scholarly journals Probing the causal role of prestimulus interregional synchrony for perceptual integration via tACS

2016 ◽  
Author(s):  
Rolandas Stonkus ◽  
Verena Braun ◽  
Jess Kerlin ◽  
Gregor Volberg ◽  
Simon Hanslmayr
Keyword(s):  
Specific Activity ◽  
Brain Regions ◽  
Causal Role ◽  
Oscillatory Activity ◽  
Perceptual Integration ◽  
After Effects ◽  
Activity Phase ◽  
Fmri Study ◽  
Transcranial Alternating Current Stimulation

The phase of prestimulus oscillations at 7-10 Hz has been shown to modulate perception of briefly presented visual stimuli. Specifically, a recent combined EEG-fMRI study suggested that a prestimulus oscillation at around 7 Hz represents open and closed windows for perceptual integration by modulating connectivity between lower order occipital and higher order parietal brain regions. We here utilized brief event-related transcranial alternating current stimulation (tACS) to specifically modulate this prestimulus 7 Hz oscillation, and the synchrony between parietal and occipital brain regions. To this end we tested for a causal role of this particular prestimulus oscillation for perceptual integration. The EEG was acquired at the same time allowing us to investigate frequency specific after effects phase-locked to stimulation offset. On a behavioural level our results suggest that the tACS did modulate perceptual integration, however, in an unexpected manner. On an electrophysiological level our results suggest that brief tACS does induce oscillatory entrainment, as visible in frequency specific activity phase-locked to stimulation offset. Together, our results do not strongly support a causal role of prestimulus 7 Hz oscillations for perceptual integration. However, our results suggest that brief tACS is capable of modulating oscillatory activity in a temporally sensitive manner.

scholarly journals Perception of Rhythmic Speech Is Modulated by Focal Bilateral Transcranial Alternating Current Stimulation

2020 ◽  
Vol 32 (2) ◽  
pp. 226-240 ◽  
Author(s):  
Benedikt Zoefel ◽  
Isobella Allard ◽  
Megha Anil ◽  
Matthew H. Davis
Keyword(s):  
Speech Perception ◽  
Speech Processing ◽  
Alternating Current ◽  
Stream Segregation ◽  
Causal Role ◽  
Oscillatory Activity ◽  
Transcranial Alternating Current Stimulation ◽  
Neural Entrainment ◽  
Actual Speech

Several recent studies have used transcranial alternating current stimulation (tACS) to demonstrate a causal role of neural oscillatory activity in speech processing. In particular, it has been shown that the ability to understand speech in a multi-speaker scenario or background noise depends on the timing of speech presentation relative to simultaneously applied tACS. However, it is possible that tACS did not change actual speech perception but rather auditory stream segregation. In this study, we tested whether the phase relation between tACS and the rhythm of degraded words, presented in silence, modulates word report accuracy. We found strong evidence for a tACS-induced modulation of speech perception, but only if the stimulation was applied bilaterally using ring electrodes (not for unilateral left hemisphere stimulation with square electrodes). These results were only obtained when data were analyzed using a statistical approach that was identified as optimal in a previous simulation study. The effect was driven by a phasic disruption of word report scores. Our results suggest a causal role of neural entrainment for speech perception and emphasize the importance of optimizing stimulation protocols and statistical approaches for brain stimulation research.

scholarly journals Binding Mechanisms in Visual Perception and Their Link With Neural Oscillations: A Review of Evidence From tACS

2021 ◽  
Vol 12 ◽  
Author(s):  
Andrea Ghiani ◽  
Marcello Maniglia ◽  
Luca Battaglini ◽  
David Melcher ◽  
Luca Ronconi
Keyword(s):  
Visual Perception ◽  
Feature Binding ◽  
Causal Role ◽  
Oscillatory Activity ◽  
Dependent Manner ◽  
Brain Oscillations ◽  
Temporal Binding ◽  
Neurophysiological Studies ◽  
Binding Mechanisms

Neurophysiological studies in humans employing magneto- (MEG) and electro- (EEG) encephalography increasingly suggest that oscillatory rhythmic activity of the brain may be a core mechanism for binding sensory information across space, time, and object features to generate a unified perceptual representation. To distinguish whether oscillatory activity is causally related to binding processes or whether, on the contrary, it is a mere epiphenomenon, one possibility is to employ neuromodulatory techniques such as transcranial alternating current stimulation (tACS). tACS has seen a rising interest due to its ability to modulate brain oscillations in a frequency-dependent manner. In the present review, we critically summarize current tACS evidence for a causal role of oscillatory activity in spatial, temporal, and feature binding in the context of visual perception. For temporal binding, the emerging picture supports a causal link with the power and the frequency of occipital alpha rhythms (8–12 Hz); however, there is no consistent evidence on the causal role of the phase of occipital tACS. For feature binding, the only study available showed a modulation by occipital alpha tACS. The majority of studies that successfully modulated oscillatory activity and behavioral performance in spatial binding targeted parietal areas, with the main rhythms causally linked being the theta (~7 Hz) and beta (~18 Hz) frequency bands. On the other hand, spatio-temporal binding has been directly modulated by parieto-occipital gamma (~40–60 Hz) and alpha (10 Hz) tACS, suggesting a potential role of cross-frequency coupling when binding across space and time. Nonetheless, negative or partial results have also been observed, suggesting methodological limitations that should be addressed in future research. Overall, the emerging picture seems to support a causal role of brain oscillations in binding processes and, consequently, a certain degree of plasticity for shaping binding mechanisms in visual perception, which, if proved to have long lasting effects, can find applications in different clinical populations.

