Attentional bias in psoriasis: The role of processing time and emotional valence.

PURPOSE: The present study explored whether people with psoriasis display an attentional bias towards disease-related threat words and whether this bias occurs relatively early during the phase of stimulus disengagement, or during a later maintained attention phase dominated by controlled strategic processes. We also explored the degree to which attentional bias is dependent on the emotional valence of control words. METHODS: Individuals with psoriasis and matched controls took part in 4 online experiments. Participants completed a spatial cueing paradigm using disease-related threat words and control words as cues, in order to obtain reaction time estimates of attentional bias. RESULTS: We did not observe evidence for attentional bias when control words were matched with threat words for emotional valence, regardless of whether processing time for the cues was limited (Experiment 1: SOA = 250 ms) or extended (Experiment 2: SOA = 1050 ms). We also did not observe evidence for attentional bias when control words of positive valence were used, but processing time was limited (Experiment 3). An attentional bias was only observed (p = .012, Cohen's d = .37) when sufficient processing time was available and positively-valanced control words were used (Experiment 4). CONCLUSION: Rather than showing large and generalized AB effects as predicted by previous accounts, our results tentatively suggest that AB in psoriasis is restricted to situations where participants have ample processing time and threat words are easily distinguishable from control words on the basis of emotional valence. The pattern of results suggests that attentional bias in psoriasis is best characterized as a relatively slow strategic process.

No preconscious attentional bias towards itch in healthy individuals.

Rapidly attending towards potentially harmful stimuli to prevent possible damage to the body is a critical component of adaptive behavior. Research suggests that individuals display an attentional bias, i.e., preferential allocation of attention, for consciously perceived bodily sensations that signal potential threat, like itch or pain. Evidence is not yet clear whether an attentional bias also exists for stimuli that have been presented for such a short duration that they do not enter the stream of consciousness. This study investigated whether a preconscious attentional bias towards itch-related pictures exists in 127 healthy participants and whether this can be influenced by priming with mild itch-related stimuli compared to control stimuli. Mild itch was induced with von Frey monofilaments and scratching sounds, while control stimuli where of matched modalities but neutral. Attentional bias was measured with a subliminal pictorial dot-probe task. Moreover, we investigated how attentional inhibition of irrelevant information and the ability to switch between different tasks, i.e., cognitive flexibility, contribute to the emergence of an attentional bias. Attentional inhibition was measured with a Flanker paradigm and cognitive flexibility was measured with a cued-switching paradigm. Contrary to our expectations, results showed that participants attention was not biased towards the itch-related pictures, in facts, attention was significantly drawn towards the neutral pictures. In addition, no effect of the itch-related priming was observed. Finally, this effect was not influenced by participants' attentional inhibition and cognitive flexibility. Therefore, we have no evidence for a preconscious attentional bias towards itch stimuli. The role of preconscious attentional bias in patients with chronic itch should be investigated in future studies.

Can contagious itch be affected by positive and negative suggestions?

Contagious itch can be evoked by observing people scratching. Verbal suggestions about to-be-received itch can influence itch intensity, as shown by placebo research, but it is unknown whether this extends to contagious itch. The current study aimed to replicate prior findings that listening to scratching and rubbing sounds elicits contagious itch, and to investigate whether suggestions can modulate this process. Healthy participants (n = 140) received positive or negative suggestions about itch in response to the sounds (aimed to decrease or increase expected itch, respectively), or no specific suggestions as a control. Participants listened to a number of audio fragments with scratching and rubbing sounds. The amount of expected itch as well as itch sensation after each audio fragment were measured by self-report. Suggestions had no effect on the expected itch. Both rubbing and scratching sounds significantly elicited itch in all groups. Scratching sounds induced more itch than rubbing sounds exclusively in the control group. These findings indicate that short suggestions might be not effective enough to modify the expectations of people regarding contagious itch. Furthermore, suggestions modulate contagious itch to some degree, but not in the hypothesized direction. Potential similarities and differences in the neurobiological mechanisms of contagious itch and nocebo effects are discussed.

Human but not robotic gaze facilitates action prediction.

