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1.
Brain Stimul ; 13(3): 655-663, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32289694

RESUMO

BACKGROUND: Transcranial direct current stimulation (tDCS) has been proven to be able to modulate motor cortical plasticity might have potential as an alternative, adjunctive therapy for Parkinson's disease (PD). However, the efficacy of tDCS in PD is still uncertain. A disease animal model may be useful to clarify the existence of a treatment effect and to explore an effective therapeutic strategy using tDCS protocols. OBJECTIVE: The current study was designed to identify the comprehensive therapeutic effects of tDCS in 6-hydroxydopamine (6-OHDA)-lesioned PD rats. METHODS: Following early and long-term tDCS application (starting 24 h after PD lesion, 300 µA anodal tDCS, 20 min/day, 5 days/week) in awake PD animals for a total of 4 weeks, the effects of tDCS on motor and non-motor behaviors as well as dopaminergic neuron degeneration levels, were identified. RESULTS: We found that the 4-week tDCS intervention significantly alleviated 6-OHDA-induced motor deficits in locomotor activity, akinesia, gait pattern and anxiety-like behavior, but not in apomorphine-induced rotations, recognition memory and depression-like behavior. Immunohistochemically, tyrosine hydroxylase (TH)-positive neurons in the substantia nigra were significantly preserved in the tDCS intervention group. CONCLUSIONS: These results suggest that early and long-term tDCS could exert neuroprotective effects and reduce the aggravation of motor dysfunctions in a 6-OHDA-induced PD rat model. Furthermore, this preclinical model may enhance the promising possibility of the potential use of tDCS and serve as a translational platform to further identify the therapeutic mechanism of tDCS for PD or other neurological disorders.

2.
Biol Psychiatry ; 87(5): 443-450, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-31563272

RESUMO

BACKGROUND: Prolonged intermittent theta burst stimulation (piTBS) with triple doses of the standard protocol is an updated form of repetitive transcranial magnetic stimulation, and it is an effective add-on intervention for major depressive disorder. In the present study, our objective was to investigate the antidepressant efficacy of piTBS monotherapy. Efficacy between the standard 5-cm method and magnetic resonance imaging (MRI)-guided coil positioning to the left dorsolateral prefrontal cortex method was also compared. METHODS: In the present double-blind, randomized, sham-controlled trial, 105 patients with recurrent depression who exhibited no responses to at least one adequate antidepressant treatment for the prevailing episode were assigned randomly to one of three groups: piTBS monotherapy (n = 35), repetitive transcranial magnetic stimulation monotherapy (n = 35), or sham stimulation (n = 35). The acute treatment period was 2 weeks. Half of the patients were randomized to MRI navigation in each group. RESULTS: No serious adverse events were observed. The piTBS group exhibited significantly greater decreases in depression scores than the sham group at week 2 (-40.0% vs. -13.9%; p < .001 after correcting for multiple comparisons by Bonferroni [effect size (Cohen's d) = 1.12]), and the odds ratio for responses was high. The MRI navigation method (-32.4%) did not yield better antidepressant effects than the standard method (-40.6%). Brain stimulation and 17-item Hamilton Depression Rating Scale changes in the first week were the most important variables for predicting antidepressant responses. CONCLUSIONS: Left prefrontal piTBS monotherapy is effective for the treatment of recurrent depression, and the MRI-guided method of coil targeting is not better than the standard method.

3.
R Soc Open Sci ; 6(11): 190540, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31827820

RESUMO

The influential hypothesis by Markus & Kitayama (Markus, Kitayama 1991. Psychol. Rev. 98, 224) postulates that individuals from interdependent cultures place others above self in interpersonal contexts. This led to the prediction and finding that individuals from interdependent cultures are less egocentric than those from independent cultures (Wu, Barr, Gann, Keysar 2013. Front. Hum. Neurosci. 7, 1-7; Wu, Keysar. 2007 Psychol. Sci. 18, 600-606). However, variation in egocentrism can only provide indirect evidence for the Markus and Kitayama hypothesis. The current study sought direct evidence by giving British (independent) and Taiwanese (interdependent) participants two perspective-taking tasks on which an other-focused 'altercentric' processing bias might be observed. One task assessed the calculation of simple perspectives; the other assessed the use of others' perspectives in communication. Sixty-two Taiwanese and British adults were tested in their native languages at their home institutions of study. Results revealed similar degrees of both altercentric and egocentric interference between the two cultural groups. This is the first evidence that listeners account for a speaker's limited perspective at the cost of their own performance. Furthermore, the shared biases point towards similarities rather than differences in perspective-taking across cultures.

