Several studies have illustrated that transcutaneous vagus nerve stimulation (tVNS) can elicit therapeutic effects that are similar to those produced by its invasive counterpart, vagus nerve stimulation (VNS). VNS is an FDA-approved therapy for the treatment of both depression and epilepsy, but it is limited to the management of more severe, intervention-resistant cases as a second or third-line treatment option due to perioperative risks involved with device implantation. In contrast, tVNS is a non-invasive technique that involves the application of electrical currents through surface electrodes at select locations, most commonly targeting the auricular branch of the vagus nerve (ABVN) and the cervical branch of the vagus nerve in the neck. Although it has been shown that tVNS elicits hypo-and hyperactivation in various regions of the brain associated with anxiety and mood regulation, the mechanism of action and influence of stimulation parameters on clinical outcomes remains predominantly hypothetical. Suppositions are largely based on correlations between the neurobiology of the vagus nerve and its effects on neural activity. However, tVNS has also been investigated for several other disorders, including tinnitus, migraine and pain, by targeting the vagus nerve at sites in both the ear and the neck. As most of the described methods differ in the parameters and protocols applied, there is currently no firm evidence on the optimal location for tVNS or the stimulation parameters that provide the greatest therapeutic effects for a specific condition. This review presents the current status of tVNS with a focus on stimulation parameters, stimulation sites, and available devices. For tVNS to reach its full potential as a non-invasive and clinically relevant therapy, it is imperative that systematic studies be undertaken to reveal the mechanism of action and optimal stimulation modalities.
Accurate identification of seizure-generating brain tissue is challenging, particularly when MRI shows no clear abnormality or extensive abnormality. Plummer et al. achieve this non-invasively by analysing the earliest detectable part of the electromagnetic seizure signal recordable across the head surface. Their findings challenge current practice with its reliance on invasive intracranial monitoring.
An influential neural model of face perception suggests that the posterior superior temporal sulcus (STS) is sensitive to those aspects of faces that produce transient visual changes, including facial expression. Other researchers note that recognition of expression involves multiple sensory modalities and suggest that the STS also may respond to crossmodal facial signals that change transiently. Indeed, many studies of audiovisual (AV) speech perception show STS involvement in AV speech integration. Here we examine whether these findings extend to AV emotion. We used magnetoencephalography to measure the neural responses of participants as they viewed and heard emotionally congruent fear and minimally congruent neutral face and voice stimuli. We demonstrate significant supra-additive responses (i.e., where AV > [unimodal auditory ؉ unimodal visual]) in the posterior STS within the first 250 ms for emotionally congruent AV stimuli. These findings show a role for the STS in processing crossmodal emotive signals.audio-visual emotion ͉ emotional faces ͉ emotional voices ͉ fear ͉ gamma S ome aspects of faces, such as identity, are relatively fixed whereas other aspects, such as facial expression, can change from moment to moment. A highly influential neural model of face perception suggests that the aspects of faces that change visibly (e.g., eye gaze, lip movement, facial expression) are processed by a neural pathway leading to the posterior superior temporal sulcus (STS) (1, 2). However, both lip movement and facial expression are generally accompanied by changing auditory signals. Indeed, in daily life emotion commonly is conveyed through multiple signals involving the face, voice, and body. Although originating from different sensory modalities, these transient emotive signals are perceived and integrated within our social interactions with seemingly minimal effort. It therefore is possible that recognition of emotional expression is an intrinsically crossmodal process and that the sensitivity of the posterior STS to the changeable aspects of faces may extend to voices, as the posterior STS could serve to integrate emotional signals arising from faces and voices (3). During emotion perception, the role of the posterior STS may extend beyond the visual function of perceiving facial emotion to serve a wider purpose related to the crossmodal integration of facial and vocal signals.The STS is a prime candidate for the integration of visual and auditory emotive signals. The STS lies between primary auditory and visual cortices, and studies of audiovisual (AV) speech integration have demonstrated supra-additive responses in the STS to congruent speech stimuli (4, 5). Supra-additivity is a stringent criterion for multisensory integrative regions and is based on the known electrophysiological behavior of signal integration (6, 7). Supra-additivity occurs when the observed multisensory effect exceeds the sum of the unisensory components, i.e., when AV Ͼ [unimodal auditory (A) ϩ unimodal visual (V)]. The purpose of the pr...
l-theanine (γ-glutamylethylamide) is an amino acid found primarily in the green tea plant. This study explored the effects of an l-theanine-based nutrient drink on mood responses to a cognitive stressor. Additional measures included an assessment of cognitive performance and resting state alpha oscillatory activity using magnetoencephalography (MEG). Thirty-four healthy adults aged 18–40 participated in this double-blind, placebo-controlled, balanced crossover study. The primary outcome measure, subjective stress response to a multitasking cognitive stressor, was significantly reduced one hour after administration of the l-theanine drink when compared to placebo. The salivary cortisol response to the stressor was reduced three hours post-dose following active treatment. No treatment-related cognitive performance changes were observed. Resting state alpha oscillatory activity was significantly greater in posterior MEG sensors after active treatment compared to placebo two hours post-dose; however, this effect was only apparent for those higher in trait anxiety. This change in resting state alpha oscillatory activity was not correlated with the change in subjective stress response or the cortisol response, suggesting further research is required to assess the functional relevance of these treatment-related changes in resting alpha activity. These findings further support the anti-stress effects of l-theanine.
