Name: transcranial direct current stimulation (tdcs) of wernicke's and broca's areas in studies of language learning and word acquisition
Uploaded: 2019-07-13T13:00:00
Description: Watch this Scientific Journal Video about Transcranial Direct Current Stimulation tDCS of Wernicke's and Broca's Areas in Studies of Language Learning and Word Acquisition at JoVE.com

Supported by RF Government grant contract No.14.W03.31.0010. We wish to thank Ekatarina Perikova and Alexander Kirsanov for their support in preparing this publication. We are grateful to Olga Shcherbakova and Margarita Filippova for their help in stimulus selection and to Anastasia Safronova and Pavel Inozemcev for their assistance in the production of video materials.

All procedures were approved by the local research ethics committee of St. Petersburg State University, St. Petersburg, with consent obtained from all participants.
NOTE: All participants must sign the informed consent and fill in a questionnaire to attest the absence of any contraindications for tDCS stimulation (see Technique and Considerations in the Use of 4 x 1 Ring High-definition Transcranial Direct Current Stimulation (HD-tDCS) by Willamar and colleagues12) and ...

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The results highlight a few important points that need to be taken into account when conducting psycholinguistic research in general, and neurolinguistics tDCS studies in particular. Stimulation of language cortices (exemplified here by Wernicke&#39;s area) produces a complex pattern of behavioral outcomes. Unlike the TMS technique, where it is possible to fully disrupt speech processing (e.g., the so-called &#34;speech arrest&#34; protocol)21, this method enables a possibly more complex, graded a...

The neurobiological mechanisms of human language function are still poorly understood. As the bedrock of our communication ability, this unique human neurocognitive trait plays a particularly important role in our personal and socio-economic lives. Any deficits affecting speech and language are devastating for the sufferers and expensive for the society. At the same time, in the clinic, procedures for treatment of speech deficits (such as aphasia) remain suboptimal, not least due to poor understanding of the neurobiological mechanisms involved1. In research, the recent advent and rapid development of neuroimaging methods have led to multiple discoveries describing activation patterns; yet, causal evidence is often still lacking. Furthermore, language areas of the brain are located somewhat suboptimally for application of mainstream neurostimulation approaches which can provide causal evidence, most importantly the transcranial magnetic stimulation technique (TMS). Whereas offline TMS protocol, such as theta burst stimulation, can cause pain due to the close proximity of the muscles to the point of stimulation, &#34;online&#34; TMS protocols can introduce sound artifacts from stimulation, which is undesirable due to interference&#160;with linguistic stimulus presentation2. Even though TMS is widely used in language studies despite such inconveniences, a welcome alternative may be provided by other stimulation methods, most notably transcranial direct-current stimulation (tDCS). In recent years, tDCS has seen a remarkable growth in its use due to its accessibility, ease of use, relative safety and often rather striking outcomes3. Even though the exact mechanisms underpinning tDCS influence on neural activity are not understood completely, the mainstream view is that, at least at low intensity levels (typically 1-2 mA for 15-60 min), it does not cause any neural excitation or inhibition per se, but instead modulates the resting transmembrane potential in a graded way towards de- or hyperpolarization, shifting the excitation thresholds up or down and thereby making the neural system more or less susceptible to modulations by other events, stimuli, states or behaviors4,5. Whereas most of the applications reported to date have focused on the motor function6 and/or motor system deficits, it has been increasingly applied to higher-level cognitive functions and their respective disabilities. There has been a rise in its application to speech and language, mostly in research aimed at the recovery of post-stroke aphasia7,8,9, even though it has so far led to mixed results with respect to the therapeutic potential, stimulation sites and hemispheres, and optimal current polarity. As this research, and particularly the application of tDCS in cognitive neurobiology of normal language function, is still in its infancy, it is crucial to delineate procedures for stimulating at least the core language cortices (most importantly Wernicke&#39;s and Broca&#39;s areas) using tDCS, which is one of the main aims of the current report.
Here, we will consider application of tDCS to language areas in a word-learning experiment. In general, the case of word learning is taken here as one example of a neurolinguistic experiment, and the tDCS part of the procedure should not change substantially for other types of language experiments targeting the same areas. Yet, we use this opportunity to also highlight major methodological considerations in a word acquisition experiment per se, which is the second main aim of the current protocol description. Brain mechanisms underpinning word acquisition &#8211;&#160;a ubiquitous human capacity at the core of our linguistic communication skill&#160;&#8211;&#160;remain largely unknown10. Complicating the picture, existing literature differs widely in how experimental protocols promote word acquisition, in control over stimulation parameters, and in tasks used to assess learning outcomes (see, e.g., Davis et al.11). Below, we describe a protocol that uses highly controlled stimuli and presentation mode, while ensuring a naturalistic context-driven acquisition of novel vocabulary. Furthermore, we use a comprehensive battery of tasks to assess the outcomes behaviorally at different levels, both immediately after learning and following an overnight consolidation stage. This is combined with sham and cathodal tDCS of language areas (we make a particular example using Wernicke&#39;s area stimulation) which can provide causal evidence on underlying neural processes and mechanisms.

