Effects of selective 5-HT1A agonist tandospirone on the rate and rhythmicity of binocular rivalry

Reviving Bistable Perception in Patients With Depression by Decreasing the Overestimation of Prior Precision

Slower perceptual alternations, a notable perceptual effect observed in psychiatric disorders, can be alleviated by antidepressant therapies that affect serotonin levels in the brain. While these phenomena have been well documented, the underlying neurocognitive mechanisms remain to be elucidated. Our study bridges this gap by employing a computational cognitive approach within a Bayesian predictive coding framework to explore these mechanisms in depression. We fitted a prediction error (PE) model to behavioral data from a binocular rivalry task, uncovering that significantly higher initial prior precision and lower PE led to a slower switch rate in patients with depression. Furthermore, serotonin-targeting antidepressant treatments significantly decreased the prior precision and increased PE, both of which were predictive of improvements in the perceptual alternation rate of depression patients. These findings indicated that the substantially slower perception switch rate in patients with depression was caused by the greater reliance on top-down priors and that serotonin treatment's efficacy was in its recalibration of these priors and enhancement of PE. Our study not only elucidates the cognitive underpinnings of depression, but also suggests computational modeling as a potent tool for integrating cognitive science with clinical psychology, advancing our understanding and treatment of cognitive impairments in depression.

Priming and reversals of the perceived ambiguous orientation of a structure-from-motion shape and relation to personality traits

We demonstrate contributions of top-down and bottom-up influences in perception as explored by priming and counts of perceived reversals and mixed percepts, as probed by an ambiguously slanted structure-from-motion (SFM) test-cylinder. We included three different disambiguated primes: a SFM cylinder, a still image of a cylinder, and an imagined cylinder. In Experiment 1 where the prime and test sequentially occupied the same location, we also administered questionnaires with the Big-5 trait openness and vividness of visual imagery to probe possible relations to top-down driven priming. Since influences of gaze or position in the prime conditions in Experiment 1 could not be ruled out completely, Experiment 2 was conducted where the test cylinder appeared at a randomly chosen position after the prime. In Experiment 2 we also measured the number of perceptual reversals and mixed percepts during prolonged viewing of our ambiguous SFM-cylinder, and administered questionnaires to measure all Big-5 traits, autism, spatial and object imagery, and rational or experiential cognitive styles, associated with bottom-up and top-down processes. The results revealed contributions of position-invariant and cue-invariant priming. In addition, residual contributions of low-level priming was found when the prime and test were both defined by SFM, and were presented at the same location, and the correlation between the SFM priming and the other two priming conditions were weaker than between the pictorial and imagery priming. As previously found with ambiguous binocular rivalry stimuli, we found positive correlations between mixed percepts and the Big-5 dimension openness to experience, and between reversals, mixed percepts and neuroticism. Surprisingly, no correlations between the scores from the vividness of imagery questionnaires and influence from any of the primes were obtained. An intriguing finding was the significant differences between the positive correlation from the experiential cognitive style scores, and the negative correlation between rational style and the cue invariant priming. Among other results, negative correlations between agreeableness and all priming conditions were obtained. These results not only support the notion of multiple processes involved in the perception of ambiguous SFM, but also link these processes in perception to specific personality traits.

The effect of intranasal oxytocin on visual processing and salience of human faces

The mechanisms underlying the role of oxytocin (OT) as a regulator of social behavior in mammals are only partly understood. Recently, it has been proposed that OT increases the salience of social stimuli. We carried out a randomized, double-blind, cross-over study of the effects of OT on binocular rivalry, a visual phenomenon underpinned by the interplay of excitation and inhibition in the cortex. A final sample of 45 participants viewed images of social stimuli (faces with different emotional expressions) and non-social stimuli (houses and Gabor patches). We demonstrate a robust effect that intranasal OT increases the salience of human faces in binocular rivalry, such that dominance durations of faces are longer-this effect is not modulated by the facial expression. We tentatively show that OT treatment increases dominance durations for non-social stimuli. Our results lend support to the social salience hypothesis of OT, and in addition offer provisional support for the role of OT in influencing excitation-inhibition balance in the brain.