4.
J Vis ; 19(14): 14, 2019 12 02.
Artigo em Inglês | MEDLINE | ID: mdl-31845974

RESUMO

The response latency of steady-state visually evoked potentials (SSVEPs) is a sensitive measurement for investigating visual functioning of the human brain, specifically in visual development and for clinical evaluation. This latency can be measured from the slope of phase versus frequency of responses by using multiple frequencies of stimuli. In an attempt to provide an alternative measurement of this latency, this study utilized an envelope response of SSVEPs elicited by amplitude-modulated visual stimulation and then compared with the envelope of the generating signal, which was recorded simultaneously with the electroencephalography recordings. The advantage of this measurement is that it successfully estimates the response latency based on the physiological envelope in the entire waveform. Results showed the response latency at the occipital lobe (Oz channel) was approximately 104.55 ms for binocular stimulation, 97.14 ms for the dominant eye, and 104.75 ms for the nondominant eye with no significant difference between these stimulations. Importantly, the response latency at frontal channels (125.84 ms) was significantly longer than that at occipital channels (104.11 ms) during binocular stimulation. Together with strong activation of the source envelope at occipital cortex, these findings support the idea of a feedforward process, with the visual stimuli propagating originally from occipital cortex to anterior cortex. In sum, these findings offer a novel method for future studies in measuring visual response latencies and also potentially shed a new light on understanding of how long collective neural activities take to travel in the human brain.

5.
Sci Rep ; 9(1): 16919, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31729410

RESUMO

Natural sensory signals have nonlinear structures dynamically composed of the carrier frequencies and the variation of the amplitude (i.e., envelope). How the human brain processes the envelope information is still poorly understood, largely due to the conventional analysis failing to quantify it directly. Here, we used a recently developed method, Holo-Hilbert spectral analysis, and steady-state visually evoked potential collected using electroencephalography (EEG) recordings to investigate how the human visual system processes the envelope of amplitude-modulated signals, in this case with a 14 Hz carrier and a 2 Hz envelope. The EEG results demonstrated that in addition to the fundamental stimulus frequencies, 4 Hz amplitude modulation residing in 14 Hz carrier and a broad range of carrier frequencies covering from 8 to 32 Hz modulated by 2 Hz amplitude modulation are also found in the two-dimensional frequency spectrum, which have not yet been recognized before. The envelope of the stimulus is also found to dominantly modulate the response to the incoming signal. The findings thus reveal that the electrophysiological response to amplitude-modulated stimuli is more complex than could be revealed by, for example, Fourier analysis. This highlights the dynamics of neural processes in the visual system.

6.
Soc Cogn Affect Neurosci ; 14(6): 645-655, 2019 08 07.
Artigo em Inglês | MEDLINE | ID: mdl-31119291

RESUMO

Working memory capacity (WMC) can predict conflict control ability. Measures of both abilities are impaired by anxiety, which is often inversely linked with mindfulness. It has been shown that a combination of high mindfulness and low anxiety is associated with better conflict control and WMC. The current study explored the electrophysiology related to such behavioral differences. Two experimental groups, one with high mindfulness and low anxiety (HMLA) and one with low mindfulness and high anxiety (LMHA), performed a color Stroop task and a change detection task, both with simultaneous electroencephalogram (EEG) recording. An advanced EEG analytical approach, Hilbert-Huang transform (HHT) analysis, was employed. This is regarded as a robust method to analyze non-linear and non-stationary signals. Lower delta activity at posterior temporal and occipital regions was seen in the HMLA group for the Stroop conflict conditions and might be generally associated with higher accuracy in this group and indicative of higher attentiveness. Higher accuracy rates and WMC were seen in the HMLA group and might be specifically associated with the higher alpha activity observed in prefrontal cortex, fronto-central and centro-parietal regions in this group. Future studies should explore how mindfulness and anxiety can independently affect these cognitive functions and their associated neurophysiology.