Modulation perception has typically been characterized by measuring detection thresholds for sinusoidally amplitude-modulated (SAM) signals. This study uses multicomponent modulations. "Second-order" temporal modulation transfer functions (TMTFs) measure detection thresholds for a sinusoidal modulation of the modulation waveform of a SAM signal [Lorenzi et al., J. Acoust. Soc. Am. 110, 1030-2038 (2001)]. The SAM signal therefore acts as a "carrier" stimulus of frequency fm, and sinusoidal modulation of the SAM signal's modulation depth (at rate f'm) generates two additional components in the modulation spectrum at fm - f'm and fm + f'm. There is no spectral energy at the envelope beat frequency f'm in the modulation spectrum of the "physical" stimulus. In the present study, second-order TMTFs were measured for three listeners when fm was 16, 64, and 256 Hz. The carrier was either a 5-kHz pure tone or a narrow-band noise with center frequency and bandwidth of 5 kHz and 2 Hz, respectively. The narrow-band noise carrier was used to prevent listeners from detecting spectral energy at the beat frequency f'm in the "internal" stimuli's modulation spectrum. The results show that, for the 5-kHz pure-tone carrier, second-order TMTFs are nearly low pass in shape; the overall sensitivity and cutoff frequency measured on these second-order TMTFs increase when fm increases from 16 to 256 Hz. For the 2-Hz-wide narrow-band noise carrier, second-order TMTFs are nearly flat in shape for fm = 16 and 64 Hz, and they show a high-pass segment for fm = 256 Hz. These results suggest that detection of spectral energy at the envelope beat frequency contributes in part to the detection of second-order modulation. This is consistent with the idea that nonlinear mechanisms in the auditory pathway produce an audible distortion component at the envelope beat frequency in the internal modulation spectrum of the sounds.
Northumbria University has developed Northumbria Research Link (NRL) to enable users to access the University's research output. Copyright © and moral rights for items on NRL are retained by the individual author(s) and/or other copyright owners. Single copies of full items can be reproduced, displayed or performed, and given to third parties in any format or medium for personal research or study, educational, or not-for-profit purposes without prior permission or charge, provided the authors, title and full bibliographic details are given, as well as a hyperlink and/or URL to the original metadata page. The content must not be changed in any way. Full items must not be sold commercially in any format or medium without formal permission of the copyright holder. The full policy is available online: http://nrl.northumbria.ac.uk/policies.html This document may differ from the final, published version of the research and has been made available online in accordance with publisher policies. To read and/or cite from the published version of the research, please visit the publisher's website (a subscription may be required.)Interactions between visual and semantic processing during object recognition revealed by modulatory effects of age of acquisition The age of acquisition (AoA) of objects and their names is a powerful determinant of processing speed in adulthood, with early-acquired objects being recognized and named faster than late-acquired objects. Previous research using fMRI . Traces of vocabulary acquisition in the brain: evidence from covert object naming. NeuroImage 33,[958][959][960][961][962][963][964][965][966][967][968] found that AoA modulated the strength of BOLD responses in both occipital and left anterior temporal cortex during object naming. We used magnetoencephalography (MEG) to explore in more detail the nature of the influence of AoA on activity in those two regions. Covert object naming recruited a network within the left hemisphere that is familiar from previous research, including visual, left occipito-temporal, anterior temporal and inferior frontal regions. Region of interest (ROI) analyses found that occipital cortex generated a rapid evoked response (~ 75-200 ms at 0-40 Hz) that peaked at 95 ms but was not modulated by AoA. That response was followed by a complex of later occipital responses that extended from ~ 300 to 850 ms and were stronger to early-than late-acquired items from ~ 325 to 675 ms at 10-20 Hz in the induced rather than the evoked component. Left anterior temporal cortex showed an evoked response that occurred significantly later than the first occipital response (~ 100-400 ms at 0-10 Hz with a peak at 191 ms) and was stronger to early-than late-acquired items from ~ 100 to 300 ms at 2-12 Hz. A later anterior temporal response from ~ 550 to 1050 ms at 5-20 Hz was not modulated by AoA. The results indicate that the initial analysis of object forms in visual cortex is not influenced by AoA. A fastforward sweep of activation from occipital and left anterior temporal cortex t...
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