A temporal model for early vision that explains detection thresholds for light pulses on flickering backgrounds

A model is presented for the early (retinal) stages of temporal processing of light inputs in the visual system. The model consists of a sequence of three adaptation processes, with two instantaneous nonlinearities in between. The three adaptation processes are, in order of processing of the light input: a divisive light adaptation, a subtractive light adaptation, and a contrast gain control. Divisive light adaptation is modeled by two gain controls. The first of these is a fast feedback loop with square-root behavior, the second a slow feedback loop with logarithm-like behavior. This can explain several aspects of the temporal behavior of photoreceptor outputs. Subtractive light adaptation is modeled by a high-pass filter equivalent to a fractional differentiation, and it can explain the attenuation of low frequencies observed in ganglion cell responses. Contrast gain control in the model is fast, and can explain the decreased detectability of test signals that are superimposed on dynamic backgrounds. We determine psychophysical detection thresholds for brief test pulses that are presented on flickering backgrounds, for a wide range of temporal modulation frequencies of these backgrounds. The model can explain the psychophysical data for the full range of modulation frequencies tested, as well as detection thresholds obtained for test pulses on backgrounds with increment and decrement steps in intensity.

Losing sight of Luck: Automatic approach tendencies toward gambling cues in Canadian moderate- to high-risk gamblers – A replication study

Evidence for approach bias tendencies to underly automatic behavioural impulses towards seeking out gambling activities in the presence of appetitive salient cues was first shown by Boffo et al. (2018) in a Dutch sample. Relative to non-problem gamblers, moderate-to-high-risk gamblers demonstrated stronger approach tendencies towards gambling-related stimuli compared with neutral ones. Moreover, gambling approach bias was associated with past-month gambling behaviour and predictive of gambling activity persistence over time. The current study aimed to replicate these findings within a Canadian sample evaluating the concurrent and longitudinal correlates of gambling approach bias. The study was conducted online, available throughout Canada. Twenty-seven non-treatment-seeking moderate-to-high-risk gamblers and 26 non-problem gamblers community-recruited via multiple channels (i.e., internet and newspaper advertisements, land-based flyers, and university recruitment portals). Participants completed two online assessment sessions 6-months apart. Each session included (1) self-report measures of gambling behaviour (frequency, duration, and expenditure), (2) self-report assessment of problem gambling severity (PGSI), and (3) a gambling approach-avoidance task, utilising culturally relevant stimuli tailored to individual gambling habits. However, our study failed to replicate Boffo et al. (2018) findings in a Canadian sample. Relative to non-problem gamblers, moderate-to-high-risk gamblers did not exhibit greater approach bias tendencies towards gambling-related stimuli compared to neutral stimuli. Moreover, gambling approach bias was not predictive of prospective gambling behaviour (frequency, duration, or expenditure) or severity of gambling problems. Reported results do not provide evidence for approach tendencies contributing to problematic gambling behaviour in a Canadian sample of moderate-to-high-risk gamblers compared to non-problematic gambler controls. Further replications on the topic are needed. Future research should evaluate approach tendencies within the gambling context, considering the potential impact of task reliability to assess approach bias in light of individual gambling modality preferences.</p

Exploring the emotional dynamics of subclinically depressed individuals with and without anhedonia:An experience sampling study

Background: Anhedonia has been linked to worse prognosis of depression. The present study aimed to construct personalized models to elucidate the emotional dynamics of subclinically depressed individuals with versus without symptoms of anhedonia. Methods: Matched subclinically depressed individuals with and without symptoms of anhedonia (N = 40) of the HowNutsAreTheDutch sample completed three experience sampling methodology assessments per day for 30 days. For each individual, the impact of physical activity, stress experience, and high/low arousal PA/NA on each other was estimated through automated impulse response function analysis (IRF). These individual IRF associations were combined to compare anhedonic versus non-anhedonic individuals. Results: Physical activity had low impact on affect in both groups. In non-anhedonic individuals, stress experience increased NA and decreased PA and physical activity more strongly. In anhedonic individuals, PA high arousal showed a diminished favorable impact on affect (increasing NA/stress experience, decreasing PA/physical activity). Finally, large heterogeneity in the personalized models of emotional dynamics were found. Limitations: Stress experience was measured indirectly by assessing level of distress; the timeframe in between measurements was relatively long with 6 h; and only information on one of the two hallmarks of anhedonia, loss of interest, was gathered. Conclusions: Our results suggest different pathways of emotional dynamics underlie depressive symptomatology. Subclinically depressed individuals with anhedonic complaints are more strongly characterized by diminished favorable impact of PA high arousal and heightened NA reactivity, whereas subclinically depressed individuals without these anhedonic complaints seem more characterized by heightened stress reactivity. The automatically generated personalized models may offer patient-specific insights in emotional dynamics, which may show clinical relevance