Assuntos
Ansiedade/psicologia , Encéfalo/fisiologia , Cognição/fisiologia , Memória de Curto Prazo/fisiologia , Atenção Plena , Adolescente , Atenção/fisiologia , Mapeamento Encefálico , Eletroencefalografia , Feminino , Humanos , Masculino , Teste de Stroop , Adulto Jovem
7.
Front Psychol ; 10: 855, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31105617

RESUMO

Complex span task is one of the commonly used cognitive tasks to evaluate an individual's working memory capacity (WMC). It is a dual task consisting of a distractor subtask and a memory subtask. Though multiple studies have utilized complex span tasks, the electrophysiological correlates underlying the encoding and retrieval processes in working memory span task remain uninvestigated. One previous study that assessed electroencephalographic (EEG) measures utilizing complex span task found no significant difference between its working memory loads, a typical index observed in other working memory tasks (e.g., n-back task and digital span task). The following design constructs of the paradigm might have been the reason. (1) The fixed-time limit of the distractor subtask may have hindered the assessment of individual WMC precisely. (2) Employing a linear-system-favoring EEG data analysis method for a non-linear system such as the human brain. In the current study, the participants perform the Raven Advanced Progressive Matrices (RAMP) task on 1 day and the symmetry span (Sspan) task on the other. Prior to the formal Sspan task, the participants were instructed to judge 15 simple symmetry questions as quickly as possible. A participant-specific time-limit is chartered from these symmetry questions. The current study utilizes the Sspan task sequential to a distractor subtask. Instead of the fixed time-limit exercised in the previous study, the distractor subtask of the current study was equipped with the participant-specific time-limit obtained from the symmetry questions. This could provide a precise measure of individual WMC. This study investigates if the complex span task resonates EEG patterns similar to the other working memory tasks in terms of working memory-load by utilizing ensemble empirical mode decomposition (EEMD) of Hilbert-Huang transform (HHT). Prior expectations were to observe a decrement in the P300 component of event-related mode (ERM) and a decrement in the power of alpha and beta band frequency with increasing working memory-load. We observed a significantly higher P300 amplitude for the low-load condition compared to the high-load condition over the circumscribed brain network across F4 and C4 electrodes. Time-frequency analysis revealed a significant difference between the high- and low-load conditions at alpha and beta band over the frontal, central, and parietal channels. The results from our study demonstrate precise differences in EEG data pertaining to varied memory-load differences in the complex span task. Thus, assessing complex span tasks with the HHT-based analysis may aid in achieving a better signal to noise ratio and effect size for the results in working memory EEG studies.

8.
Neural Plast ; 2019: 4252943, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31949429

RESUMO

Transcranial direct current stimulation (tDCS) is a noninvasive technique for modulating neural plasticity and is considered to have therapeutic potential in neurological disorders. For the purpose of translational neuroscience research, a suitable animal model can be ideal for providing a stable condition for identifying mechanisms that can help to explore therapeutic strategies. Here, we developed a tDCS protocol for modulating motor excitability in anesthetized rats. To examine the responses of tDCS-elicited plasticity, the motor evoked potential (MEP) and MEP input-output (IO) curve elicited by epidural motor cortical electrical stimulus were evaluated at baseline and after 30 min of anodal tDCS or cathodal tDCS. Furthermore, a paired-pulse cortical electrical stimulus was applied to assess changes in the inhibitory network by measuring long-interval intracortical inhibition (LICI) before and after tDCS. In the results, analogous to those observed in humans, the present study demonstrates long-term potentiation- (LTP-) and long-term depression- (LTD-) like plasticity can be induced by tDCS protocol in anesthetized rats. We found that the MEPs were significantly enhanced immediately after anodal tDCS at 0.1 mA and 0.8 mA and remained enhanced for 30 min. Similarly, MEPs were suppressed immediately after cathodal tDCS at 0.8 mA and lasted for 30 min. No effect was noted on the MEP magnitude under sham tDCS stimulation. Furthermore, the IO curve slope was elevated following anodal tDCS and presented a trend toward diminished slope after cathodal tDCS. No significant differences in the LICI ratio of pre- to post-tDCS were observed. These results indicated that developed tDCS schemes can produce consistent, rapid, and controllable electrophysiological changes in corticomotor excitability in rats. This newly developed tDCS animal model could be useful to further explore mechanical insights and may serve as a translational platform bridging human and animal studies, establishing new therapeutic strategies for neurological disorders.