transcranial direct current stimulation (tdcs) of wernicke's and broca's areas in studies of language learning and word acquisition

Language is a highly important yet poorly understood function of the human brain. While studies of brain activation patterns during language comprehension are abundant, what is often critically missing is causal evidence of brain areas&#39; involvement in a particular linguistic function, not least due to the unique human nature of this ability and a shortage of neurophysiological tools to study causal relationships in the human brain noninvasively. Recent years have seen a rapid rise in the use of transcranial direct current stimulation (tDCS) of the human brain, an easy, inexpensive and safe noninvasive technique that can modulate the state of the stimulated brain area (putatively by shifting excitation/inhibition thresholds), enabling a study of its particular contribution to specific functions. While mostly focusing on motor control, the use of tDCS is becoming more widespread in both basic and clinical research on higher cognitive functions, language included, but the procedures for its application remain variable. Here, we describe the use of tDCS in a psycholinguistic word-learning experiment. We present the techniques and procedures for application of cathodal and anodal stimulation of core language areas of Broca and Wernicke in the left hemisphere of the human brain, describe the procedures of creating balanced sets of psycholinguistic stimuli, a controlled yet naturalistic learning regime, and a comprehensive set of techniques to assess the learning outcomes and tDCS effects. As an example of tDCS application, we show that cathodal stimulation of Wernicke&#39;s area prior to a learning session can impact word learning efficiency. This impact is both present immediately after learning and, importantly, preserved over longer time after the physical effects of stimulation wear off, suggesting that tDCS can have long-term influence on linguistic storage and representations in the human brain.

While the data were analyzed for the specific set of tasks, it should be emphasized that the developed set of tests and the paradigm could be adapted to a variety of psycholinguistic experiments. The results were analyzed in terms of accuracy scores (number of correct answers) and the reaction time (RT) using non-parametric Wilcoxon signed rank&#160;test and Mann-Whitney U test across groups (cathodal and sham stimulation conditions). Significant differences for tasks within each group ar...

Watch this Scientific Journal Video about Transcranial Direct Current Stimulation tDCS of Wernicke's and Broca's Areas in Studies of Language Learning and Word Acquisition at JoVE.com

Transcranial Direct Current Stimulation tDCS of Wernicke's and Broca's Areas in Studies of Language Learning and Word Acquisition

Here, we describe a protocol for using transcranial direct current stimulation for psycho- and neurolinguistic experiments aimed at studying, in a naturalistic yet fully controlled way, the role of cortical areas of the human brain in word learning, and a comprehensive set of behavioral procedures for assessing the outcomes.

Transcranial Direct Current Stimulation (tDCS) of Wernicke's and Broca's Areas in Studies of Language Learning and Word Acquisition

Language is a highly important yet poorly understood function of the human brain. While studies of brain activation patterns during language comprehension ...

