Pupillometry in auditory multistability

In multistability, a constant stimulus induces alternating perceptual interpretations. For many forms of visual multistability, the transition from one interpretation to another (“perceptual switch”) is accompanied by a dilation of the pupil. Here we ask whether the same holds for auditory multistability, specifically auditory streaming. Two tones were played in alternation, yielding four distinct interpretations: the tones can be perceived as one integrated percept (single sound source), or as segregated with either tone or both tones in the foreground. We found that the pupil dilates significantly around the time a perceptual switch is reported (“multistable condition”). When participants instead responded to actual stimulus changes that closely mimicked the multistable perceptual experience (“replay condition”), the pupil dilated more around such responses than in multistability. This still held when data were corrected for the pupil response to the stimulus change as such. Hence, active responses to an exogeneous stimulus change trigger a stronger or temporally more confined pupil dilation than responses to an endogenous perceptual switch. In another condition, participants randomly pressed the buttons used for reporting multistability. In Study 1, this “random condition” failed to sufficiently mimic the temporal pattern of multistability. By adapting the instructions, in Study 2 we obtained a response pattern more similar to the multistable condition. In this case, the pupil dilated significantly around the random button presses. Albeit numerically smaller, this pupil response was not significantly different from the multistable condition. While there are several possible explanations–related, e.g., to the decision to respond–this underlines the difficulty to isolate a purely perceptual effect in multistability. Our data extend previous findings from visual to auditory multistability. They highlight methodological challenges in interpreting such data and suggest possible approaches to meet them, including a novel stimulus to simulate the experience of perceptual switches in auditory streaming.

Early, color-specific neural responses to object color knowledge

Some familiar objects are associated with specific colors, e.g., rubber ducks with yellow. Whether and at what stage neural responses occur to these color associations remain open questions. We tested for frequency-tagged electroencephalogram (EEG) responses to periodic presentations of yellow-associated objects, shown among sequences of non-periodic blue-, red-, and green-associated objects. Both color and grayscale versions of the objects elicited yellow-specific responses, indicating an automatic activation of color knowledge from object shape. Follow-up experiments replicated these effects with green-specific responses, and demonstrated modulated responses for incongruent color-object associations. Importantly, the onset of color-specific responses was as early to grayscale as actually colored stimuli (before 100 ms), the latter additionally eliciting a conventional later response (approximately 140-230 ms) to actual stimulus color. This suggests that the neural representation of familiar objects includes both diagnostic shape and color properties, such that shape can elicit associated color-specific responses before actual color-specific responses occur.

Response Preparation With Reliable Cues Decreases Response Competition in the Flanker Task

We tested the hypothesis that selective response preparation, based on reliable response cues, reduces response conflict in an Eriksen flanker task. Previous studies of this issue produced inconclusive results because presenting an always valid response cue before the stimulus display turns a choice-response task into a simple-response task, in which full processing of the actual stimulus display is no longer necessary. We conducted two experiments in which we matched stimulus processing in conditions without cues and with reliable cues as far as possible. In both experiments, we presented a nogo target stimulus in 25% of the trials. The different cueing conditions were presented in separate blocks in Experiment 1 but mixed within blocks in Experiment 2. The most important result was the reduction of response conflict as induced by incompatible flanker stimuli in both experiments with reliable response cues. This finding supports the notion of a negative preparation-interference relationship.

Beauty-in-averageness and its contextual modulations: A Bayesian statistical account

Understanding how humans perceive the likability of high-dimensional “objects” such as faces is an important problem in both cognitive science and AI/ML. Existing models of human preferences generally assume these preferences to be fixed. However, human assessment of facial attractiveness have been found to be highly context-dependent. Specifically, the classical Beauty-in-Averageness (BiA) effect, whereby a face blended from two original faces is judged to be more attractive than the originals, is significantly diminished or reversed when the original faces are recognizable, or when the morph is mixed-race/mixed gender and the attractiveness judgment is preceded by a race/gender categorization. This effect, dubbed Ugliness-in-Averageness (UiA), has previously been attributed to a disfluency account, which is both qualitative and clumsy in explaining BiA. We hypothesize, instead, that these contextual influences on face processing result from the dependence of attractiveness perception on an element of statistical typicality, and from an attentional mechanism that restricts face representation to a task-relevant subset of features, thus redefining typicality within that subspace. Furthermore, we propose a principled explanation of why statistically atypical objects are less likable: they incur greater encoding or processing cost associated with a greater prediction error, when the brain uses predictive coding to compare the actual stimulus properties with those expected from its associated categorical prototype. We use simulations to show our model provides a parsimonious, statistically grounded, and quantitative account of contextual dependence of attractiveness. We also validate our model using experimental data from a gender categorization task. Finally, we make model predictions for a proposed experiment that can disambiguate the previous disfluency account and our statistical typicality theory.

Want to gain height? How body motion makes you taller.

Body height and expansiveness of body motion both affect perceived dominance and status. We investigated whether expansiveness of body motion also has a direct impact on perceptions of height. For two independent rating experiments we turned the body movements of politicians giving a speech into short clips of animated stick-figures. In experiment one, participants judged these stimuli on dominance, trustworthiness, and competence. In experiment two participants assessed the stick-figures’ heights. Perceptions of stick-figure heights were related to ratings of dominance even after controlling for actual stimulus height. We concluded that perceived height was influenced by motion cues. Detailed analyses of hand and torso movements revealed that expansive vertical arm movements made our stimuli appear taller. In conclusion, our findings indicate that motion cues do not only affect attributions of personality traits but also distort perceptions of physiognomic features such as body height.