9.
Front Neurosci ; 12: 421, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29997471

RESUMO

Learning regularities that exist in the environment can help the visual system achieve optimal efficiency while reducing computational burden. Using a pro- and anti-saccade task, studies have shown that probabilistic information regarding spatial locations can be a strong modulator of frontal eye fields (FEF) activities and consequently alter saccadic behavior. One recent study has also shown that FEF activities can be modulated by transcranial direct current stimulation, where anodal tDCS facilitated prosaccades but cathodal tDCS prolonged antisaccades. These studies together suggest that location probability and tDCS can both alter FEF activities and oculomotor performance, yet how these two modulators interact with each other remains unclear. In this study, we applied anodal or cathodal tDCS over right FEF, and participants performed an interleaved pro- and anti-saccade task. Location probability was manipulated in prosaccade trials but not antisaccade trials. We observed that anodal tDCS over rFEF facilitated prosaccdes toward low-probability locations but not to high-probability locations; whereas cathodal tDCS facilitated antisaccades away from the high-probability location (i.e., same location as the low-probability locations in prosaccades). These observed effects were specific to rFEF as tDCS over the SEF in a separate control experiment did not yield similar patterns. These effects were also more pronounced in low-performers who had slower saccade reaction time. Together, we conclude that (1) the overlapping spatial endpoint between prosaccades (i.e., toward low-probability location) and antisaccades (i.e., away from high-probability location) possibly suggest an endpoint-selective mechanism within right FEF, (2) anodal tDCS and location probability cannot be combined to produce a bigger facilitative effect, and (3) anodal rFEF tDCS works best on low-performers who had slower saccade reaction time. These observations are consistent with the homeostasis account of tDCS effect and FEF functioning.

10.
Front Psychol ; 9: 1105, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29973902

RESUMO

[This corrects the article on p. 627 in vol. 9, PMID: 29780338.].

11.
Front Integr Neurosci ; 12: 17, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29867385

RESUMO

Prior studies have reported that meditation may improve cognitive functions and those related to attention in particular. Here, the dynamic process of attentional control, which allows subjects to focus attention on their current interests, was investigated. Concentrative meditation aims to cultivate the abilities of continuous focus and redirecting attention from distractions to the object of focus during meditation. However, it remains unclear how meditation may influence attentional reorientation, which involves interaction between both top-down and bottom-up processes. We aimed to investigate the modulating effect of meditation on the mechanisms of contingent reorienting by employing a rapid serial visual presentation (RSVP) task in conjunction with electrophysiological recording. We recruited 26 meditators who had an average of 2.9 years of meditation experience and a control group comprising 26 individuals without any prior experience of meditation. All subjects performed a 30-min meditation and a rest condition with data collected pre- and post-intervention, with each intervention given on different days. The state effect of meditation improved overall accuracy for all subjects irrespective of their group. A group difference was observed across interventions, showing that meditators were more accurate and more efficient at attentional suppression, represented by a larger Pd (distractor positive) amplitude of event related modes (ERMs), for target-like distractors than the control group. The findings suggested that better attentional control with respect to distractors might be facilitated by acquiring experience of and skills related to meditation training.