Do people ascribe intentions to humanoid robots as they would to humans or non-human-like animated objects? In six experiments, we compared people's ability to extract non-mentalistic (i.e., where an agent is looking) and mentalistic (i.e., what an agent is looking at; what an agent is going to do) information from gaze and directional cues performed by humans, human-like robots, and a non-human-like object. People were faster to infer the mental content of human agents compared to robotic agents. Furthermore, although the absence of differences in control conditions rules out the use of non-mentalizing strategies, the human-like appearance of non-human agents may engage mentalizing processes to solve the task. Overall, results suggest that human-like robotic actions may be processed differently from humans' and objects' behavior. These findings inform our understanding of the relevance of an object's physical features in triggering mentalizing abilities and its relevance for human-robot interaction.

Acute Itch Induces Attentional Avoidance of Itch-related Information.

Attention is known to modulate itch intensity. In contrast, the reverse relationship, i.e. the degree to which the presence of an acute itch affects attention, is currently not well understood. The aims of this study were to investigate whether acute itch induces an attentional bias towards or away from visual itch-related stimuli, and if so, whether it occurs in the early or later stages of processing. A volunteer sample of 60 healthy individuals were subjected to a skin prick (either histamine or placebo), followed by completion of a spatial cueing paradigm using itch-related and neutral words as cues, in order to obtain reaction time estimates of attentional bias. The results suggest that experience of acute itch induces attentional avoidance of visual itch threats. This attentional avoidance occurs at a later processing stage in the form of facilitated disengagement of attention from itch and/or delayed disengagement from neutral information.

Transcranial magnetic stimulation over contralateral primary somatosensory cortex disrupts perception of itch intensity.

Itch, a complex unpleasant sensation causing the desire to scratch, results from the activity of a network of brain regions. However, the specific functional contributions of individual regions within this network remain poorly understood. We investigated whether contralateral primary and secondary somatosensory cortices (S1, S2) and ipsilateral inferior frontal gyrus (IFG) are critically involved in the cortical processing of acute itch. Continuous theta burst transcranial magnetic stimulation (cTBS) was applied to either S1, S2 or IFG, followed by itch induction using a histamine prick. Results indicate a significant reduction in itch intensity when cTBS was applied to S1. Stimulation of S2 or the IFG was not associated with a significant reduction in itch intensity. The novel finding of an antipruritic effect elicited by disruption of activity in contralateral S1 suggests a causal role of S1 in encoding the sensory-discriminative aspect of itch and might be important in future studies on brain interventions for the treatment of itch.

Effects of Short-term Temperature Change in the Innocuous Range on Histaminergic and Non-histaminergic Acute Itch.

While temperatures in the noxious range are well-known to inhibit acute itch, the impact of temperature in the innocuous temperature range is less well understood. We investigated the effect of alternating short-term temperature changes in the innocuous range on histamine and cowhage-induced acute itch, taking into account individual differences in baseline skin temperature and sensory thresholds. Results indicate that cooling the skin to the cold threshold causes a temporary increase in the intensity of histamine-induced itch, in line with previous findings. Skin warming increased cowhage-induced itch intensity. Potential mecha-nisms of this interaction between thermosensation and pruritoception could involve cold-sensitive channels such as TRPM8, TREK-1 or TRPC5 in the case of histamine. The rapid modulation of cowhage induced itch - but not histamine-induced itch - by transient skin warming could be related to the lower temperature threshold of pruriceptive polymodal C-fibres (cowhage) as compared to the higher temperature threshold of the mechanoinsensitive C-fibres conveying histaminergic itch.

Transcranial Magnetic Stimulation over Left Inferior Frontal and Posterior Temporal Cortex Disrupts Gesture-Speech Integration.

