No Frequency-Specific Effect of Transcranial Random Noise Stimulation on Resting EEG.

BACKGROUND: Transcranial random noise stimulation (tRNS) is a form of noninvasive transcranial electrical stimulation that applies alternating current in various randomized frequencies to the cortex, thereby improving cognitive functioning in multiple domains. However, the precise mechanism of tRNS, as well as its impact on human electroencephalography (EEG), remains unclear. This is partly because most studies have used tRNS in conjunction with a cognitive task, making it difficult to tease apart whether the observed changes in EEG are a result of tRNS, the cognitive task, or their interaction. METHODS: Forty-nine healthy individuals participated in this study and were randomly assigned to active tRNS (n = 24) and sham (n = 25) groups. tRNS was delivered for 20 minutes over Fp1/Fp2 and Oz. Resting-state EEG data were collected before and after either tRNS or sham stimulation. RESULTS: Cluster-based permutation tests using FieldTrip revealed no frequency-specific effect of tRNS on resting-state EEG data across four frequency bands (theta, alpha, beta, gamma). CONCLUSIONS: These observations suggest that tRNS itself does not target or alter specific EEG frequencies. Rather, tRNS most likely interacts with the cognitive task/activity at hand to produce an observable difference in post-tRNS EEG. Positive tRNS-EEG findings from previous studies are also likely to have resulted from the interactive and cognitive activity-dependent nature of tRNS.

Functional blindsight and its diagnosis.

Even when brain scans fail to detect a striate lesion, functional evidence for blindsight can be adduced. In the aftermath of an automobile accident, JK became blind. Results of ophthalmic exams indicated that the blindness must be cortical. Nevertheless, multiple MRI scans failed to detect structural damage to the striate cortex. Prior to the accident JK had been an athlete; after the accident he retained some athletic abilities, arousing suspicions that he might be engaged in fraud. His residual athletic abilities-e.g., hitting a handball or baseball, or catching a Frisbee-coupled with his experienced blindness, suggested blindsight. But due to the apparent absence of striate lesions, we designed a series of tasks for temporal and spatial dimensions in an attempt to detect functional evidence of his disability. Indeed, test results revealed compelling neural evidence that comport with his subjective reports. This spatiotemporal task-related method that includes contrasts with healthy controls, and detailed understanding of the patient's conscious experience, can be generalized for clinical, scientific and forensic investigations of blindsight.

Family favouring effects across intent and outcome-based moral judgements and decisions.

Doing harm is a moral violation, but helping a family member is morally obligatory. In this study, participants encountered this ethical dilemma through stories featuring their sibling (i.e., brother) as either the perpetrator or victim in various moral scenarios. Subsequently, they provided their moral judgements (i.e., moral acceptability and perceived transgression) and made decisions (i.e., willingness and difficulty to disclose what the agent did to the police) regarding the perpetrator. The manipulation of family membership was integrated into the moral scenarios, which were crafted based on whether the perpetrator had malicious intent and whether those intentions resulted in a harmful outcome (i.e., intentional harm, failed attempts to harm, accidental harm, and a harmless/baseline). While we initially expected that individuals would exhibit favouritism towards their brother when harmful intent or outcomes were absent, our findings revealed that both agent/victim identities (brother/stranger) and intent-outcome-based moral scenarios had an additive effect on both measures of moral judgement. This suggests that the family favouring effect was observed across all intent-outcome scenarios, with a slightly more pronounced effect when the brother accidentally harmed a stranger compared to a stranger accidentally harming the brother. Regarding moral decisions, participants demonstrated a willingness to disclose what they witnessed regardless of their familial relationship with the agent or victim, but it was universally perceived as a difficult decision to make. Together, our results underscore the context-specific nature of moral judgements and decisions, emphasising the significant impact of family members when they are involved as moral characters.

Driving Frequency Modulates Correlations Between Executive Functions and Driving Performance: A Driving Simulator Study.