Difference in binocular rivalry rate between major depressive disorder and generalized anxiety disorder

Binocular rivalry (BR) occurs when monocular images are presented simultaneously to corresponding regions of the two eyes. Rather than forming a stable composite, perception alternates spontaneously between each monocular view. Over recent decades, considerable interest in examining BR in psychiatric populations has demonstrated clear differences in the dynamics of BR when compared to healthy populations. However, the available data with respect to rivalry rates in depression and anxiety are limited, and previous studies have shown inconsistent results. Also, depression and anxiety are highly comorbid and can be difficult to distinguish. Therefore, we aimed to investigate whether patients with depression and anxiety have abnormal rivalry rates and whether rivalry rates differ between these conditions. Thirty-five patients with major depressive disorder (MDD), 30 patients with generalized anxiety disorder (GAD), and 30 control participants matched on sex, age and education were recruited. Our results showed MDD participants had slower BR rates than controls and GAD, and controls were significantly slower than GAD. Our findings raise prospects that BR could be a promising behavioral tool to differentiate depressive and anxiety disorders.

Relating excitatory and inhibitory neurochemicals to visual perception: A magnetic resonance study of occipital cortex between migraine events

Certain perceptual measures have been proposed as indirect assays of brain neurochemical status in people with migraine. One such measure is binocular rivalry, however, previous studies have not measured rivalry characteristics and brain neurochemistry together in people with migraine. This study compared spectroscopy-measured levels of GABA and Glx (glutamine and glutamate complex) in visual cortex between 16 people with migraine and 16 non-headache controls, and assessed whether the concentration of these neurochemicals explains, at least partially, inter-individual variability in binocular rivalry perceptual measures. Mean Glx level was significantly reduced in migraineurs relative to controls, whereas mean occipital GABA levels were similar between groups. Neither GABA levels, nor Glx levels correlated with rivalry percept duration. Our results thus suggest that the previously suggested relationship between rivalry percept duration and GABAergic inhibitory neurotransmitter concentration in visual cortex is not strong enough to enable rivalry percept duration to be reliably assumed to be a surrogate for GABA concentration, at least in the context of healthy individuals and those that experience migraine.

Slower and Less Variable Binocular Rivalry Rates in Patients With Bipolar Disorder, OCD, Major Depression, and Schizophrenia

When two different images are presented to the two eyes dichoptically, observers usually experience a perceptual alternation between the two images. This phenomenon, known as binocular rivalry, has been used as a powerful tool to investigate mechanisms of visual awareness. It was also found that the rates of perceptual alternation are slower in patients with bipolar disorder than in healthy controls (Pettigrew and Miller, 1998; Miller et al., 2003). To investigate the broader clinical relevance of binocular rivalry in psychiatric disorders, we measured the perceptual alternation rates during rivalry in healthy controls (n = 39) and in patients with different types of psychiatric disorders, including bipolar disorder type I (BD, n = 28), obsessive-compulsive disorder (OCD, n = 22), major depression (MD, n = 50), schizophrenia (SCZ, n = 44), and first-degree relatives (FDRs) of SCZ patients (n = 32). Participants viewed competing red-green images on a computer monitor through red-green anaglyph glasses and pressed buttons to record their perceptual alternations. The distributions of the rivalry rates were well described by a lognormal function in all groups. Critically, the median rate of perceptual alternation was 0.27 Hz for BD patients, 0.26 Hz for the OCD patients, 0.25 Hz for the MD patients, and 0.23 Hz and 0.27 Hz for the SCZ patients and their FDRs, respectively. All of which were significantly slower than the rate of 0.41 Hz obtained for the healthy controls, suggesting there may be shared genotypes between these different disorders. While rivalry alternations were generally slower in different types of psychiatric disorders compared to healthy controls, adding variance of rivalry rates in the analysis helped to partially separate among the different patient groups. Our results suggest that the slowing of binocular rivalry is likely due to certain common factors among the patient groups, but more subtle differences between different patient groups could be revealed when additional properties of rivalry dynamics are considered.