Language and action naturally occur together in the form of cospeech gestures, and there is now convincing evidence that listeners display a strong tendency to integrate semantic information from both domains during comprehension. A contentious question, however, has been which brain areas are causally involved in this integration process. In previous neuroimaging studies, left inferior frontal gyrus (IFG) and posterior middle temporal gyrus (pMTG) have emerged as candidate areas; however, it is currently not clear whether these areas are causally or merely epiphenomenally involved in gesture-speech integration. In the present series of experiments, we directly tested for a potential critical role of IFG and pMTG by observing the effect of disrupting activity in these areas using transcranial magnetic stimulation in a mixed gender sample of healthy human volunteers. The outcome measure was performance on a Stroop-like gesture task (Kelly et al., 2010a), which provides a behavioral index of gesture-speech integration. Our results provide clear evidence that disrupting activity in IFG and pMTG selectively impairs gesture-speech integration, suggesting that both areas are causally involved in the process. These findings are consistent with the idea that these areas play a joint role in gesture-speech integration, with IFG regulating strategic semantic access via top-down signals acting upon temporal storage areas.SIGNIFICANCE STATEMENT Previous neuroimaging studies suggest an involvement of inferior frontal gyrus and posterior middle temporal gyrus in gesture-speech integration, but findings have been mixed and due to methodological constraints did not allow inferences of causality. By adopting a virtual lesion approach involving transcranial magnetic stimulation, the present study provides clear evidence that both areas are causally involved in combining semantic information arising from gesture and speech. These findings support the view that, rather than being separate entities, gesture and speech are part of an integrated multimodal language system, with inferior frontal gyrus and posterior middle temporal gyrus serving as critical nodes of the cortical network underpinning this system.

Hand gestures as visual prosody: BOLD responses to audio-visual alignment are modulated by the communicative nature of the stimuli.

During public addresses, speakers accompany their discourse with spontaneous hand gestures (beats) that are tightly synchronized with the prosodic contour of the discourse. It has been proposed that speech and beat gestures originate from a common underlying linguistic process whereby both speech prosody and beats serve to emphasize relevant information. We hypothesized that breaking the consistency between beats and prosody by temporal desynchronization, would modulate activity of brain areas sensitive to speech-gesture integration. To this aim, we measured BOLD responses as participants watched a natural discourse where the speaker used beat gestures. In order to identify brain areas specifically involved in processing hand gestures with communicative intention, beat synchrony was evaluated against arbitrary visual cues bearing equivalent rhythmic and spatial properties as the gestures. Our results revealed that left MTG and IFG were specifically sensitive to speech synchronized with beats, compared to the arbitrary vision-speech pairing. Our results suggest that listeners confer beats a function of visual prosody, complementary to the prosodic structure of speech. We conclude that the emphasizing function of beat gestures in speech perception is instantiated through a specialized brain network sensitive to the communicative intent conveyed by a speaker with his/her hands.

The Role of Auditory Itch Contagion in Psoriasis.

Itch and associated scratching is a common and distressing symptom of psoriasis. Here, we tested whether people with psoriasis, relative to healthy controls, show an increased vulnerability to auditory itch contagion (a deleterious influence) when presented with sounds of itch-associated actions of scratching and rubbing. We were also interested in whether manipulating the high frequency volume of these sounds alters itch perception. Results show that both groups rated scratching sounds as more itch-inducing than rubbing sounds, and the amount of induced itch increased as a function of high frequency volume. Furthermore, the influence of high frequency volume on induced itch was more pronounced in the psoriasis group, relative to controls. These findings demonstrate the role of auditory cues in eliciting sensations of itchiness in the absence of peripheral stimulation. Reducing the high frequency volume of itch-associated sounds may offer a novel approach for targeted multisensory itch interventions.

Brain oxygenation patterns during the execution of tool use demonstration, tool use pantomime, and body-part-as-object tool use.

Divergent findings exist whether left and right hemispheric pre- and postcentral cortices contribute to the production of tool use related hand movements. In order to clarify the neural substrates of tool use demonstrations with tool in hand, tool use pantomimes without tool in hand, and body-part-as-object presentations of tool use (BPO) in a naturalistic mode of execution, we applied functional Near InfraRed Spectroscopy (fNIRS) in twenty-three right-handed participants. Functional NIRS techniques allow for the investigation of brain oxygenation during the execution of complex hand movements with an unlimited movement range. Brain oxygenation patterns were retrieved from 16 channels of measurement above pre- and postcentral cortices of each hemisphere. The results showed that tool use demonstration with tool in hand leads to increased oxygenation as compared to tool use pantomimes in the left hemispheric somatosensory gyrus. Left hand executions of the demonstration of tool use, pantomime of tool use, and BPO of tool use led to increased oxygenation in the premotor and somatosensory cortices of the left hemisphere as compared to right hand executions of either condition. The results indicate that the premotor and somatosensory cortices of the left hemisphere constitute relevant brain structures for tool related hand movement production when using the left hand, whereas the somatosensory cortex of the left hemisphere seems to provide specific mental representations when performing tool use demonstrations with the tool in hand.