12.
Front Psychol ; 9: 627, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29780338

RESUMO

There are several ways in which cognitive and neurophysiological parameters have been consistently used to explain the variability in cognitive ability between people. However, little has been done to explore how such cognitive abilities are influenced by differences in personality traits. Dispositional mindfulness and anxiety are two inversely linked traits that have been independently attributed to a range of cognitive functions. The current study investigated these two traits in combination along with measures of the attentional network, cognitive inhibition, and visual working memory (VWM) capacity. A total of 392 prospective participants were screened to select two experimental groups each of 30 healthy young adults, with one having high mindfulness and low anxiety (HMLA) and the second having low mindfulness and high anxiety (LMHA). The groups performed an attentional network task, a color Stroop task, and a change detection test of VWM capacity. Results showed that the HMLA group was more accurate than the LMHA group on the Stroop and change detection tasks. Additionally, the HMLA group was more sensitive in detecting changes and had a higher WMC than the LMHA group. This research adds to the literature that has investigated mindfulness and anxiety independently with a comprehensive investigation of the effects of these two traits in conjunction on executive function.

13.
Brain Stimul ; 11(5): 1054-1062, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29730251

RESUMO

BACKGROUND: Theta-burst transcranial magnetic stimulation (TBS) can quickly modulate brain activity and can be used to treat treatment-resistant depression (TRD). Whole-brain analytical research has revealed that left high-frequency PFC rTMS modulates brain activity in anterior cingulate cortex (ACC) and the fronto-cingulo-temporal circuit. We aimed to investigate whether the prefrontal TBS's antidepressant mechanisms involve these regions. METHODS: We designed a randomized, double-blind, sham-controlled neuroimaging study to investigate different mechanisms of TBS [i.e., continuous TBS (cTBS) and intermittent TBS (iTBS)]. This study included 56 TRD patients [67.8%: women; mean age (SD): 45.5 (10.6) years], who were randomly assigned to one of four groups [A: right prefrontal cTBS; B: left prefrontal iTBS; C: combined right prefrontal cTBS and left prefrontal iTBS; and D: sham-TBS]. We measured standard uptake values (SUV) of cerebral glucose metabolism, at rest, both before and after ten daily treatment sessions. RESULTS: Group B and Group C had more responders than Group A and Group D (χ2 = 9.161, p = 0.027). In Group A, the SUV was significantly increased in the ACC and medial PFC (mPFC) after treatment, while the SUV was decreased in the right temporal cortex (p < 0.05, FWE-corrected for multiple comparisons). In contrast, in Group B, SUV was decreased in the ACC and mPFC and increased in the bilateral temporal cortex. Group C also had increased SUV in the bilateral temporal cortices. CONCLUSION: Instead of observing inhibitory or facilitatory effects on the targeted prefrontal cortex, we found that the two-week prefrontal TBS protocols primarily modulated the fronto-cingulo-temporal circuit.


Assuntos
Transtorno Depressivo Resistente a Tratamento/diagnóstico por imagem , Transtorno Depressivo Resistente a Tratamento/terapia , Neuroimagem/métodos , Córtex Pré-Frontal/diagnóstico por imagem , Córtex Pré-Frontal/fisiologia , Ritmo Teta/fisiologia , Estimulação Magnética Transcraniana/métodos , Adulto , Transtorno Depressivo Resistente a Tratamento/psicologia , Método Duplo-Cego , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Tomografia por Emissão de Pósitrons/métodos , Resultado do Tratamento
14.
Sci Rep ; 8(1): 349, 2018 01 10.
Artigo em Inglês | MEDLINE | ID: mdl-29321584