Driving a car requires a complex combination of various cognitive functions (e.g., visual perception, motor control, decision making, and others), and deficits in any of these processes may compromise driving safety. Amongst these, executive functions such as inhibitory control, task switching, and decision-making are important, as they enable drivers to process information from their surroundings and respond appropriately to changing road conditions. Although previous research has focused on laboratory measures of individual executive functions, it remains unclear whether performance on such laboratory tests readily translates to actual on-the-road driving performance, especially since drivers' skill levels can vary widely, based on their driving frequency. To this end, we divided 30 participants into two categories based on their driving frequency (i.e., daily commuter vs. weekend only drivers), and we used three well-known executive functioning tasks (the stop signal task, Iowa gambling task or IGT, and a task-switching test) to see whether scores on these tasks predicted such driving performances and behaviors such as braking time, lane-keeping, speed limit violations, and inter-vehicle distance (e.g., in a driving simulator). Participants went through a follow-lead-car scenario in the driving simulator for 20 minutes and then completed the three executive tasks. We found that stop signal reaction time (SSRT) best predicted driving performance, and remained predictive against driver distraction, as well as variabilities in driving frequency. The IGT predicted speed limit violations in high-frequency drivers, whereas task-switching cost predicted lane keeping performance in low-frequency drivers. Together, these results highlight the importance of driving frequency when considering correlates between executive functions and driving performance and behavior. They also imply that executive tasks better predict driving performance in low-frequency (or inexperienced) drivers, while driver temperament (i.e., impulsiveness as indicated by IGT) better predicted driving performance in high-frequency (or experienced) drivers.

Neuroimmunomodulation of vagus nerve stimulation and the therapeutic implications.

Vagus nerve stimulation (VNS) is a technology that provides electrical stimulation to the cervical vagus nerve and can be applied in the treatment of a wide variety of neuropsychiatric and systemic diseases. VNS exerts its effect by stimulating vagal afferent and efferent fibers, which project upward to the brainstem nuclei and the relayed circuits and downward to the internal organs to influence the autonomic, neuroendocrine, and neuroimmunology systems. The neuroimmunomodulation effect of VNS is mediated through the cholinergic anti-inflammatory pathway that regulates immune cells and decreases pro-inflammatory cytokines. Traditional and non-invasive VNS have Food and Drug Administration (FDA)-approved indications for patients with drug-refractory epilepsy, treatment-refractory major depressive disorders, and headaches. The number of clinical trials and translational studies that explore the therapeutic potentials and mechanisms of VNS is increasing. In this review, we first introduced the anatomical and physiological bases of the vagus nerve and the immunomodulating functions of VNS. We covered studies that investigated the mechanisms of VNS and its therapeutic implications for a spectrum of brain disorders and systemic diseases in the context of neuroimmunomodulation.

The hidden arrow in the FedEx logo: Do we really unconsciously "see" it?

The FedEx logo makes clever use of figure-ground ambiguity to create an "invisible" arrow in the background space between "E" and "x". Most designers believe the hidden arrow can convey an unconscious impression of speed and precision about the FedEx brand, which may influence subsequent behavior. To test this assumption, we designed similar images with hidden arrows to serve as endogenous (but camouflaged) directional cues in a Posner's orienting task, where a cueing effect would suggest subliminal processing of the hidden arrow. Overall, we observed no cue congruency effect, unless the arrow is explicitly highlighted (Experiment 4). However, there was a general effect of prior knowledge: when people were under pressure to suppress background information, those who knew about the arrow could do so faster in all congruence conditions (i.e., neutral, congruent, incongruent), although they fail to report seeing the arrow during the experiment. This was true in participants from North America who had heard of the FedEx arrow before (Experiment 1 & 3), and also in our Taiwanese sample who were just informed of such design (Experiment 2). These results can be well explained by the Biased Competition Model in figure-ground research, and together suggest: (1) people do not unconsciously perceive the FedEx arrow, at least not enough to exhibit a cueing effect in attention, but (2) knowing about the arrow can fundamentally change the way we visually process these negative-space logos in the future, making people react faster to images with negative space regardless of the hidden content.

Gamma sensory entrainment for cognitive improvement in neurodegenerative diseases: opportunities and challenges ahead.

Neural oscillations have been categorized into various frequency bands that are mechanistically associated with different cognitive functions. Specifically, the gamma band frequency is widely implicated to be involved in a wide range of cognitive processes. As such, decreased gamma oscillation has been associated with cognitive declines in neurological diseases, such as memory dysfunction in Alzheimer's disease (AD). Recently, studies have attempted to artificially induce gamma oscillations by using 40 Hz sensory entrainment stimulation. These studies reported attenuation of amyloid load, hyper-phosphorylation of tau protein, and improvement in overall cognition in both AD patients and mouse models. In this review, we discuss the advancements in the use of sensory stimulation in animal models of AD and as a therapeutic strategy in AD patients. We also discuss future opportunities, as well as challenges, for using such strategies in other neurodegenerative and neuropsychiatric diseases.

Thalamocortical coherence predicts persistent postconcussive symptoms.

