Self-initiation enhances perceptual processing of auditory stimuli in an online study.

Understanding how the brain incorporates sensory and motor information will enable better theory building on human perception and behavior. In this study, we aimed to estimate the influence of predictive mechanisms on the magnitude and variability of sensory attenuation in two online samples. After the presentation of a visual cue stimulus, participants (Experiment 1: N = 224, Experiment 2: N = 84) compared the loudness of two consecutive tones in a two-alternative forced-choice task. In Experiment 1, the first tone was either self-initiated or not; in Experiment 2, the second tone was either self-initiated or not (active and passive condition, respectively). We further manipulated identity prediction (i.e., the congruence of pre-learned cue-sound combinations; congruent vs. incongruent), and the duration of the onset delay (to account for effects of attentional differences between the passive and active condition, 50 ms vs. 0 ms). We critically discuss our results within the framework of both classical (i.e., motor-based forward models) and contemporary approaches (i.e., predictive processing framework). Contrary to our preregistered hypothesis, we observed enhanced perceptual processing, instead of attenuation, for self-initiated auditory sensory input. Further, our results reveal an effect of fixed sound delays on the processing of motor and non-motor-based predictive information, and may point to according shifts in attention, leading to a perceptual bias. These results might best be captured by a hybrid explanatory model, combining predictions based on self-initiated motor action with a global predictive mechanism.

The impact of affective states and traits on perceptual stability during binocular rivalry.

Affective states and traits have been associated with different measures of perceptual stability during binocular rivalry. Diverging approaches to measuring perceptual stability as well as to examination of the role of affective variables have contributed to an inconclusive pattern of findings. Here, we studied the influence of affective traits, such as depressiveness and trait anxiety, and states, which were manipulated with a musical mood induction paradigm, on different measures of perceptual stability (dominance ratios and phase durations) during binocular rivalry. Fifty healthy participants reported alternations in two conditions: a biased perception condition with an unequal probability of perceiving stimuli, using an upright versus a tilted face with a neutral expression, and a control condition with equal chances of perceiving stimuli, using Gabors of different orientations. Baseline positive state affect significantly predicted longer phase durations whereas affective traits did not yield any such effect. Furthermore, in an exploratory analysis, induced negative affect attenuated stimulus related bias in predominance ratios. Overall, we found a strong correlation between both measures of perceptual stability (phase durations and dominance ratios). Our findings thus question the distinction between different measures of perceptual stability during binocular rivalry and highlight the role of affective states in its formation.

Virtual occlusion effects on the perception of self-initiated visual stimuli.

Virtual reality (VR) has established itself as a useful tool in the study of human perception in the laboratory. A recent study introduced a new approach to examine visual sensory attenuation (SA) effects in VR. Hand movements triggered the appearance of Gabor stimuli, which were either presented behind the participant's hand - not rendered in VR ("virtual occlusion") - or elsewhere on the display. Virtual occlusion led to a rightward shift of the psychometric curve, suggesting that self-generated hand movements reduced the perceived contrast of the stimulus. Since such attenuation effects might provide a window into the predictive processing of the sensory and cognitive apparatus, we sought to better understand the nature of the virtual occlusion effects. In our study, the presentation of test stimuli was either self-initiated, self-initiated with a variable delay, or triggered externally; the test stimuli were occluded or not. In conflict with our hypothesis, we found moderate to strong evidence for an absence of any horizontal shifts between the psychometric curves. However, virtual occlusion was associated with a decrease in the slope of the psychometric function. Our results suggest that virtual occlusion attenuated the relative perceptual sensitivity, so that participants had more difficulty discriminating contrast differences when the test stimulus was presented behind the hand. We tentatively conclude that, in the visual domain, the discriminability of stimulus intensity is modified by internal predictive cues (i.e., proprioception), possibly linked to shifts in covert spatial attention.

Sensory Attenuation in the Auditory Modality as a Window Into Predictive Processing.

Self-generated auditory input is perceived less loudly than the same sounds generated externally. The existence of this phenomenon, called Sensory Attenuation (SA), has been studied for decades and is often explained by motor-based forward models. Recent developments in the research of SA, however, challenge these models. We review the current state of knowledge regarding theoretical implications about the significance of Sensory Attenuation and its role in human behavior and functioning. Focusing on behavioral and electrophysiological results in the auditory domain, we provide an overview of the characteristics and limitations of existing SA paradigms and highlight the problem of isolating SA from other predictive mechanisms. Finally, we explore different hypotheses attempting to explain heterogeneous empirical findings, and the impact of the Predictive Coding Framework in this research area.