RESUMO

Visual working memory (VWM) refers to people's ability to maintain and manipulate visual information on line. Its capacity varies between individuals, and neuroimaging studies have suggested a link between one's VWM capacity and theta power in the parietal cortex. However, it is unclear how the parietal cortices communicate with each other in order to support VWM processing. In two experiments we employed transcranial alternate current stimulation (tACS) to use frequency-specific (6 Hz) alternating current to modulate theta oscillation between the left and right parietal cortex with either in-phase (0° difference, Exp 1), anti-phase (180° difference, Exp 2), or sham sinusoidal current stimulation. In Experiment 1, in-phase theta tACS induced an improved VWM performance, but only in low-performers, whereas high-performers suffered a marginally-significant VWM impairment. In Experiment 2, anti-phase theta tACS did not help the low-performers, but significantly impaired high-performers' VWM capacity. These results not only provide causal evidence for theta oscillation in VWM processing, they also highlight the intricate interaction between tACS and individual differences-where the same protocol that enhances low-performers' VWM can backfire for the high-performers. We propose that signal complexity via coherent timing and phase synchronization within the bilateral parietal network is crucial for successful VWM functioning.


Assuntos
Memória de Curto Prazo , Lobo Parietal/fisiologia , Ritmo Teta , Percepção Visual , Adulto , Análise de Variância , Eletroencefalografia , Feminino , Humanos , Masculino , Estimulação Luminosa , Adulto Jovem
15.
J Neurosci ; 37(48): 11647-11661, 2017 11 29.
Artigo em Inglês | MEDLINE | ID: mdl-29109242

RESUMO

Both humans and animals are known to exhibit a violation of rationality known as "decoy effect": introducing an irrelevant option (a decoy) can influence choices among other (relevant) options. Exactly how and why decoys trigger this effect is not known. It may be an example of fast heuristic decision-making, which is adaptive in natural environments, but may lead to biased choices in certain markets or experiments. We used fMRI and transcranial magnetic stimulation to investigate the neural underpinning of the decoy effect of both sexes. The left ventral striatum was more active when the chosen option dominated the decoy. This is consistent with the hypothesis that the presence of a decoy option influences the valuation of other options, making valuation context-dependent even when choices appear fully rational. Consistent with the idea that control is recruited to prevent heuristics from producing biased choices, the right inferior frontal gyrus, often implicated in inhibiting prepotent responses, connected more strongly with the striatum when subjects successfully overrode the decoy effect and made unbiased choices. This is further supported by our transcranial magnetic stimulation experiment: subjects whose right inferior frontal gyrus was temporarily disrupted made biased choices more often than a control group. Our results suggest that the neural basis of the decoy effect could be the context-dependent activation of the valuation area. But the differential connectivity from the frontal area may indicate how deliberate control monitors and corrects errors and biases in decision-making.SIGNIFICANCE STATEMENT Standard theories of rational decision-making assume context-independent valuations of available options. Motivated by the importance of this basic assumption, we used fMRI to study how the human brain assigns values to available options. We found activity in the valuation area to be consistent with the hypothesis that values depend on irrelevant aspects of the environment, even for subjects whose choices appear fully rational. Such context-dependent valuations may lead to biased decision-making. We further found differential connectivity from the frontal area to the valuation area depending on whether biases were successfully overcome. This suggests a mechanism for making rational choices despite the potential bias. Further support was obtained by a transcranial magnetic stimulation experiment, where subjects whose frontal control was temporarily disrupted made biased choices more often than a control group.


Assuntos
Encéfalo/fisiologia , Tomada de Decisões/fisiologia , Imagem por Ressonância Magnética/métodos , Estimulação Magnética Transcraniana/métodos , Comportamento de Escolha/fisiologia , Feminino , Humanos , Masculino , Adulto Jovem
16.
Cogn Affect Behav Neurosci ; 17(5): 973-983, 2017 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-28656503

RESUMO

Few studies have investigated the effects of anxiety on contingent attentional capture. The present study examined contingent attentional capture in trait anxiety by applying a rapid serial visual presentation (RSVP) paradigm during electroencephalographic recording. Overall, the behavioral and electrophysiological results showed a larger capture effect when a distractor was the same color as the target compared to when the distractor was not of the target color. Moreover, high-anxiety individuals showed a larger N2pc in the target colored distractor condition and nontarget colored distractor condition compared to the distractor-absent condition. In addition, the reaction time was slower when distractors were presented in the left visual field compared to when they were in the right visual field. This pattern was not seen in low-anxiety individuals. The findings may indicate that high-anxiety individuals allocate attention to the target less efficiently and have reduced suppression of distractors compared to low-anxiety individuals who could suppress attention to the distractors more efficiently. Future work could valuably investigate the consequences of such differences in terms of benefits and disruption associated with attentional capture differences in a range of anxious populations in different risk monitoring situations.