The pathogenetic mechanism of persistent post-concussive symptoms (PCS) following concussion remains unclear. Thalamic damage is known to play a role in PCS prolongation while the evidence and biomarkers that trigger persistent PCS have never been elucidated. We collected longitudinal neuroimaging and behavior data from patients and rodents after concussion, complemented with rodents' histological staining data, to unravel the early biomarkers of persistent PCS. Diffusion tensor imaging (DTI) were acquired to investigated the thalamic damage, while quantitative thalamocortical coherence was derived through resting-state functional MRI for evaluating thalamocortical functioning and predicting long-term behavioral outcome. Patients with prolonged symptoms showed abnormal DTI-derived indices at the boundaries of bilateral thalami (peri-thalamic regions). Both patients and rats with persistent symptoms demonstrated enhanced thalamocortical coherence between different thalamocortical circuits, which disrupted thalamocortical multifunctionality. In rodents, the persistent DTI abnormalities were validated in thalamic reticular nucleus (TRN) through immunohistochemistry, and correlated with enhanced thalamocortical coherence. Strong predictive power of these coherence biomarkers for long-term PCS was also validated using another patient cohort. Postconcussive events may begin with persistent TRN injury, followed by disrupted thalamocortical coherence and prolonged PCS. Functional MRI-based coherence measures can be surrogate biomarkers for early prediction of long-term PCS.

Comparative effectiveness of psychotherapies in adults with posttraumatic stress disorder: a network meta-analysis of randomised controlled trials.

BACKGROUND: Evidence on the long-term comparative effectiveness of posttraumatic stress disorder (PTSD) psychotherapies in adults remains unknown. Therefore, we performed an extensive network meta-analysis of randomised controlled trials (RCTs) to determine the comparative effectiveness of psychotherapies for people diagnosed with PTSD. METHODS: A comprehensive search was conducted in Cochrane library, Embase, Medline-OVID, PubMed, Scopus, and Psych-Info until March 2021. Studies on the effectiveness of cognitive processing therapy (CPT), cognitive therapy (CT), eye movement desensitisation reprocessing (EMDR), narrative exposure therapy (NET), prolonged exposure (PE), cognitive behavioural therapy (CBT), present-centred therapy (PCT), brief eclectic psychotherapies (BEP), psychodynamic therapy (PDT) or combination therapies compared to no treatment (NT) or treatment as usual (TAU) in adults with PTSD were included. Frequentist and Bayesian approaches were used for analysis in R-software. RESULTS: We included 98 RCTs with 5567 participants from 18 897 studies. CPT, EMDR, CT, NET, PE, CBT, and PCT were significant to reduce PTSD symptoms (SMD range: -1.53 to -0.75; Certainty: very low to high) at immediate post-treatment and ranked accordingly. Longitudinal analysis found EMDR (1.02) and CPT (0.85) as the significant therapies with large effect size in short-term and long-term follow-up, respectively. NET and CPT showed higher proportion of loss of PTSD diagnosis (RR range: 5.51-3.45) while there were no significant psychotherapies for retention rate compared to NT. CONCLUSIONS: Our findings provide evidence for improving current guidelines and informing clinical decision-making for PTSD management. However, the best PTSD treatment plan should be tailored to patients' needs, characteristics, and clinician expertise. REGISTRATION: PROSPERO CRD42020162143.

Hip fracture or not? The reversed prevalence effect among non-experts' diagnosis.

Despite numerous investigations of the prevalence effect on medical image perception, little research has been done to examine the effect of expertise, and its possible interaction with prevalence. In this study, medical practitioners were instructed to detect the presence of hip fracture in 50 X-ray images with either high prevalence (Nsignal = 40) or low prevalence (Nsignal = 10). Results showed that compared to novices (e.g., pediatricians, dentists, neurologists), the manipulation of prevalence shifted participant's criteria in a different direction for experts who perform hip fracture diagnosis on a daily basis. That is, when prevalence rate is low (pfracture-present = 0.2), experts held more conservative criteria in answering "fracture-present," whereas novices were more likely to believe there was fracture. Importantly, participants' detection discriminability did not vary by the prevalence condition. In addition, all participants were more conservative with "fracture-present" responses when task difficulty increased. We suspect the apparent opposite criteria shift between experts and novices may have come from medical training that made novices to believe that a miss would result in larger cost compared to false positive, or because they failed to update their prior belief about the signal prevalence in the task, both would suggest that novices and experts may have different beliefs in placing the optimal strategy in the hip fracture diagnosis. Our work can contribute to medical education training as well as other applied clinical diagnosis that aims to mitigate the prevalence effect.