In this video, we describe a simple time and cost efficient protocol for using transcranial direct current stimulation for psycho and neurolinguistic experiments aimed at studying in a naturalistic, yet fully controlled way the role of the cortical areas of the human brain in word learning, and a comprehensive set of behavioral procedures for assessing the outcomes. Language is a highly important, yet poorly understood, function of the human brain. While studies of brain activation patterns during language comprehension are abundant what is often critically missing is causal evidence of brain areas'involvement in a particular function, not least due to the unique human nature of this ability, and a shortage of neurophysiological tools to study causal relationships in the brain non-invasively.Recent years have seen a rapid rise in the use of transcranial direct current stimulation, or tDCS, which is an easy, inexpensive, and safe non-invasive technique that can modulate the state of the stimulated brain area which it does putatively by shifting the excitation and inhibition thresholds, and thus enables the study of its particular contribution to specific functions. Here, we will describe the use of tDCS in a psycholinguistic word learning experiment. Here, we will consider application of tDCS to language areas in a word learning experiment.In general, the case of word learning is taken here as one example of a neurolinguistic experiment, and the tDCS part of the procedure should not change substantially for other types of language experiments which target the same areas. Yet, we use this opportunity to also highlight major methodological considerations in the word acquisition experiment per se, which is the second main aim of the current report. It is important to obtain all legal and ethical permissions for studies on human subjects that are required by your local legislation.In our study, the permission was granted by the University of St.Petersburg Research Ethics Committee. Conduct all measurements in a soundproof, or at least sound attenuated, camera. Sound insulation is very important, since any extraneous sound, noise, human speech, and so on can significantly affect the performance, and thus influence the data.To avoid interference by unnecessary subject experimenter contact, only the screen, headphones, or speakers, and any input devices, such as keyboard or button boxes are to be located inside the camera. Interaction with the experimenter is to be held over intercom, unless personal contact is required. The optimal parameters for text presentation are black text on gray background.We use font face Arial size 27. To reduce delays and jitter in visual presentation, we recommend using a video card and a monitor with a refresh rate of 100 hertz and higher. To measure reaction times, use research grade response pads which have been ergonomics and more precise timing in comparison with conventional keyboards.We have chosen words of Russian language which were controlled for their length and overall structure to avoid any basic effect of surface properties on higher level processing. To create multiple lists, we divided the word into sets which didn't differ statistically on their and syllabic frequency. This was established using T-tests.Novel word forms were created by transposing the alternate syllables within each set of words. So, thus the novel words resembled existing words in terms of orthographic and phonological structure. As a result, we created a list of word forms to be learned and a list of similar unlearned pseudo words from one set of existing words.All three stimulus types that shared one set would therefore potentially enter into lexical competition as neighbors after the learning stage. Further control list of words and pseudo words that didn't share this similarity were also prepared. The sets were counterbalanced around the subject groups in the way that they played different experimental roles to minimize any effects of surface form on newly acquired semantics.We also created novel meanings associated with the new words in the process of learning. They were made of obsolete or real concepts not present in the participants'language. For contextual learning of novel semantics, we created five sentences for each of the new concept describing situations through which one could understand the meaning of the novel words gradually from general to more specific context.Novel words were represented in their base form. The length of the sentences and the number of words were controlled and balance between conditions. Each sentence consisted of eight words according to the minimal length of sentences in Russian, which allow you to understand the context.As you are reading these sentences, you can understand that circunal is a kind of negative feeling which appears when you have to remember too many passwords from your accounts. To assess acquisition and comprehension of word forms and semantics we use several tasks, free recall, cue recognition, lexical decisions, semantic definition, and semantic judgment. In the free recall task, participants had to reproduce as many new word forms as they could remember by typing them into the prepared spreadsheet.The recognition and lexical decisions tasks were used the same stimuli and speed of presentation and differ only in instructions. The items were presented sequentially and randomly. In the recognition task participants had to press button one if they encountered the word during the experiment or press two if they didn't.In the lexical decision, they had to press button one if presented what made sense or press two if it didn't. Semantic tasks were used to estimate the acquisition of normal meanings and the correspondence between that meaning and the surface form. In the semantic definition task, participants are given a list of the items, those