Assuntos
Ansiedade/fisiopatologia , Atenção/fisiologia , Percepção de Cores/fisiologia , Potenciais Evocados/fisiologia , Reconhecimento Visual de Modelos/fisiologia , Desempenho Psicomotor/fisiologia , Campos Visuais/fisiologia , Adolescente , Adulto , Eletroencefalografia , Feminino , Humanos , Masculino , Adulto Jovem
17.
Brain Stimul ; 10(3): 604-608, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28040450

RESUMO

BACKGROUND: A growing body of evidence suggests that deficits in GABAergic inhibitory and glutamatergic excitatory neurotransmission may be involved in the core pathophysiology of generalized anxiety disorder (GAD), a disease characterized by pathological anxious worrying. The aim of the present study was to measure motor cortical excitability by paired-pulse transcranial magnetic stimulation (ppTMS) in patients with GAD. METHODS: ppTMS measurements of excitation and inhibition from bilateral motor cortices were investigated in 26 right-handed GAD patients who were drug-naïve (half of them with a comorbidity of major depressive disorder) and 35 right-handed age- and sex-matched healthy controls. Short-interval intracortical inhibition (SICI), intracortical facilitation (ICF), and long-interval intracortical inhibition (LICI) were studied; evidence indicated that these are mainly mediated by GABA-A receptors, glutamate receptors, and GABA-B receptors, respectively. RESULTS: After correcting for multiple comparisons, GAD patients had significantly lower left ICF (p < 0.001, Cohen's d = 1.348) and right ICF (p = 0.001, Cohen's d = 0.963), but not SICI and LICI, than did healthy controls. No significant difference of the ICF values was found between GAD with and without depressive disorders. Multivariate linear regression analysis revealed that left ICF (B = -4.990, 95% CI = -8.821 to -1.039, p = 0.007) and group (B = 13.179, 95% CI = 10.208 to 16.149, p = 0.001) predicted anxiety symptoms significantly. CONCLUSION: The present study provided direct evidence to support that generalized anxiety disorder is characterized by impaired intra-cortical facilitation of motor cortex, suggesting glutamate-related excitatory dysfunction may play a key role in pathological anxiety.


Assuntos
Transtorno Depressivo Maior/fisiopatologia , Potencial Evocado Motor , Córtex Motor/fisiopatologia , Inibição Neural , Adulto , Estudos de Casos e Controles , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estimulação Magnética Transcraniana
18.
Hum Brain Mapp ; 38(1): 339-351, 2017 01.
Artigo em Inglês | MEDLINE | ID: mdl-27611342

RESUMO

It is widely accepted that the supplementary eye fields (SEF) are involved in the control of voluntary eye movements. However, recent evidence suggests that SEF may also be important for unconscious and involuntary motor processes. Indeed, Sumner et al. ([2007]: Neuron 54:697-711) showed that patients with micro-lesions of the SEF demonstrated an absence of subliminal inhibition as evoked by masked-prime stimuli. Here, we used double-pulse transcranial magnetic stimulation (TMS) in healthy volunteers to investigate the role of SEF in subliminal priming. We applied double-pulse TMS at two time windows in a masked-prime task: the first during an early phase, 20-70 ms after the onset of the mask but before target presentation, during which subliminal inhibition is present; and the second during a late phase, 20-70 ms after target onset, during which the saccade is being prepared. We found no effect of TMS with the early time window of stimulation, whereas a reduction in the benefit of an incompatible subliminal prime stimulus was found when SEF TMS was applied at the late time window. These findings suggest that there is a role for SEF related to the effects of subliminal primes on eye movements, but the results do not support a role in inhibiting the primed tendency. Hum Brain Mapp 38:339-351, 2017. © 2016 Wiley Periodicals, Inc.