Taking Conceptual Issues Really Seriously: One Next Step for the Cognitive Science of Consciousness.

In this letter we focus on the cognitive science of consciousness. The general message is that, while this interdisciplinary area has made much progress in recent years, there is a tendency of downplaying conceptual issues, and therefore underestimating the difficulties of various problems. We briefly focus on a few prominent examples only, due to the space limit, but the general message should be clear: this recent tendency can be problematic for the progress of the consciousness branch of cognitive sciences.

Academy of Medicine, Singapore clinical guideline on the use of sedation by non-anaesthesiologists during gastrointestinal endoscopy in the hospital setting.

INTRODUCTION: In Singapore, non-anaesthesiologists generally administer sedation during gastrointestinal endoscopy. The drugs used for sedation in hospital endoscopy centres now include propofol in addition to benzodiazepines and opiates. The requirements for peri-procedural monitoring and discharge protocols have also evolved. There is a need to develop an evidence-based clinical guideline on the safe and effective use of sedation by non-anaesthesiologists during gastrointestinal endoscopy in the hospital setting. METHODS: The Academy of Medicine, Singapore appointed an expert workgroup comprising 18 gastroenterologists, general surgeons and anaesthesiologists to develop guidelines on the use of sedation during gastrointestinal endoscopy. The workgroup formulated clinical questions related to different aspects of endoscopic sedation, conducted a relevant literature search, adopted Grading of Recommendations, Assessment, Development and Evaluation (GRADE) methodology and developed recommendations by consensus using a modified Delphi process. RESULTS: The workgroup made 16 recommendations encompassing 7 areas: (1) purpose of sedation, benefits and disadvantages of sedation during gastrointestinal endoscopy; (2) pre-procedural assessment, preparation and consent taking for sedation; (3) Efficacy and safety of drugs used in sedation; (4) the role of anaesthesiologist administered sedation during gastrointestinal endoscopy; (5) performance of sedation; (6) post-sedation care and discharge after sedation; and (7) training in sedation for gastrointestinal endoscopy for non-anaesthesiologists. CONCLUSION: These recommendations serve to guide clinical practice during sedation for gastrointestinal endoscopy by non-anaesthesiologists in the hospital setting.

Role of the frontal eye field in human microsaccade responses: A TMS study.

Microsaccade is a type of fixational eye movements that is modulated by various sensory and cognitive processes, and impact our visual perception. Although studies in monkeys have demonstrated a functional role for the superior colliculus and frontal eye field (FEF) in controlling microsaccades, our understanding of the neural mechanisms underlying the generation of microsaccades is still limited. By applying continuous theta-burst stimulation (cTBS) over the right FEF and the vertex, we investigated the role of the FEF in generating human microsaccade responses evoked by salient stimuli or by changes in background luminance. We observed higher microsaccade rates prior to target appearance, and larger rebound in microsaccade occurrence following salient stimuli, when disruptive cTBS was applied over FEF compared to vertex stimulation. Moreover, the microsaccade direction modulation after changes in background luminance was disrupted with FEF stimulation. Together, our results constitute the first evidence of FEF modulation in human microsaccade responses.

Effect of Non-canonical Spatial Symmetry on Subitizing.

Subitizing refers to ability of people to accurately and effortlessly enumerate a small number of items, with a capacity around four elements. Previous research showed that "canonical" organizations, such as familiar layouts on a dice, can readily improve subitizing performance of people. However, almost all canonical shapes found in the world are also highly symmetrical; therefore, it is unclear whether previously reported facilitative effect of canonical organization is really due to canonicality, or simply driven by spatial symmetry. Here, we investigated the possible effect of symmetry on subitizing by using symmetrical, yet non-canonical, shape structures. These symmetrical layouts were compared with highly controlled random patterns (Experiment 1), as well as fully random and canonical patterns (Experiment 2). Our results showed that symmetry facilitates subitizing performance, but only at set size of 6, suggesting that the effect is insufficient to improve performance of people in the lower or upper range. This was also true, although weaker, in reaction time (RT), error distance measures, and Weber Fractions. On the other hand, canonical layouts produced faster and more accurate subitizing performances across multiple set sizes. We conclude that, although previous findings mixed symmetry in their canonical shapes, their findings on shape canonicality cannot be explained by symmetry alone. We also propose that our symmetrical and canonical results are best explained by the "groupitizing" and pattern recognition accounts, respectively.