presented previously in the learning phase.They should try to define each of them and type their definitions into the spreadsheet. In the semantic judgment task, participants were presented with a word and three definitions. They should choose one correct definition for each word by pressing the corresponding button.Only one of the definitions were correct. In addition, we suggest including none of this or not sure option. Transcranial direct current electrical stimulation, tDCS, generates neuro modulations and spontaneous and neuronal activity.Dependent on the orientation of the cells with respect to current, the membrane potential can be shifted slightly towards hyperpolarization. For instance, for motor system it happens during anodal stimulation, or depolarization for cathodal stimulation. This change in your neural excitability will lead to various temporary alterations in the brain function, including the motor sensory and high level cognitive functions.Here, we will consider application of tDCS to language areas such as Wernicke's and Broca's areas of human in a word learning experiment. It's important to remember the main difference between tDCS and other non-invasive brain stimulation methods, such as transcranial magnetic stimulation, first, since there is not a simpler way to determine sensitivity to tDCS by threshold assessment, a single protocol is applied for all subjects. Second, it's very difficult to accurately estimate the stimulation area.One can only speak about the hypothetical area. Third, it's also difficult to estimate the duration of offline stimulation effects. Presumably, the main effect of stimulation are observed up to one hour after the termination of stimulation.However, the effect of stimulation can sometimes be detected even one day after stimulation. There are three types of stimulation, cathodal, with a cathode electrode over target area, anodal, with the anode over target area, and placebo, or sham stimulation. Use sponge electrodes measuring five by five centimeters.The electrodes should be soaked in physiological saline solution for five minutes before application. In order to minimize the effect of stimulation on other areas of the brain put the anodal electrode at the base of the neck on the right side. We use spongy electrodes measuring two by five centimeters.Particular attention should be paid to prevent spreading of the solution beyond the boundaries of the electrode application zone. Special care should be taken to keep the surrounding electrode area dry. The optimal protocol for cathode stimulation is the stimulation by one milliamp current for 10 minutes.First, the current rises to one milliamp over the initial 20 seconds, and at the end of the stimulation it decreases to zero in the last 20 seconds of the stimulation. The sets with contextual sentences containing the novel words are presented in a random order. Each sentence starts with a word by word presentation.After this, the entire sentence appears on the screen to ensure its full understanding. Participants have to press an indicated response button with their index finger of the left hand after reading the whole sentence. The left hand is used to reduce interference with the language errors of the left hemisphere.Duration of sentence presentation is five seconds. Then a crosshair appears at the center of the screen for 500 milliseconds and the next sentence begins. The sets of the sentences are separated from each other by appearance of three crosshairs for two seconds.Each new concept presentation starts with another crosshair present for 500 milliseconds before the sentence words are flashed. Each word is presented for 500 milliseconds, the empty screen and the background color between the words within one sentence for 300 milliseconds. We used a battery of different tests since tDCS effects on language processing are not well known.To assess learning effects both immediately and following the overnight consolidation stage we recommend breaking the stimulus set into two subset, equally distributed across stimulus conditions and counterbalanced across the subject group. We are running the assessment tasks immediately after the learning protocol and after a 24 hour delay. This protocol allows data analysis using different tests comparing two sets of samples coming from continuous distributions with equal medians, like Wilcox and Rank Sum test, or Mann-Whitney U test, or medians to sample T-test if the distribution is normal.Within each group, there were notable differences in accuracy scores and reaction times between the two assessment sessions. In the sham group novel word recognition was significantly better on the first day than on the second one. In the cathodal group reaction time latency in the recognition task was significantly faster for novel words than for competitor pseudo words on the first day, but not on the second one.The results of lexical decision task showed that after cathodal stimulation both on the first and on the second day there was significantly better performance for novel words than for pseudo word competitors. In the sham group, however, this effect was significant on the second day only. tDCS of language cortices exemplified here by Wernicke's area produces a complex pattern of behavioral outcomes.Contextual presentation of new words after tDCS significantly expands the possibilities of simultaneous study of acquisition of word form per se and of its semantics. To disengage the various effects a battery of different tests is needed, which could test the processes at different levels of short and long term memory, lexical access, semantic processing, and so on. The cognitive effects achieved during the transient stimulation phase are maintained over a longer period and may therefore be possibly used for modulating word acquisition and processing in practical settings.