scholarly journals Basal ganglia and cerebellar contributions to vocal emotion processing: a high resolution fMRI study

2020 ◽  
Author(s):  
Leonardo Ceravolo ◽  
Sascha Frühholz ◽  
Jordan Pierce ◽  
Didier Grandjean ◽  
Julie Péron
Keyword(s):  
Basal Ganglia ◽  
High Resolution ◽  
Globus Pallidus ◽  
Subthalamic Nucleus ◽  
Effective Connectivity ◽  
Emotion Processing ◽  
Brain Regions ◽  
Fmri Study ◽  
Vocal Emotion

AbstractUntil recently, brain networks underlying emotional voice prosody decoding and processing were focused on modulations in primary and secondary auditory, ventral frontal and prefrontal cortices, and the amygdala. Growing interest for a specific role of the basal ganglia and cerebellum was recently brought into the spotlight. In the present study, we aimed at characterizing the role of such subcortical brain regions in vocal emotion processing, at the level of both brain activation and functional and effective connectivity, using high resolution functional magnetic resonance imaging. Variance explained by low-level acoustic parameters (fundamental frequency, voice energy) was also modelled. Wholebrain data revealed expected contributions of the temporal and frontal cortices, basal ganglia and cerebellum to vocal emotion processing, while functional connectivity analyses highlighted correlations between basal ganglia and cerebellum, especially for angry voices. Seed-to-seed and seed-to-voxel effective connectivity revealed direct connections within the basal ganglia ̶ especially between the putamen and external globus pallidus ̶ and between the subthalamic nucleus and the cerebellum. Our results speak in favour of crucial contributions of the basal ganglia, especially the putamen, external globus pallidus and subthalamic nucleus, and several cerebellar lobules and nuclei for an efficient decoding of and response to vocal emotions.

scholarly journals A causal role for the right frontal eye fields in value comparison

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Ian Krajbich ◽  
Andres Mitsumasu ◽  
Rafael Polania ◽  
Christian C Ruff ◽  
Ernst Fehr
Keyword(s):  
Decision Making ◽  
Visual Attention ◽  
Reaction Times ◽  
Underlying Mechanism ◽  
Brain Regions ◽  
Causal Role ◽  
Frontal Eye Field ◽  
Eye Field ◽  
The Right

Recent studies have suggested close functional links between overt visual attention and decision making. This suggests that the corresponding mechanisms may interface in brain regions known to be crucial for guiding visual attention – such as the frontal eye field (FEF). Here, we combined brain stimulation, eye tracking, and computational approaches to explore this possibility. We show that inhibitory transcranial magnetic stimulation (TMS) over the right FEF has a causal impact on decision making, reducing the effect of gaze dwell time on choice while also increasing reaction times. We computationally characterize this putative mechanism by using the attentional drift diffusion model (aDDM), which reveals that FEF inhibition reduces the relative discounting of the non-fixated option in the comparison process. Our findings establish an important causal role of the right FEF in choice, elucidate the underlying mechanism, and provide support for one of the key causal hypotheses associated with the aDDM.

scholarly journals Probing the causal role of prestimulus interregional synchrony for perceptual integration via tACS

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Rolandas Stonkus ◽  
Verena Braun ◽  
Jess R. Kerlin ◽  
Gregor Volberg ◽  
Simon Hanslmayr
Keyword(s):  
Causal Role ◽  
Perceptual Integration

scholarly journals Reading in a Regular Orthography: An fMRI Study Investigating the Role of Visual Familiarity

2004 ◽  
Vol 16 (5) ◽  
pp. 727-741 ◽  
Author(s):  
Anja Ischebeck ◽  
Peter Indefrey ◽  
Nobuo Usui ◽  
Izuru Nose ◽  
Frauke Hellwig ◽  
...  
Keyword(s):  
Semantic Processing ◽  
Brain Activity ◽  
Brain Regions ◽  
Decision Task ◽  
Phonological Encoding ◽  
Fmri Study ◽  
Dual Route Model ◽  
Japanese Kana ◽  
Familiar Form

