The Inter-Subject Correlation of EEG in Response to Naturalistic Stimuli

Inter-subject correlation is a measure of the similarity of the brain activity of a group of people as they respond to the same naturalistic stimulus, typically a story or video, meant to simulate a real world experience. This thesis tests the hypothesis that the correlation of the brain responses of a group of people is indicative of stimulus engagement. The rationale is that the content of the stimulus drives brain activity in a consistent manner, while internal thoughts are divergent and result in uncorrelated activity. The inter-subject correlation (ISC) of neural responses have previously been assessed with fMRI, EEG, and MEG. Here, EEG will assess ISC, thereby examining the correlation of the early responses to a stimulus. Engagement has been examined previously with self-report assessments of interest. These ratings are noisy, subject to bias, and do not measure how engagement evolves over time. In this thesis, engagement is defined as a commitment to devote a scarce resource, such as attention or time, to a stimulus. In the experiment presented here, subjects were allowed limited time with the stimuli, thus forcing them to engage with the content they determined to be most compelling. This behavioral metric strongly correlated with ISC of the EEG, thus validating it as a measure of neural engagement. Interestingly, higher ISC was also indicative of a shared perception of the passage of time across subjects. This suggests that when people are engaged with a stimulus, their perception of time is also driven by that stimulus, rather than by an internal sense of time. If people are more engaged at the time of encoding, it is likely that they will better remember their experiences. Memory was therefore assessed three weeks after subjects heard salient emotional narratives. Individuals whose EEG responses during the stories correlated more strongly with their peers had stronger memories of the events in the stories. ISC was also tested as a predictor of retention in the context of online educational videos. Again, the similarity between each subject’s brain activity and that of his or her peers corresponded with memory for factual information in a subsequent test. It is possible that people with different backgrounds do not engage with the world in similar ways, and their neural responses will therefore correlate more strongly with people who are most similar to them. To address this notion, ISC was compared across the dimensions of age and gender. In a population with ages ranging from 5 - 44 years old, ISC weakens with age and is stronger in males than it is in females. This result is consistent with the idea that age and experience are marked by an increase in the repertoire of neural representations. Adults may therefore have more variable interpretations that mediate their sensory responses to stimuli. Alternatively, if ISC is truly assessing engagement in this context, the result may demonstrate that adults are less susceptible to the influence of outside stimuli since they have more powerful internal voices that distract them. Whichever the ultimate reason for this change, the gender disparity may also be related to a developmental difference because the deviation between males and females in ISC is strongest in young ages, a period when anatomical findings show that young males are less neurally mature than young females. Although ISC is implicated in fundamental processes such as engagement, memory, and development, the neural underpinnings of this signal are unclear. The spatial distribution of the EEG signal that drives ISC appears similar on the surface of the scalp across stimuli with different narrative content, and between different stimulus modalities. The similarity of the topography of correlated activity across sensory modalities may indicate that this activity is supramodal and is therefore generated by a region that is impervious to the stimulus modality. To assess ISC’s dependence on stimulus modality and stimulus type, the modulation of ISC was compared with the fMRI BOLD responses to the same stimuli. This analysis revealed that ISC is mostly modulated by sensory regions, and that the extent of the regions involved depends on the content of the stimulus. These areas, which are largely driven by immediate processing of the stimulus at a fast timescale, are therefore implicated in higher-level behaviors such as engagement and memory

Memorable Audiovisual Narratives Synchronize Sensory and Supramodal Neural Responses

Our brains integrate information across sensory modalities to generate perceptual experiences and form memories. However, it is difficult to determine the conditions under which multisensory stimulation will benefit or hinder the retrieval of everyday experiences. We hypothesized that the determining factor is the reliability of information processing during stimulus presentation, which can be measured through intersubject correlation of stimulus-evoked activity. We therefore presented biographical auditory narratives and visual animations to 72 human subjects visually, auditorily, or combined, while neural activity was recorded using electroencephalography. Memory for the narrated information, contained in the auditory stream, was tested 3 weeks later. While the visual stimulus alone led to no meaningful retrieval, this related stimulus improved memory when it was combined with the story, even when it was temporally incongruent with the audio. Further, individuals with better subsequent memory elicited neural responses during encoding that were more correlated with their peers. Surprisingly, portions of this predictive synchronized activity were present regardless of the sensory modality of the stimulus. These data suggest that the strength of sensory and supramodal activity is predictive of memory performance after 3 weeks, and that neural synchrony may explain the mnemonic benefit of the functionally uninformative visual context observed for these real-world stimuli