transcranial-direct-current-stimulation-tdcs-wernicke-s-broca-s-areas

Research

JoVE Journal

Behavior

Simultaneous EEG Monitoring During Transcranial Direct Current Stimulation

Transcranial direct current stimulation (tDCS) is a technique that delivers weak electric currents through the scalp. This constant electric current induces shifts in neuronal membrane excitability, resulting in secondary changes in cortical activity. Although tDCS has most of its neuromodulatory effects on the underlying cortex, tDCS effects can also be observed in distant neural networks. Therefore, concomitant EEG monitoring of the effects of tDCS can provide valuable information on the mechanisms of tDCS. In addition, EEG findings can be an important surrogate marker for the effects of tDCS and thus can be used to optimize its parameters. This combined EEG-tDCS system can also be used for preventive treatment of neurological conditions characterized by abnormal peaks of cortical excitability, such as seizures. Such a system would be the basis of a non-invasive closed-loop device. In this article, we present a novel device that is capable of utilizing tDCS and EEG simultaneously. For that, we describe in a step-by-step fashion the main procedures of the application of this device using schematic figures, tables and video demonstrations. Additionally, we provide a literature review on clinical uses of tDCS and its cortical effects measured by EEG techniques.

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique that has shown initial therapeutic effects in several neurological conditions. The main mechanism underlying these therapeutic effects is the modulation of cortical excitability. Therefore, online monitoring of cortical excitability would help guide stimulation parameters and optimize its therapeutic effects. In the present article we review the use of a novel device that combines simultaneous tDCS and EEG monitoring in real time.

Transcranial  direct current stimulation (tDCS) is a technique that delivers weak electric  currents through the scalp. This constant electric current ...

Transcranial Direct Current Stimulation and Simultaneous  Functional Magnetic Resonance Imaging

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that uses weak electrical currents administered to the scalp to manipulate cortical excitability and, consequently, behavior and brain function. In the last decade, numerous studies have addressed short-term and long-term effects of tDCS on different measures of behavioral performance during motor and cognitive tasks, both in healthy individuals and in a number of different patient populations. So far, however, little is known about the neural underpinnings of tDCS-action in humans with regard to large-scale brain networks. This issue can be addressed by combining tDCS with functional brain imaging techniques like functional magnetic resonance imaging (fMRI) or electroencephalography (EEG).
In particular, fMRI is the most widely used brain imaging technique to investigate the neural mechanisms underlying cognition and motor functions. Application of tDCS during fMRI allows analysis of the neural mechanisms underlying behavioral tDCS effects with high spatial resolution across the entire brain. Recent studies using this technique identified stimulation induced changes in task-related functional brain activity at the stimulation site&#160;and also in more distant brain regions, which were associated with behavioral improvement. In addition, tDCS administered during resting-state fMRI allowed identification of widespread changes in whole brain functional connectivity.
Future studies using this combined protocol should yield new insights into the mechanisms of tDCS action in health and disease and new options for more targeted application of tDCS in research and clinical settings. The present manuscript describes this novel technique in a step-by-step fashion, with a focus on technical aspects of tDCS administered during fMRI.

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique. It has successfully been used in basic research and clinical settings to modulate brain function in humans. This article describes the implementation of tDCS and simultaneous functional magnetic resonance imaging (fMRI), to investigate the neural basis of tDCS effects.

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that uses weak electrical currents administered to the scalp ...

Modulating Cognition Using Transcranial Direct Current Stimulation of the Cerebellum