Frontoparietal theta tACS nonselectively enhances encoding, maintenance, and retrieval stages in visuospatial working memory.

Neurobiological and cognitive evidence suggests that working memory is processed through three distinctive and well-characterized phases: encoding, maintenance, and retrieval. Several studies have reported that applying theta transcranial alternating current stimulation (tACS) to the right prefrontal and parietal cortices can significantly improve visual working memory performance. However, it remains unclear whether the facilitative effect of tACS on visual working memory is due to a domain-general or stage-specific process. In this study, we combined pre-task right frontoparietal theta tACS (6 Hz, 15 min) with a stage-specific change detection paradigm that provided retro-cues during various stages of working memory. This stage-specific tagging via the use of retro-cues enabled us to probe whether theta tACS would create a nonspecific/additive effect that is equal in magnitude across all cognitive stages or would create a stage-specific effect that is interactive with the retro-cue in a particular stage (e.g., maintenance, retrieval). We observed significant retro-cue and theta tACS effects on visual working memory performance, but no interaction between them. This finding suggests that the aforementioned two factors can facilitate visual working memory processing independently in an additive manner. Furthermore, low-performers benefited more from tACS, and their VWM deficit seemed to have originated from the second half of the memory retention stage, which possibly suggests faster memory decay as the key to poor VWM performance. Together, we conclude that frontoparietal theta tACS likely creates a domain-general boost in visual attention, which in turn benefits overall visual working memory processes that are not specific to the information maintenance or retrieval stages.

Frontoparietal Beta Amplitude Modulation and its Interareal Cross-frequency Coupling in Visual Working Memory.

Visual working memory (VWM) relies on sustained neural activities that code information via various oscillatory frequencies. Previous studies, however, have emphasized time-frequency power changes, while overlooking the possibility that rhythmic amplitude variations can also code frequency-specific VWM information in a completely different dimension. Here, we employed the recently-developed Holo-Hilbert spectral analysis to characterize such nonlinear amplitude modulation(s) (AM) underlying VWM in the frontoparietal systems. We found that the strength of AM in mid-frontal beta and gamma oscillations during late VWM maintenance and VWM retrieval correlated with people's VWM performance. When behavioral performance was altered with transcranial electric stimulation, AM power changes during late VWM maintenance in beta, but not gamma, tracked participants' VWM variations. This beta AM likely codes information by varying its amplitude in theta period for long-range propagation, as our connectivity analysis revealed that interareal theta-beta couplings-bidirectional between mid-frontal and right-parietal during VWM maintenance and unidirectional from right-parietal to left-middle-occipital during late VWM maintenance and retrieval-underpins VWM performance and individual differences.

The effect of visual statistical learning in RSVP: Implicit learning or stream location artifact?

Visual statistical learning (VSL) occurs when participants are exposed to spatially or temporally ordered stimuli, and become increasingly sensitive to them without explicitly realizing the hidden regularities. In the temporal domain of VSL, participants are usually exposed to shape-triplets, followed by the use of familiarity judgments and recognition tasks to directly probe VSL. Other methods, such as the rapid serial visual presentation (RSVP) task, indirectly probe the learning of temporal sequences, and provide evidence of learning within the triplets. Despite the RSVP's success, however, previous implementations of the RSVP task have only pseudorandomized the triplets to form the test sequence, such that the task permits only two stream locations for a given target shape (belonging to a certain within-triplet position), out of six available locations. These fixed locations may result in confounded response time (RT) findings and potentially lead to an overestimation of a weak (or nonexistent) VSL effect. In this study, we conduct 4 experiments and show that the previously reported VSL effect in RSVP is eliminated when the RSVP stream is fully counterbalanced (Experiment 1), and resurfaces again when the RSVP stream returns to its original pseudorandomized design (Experiment 2). Importantly, in both, we observe a "stream location effect," where RT gradually becomes faster to reflect the hazard rate of target appearance, which may have been the factor driving previously reported VSL effects. Follow-up experiments show that results from Experiment 1 are not due to the absence of implicit learning (Experiment 3), although the stream location effect can occur without any learning, suggesting that it is something inherent to the RSVP task (Experiment 4). Together, these results identify an influential effect, the stream location effect, inherently present in the RSVP task, and show how misinforming the RSVP task can be, when not used with properly controlled parameters, and demand a reexamination of the effects found in previous studies which could have been the effect of detection stream locations, misconstrued as VSL. (PsycInfo Database Record (c) 2021 APA, all rights reserved).