Somatosensory perception–action binding in Tourette syndrome

It is a common phenomenon that somatosensory sensations can trigger actions to alleviate experienced tension. Such “urges” are particularly relevant in patients with Gilles de la Tourette (GTS) syndrome since they often precede tics, the cardinal feature of this common neurodevelopmental disorder. Altered sensorimotor integration processes in GTS as well as evidence for increased binding of stimulus- and response-related features (“hyper-binding”) in the visual domain suggest enhanced perception–action binding also in the somatosensory modality. In the current study, the Theory of Event Coding (TEC) was used as an overarching cognitive framework to examine somatosensory-motor binding. For this purpose, a somatosensory-motor version of a task measuring stimulus–response binding (S-R task) was tested using electro-tactile stimuli. Contrary to the main hypothesis, there were no group differences in binding effects between GTS patients and healthy controls in the somatosensory-motor paradigm. Behavioral data did not indicate differences in binding between examined groups. These data can be interpreted such that a compensatory “downregulation” of increased somatosensory stimulus saliency, e.g., due to the occurrence of somatosensory urges and hypersensitivity to external stimuli, results in reduced binding with associated motor output, which brings binding to a “normal” level. Therefore, “hyper-binding” in GTS seems to be modality-specific.

When Abstract Concepts Rely on Multiple Metaphors: Metaphor Selection in the Case of Power

The study examines metaphor selection for the same abstract concept when multiple concrete dimensions are available for use. Drawing on the power concept, four studies investigated the roles of attention and visual features of concrete dimensions in metaphoric mapping. In Studies 1 and 2, two concrete dimensions (vertical space and size) were visually connected to power-related target words simultaneously, and one was salient. Attention driven by stimulus saliency allowed the attended concrete dimension to have a higher activation level and to be used. In Studies 3 and 4, the attended and the non-attended concrete dimensions were presented separately, and the latter was visually associated with power-related target words. This time, the attended dimension did not have an activation advantage, allowing the non-attended dimension to be used for metaphoric mapping simultaneously. The findings suggest that attention is important, but not necessary, and that features of concrete dimensions can guide metaphor use.

Factors Influencing Saccadic Reaction Time: Effect of Task Modality, Stimulus Saliency, Spatial Congruency of Stimuli, and Pupil Size

It is often assumed that the reaction time of a saccade toward visual and/or auditory stimuli reflects the sensitivities of our oculomotor-orienting system to stimulus saliency. Endogenous factors, as well as stimulus-related factors, would also affect the saccadic reaction time (SRT). However, it was not clear how these factors interact and to what extent visual and auditory-targeting saccades are accounted for by common mechanisms. The present study examined the effect of, and the interaction between, stimulus saliency and audiovisual spatial congruency on the SRT for visual- and for auditory-target conditions. We also analyzed pre-target pupil size to examine the relationship between saccade preparation and pupil size. Pupil size is considered to reflect arousal states coupling with locus-coeruleus (LC) activity during a cognitive task. The main findings were that (1) the pattern of the examined effects on the SRT varied between visual- and auditory-auditory target conditions, (2) the effect of stimulus saliency was significant for the visual-target condition, but not significant for the auditory-target condition, (3) Pupil velocity, not absolute pupil size, was sensitive to task set (i.e., visual-targeting saccade vs. auditory-targeting saccade), and (4) there was a significant correlation between the pre-saccade absolute pupil size and the SRTs for the visual-target condition but not for the auditory-target condition. The discrepancy between target modalities for the effect of pupil velocity and between the absolute pupil size and pupil velocity for the correlation with SRT may imply that the pupil effect for the visual-target condition was caused by a modality-specific link between pupil size modulation and the SC rather than by the LC-NE (locus coeruleus-norepinephrine) system. These results support the idea that different threshold mechanisms in the SC may be involved in the initiation of saccades toward visual and auditory targets.