Genomic Analyses of Visual Cognition: Perceptual Rivalry and Top-Down Control

Visual cognition in humans has traditionally been studied with cognitive behavioral methods and brain imaging, but much less with genetic methods. Perceptual rivalry, an important phenomenon in visual cognition, is the spontaneous perceptual alternation that occurs between two distinct interpretations of a physically constant visual stimulus (e.g., binocular rivalry stimuli) or a perceptually ambiguous stimulus (e.g., the Necker cube). The switching rate varies dramatically across individuals and can be voluntarily modulated by observers. Here, we adopted a genomic approach to systematically investigate the genetics underlying binocular rivalry, Necker cube rivalry and voluntary modulation of Necker cube rivalry in young Chinese adults (Homo sapiens, 81% female, 20 ± 1 years old) at multiple levels, including common single nucleotide polymorphism (SNP)-based heritability estimation, SNP-based genome-wide association study (GWAS), gene-based analysis, and pathway analysis. We performed a pilot GWAS in 2441 individuals and replicated it in an independent cohort of 943 individuals. Common SNP-based heritability was estimated to be 25% for spontaneous perceptual rivalry. SNPs rs184765639 and rs75595941 were associated with voluntary modulation, and imaging data suggested genotypic difference of rs184765639 in the surface area of the left caudal-middle frontal cortex. Additionally, converging evidence from multilevel analyses associated genes such as PRMT1 with perceptual switching rate, and MIR1178 with voluntary modulation strength. In summary, this study discovered specific genetic contributions to perceptual rivalry and its voluntary modulation in human beings. These findings may promote our understanding of psychiatric disorders, as perceptual rivalry is a potential psychiatric biomarker.SIGNIFICANCE STATEMENT Perceptual rivalry is an important visual phenomenon in which our perception of a physically constant visual input spontaneously switches between two different states. There are individual variations in perceptual switching rate and voluntary modulation strength. Our genomic analyses reveal several loci associated with these two kinds of variation. Because perceptual rivalry is thought to be relevant to and potentially an endophenotype for psychiatric disorders, these results may help understand not only visual cognition, but also psychiatric disorders.

The time course of binocular rivalry during the phases of the menstrual cycle

Binocular rivalry occurs when markedly different inputs to the two eyes initiate alternations in perceptual dominance between the two eyes' views. A link between individual differences in perceptual dynamics of rivalry and concentrations of GABA, a prominent inhibitory neurotransmitter in the brain, has highlighted binocular rivalry as a potential tool to investigate inhibitory processes in the brain. The present experiment investigated whether previously reported fluctuations of GABA concentrations in a healthy menstrual cycle (Epperson et al., 2002) also are associated with measurable changes in rivalry dynamics within individuals. We obtained longitudinal measures of alternation rate, dominance, and mixture durations in 300 rivalry tracking blocks measured over 5 weeks from healthy female participants who monitored the start of the follicular and luteal phases of their cycle. Although we demonstrate robust and stable individual differences in rivalry dynamics, across analytic approaches and dependent measures, we found no significant change or even trends across menstrual phases in the temporal dynamics of dominance percepts. We found only sparse between-phase differences in skew and kurtosis on mixture percepts when data were pooled across sessions and blocks. These results suggest a complex dynamic between hormonal steroids, binocular rivalry, and GABAeric signaling in the brain and thus implicate the need to consider a systemic perspective when linking GABA with perceptual alternations in binocular rivalry.