In order to separate the cognitive processes associated with phonological encoding and the use of a visual word form lexicon in reading, it is desirable to compare the processing of words presented in a visually familiar form with words in a visually unfamiliar form. Japanese Kana orthography offers this possibility. Two phonologically equivalent but visually dissimilar syllabaries allow the writing of, for example, foreign loanwords in two ways, only one of which is visually familiar. Familiarly written words, unfamiliarly written words, and pseudowords were presented in both Kana syllabaries (yielding six conditions in total) to participants during an fMRI measurement with a silent articulation task (Experiment 1) and a phonological lexical decision task (Experiment 2) using an event-related design. Consistent over two experimental tasks, the three different stimulus types (familiar, unfamiliar, and pseudoword) were found to activate selectively different brain regions previously associated with phonological encoding and word retrieval or meaning. Compatible with the predictions of the dual-route model for reading, pseudowords and visually unfamiliar words, which have to be read using phonological assembly, caused an increase in brain activity in left inferior frontal regions (BA 44/47), as compared to visually familiar words. Visually familiar and unfamiliar words were found to activate a range of areas associated with lexico-semantic processing more strongly than pseudowords, such as the left and right temporo-parietal region (BA 39/40), a region in the left middle/inferior temporal gyrus (BA 20/21), and the posterior cingulate (BA 31).

scholarly journals The causal role of transcranial alternating current stimulation at alpha frequency in boosting visual perceptual learning

2021 ◽  
Author(s):  
Qing He ◽  
Baoqi Gong ◽  
Keyan Bi ◽  
Fang Fang
Keyword(s):  
Perceptual Learning ◽  
Discrimination Learning ◽  
Alternating Current ◽  
Causal Role ◽  
Orientation Discrimination ◽  
Visual Perceptual Learning ◽  
Specific Manner ◽  
Transcranial Alternating Current Stimulation ◽  
40 Hz

Extensive training improves our ability to perceive visual contents around us, a phenomenon known as visual perceptual learning (VPL). Numerous studies have been conducted to understand the mechanisms of VPL, while the neural oscillatory mechanisms underpinning VPL has yet to be elucidated. To this end, we adopted transcranial alternating current stimulation (tACS), a neuromodulatory technique that can alter ongoing brain rhythms in a frequency-specific manner by applying external weak electric fields, to stimulate targeted cortical areas in human subjects while they performed an orientation discrimination learning task. Five groups of subjects undertook five daily training sessions to execute the task. Four groups received occipital tACS stimulation at 10 Hz (alpha band), 20 Hz (beta band), 40 Hz (gamma band), or sham 10 Hz (sham), and one group was stimulated at the sensorimotor regions by 10 Hz tACS. Compared with the sham stimulation, occipital tACS at 10 Hz, but not at 20 Hz or 40 Hz, increased both the learning rate and performance improvement. However, when 10 Hz tACS was delivered to the sensorimotor areas, the modulatory effects of tACS were absent, suggesting that tACS modulated the orientation discrimination learning in a frequency- and location-specific manner. Moreover, the tACS-induced enhancement lasted at least two months after the termination of training. Our findings provide strong evidence for the causal role of alpha oscillations in VPL and shed new light on the design of effective neuromodulation protocols that might facilitate rehabilitation for patients with neuro-ophthalmological disorders.

scholarly journals Transcranial alternating current stimulation (tACS) reveals causal role of brain oscillations in visual attention

2016 ◽  
Vol 16 (12) ◽  
pp. 937 ◽  
Author(s):  
Daniel Baldauf ◽  
Nir Grossman ◽  
An-Ming Hu ◽  
Ed Boyden ◽  
Robert Desimone
Keyword(s):  
Visual Attention ◽  
Alternating Current ◽  
Causal Role ◽  
Brain Oscillations ◽  
Transcranial Alternating Current Stimulation

scholarly journals Disorganization of Oscillatory Activity in Animal Models of Schizophrenia

2021 ◽  
Vol 15 ◽  
Author(s):  
Lucinda J. Speers ◽  
David K. Bilkey
Keyword(s):  
Animal Models ◽  
Time Window ◽  
Research Effort ◽  
Brain Regions ◽  
Brain Dysfunction ◽  
Oscillatory Activity ◽  
Oscillation Phase ◽  
Phase Precession ◽  
Sequential Information

Schizophrenia is a chronic, debilitating disorder with diverse symptomatology, including disorganized cognition and behavior. Despite considerable research effort, we have only a limited understanding of the underlying brain dysfunction. In this article, we review the potential role of oscillatory circuits in the disorder with a particular focus on the hippocampus, a region that encodes sequential information across time and space, as well as the frontal cortex. Several mechanistic explanations of schizophrenia propose that a loss of oscillatory synchrony between and within these brain regions may underlie some of the symptoms of the disorder. We describe how these oscillations are affected in several animal models of schizophrenia, including models of genetic risk, maternal immune activation (MIA) models, and models of NMDA receptor hypofunction. We then critically discuss the evidence for disorganized oscillatory activity in these models, with a focus on gamma, sharp wave ripple, and theta activity, including the role of cross-frequency coupling as a synchronizing mechanism. Finally, we focus on phase precession, which is an oscillatory phenomenon whereby individual hippocampal place cells systematically advance their firing phase against the background theta oscillation. Phase precession is important because it allows sequential experience to be compressed into a single 120 ms theta cycle (known as a ‘theta sequence’). This time window is appropriate for the induction of synaptic plasticity. We describe how disruption of phase precession could disorganize sequential processing, and thereby disrupt the ordered storage of information. A similar dysfunction in schizophrenia may contribute to cognitive symptoms, including deficits in episodic memory, working memory, and future planning.

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