Numerous studies have emerged recently that demonstrate the possibility of modulating, and in some cases enhancing, cognitive processes by exciting brain regions involved in working memory and attention using transcranial electrical brain stimulation. Some researchers now believe the cerebellum supports cognition, possibly via a remote neuromodulatory effect on the prefrontal cortex. This paper describes a procedure for investigating a role for the cerebellum in cognition using transcranial direct current stimulation (tDCS), and a selection of information-processing tasks of varying task difficulty, which have previously been shown to involve working memory, attention and cerebellar functioning. One task is called the Paced Auditory Serial Addition Task (PASAT) and the other a novel variant of this task called the Paced Auditory Serial Subtraction Task (PASST). A verb generation task and its two controls (noun and verb reading) were also investigated. All five tasks were performed by three separate groups of participants, before and after the modulation of cortico-cerebellar connectivity using anodal, cathodal or sham tDCS over the right cerebellar cortex. The procedure demonstrates how performance (accuracy, verbal response latency and variability) could be selectively improved after cathodal stimulation, but only during tasks that the participants rated as difficult, and not easy. Performance was unchanged by anodal or sham stimulation. These findings demonstrate a role for the cerebellum in cognition, whereby activity in the left prefrontal cortex is likely dis-inhibited by cathodal tDCS over the right cerebellar cortex. Transcranial brain stimulation is growing in popularity in various labs and clinics. However, the after-effects of tDCS are inconsistent between individuals and not always polarity-specific, and may even be task- or load-specific, all of which requires further study. Future efforts might also be guided towards neuro-enhancement in cerebellar patients presenting with cognitive impairment once a better understanding of brain stimulation mechanisms has emerged.

Transcranial direct current stimulation (tDCS) over the cerebellum exerts a remote effect on the prefrontal cortex, which can modulate cognition and performance. This was demonstrated using two information-processing tasks of varying complexity, whereby only cathodal tDCS improved performance when the task was difficult, but not easy.

Numerous studies have emerged recently that demonstrate the possibility of modulating, and in some cases enhancing, cognitive processes by exciting brain ...

Concurrent Electroencephalography Recording During Transcranial Alternating Current Stimulation (tACS)

Oscillatory brain activities are considered to reflect the basis of rhythmic changes in transmission efficacy across brain networks and are assumed to integrate cognitive neural processes. Transcranial alternating current stimulation (tACS) holds the promise to elucidate the causal link between specific frequencies of oscillatory brain activity and cognitive processes. Simultaneous electroencephalography (EEG) recording during tACS would offer an opportunity to directly explore immediate neurophysiological effects of tACS. However, it is not trivial to measure EEG signals during tACS, as tACS creates a huge artifact in EEG data. Here we explain how to set up concurrent tACS-EEG experiments. Two necessary considerations for successful EEG recording while applying tACS are highlighted. First, bridging of the tACS and EEG electrodes via leaking EEG gel immediately saturates the EEG amplifier. To avoid bridging via gel, the viscosity of the EEG gel is the most important parameter. The EEG gel must be viscous to avoid bridging, but at the same time sufficiently fluid to create contact between the tACS electrode and the scalp. Second, due to the large amplitude of the tACS artifact, it is important to consider using an EEG system with a high resolution analog-to-digital (A/D) converter. In particular, the magnitude of the tACS artifact can exceed 100 mV at the vicinity of a stimulation electrode when 1 mA tACS is applied. The resolution of the A/D converter is of importance to measure good quality EEG data from the vicinity of the stimulation site. By following these guidelines for the procedures and technical considerations, successful concurrent EEG recording during tACS will be realized.

Concurrent Electroencephalography Recording During Transcranial Alternating Current Stimulation tACS

In this article we explain how to set up a concurrent transcranial alternating current stimulation and EEG experiment.

Oscillatory brain activities are considered to reflect the basis of rhythmic changes in transmission efficacy across brain networks and are assumed to ...

Repetitive Transcranial Magnetic Stimulation to the Unilateral Hemisphere of Rat Brain

Previous rodent models of repetitive transcranial magnetic stimulation (rTMS) adopted whole-brain stimulation instead of unilateral hemispheric rTMS, which is unlike the protocols used for human subjects. We report a successful application of rTMS to the unilateral hemisphere of rat brain. The rTMS was delivered with a low-frequency (1 Hz), high-frequency (20 Hz), or sham stimulation protocol to one side of the brain by using a small 25-mm figure-8 coil. We placed the center of the coil 1 cm lateral to the vertex on the biauricular line and angulated the coil 45&#176; to the ground to minimize a potential direct effect of rTMS on the contralateral cortex. We also used an in-house water cooling system to enable repetitive magnetic stimulation for more than 20 min, even at a 20-Hz stimulation frequency. Increases in the transcriptions of immediate early genes (Arc, Junb, and Egr2) were greater after rTMS than after sham stimulation. After 5 consecutive days of 20-min 1-Hz rTMS, bdnf mRNA expression was significantly higher in stimulated cortex than in contralateral side. The model presented herein will elucidate the molecular mechanisms of rTMS by allowing analysis of the inter-hemispheric difference in its effect.