Top-down influences on ambiguous perception: the role of stable and transient states of the observer

The world as it appears to the viewer is the result of a complex process of inference performed by the brain. The validity of this apparently counter-intuitive assertion becomes evident whenever we face noisy, feeble or ambiguous visual stimulation: in these conditions, the state of the observer may play a decisive role in determining what is currently perceived. On this background, ambiguous perception and its amenability to top-down influences can be employed as an empirical paradigm to explore the principles of perception. Here we offer an overview of both classical and recent contributions on how stable and transient states of the observer can impact ambiguous perception. As to the influence of the stable states of the observer, we show that what is currently perceived can be influenced (1) by cognitive and affective aspects, such as meaning, prior knowledge, motivation, and emotional content and (2) by individual differences, such as gender, handedness, genetic inheritance, clinical conditions, and personality traits and by (3) learning and conditioning. As to the impact of transient states of the observer, we outline the effects of (4) attention and (5) voluntary control, which have attracted much empirical work along the history of ambiguous perception. In the huge literature on the topic we trace a difference between the observer's ability to control dominance (i.e., the maintenance of a specific percept in visual awareness) and reversal rate (i.e., the switching between two alternative percepts). Other transient states of the observer that have more recently drawn researchers' attention regard (6) the effects of imagery and visual working memory. (7) Furthermore, we describe the transient effects of prior history of perceptual dominance. (8) Finally, we address the currently available computational models of ambiguous perception and how they can take into account the crucial share played by the state of the observer in perceiving ambiguous displays.

Dichoptic Viewing Methods for Binocular Rivalry Research: Prospects for Large-Scale Clinical and Genetic Studies

Binocular rivalry (BR) is an intriguing phenomenon that occurs when two different images are presented, one to each eye, resulting in alternation orrivalrybetween the percepts. The phenomenon has been studied for nearly 200 years, with renewed and intensive investigation over recent decades. Therateof perceptual switching has long been known to vary widely between individuals but to be relatively stable within individuals. A recent twin study demonstrated that individual variation in BR rate is under substantial genetic control, a finding that also represented the first report, using a large study, of genetic contribution for any post-retinal visual processing phenomenon. The twin study had been prompted by earlier work showing BR rate was slow in the heritable psychiatric condition, bipolar disorder (BD). Together, these studies suggested that slow BR may represent an endophenotype for BD, and heralded the advent of modern clinical and genetic studies of rivalry. This new focus has coincided with rapid advances in 3D display technology, but despite such progress, specific development of technology for rivalry research has been lacking. This review therefore compares different display methods for BR research across several factors, including viewing parameters, image quality, equipment cost, compatibility with other investigative methods, subject group, and sample size, with a focus on requirements specific to large-scale clinical and genetic studies. It is intended to be a resource for investigators new to BR research, such as clinicians and geneticists, and to stimulate the development of 3D display technology for advancing interdisciplinary studies of rivalry.

Attentional switching in humans and flies: rivalry in large and miniature brains

Human perception, and consequently behavior, is driven by attention dynamics. In the special case of rivalry, where attention alternates between competing percepts, such dynamics can be measured and their determinants investigated. A recent study in the fruit fly, Drosophila melanogaster, now shows that the origins of attentional rivalry may be quite ancient. Furthermore, individual variation exists in the rate of attentional rivalry in both humans and flies, and in humans this is under substantial genetic influence. In the pathophysiological realm, slowing of rivalry rate is associated with the heritable psychiatric condition, bipolar disorder. Fly rivalry may therefore prove a powerful model to examine genetic and molecular influences on rivalry rate, and may even shed light on human cognitive and behavioral dysfunction.