Involuntary Markers of Saliency and Surprise Revealed by Oculomotor Inhibition in Response to Auditory Sequences

Our eyes move constantly but are often inhibited momentarily in response to external stimuli. The properties of this Oculomotor-Inhibition (OMI) depend on the stimulus saliency, anticipation, and attention. Previous studies have shown prolonged saccadic inhibition for auditory oddballs; however, they required active counting of the oddballs. Here we investigated whether the OMI response to auditory deviants can provide a quantitative measure of deviance strength (auditory pitch difference) and investigated its dependence on the Inter-Stimulus Interval (ISI), without requesting a voluntary attention to the deviant stimulus. Observers fixated on a central fixation stimulus and passively listened to repeated short sequences of pure tones that contained a deviant tone either regularly or with 20% probability (the Oddball paradigm). The results showed, as in previous studies, prolonged microsaccade inhibition following the deviant tone. Moreover, the inhibition onset latency was shorter in proportion to the pitch deviance (the saliency effect) and the release was significantly longer for rare deviants (the surprise effect) as long as the ISI was short (<2.5s). Taken together, these results suggest that OMI provides involuntary markers of saliency and surprise, which can be obtained without the observer’s response.

A window of subliminal perception

Under labels such as unconscious processing and subliminal perception, identification of stimuli falling below the subjective threshold has been found remarkably accurate in some experiments while completely at chance in others. Here, we first demonstrate the existence of a window of subliminal perception in humans using different experimental paradigms and analysis methods. We then show that the standard signal detection theory (SDT) model is unable to accounts for this window and extend it until it is. We finally compare a range of models on empirical data. The models performing best are notable for their absence of hierarchical levels, indicating that the window could be a base property of any phenomenally conscious system. The models further explain previously incompatible findings in the literature, and they allow for estimations of peaks in subthreshold perception across the spectrum of stimulus saliency, which may be used in further studies of subliminal perception.

Brain-wide visual habituation networks in wild type and fmr1 zebrafish

Habituation is a form of learning during which animals stop responding to repetitive stimuli, and deficits in habituation are characteristics of several psychiatric disorders. Due to the technical challenges of measuring brain activity comprehensively and at cellular resolution, the brain-wide networks mediating habituation are poorly understood. Here we report brain-wide calcium imaging during visual learning in larval zebrafish as they habituate to repeated threatening loom stimuli. We show that different functional categories of loom-sensitive neurons are located in characteristic locations throughout the brain, and that both the functional properties of their networks and the resulting behavior can be modulated by stimulus saliency and timing. Using graph theory, we identify a principally visual circuit that habituates minimally, a moderately habituating midbrain population proposed to mediate the sensorimotor transformation, and downstream circuit elements responsible for higher order representations and the delivery of behavior. Zebrafish larvae carrying a mutation in the fmr1 gene have a systematic shift towards sustained premotor activity in this network, and show slower behavioral habituation. This represents the first description of a visual learning network across the brain at cellular resolution, and provides insights into the circuit-level changes that may occur in people with Fragile X syndrome and related psychiatric conditions.

Conscious Perception: Time for an Update?

Understanding the neural mechanisms underlying conscious perception has become a central endeavor in cognitive neuroscience. In theories of conscious perception, a stimulus gaining conscious access is usually considered as a discrete neuronal event to be characterized in time or space, sometimes referred to as a conscious “episode.” Surprisingly, the alternative hypothesis according to which conscious perception is a dynamic process has rarely been considered. Here, we discuss this hypothesis and its implications. We show how it can reconcile inconsistent empirical findings on the timing of the neural correlates of consciousness and make testable predictions. According to this hypothesis, a stimulus is consciously perceived for as long as it is recoded to fit an ongoing stream composed of all other perceived stimuli. We suggest that this “updating” process is governed by at least three factors (1) context, (2) stimulus saliency, and (3) observers' goals. Finally, this framework forces us to reconsider the typical distinction between conscious and unconscious information processing.

Temporal Cognition Can Affect Spatial Cognition More Than Vice Versa: The Effect of Task-Related Stimulus Saliency

Cognition of space and time affect each other; a line with longer length appears to be longer in exposure duration (space on time), and a line with longer exposure duration appears to be longer in length (time on space). This cognitive interaction is known to be asymmetric; the effect of space on time is larger than that of time on space. We conjectured that this asymmetry is not intrinsic but may depend on the saliency of relevant signals. Participants were asked to judge the visual exposure duration of lines that varied in length or the lengths of the lines with different exposure times. The ranges of task-relevant and -irrelevant stimulus values were the same in the spatial and temporal tasks. Task difficulty was also evaluated by subjective rating. We found that duration affected the judgment of length more than vice versa, when the spatial task was significantly more difficult than the temporal task. Together with our previous results that showed the opposite effect, our conjecture is supported that the saliency of stimuli should affect the balance of interactions.