Inconsistent use of gesture space during abstract pointing impairs language comprehension.

Pointing toward concrete objects is a well-known and efficient communicative strategy. Much less is known about the communicative effectiveness of abstract pointing where the pointing gestures are directed to "empty space." McNeill's (2003) observations suggest that abstract pointing can be used to establish referents in gesture space, without the referents being physically present. Recently, however, it has been shown that abstract pointing typically provides redundant information to the uttered speech thereby suggesting a very limited communicative value (So et al., 2009). In a first approach to tackle this issue we were interested to know whether perceivers are sensitive at all to this gesture cue or whether it is completely discarded as irrelevant add-on information. Sensitivity to for instance a gesture-speech mismatch would suggest a potential communicative function of abstract pointing. Therefore, we devised a mismatch paradigm in which participants watched a video where a female was interviewed on various topics. During her responses, she established two concepts in space using abstract pointing (e.g., pointing to the left when saying Donald, and pointing to the right when saying Mickey). In the last response to each topic, the pointing gesture accompanying a target word (e.g., Donald) was either consistent or inconsistent with the previously established location. Event related brain potentials showed an increased N400 and P600 when gesture and speech referred to different referents, indicating that inconsistent use of gesture space impairs language comprehension. Abstract pointing was found to influence comprehension even though gesture was not crucial to understanding the sentences or conducting the experimental task. These data suggest that a referent was retrieved via abstract pointing and that abstract pointing can potentially be used for referent indication in a discourse. We conclude that abstract pointing has a potential communicative function.

EasyDIAg: A tool for easy determination of interrater agreement.

Reliable measurements are fundamental for the empirical sciences. In observational research, measurements often consist of observers categorizing behavior into nominal-scaled units. Since the categorization is the outcome of a complex judgment process, it is important to evaluate the extent to which these judgments are reproducible, by having multiple observers independently rate the same behavior. A challenge in determining interrater agreement for timed-event sequential data is to develop clear objective criteria to determine whether two raters' judgments relate to the same event (the linking problem). Furthermore, many studies presently report only raw agreement indices, without considering the degree to which agreement can occur by chance alone. Here, we present a novel, free, and open-source toolbox (EasyDIAg) designed to assist researchers with the linking problem, while also providing chance-corrected estimates of interrater agreement. Additional tools are included to facilitate the development of coding schemes and rater training.

Functional and structural brain differences associated with mirror-touch synaesthesia.

Observing touch is known to activate regions of the somatosensory cortex but the interpretation of this finding is controversial (e.g. does it reflect the simulated action of touching or the simulated reception of touch?). For most people, observing touch is not linked to reported experiences of feeling touch but in some people it is (mirror-touch synaesthetes). We conducted an fMRI study in which participants (mirror-touch synaesthetes, controls) watched movies of stimuli (face, dummy, object) being touched or approached. In addition we examined whether mirror touch synaesthesia is associated with local changes of grey and white matter volume in the brain using VBM (voxel-based morphometry). Both synaesthetes and controls activated the somatosensory system (primary and secondary somatosensory cortices, SI and SII) when viewing touch, and the same regions were activated (by a separate localiser) when feeling touch--i.e. there is a mirror system for touch. However, when comparing the two groups, we found evidence that SII seems to play a particular important role in mirror-touch synaesthesia: in synaesthetes, but not in controls, posterior SII was active for watching touch to a face (in addition to SI and posterior temporal lobe); activity in SII correlated with subjective intensity measures of mirror-touch synaesthesia (taken outside the scanner), and we observed an increase in grey matter volume within the SII of the synaesthetes' brains. In addition, the synaesthetes showed hypo-activity when watching touch to a dummy in posterior SII. We conclude that the secondary somatosensory cortex has a key role in this form of synaesthesia.

Neural basis of contagious itch and why some people are more prone to it.