Separability and commonality of auditory and visual bistable perception

It is unclear what neural processes induce individual differences in perceptual organization in different modalities. To examine this issue, the present study used different forms of bistable perception: auditory streaming, verbal transformations, visual plaids, and reversible figures. We performed factor analyses on the number of perceptual switches in the tasks. A 3-factor model provided a better fit to the data than the other possible models. These factors, namely the "auditory," "shape," and "motion" factors, were separable but correlated with each other. We compared the number of perceptual switches among genotype groups to identify the effects of neurotransmitter functions on the factors. We focused on polymorphisms of catechol-O-methyltransferase (COMT) Val(158)Met and serotonin 2A receptor (HTR2A) -1438G/A genes, which are involved in the modulation of dopamine and serotonin, respectively. The number of perceptual switches in auditory streaming and verbal transformations differed among COMT genotype groups, whereas that in reversible figures differed among HTR2A genotype groups. The results indicate that the auditory and shape factors reflect the functions of the dopamine and serotonin systems, respectively. Our findings suggest that the formation and selection of percepts involve neural processes in cortical and subcortical areas.

Visual and auditory perceptual rivalry in migraine

INTRODUCTION

Recent evidence demonstrates that perceptual rivalry rate can be modulated by perturbation of the serotonergic system. Specifically, pharmacologically lowering the availability of serotonin results in slower rivalry rates. As it has been suggested that brain serotonin is low during the interictal phase of migraine, we hypothesized that perceptual rivalry rates would be reduced in individuals with migraine.

METHODS

Visual and auditory perceptual rivalry measures were obtained for a group of 30 participants with migraine (15 migraine with aura, 15 migraine without aura) and 20 non-headache control individuals.

RESULTS

Our experiments reveal fewer perceptual rivalry switches within both visual and auditory domains for our migraine without aura group, while the with-aura group performed similarly to non-headache controls. Dividing the data by headache frequency rather than headache subtype classification revealed fewer perceptual switches in those with more frequent headaches.

CONCLUSIONS

Our data provides further support for interictal differences in brain sensory reactivity in migraine, with the observed effects being in the same direction as those caused by pharmacologically reducing brain availability of serotonin in normal observers.

Genes contribute to the switching dynamics of bistable perception

Ordinarily, the visual system provides an unambiguous representation of the world. However, at times alternative plausible interpretations of a given stimulus arise, resulting in a dynamic perceptual alternation of the differing interpretations, commonly referred to as bistable or rivalrous perception. Recent research suggests that common neural mechanisms may be involved in the dynamics of very different types of bistable phenomena. Further, evidence has emerged that genetic factors may be involved in determining the rate of switch for at least one form of bistable perception, known as binocular rivalry. The current study evaluated whether genetic factors contribute to the switching dynamics for distinctly different variants of bistable perception in the same participant sample. Switching rates were recorded for MZ and DZ twin participants in two different bistable perception tasks, binocular rivalry and the Necker Cube. Strong concordance in switching rates across both tasks was evident for MZ but not DZ twins, indicating that genetic factors indeed contribute to the dynamics of multiple forms of bistable perception.

Genetic contribution to individual variation in binocular rivalry rate

Binocular rivalry occurs when conflicting images are presented in corresponding locations of the two eyes. Perception alternates between the images at a rate that is relatively stable within individuals but that varies widely between individuals. The determinants of this variation are unknown. In addition, slow binocular rivalry has been demonstrated in bipolar disorder, a psychiatric condition with high heritability. The present study therefore examined whether there is a genetic contribution to individual variation in binocular rivalry rate. We employed the twin method and studied both monozygotic (MZ) twins (n = 128 pairs) who are genetically identical, and dizygotic (DZ) twins (n = 220 pairs) who share roughly half their genes. MZ and DZ twin correlations for binocular rivalry rate were 0.51 and 0.19, respectively. The best-fitting genetic model showed 52% of the variance in binocular rivalry rate was accounted for by additive genetic factors. In contrast, nonshared environmental influences accounted for 18% of the variance, with the remainder attributed to measurement error. This study therefore demonstrates a substantial genetic contribution to individual variation in binocular rivalry rate. The results support the vigorous pursuit of genetic and molecular studies of binocular rivalry and further characterization of slow binocular rivalry as an endophenotype for bipolar disorder.