. As in the rehearsal conditions, the topography of activations under articulatory suppression was nearly identical for the verbal as compared to the tonal task. Results indicate that both the rehearsal of verbal and tonal information, as well as storage of verbal and tonal information relies on strongly overlapping neuronal networks. These networks appear to partly consist of sensorimotor-related circuits which provide resources for the representation and maintenance of information, and which are remarkably similar for the production of speech and song.
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