Musicality as a predictive process.

Savage et al. argue for musicality as having evolved for the overarching purpose of social bonding. By way of contrast, we highlight contemporary predictive processing models of human cognitive functioning in which the production and enjoyment of music follows directly from the principle of prediction error minimization.

[Healthcare epidemiology of mental disorders : Why is the prevalence not declining despite growing provision of care?] / Versorgungsepidemiologie psychischer Störungen : Warum sinken die Prävalenzen trotz vermehrter Versorgungsangebote nicht ab?

In Germany, the significant increase of healthcare provision and service use in recent decades has not resulted in a decreasing prevalence of mental disorders.Three explanations for this phenomenon are considered: 1) prevention and the healthcare system are insufficient and ineffective, 2) the success of the healthcare service is masked by growing morbidity due to increasing societal risks, and 3) a fundamental shift towards a psychological culture accounts for an increasing perception and treatment of mental disorders and their symptoms at the same time. In order to review these three theoretical approaches, results from population-based health surveys and healthcare research in Germany as well as the international debate are presented and discussed.The present results provide evidence for each of the three explanations: 1) problems with implementation of preventive actions and access to healthcare services are well documented, 2) influences of the multifaceted development of risk factors on the prevalence and disease burden of mental disorders cannot be ruled out, and 3) a growing mental health literacy implies that problems (in everyday life) are currently more often interpreted and treated psychologically.For the purpose of evaluating changes in the healthcare system, not only should the prevalence of mental disorders be considered, but also incidence (and their potential reduction by preventive measures) as well as indicators of need for treatment (i. e. functional impairment) and mortality (i. e. suicides and reduced life expectancy).

Body weight predicts Nicotinamide N-Methyltransferase activity in mouse fat.

AIM: Nicotinamide N-methyltransferase (NNMT) is a novel regulator of energy homeostasis in adipose tissue. NNMT expression is higher in obese mice than in lean mice, and NNMT knockdown prevents diet-induced obesity. Little is known about the regulation of enzyme activity during the development of obesity. The aim of this study was to analyze NNMT activity in tissues of mice with incipient and established obesity. METHODS: A fluorescence-based, sensitive, low-volume, high-throughput method was developed to assay NNMT activity. C57BL/6 mice were fed a high-fat diet for 4 weeks (incipient obesity) and for 12 weeks (established obesity). Tissues and serum were harvested and analyzed. RESULTS: NNMT activity was highest in subcutaneous white fat (55.0 µU/mg), followed by epididymal white fat (35.6 µU/mg), brown adipose tissue (7.8 µU/mg), liver (7.6 µU/mg), and lung (7.3 µU/mg). Little activity was detected in heart, skeletal muscle, and kidney. No activity was found in serum samples. Body weight predicted NNMT activity in white fat, but not in brown fat or any other tissue, and only in incipient obesity. With established obesity, this association was lost. CONCLUSIONS: As obesity develops, body weight predicts NNMT activity in white adipose tissue, but not in any other tissue, consistent with a specific role of adipose-tissue NNMT in the regulation of body weight.

Quantitative assessment of adipocyte differentiation in cell culture.

Adipocyte cell culture is an important tool for mechanistic studies of energy metabolism. Many factors affect the differentiation of adipocytes in culture. Oil red O staining can be used to assess the degree of differentiation. However, the validity of this method for quantitative analysis has not yet been established. Here we show that a protocol with arbitrarily chosen parameters does not measure in the linear range and is not suitable for quantitative analysis (R2 = 0.077, p = 0.382), and develop and validate an optimized protocol for quantitative oil red O staining of cultured adipocytes. 3T3-L1 preadipocytes and adipocytes are fixed with 4% formaldehyde and stained with 0.2% oil red O solution in 40% 2-propanol for 30 minutes. Dye is eluted with 2-propanol, and absorption of the eluate is measured photometrically at 510 nm. This optimized protocol achieves excellent correlation between defined amounts of differentiated adipocytes on constant-size culture plates and photometric absorption (R2 = 0.972, p = 6.585E-14). The performance of the method is independent of the culture plates used. Thus, the optimized oil red O staining protocol can be universally employed to quantitatively assess adipocyte differentiation.