Vacuum structure of CP^N sigma models at theta=pi

We show that parity symmetry is not spontaneously broken in the CP^N sigma model for any value of N when the coefficient of the $\theta$--term becomes $\theta=\pi$ (mod $2\pi$). The result follows from a non-perturbative analysis of the nodal structure of the vacuum functional $\psi_0(z)$. The dynamical role of sphalerons turns out to be very important for the argument. The result introduces severe constraints on the possible critical behavior of the models at $\theta=\pi$ (mod $2\pi$).Comment: 8 pages, revtex, to appear in Phys. Rev. Let

Ecological momentary assessment as a clinical tool in psychiatry:promises, pitfalls, and possibilities

Achtergrond: Ecological momentary assessment (EMA) is een veelbelovende methode om meer inzicht te krijgen in het dagelijks leven van mensen met psychische problemen. Met EMA houden patiënten meermaals per dag hun symptomen, emoties, (sociale) activiteiten en gebeurtenissen bij. Door statistische methodieken, zoals netwerkanalyse, zou EMA-feedback nieuwe inzichten kunnen opleveren in de psychiatrische zorg.Doel: De belofte, valkuilen en mogelijkheden van EMA en netwerkanalyse voor de psychiatrische zorg onderzoeken.Methode: We gebruikten empirische netwerkstudies, reviews en kwalitatief onderzoek om de stand van onderzoek en de perspectieven van patiënten en behandelaars op EMA en netwerkanalyse in kaart te brengen. Daarnaast bespreken we een studie waarbij 20 patiënten met een bipolaire stoornis 4 maanden lang 5 maal per dag EMA-dagboeken invulden binnen hun behandeling.Resultaten: Studies naar netwerkanalyse lieten inconsistente bevindingen zien. Kwalitatief onderzoek wees uit dat patiënten met bipolaire stoornis en hun behandelaars de meerwaarde van EMA voor de zorg zien, met name in het versterken van inzicht en eigen regie. Tegelijkertijd vonden sommigen EMA belastend. Integratie van EMA in de zorg vereist personalisatie en goede aansluiting met bestaande behandelmethoden.Conclusie: EMA heeft toegevoegde waarde voor de psychiatrische zorg, mits het zorgvuldig ingezet wordt.BACKGROUND: Ecological momentary assessment (EMA) is a promising method to gain insight into the daily lives of people with mental disorders. EMA can be used to monitor mood, symptoms, and experiences multiple times per day. Using advanced statistical methods, such as network analysis, as EMA feedback might result in novel insights that are relevant to psychiatric care. AIM: To investigate the promise, pitfalls, and possibilities of EMA and network analysis for psychiatric care. METHOD: Empirical network studies, reviews, and qualitative research were employed to investigate the state of research and the perspectives of patients and clinicians on EMA and network analysis. Furthermore, an empirical study will be discussed, in which twenty patients with bipolar disorders completed five EMA diaries per day for four months within treatment. RESULTS: Studies using network analysis demonstrated conflicting results. Qualitative research indicated that bipolar patients and clinicians are aware of the added benefit of EMA for psychiatric care, especially for improving insight and self-management. At the same time, EMA was seen as burdensome. Personalization and integration with existing treatment protocols emerged as necessary requirements for adequate implementation of EMA in psychiatric care. CONCLUSION: EMA can have added value for psychiatric care, provided it is adequately implemented. BACKGROUND: Ecological momentary assessment (EMA) is a promising method to gain insight into the daily lives of people with mental disorders. EMA can be used to monitor mood, symptoms, and experiences multiple times per day. Using advanced statistical methods, such as network analysis, as EMA feedback might result in novel insights that are relevant to psychiatric care. AIM: To investigate the promise, pitfalls, and possibilities of EMA and network analysis for psychiatric care. METHOD: Empirical network studies, reviews, and qualitative research were employed to investigate the state of research and the perspectives of patients and clinicians on EMA and network analysis. Furthermore, an empirical study will be discussed, in which twenty patients with bipolar disorders completed five EMA diaries per day for four months within treatment. RESULTS: Studies using network analysis demonstrated conflicting results. Qualitative research indicated that bipolar patients and clinicians are aware of the added benefit of EMA for psychiatric care, especially for improving insight and self-management. At the same time, EMA was seen as burdensome. Personalization and integration with existing treatment protocols emerged as necessary requirements for adequate implementation of EMA in psychiatric care. CONCLUSION: EMA can have added value for psychiatric care, provided it is adequately implemented.</p