Assuntos
Lobo Frontal/fisiologia , Movimentos Sacádicos , Estimulação Subliminar , Estimulação Magnética Transcraniana/métodos , Adulto , Feminino , Lobo Frontal/efeitos dos fármacos , Humanos , Imagem por Ressonância Magnética , Masculino , Estimulação Luminosa , Tempo de Reação/fisiologia , Fatores de Tempo , Adulto Jovem
19.
Front Hum Neurosci ; 10: 479, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27733822

RESUMO

Diabetes mellitus can lead to diabetic polyneuropathy (DPN) and cognitive deficits that manifest as peripheral and central neuropathy, respectively. In this study we investigated the relationship between visuospatial working memory (VSWM) capacity and DPN severity, and attempted to improve VSWM in DPN patients via the use of transcranial direct current stimulation (tDCS). Sixteen DPN patients and 16 age- and education-matched healthy control subjects received Wechsler Adult Intelligence Scale-Fourth Edition (WAIS-IV) and Montreal Cognitive Assessment (MOCA) for baseline cognitive assessment. A forward- and backward-recall computerized Corsi block tapping task (CBT), both with and without a concurrent motor interference task was used to measure VSWM capacity. Each DPN patient underwent a pre-treatment CBT, followed by tDCS or sham treatment, then a post-treatment CBT on two separate days. We found that although patients with severe DPN (Dyck's grade 2a or 2b) showed comparable general intelligence scores on WAIS-IV as their age- and education-matched healthy counterparts, they nonetheless showed mild cognitive impairment (MCI) on MOCA and working memory deficit on digit-span test of WAIS-IV. Furthermore, patients' peripheral nerve conduction velocity (NCV) was positively correlated with their VSWM span in the most difficult CBT condition that involved backward-recall with motor interference such that patients with worse NCV also had lower VSWM span. Most importantly, anodal tDCS over the right DLPFC was able to improve low-performing patients' VSWM span to be on par with the high-performers, thereby eliminating the correlation between NCV and VSWM. In summary, these findings suggest that (1) MCI and severe peripheral neuropathy can coexist with unequal severity in diabetic patients, (2) the positive correlation of VSWM and NCV suggests a link between peripheral and central neuropathies, and (3) anodal tDCS over the right DLPFC can improve DPN patients' VSWM, particularly for the low-performing patients.

20.
Sci Rep ; 6: 32138, 2016 08 30.
Artigo em Inglês | MEDLINE | ID: mdl-27573864

RESUMO

How does the brain enable us to remember two or more object representations in visual working memory (VWM) without confusing them? This "gluing" process, or feature binding, refers to the ability to join certain features together while keeping them segregated from others. Recent neuroimaging research has reported higher BOLD response in the left temporal and parietal cortex during a binding-VWM task. However, less is known about how the two regions work in synchrony to support such process. In this study, we applied transcranial alternating current stimulation (tACS) over the left temporal and parietal cortex in gamma and theta frequency, with a phase difference of either 0° (in-phase) or 180° (anti-phase) to account for the different ways through which neural synchronization may occur. We found no facilitatory or inhibitory effect from sham, theta, and in-phase gamma stimulation. Importantly, there was an enhancement effect from anti-phase gamma tACS that was binding-specific, and such effect was only apparent in low-performing individuals who had room for improvement. Together, these results demonstrate that binding-VWM is supported by a temporally-precise oscillatory mechanism within the gamma frequency range, and that the advantageous 180°-apart phase relationship also implies a possible temporal driver-to-receiver time-lag between the temporal and parietal cortex.


Assuntos
Ritmo Gama/fisiologia , Memória de Curto Prazo/fisiologia , Rede Nervosa/fisiologia , Lobo Parietal/fisiologia , Lobo Temporal/fisiologia , Percepção Visual/fisiologia , Adulto , Feminino , Humanos , Masculino
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