We applied repetitive transcranial magnetic stimulation (rTMS) to the unilateral hemisphere of rat brain, by placing a 25-mm figure-8 coil 1 cm lateral to the vertex on the biauricular line and angulating the coil by 45&#176;. An in-house water cooling system was used for rTMS for more than 20 min.

Previous rodent models of repetitive transcranial magnetic stimulation (rTMS) adopted whole-brain stimulation instead of unilateral hemispheric rTMS, ...

Simultaneous Transcranial Alternating Current Stimulation and Functional Magnetic Resonance Imaging

Transcranial alternating current stimulation (tACS) is a promising tool for noninvasive investigation of brain oscillations. TACS employs frequency-specific stimulation of the human brain through current applied to the scalp with surface electrodes. Most current knowledge of the technique is based on behavioral studies; thus, combining the method with brain imaging holds potential to better understand the mechanisms of tACS. Because of electrical and susceptibility artifacts, combining tACS with brain imaging can be challenging, however, one brain imaging technique that is well suited to be applied simultaneously with tACS is functional magnetic resonance imaging (fMRI). In our lab, we have successfully combined tACS with simultaneous fMRI measurements to show that tACS effects are state, current, and frequency dependent, and that modulation of brain activity is not limited to the area directly below the electrodes. This article describes a safe and reliable setup for applying tACS simultaneously with visual task fMRI studies, which can lend to understanding oscillatory brain function as well as the effects of tACS on the brain.

Transcranial alternating current stimulation (tACS) is a promising tool for noninvasive investigation of brain oscillations, though its effects are not completely understood. This article describes a safe and reliable setup for applying tACS simultaneously with functional magnetic resonance imaging, which can increase understanding oscillatory brain function and effects of tACS.

Transcranial alternating current stimulation (tACS) is a promising tool for noninvasive investigation of brain oscillations. TACS employs ...

Eye Tracking During Visually Situated Language Comprehension: Flexibility and Limitations in Uncovering Visual Context Effects

The present work is a description and an assessment of a methodology designed to quantify different aspects of the interaction between language processing and the perception of the visual world. The recording of eye-gaze patterns has provided good evidence for the contribution of both the visual context and linguistic/world knowledge to language comprehension. Initial research assessed object-context effects to test&#160;theories of modularity in language processing. In the introduction, we describe how subsequent investigations have taken the role of the wider visual context in language processing as a research topic in its own right, asking questions such as how our visual perception of events and of speakers contributes to&#160;comprehension informed by&#160;comprehenders&#39; experience. Among the examined aspects of the visual context are actions, events, a speaker&#39;s gaze, and emotional facial expressions, as well as spatial object configurations. Following an overview of the eye-tracking method and its different applications, we list the key steps of the methodology in the protocol, illustrating how to successfully use it to study visually-situated language comprehension. A final section presents three sets of representative results and illustrates the benefits and limitations of eye tracking for investigating the interplay between the perception of the visual world and language comprehension.

The present article reviews an eye-tracking methodology for studies on language comprehension. To obtain reliable data, key steps of the protocol must be followed. Among these are the correct set-up of the eye tracker (e.g., ensuring good quality of the eye and head images) and accurate calibration.

The present work is a description and an assessment of a methodology designed to quantify different aspects of the interaction between language processing ...