Engaging narratives evoke similar neural activity and lead to similar time perception

It is said that we lose track of time - that “time flies” - when we are engrossed in a story. How does engagement with the story cause this distorted perception of time, and what are its neural correlates? People commit both time and attentional resources to an engaging stimulus. For narrative videos, attentional engagement can be represented as the level of similarity between the electroencephalographic responses of different viewers. Here we show that this measure of neural engagement predicted the duration of time that viewers were willing to commit to narrative videos. Contrary to popular wisdom, engagement did not distort the average perception of time duration. Rather, more similar brain responses resulted in a more uniform perception of time across viewers. These findings suggest that by capturing the attention of an audience, narrative videos bring both neural processing and the subjective perception of time into synchrony

The Variability of Neural Responses to Naturalistic Videos Change with Age and Sex

Neural development is generally marked by an increase in the efficiency and diversity of neural processes. In a large sample (n=114) of human children and adults with ages ranging from 5 to 44 yr, we investigated the neural responses to naturalistic video stimuli. Videos from both real-life classroom settings and Hollywood feature films were used to probe different aspects of attention and engagement. For all stimuli, older ages were marked by more variable neural responses. Variability was assessed by the intersubject correlation of evoked electroencephalographic responses. Young males also had less-variable responses than young females. These results were replicated in an independent cohort (n = 303). When interpreted in the context of neural maturation, we conclude that neural function becomes more variable with maturity, at least during the passive viewing of real-world stimuli.Fil: Petroni, Agustín. City University of New York; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Cohen, Samantha S.. City University of New York; Estados UnidosFil: Ai, Lei. City University of New York; Estados UnidosFil: Langer, Nicolas. City University of New York; Estados UnidosFil: Henin, Simon. City University of New York; Estados UnidosFil: Vanderwal, Tamara. City University of New York; Estados UnidosFil: Milham, Michael P.. City University of New York; Estados UnidosFil: Parra, Lucas C.. City University of New York; Estados Unido

The Variability of Neural Responses to Naturalistic Videos Change with Age and Sex

Neural development is generally marked by an increase in the efficiency and diversity of neural processes. In a large sample ( = 114) of human children and adults with ages ranging from 5 to 44 yr, we investigated the neural responses to naturalistic video stimuli. Videos from both real-life classroom settings and Hollywood feature films were used to probe different aspects of attention and engagement. For all stimuli, older ages were marked by more variable neural responses. Variability was assessed by the intersubject correlation of evoked electroencephalographic responses. Young males also had less-variable responses than young females. These results were replicated in an independent cohort ( = 303). When interpreted in the context of neural maturation, we conclude that neural function becomes more variable with maturity, at least during the passive viewing of real-world stimuli

Perceived barriers and facilitators to positive therapeutic change for people with intellectual disabilities: client, carer and clinical psychologist perspectives

Studies have highlighted successful outcomes of psychological therapies for people with intellectual disabilities. However, processes underlying these outcomes are uncertain. Thematic analysis was used to explore the perceptions of three clinical psychologists, six clients and six carers of barriers and facilitators to therapeutic change for people with intellectual disabilities. Six themes were identified relating to: what the client brings as an individual and with regard to their wider system; therapy factors, including the therapeutic relationship and adaptations; psychologists acting as a ‘mental health GP’ to coordinate care; systemic dependency; and the concept of the revolving door in intellectual disability services. The influence of barriers and facilitators to change is complex, with facilitators overcoming barriers and yet simultaneously creating more barriers. Given their potential impact on the psychologists’ roles and access to therapy for people with intellectual disabilities, findings suggest these factors should be formulated as part of the therapeutic process

Incidence, Patterns, and Associations Between Dual-Antiplatelet Therapy Cessation and Risk for Adverse Events Among Patients With and Without Diabetes Mellitus Receiving Drug-Eluting Stents: Results From the PARIS Registry.