Ethics and Aesthetics–Philosophical Perspectives

European intellectual history teaches us that beauty is not just an adornment to life but is also a major source of strength for our life. Moreover, the positive aesthetic experience also has healing power. That beauty is a highly effective antidote to life's suffering, i.e. acts as an anti-depressant, has been documented in the tradition of philosophical aesthetics from Plato to Bloch. Beauty reveals truth and goodness (Plato), it shows the harmonious order and the glory of things (Pseudo-Dionysius the Areopagite), it is one of the transcendental names of God (Thomas of Aquinas), in beauty the world appears in its perfection (Baumgarten), beauty is the daughter of freedom (Schiller), it offers a temporary escape from the suffering of existence (Schopenhauer), aesthetic values are the only values that withstand nihilism and the meaninglessness of existence and are thus the actual stimulus of life (Nietzsche), the beautiful is the sensual appearance of the idea (Hegel), beauty is an anti-depressant and Weckamin of being, it tears people out of their forgetfulness of Being (Heidegger), there is a close relationship between the shining forth of the Beautiful and the evidentness of the Understandable (Gadamer), in an artwork and through the aesthetic attitude the Other, foreign, the non-identical that is mangled and mutilated in the administered world is preserved and saved (Adorno). Many more positive affirmative descriptions from the tradition of philosophical aesthetics demonstrate that beauty and the aesthetic have a therapeutic dimension.Disclosure of interestThe author declares that he has no competing interest.

Decoding the future from past experience: learning shapes predictions in early visual cortex

Learning the structure of the environment is critical for interpreting the current scene and predicting upcoming events. However, the brain mechanisms that support our ability to translate knowledge about scene statistics to sensory predictions remain largely unknown. Here we provide evidence that learning of temporal regularities shapes representations in early visual cortex that relate to our ability to predict sensory events. We tested the participants' ability to predict the orientation of a test stimulus after exposure to sequences of leftward- or rightward-oriented gratings. Using fMRI decoding, we identified brain patterns related to the observers' visual predictions rather than stimulus-driven activity. Decoding of predicted orientations following structured sequences was enhanced after training, while decoding of cued orientations following exposure to random sequences did not change. These predictive representations appear to be driven by the same large-scale neural populations that encode actual stimulus orientation and to be specific to the learned sequence structure. Thus our findings provide evidence that learning temporal structures supports our ability to predict future events by reactivating selective sensory representations as early as in primary visual cortex.

Prior Expectations Evoke Stimulus Templates in the Primary Visual Cortex

Sensory processing is strongly influenced by prior expectations. Valid expectations have been shown to lead to improvements in perception as well as in the quality of sensory representations in primary visual cortex. However, very little is known about the neural correlates of the expectations themselves. Previous studies have demonstrated increased activity in sensory cortex following the omission of an expected stimulus, yet it is unclear whether this increased activity constitutes a general surprise signal or rather has representational content. One intriguing possibility is that top–down expectation leads to the formation of a template of the expected stimulus in visual cortex, which can then be compared with subsequent bottom–up input. To test this hypothesis, we used fMRI to noninvasively measure neural activity patterns in early visual cortex of human participants during expected but omitted visual stimuli. Our results show that prior expectation of a specific visual stimulus evokes a feature-specific pattern of activity in the primary visual cortex (V1) similar to that evoked by the corresponding actual stimulus. These results are in line with the notion that prior expectation triggers the formation of specific stimulus templates to efficiently process expected sensory inputs.

Neural Information Processing with Feedback Modulations

Descending feedback connections, together with ascending feedforward ones, are the indispensable parts of the sensory pathways in the central nervous system. This study investigates the potential roles of feedback interactions in neural information processing. We consider a two-layer continuous attractor neural network (CANN), in which neurons in the first layer receive feedback inputs from those in the second one. By utilizing the intrinsic property of a CANN, we use a projection method to reduce the dimensionality of the network dynamics significantly. The simplified dynamics allows us to elucidate the effects of feedback modulation analytically. We find that positive feedback enhances the stability of the network state, leading to an improved population decoding performance, whereas negative feedback increases the mobility of the network state, inducing spontaneously moving bumps. For strong, negative feedback interaction, the network response to a moving stimulus can lead the actual stimulus position, achieving an anticipative behavior. The biological implications of these findings are discussed. The simulation results agree well with our theoretical analysis.

Hearing a voice in the noise: auditory hallucinations and speech perception

BackgroundIt has recently been suggested that auditory hallucinations are the result of a criterion shift when deciding whether or not a meaningful signal has emerged. The approach proposes that a liberal criterion may result in increased false-positive identifications, without additional perceptual deficit. To test this hypothesis, we devised a speech discrimination task and used signal detection theory (SDT) to investigate the underlying cognitive mechanisms.MethodSchizophrenia patients with and without auditory hallucinations and a healthy control group completed a speech discrimination task. They had to decide whether a particular spoken word was identical to a previously presented speech stimulus, embedded in noise. SDT was used on the accuracy data to calculate a measure of perceptual sensitivity (Az) and a measure of response bias (β). Thresholds for the perception of simple tones were determined.ResultsCompared to healthy controls, perceptual thresholds were higher and perceptual sensitivity in the speech task was lower in both patient groups. However, hallucinating patients showed increased sensitivity to speech stimuli compared to non-hallucinating patients. In addition, we found some evidence of a positive response bias in hallucinating patients, indicating a tendency to readily accept that a certain stimulus had been presented.ConclusionsWithin the context of schizophrenia, patients with auditory hallucinations show enhanced sensitivity to speech stimuli, combined with a liberal criterion for deciding that a perceived event is an actual stimulus.