Dissociation of the Confounding Influences of Expectancy and Integrative Difficulty Residing in Anomalous Sentences in Event-related Potential Studies

The confounding factors of unexpectedness and semantic integration difficulty naturally residing in anomalous sentences in language studies make it difficult to determine the underlying processing mechanism of ERP components. Unlike the traditional static approach of manipulating expectancy through corpus frequency or cloze probability, this protocol proposes a dynamic method to enhance participants&#39; expectancy for rarely-met anomalous sentences by multiple repetitions while maintaining their semantic integration difficulties. To address the time cost increase resulting from multiple repetitions, this protocol proposes to repeat only the strictly simplified core structure extracted from the anomalous sentence before presenting the semantically enriched, much more informative complete anomalous sentence containing the anomalous core structure to reinitiate the semantic integration processing. The complete anomalous sentence elicited a P600 effect. It suggests that the participants did not give up processing the anomalous information after repetitions and the same semantic integration difficulty was successfully reinitiated. Importantly, the representative experimental results reveal that the greatly attenuated N400 effect caused by multiple repetitions was not recovered by the follow-up reinitiated semantic integration difficulty. It suggests that the attenuated N400 effect should be mainly attributed to the enhancement of expectancy for anomalous information by multiple repetitions. The experimental results show that this method can effectively enhance participants&#39; expectancy for anomalous sentences while retaining the semantic integration difficulty.

We present a protocol to dissociate the intertwining factors of integrative difficulty and unexpectedness in semantically anomalous sentences by applying multiple repetitions to enhance participant&#39;s expectancy for anomalous sentences. The dissociation helps to investigate the major contributor of elicited event-related potentials (ERP) effects such as N400 in language studies.

The confounding factors of unexpectedness and semantic integration difficulty naturally residing in anomalous sentences in language studies make it ...

Brain State-dependent Brain Stimulation with Real-time Electroencephalography-Triggered Transcranial Magnetic Stimulation

The effect of a stimulus to the brain depends not only on the parameters of the stimulus but also on the dynamics of brain activity at the time of the stimulation. The combination of electroencephalography (EEG) and transcranial magnetic stimulation (TMS) in a real-time brain state-dependent stimulation system allows the study of relations of dynamics of brain activity, cortical excitability, and plasticity induction. Here, we demonstrate a newly developed method to synchronize the timing of brain stimulation with the phase of ongoing EEG oscillations using a real-time data analysis system. This real-time EEG-triggered TMS of the human motor cortex, when TMS is synchronized with the surface EEG negative peak of the sensorimotor &#181;-alpha (8-14 Hz) rhythm, has shown differential corticospinal excitability and plasticity effects. The utilization of this method suggests that real-time information about the instantaneous brain state can be used for efficacious plasticity induction. Additionally, this approach enables personalized EEG-synchronized brain stimulation which may lead to the development of more effective therapeutic brain stimulation protocols.

This paper describes real-time electroencephalography-triggered transcranial magnetic stimulation to study and modulate human brain networks.

The effect of a stimulus to the brain depends not only on the parameters of the stimulus but also on the dynamics of brain activity at the time of the ...

Lexical Decision Task for Studying Written Word Recognition in Adults with and without Dementia or Mild Cognitive Impairment

Older adults are slower at recognizing visual objects than younger adults. The same is true for recognizing that a letter string is a real word. People with Alzheimer&#39;s disease (AD) or Mild Cognitive Impairment (MCI) demonstrate even longer responses in written word recognition than elderly controls. Despite the general tendency towards slower recognition in aging and neurocognitive disorders, certain characteristics of words influence word recognition speed regardless of age or neuropathology (e.g., a word&#8217;s frequency of use). We present here a protocol for examining the influence of lexical characteristics on word recognition response times in a simple lexical decision experiment administered to younger and older adults and people with MCI or AD. In this experiment, participants are asked to decide as quickly and accurately as possible whether a given letter string is an actual word or not. We also describe mixed-effects models and principal components analysis that can be used to detect the influence of different types of lexical variables or individual characteristics of participants on word recognition speed.

This article describes how to implement a simple lexical decision experiment to assess written word recognition in neurologically healthy participants and in individuals with dementia and cognitive decline. We also provide a detailed description of reaction time analysis using principal components analysis (PCA) and mixed-effects modeling.

Older adults are slower at recognizing visual objects than younger adults. The same is true for recognizing that a letter string is a real word. People ...