OBJECTIVES: The aim of this study was to examine the frequency and clinical impact of different cessation patterns of dual-antiplatelet therapy (DAPT) after percutaneous coronary intervention with drug-eluting stents among patients with and those without diabetes mellitus (DM). BACKGROUND: Early DAPT suspension after percutaneous coronary intervention increases the risk for major adverse cardiac events. However, temporal variability in risk and relation to DAPT cessation patterns among patients with DM remain unclear. METHODS: Using data from the PARIS (Patterns of Non-Adherence to Anti-Platelet Regimens in Stented Patients) registry, 1,430 patients with DM (34%) and 2,777 without DM (66%) treated with drug-eluting stents were identified. DAPT cessation modes were classified as temporary interruption (<14 days), disruption because of bleeding or poor compliance, and physician-recommended discontinuation. RESULTS: During 2-year follow-up, DM was associated with an increased risk for thrombotic events but a similar risk for bleeding. The cumulative incidence of DAPT cessation was significantly lower in patients with versus those without DM (50.1% vs. 55.4%; p < 0.01), driven largely by less frequent physician-guided discontinuation beyond 1 year. In contrast, 2-year rates of interruption and disruption were similar between groups. When DAPT was interrupted or discontinued under physician guidance, the risk for major adverse cardiac events was unchanged compared with patients with DM on uninterrupted DAPT. Conversely, when DAPT was disrupted, the risk for major adverse cardiac events increased compared with uninterrupted DAPT, regardless of diabetic status, with no evidence of statistical interaction. CONCLUSIONS: DAPT cessation patterns vary according to diabetic status, with less frequent physician-guided discontinuation among patients with DM. The presence of DM does not emerge as a modifier of cardiovascular risk after DAPT cessation

Tracking Official Development Assistance for Reproductive Health in Conflict-Affected Countries

Preeti Patel and colleagues report inequity in the disbursement of official development assistance for reproductive health between countries affected by conflict and those unaffected

Effect of bilberry juice on indices of muscle damage and inflammation in runners completing a half-marathon: a randomised, placebo-controlled trial.

Background: Emerging evidence indicates that fruits rich in polyphenols may attenuate exercise-induced muscle damage and associated markers of inflammation and soreness. This study was conducted to determine whether bilberry juice (BJ), which is particularly rich in polyphenols, reduces markers of muscle damage in runners completing a half marathon. Methods: A total of 21 recreationally trained runners (age 30.9 ± 10.4 y; mass 71.6 ± 11.0 kg; M=16; F=5) were recruited to a single blind, randomised, placebo-controlled, parallel study. Participants were block randomised to consume 2 x 200 ml of BJ or energy-matched control drink (PLA) for 5 d before the Sheffield Half Marathon, on race day, and for 2 days post-race. Measurements of delayed onset muscle soreness (DOMS), muscle damage (creatine kinase; CK) and inflammation (c-reactive protein ; CRP) were taken at baseline, pre-race, post-race, 24 h post-race and 48 h post-race. The effect of treatment on outcome measures was analysed using magnitude-based inferences based on data from 19 participants; 2 participants were excluded from the analyses because they did not provide samples for all time points. Results: The half marathon caused elevations in DOMS, CRP and CK. BJ had a possibly harmful effect on DOMS from pre-race to immediately post-race (11.6%, 90% CI ± 14.7%), a likely harmful effect on CRP from pre-race to 24 h post-race (mean difference ES 0.56, 90% CI ± 0.72) and a possibly harmful effect on CRP from pre-race to 48 h post-race (ES 0.12, 90% CI ± 0.69). At other time points, the differences between the BJ and PLA groups in DOMS and CRP were unclear, possibly trivial or likely trivial. Differences in the changes in CK between BJ and PLA were unclear at every time point other than from baseline to pre-race, where BJ had a possibly harmful effect on reducing muscle damage (ES 0.23, 90% CI ± 0.57). Conclusion: Despite being a rich source of antioxidant and anti-inflammatory phytochemicals, BJ evoked small to moderate increases in exercise-induced DOMS and CRP. Further larger studies are required to confirm these unexpected preliminary results