Watching someone scratch himself can induce feelings of itchiness in the perceiver. This provides a unique opportunity to characterize the neural basis of subjective experiences of itch, independent of changes in peripheral inputs. In this study, we first established that the social contagion of itch is essentially a normative response (experienced by most people), and that the degree of contagion is related to trait differences in neuroticism (i.e., the tendency to experience negative emotions), but not to empathy. Watching video clips of someone scratching (relative to control videos of tapping) activated, as indicated by functional neuroimaging, many of the neural regions linked to the physical perception of itch, including anterior insular, primary somatosensory, and prefrontal (BA44) and premotor cortices. Moreover, activity in the left BA44, BA6, and primary somatosensory cortex was correlated with subjective ratings of itchiness, and the responsivity of the left BA44 reflected individual differences in neuroticism. Our findings highlight the central neural generation of the subjective experience of somatosensory perception in the absence of somatosensory stimulation. We speculate that the habitual activation of this central "itch matrix" may give rise to psychogenic itch disorders.

Gesture facilitates the syntactic analysis of speech.

Recent research suggests that the brain routinely binds together information from gesture and speech. However, most of this research focused on the integration of representational gestures with the semantic content of speech. Much less is known about how other aspects of gesture, such as emphasis, influence the interpretation of the syntactic relations in a spoken message. Here, we investigated whether beat gestures alter which syntactic structure is assigned to ambiguous spoken German sentences. The P600 component of the Event Related Brain Potential indicated that the more complex syntactic structure is easier to process when the speaker emphasizes the subject of a sentence with a beat. Thus, a simple flick of the hand can change our interpretation of who has been doing what to whom in a spoken sentence. We conclude that gestures and speech are integrated systems. Unlike previous studies, which have shown that the brain effortlessly integrates semantic information from gesture and speech, our study is the first to demonstrate that this integration also occurs for syntactic information. Moreover, the effect appears to be gesture-specific and was not found for other stimuli that draw attention to certain parts of speech, including prosodic emphasis, or a moving visual stimulus with the same trajectory as the gesture. This suggests that only visual emphasis produced with a communicative intention in mind (that is, beat gestures) influences language comprehension, but not a simple visual movement lacking such an intention.

"That's not a real body": identifying stimulus qualities that modulate synaesthetic experiences of touch.

Mirror-touch synaesthesia is a condition where observing touch to another's body induces a subjective tactile sensation on the synaesthetes body. The present study explores which characteristics of the inducing stimulus modulate the synaesthetic touch experience. Fourteen mirror-touch synaesthetes watched videos depicting a touch event while indicating (i) whether the video induced a tactile sensation, (ii) on which side of their body they felt this sensation and (iii) the intensity of the experienced sensation. Results indicate that the synaesthetes experience stronger tactile sensations when observing touch to real bodies, whereas observing touch to dummy bodies, pictures of bodies and disconnected dummy body parts elicited weaker sensations. These results suggest that mirror-touch synaesthesia is not entirely bottom-up driven, but top-down information, such as knowledge about real and dummy body parts, also modulate the intensity of the experience.

What iconic gesture fragments reveal about gesture-speech integration: when synchrony is lost, memory can help.

The present series of experiments explores several issues related to gesture-speech integration and synchrony during sentence processing. To be able to more precisely manipulate gesture-speech synchrony, we used gesture fragments instead of complete gestures, thereby avoiding the usual long temporal overlap of gestures with their coexpressive speech. In a pretest, the minimal duration of an iconic gesture fragment needed to disambiguate a homonym (i.e., disambiguation point) was therefore identified. In three subsequent ERP experiments, we then investigated whether the gesture information available at the disambiguation point has immediate as well as delayed consequences on the processing of a temporarily ambiguous spoken sentence, and whether these gesture-speech integration processes are susceptible to temporal synchrony. Experiment 1, which used asynchronous stimuli as well as an explicit task, showed clear N400 effects at the homonym as well as at the target word presented further downstream, suggesting that asynchrony does not prevent integration under explicit task conditions. No such effects were found when asynchronous stimuli were presented using a more shallow task (Experiment 2). Finally, when gesture fragment and homonym were synchronous, similar results as in Experiment 1 were found, even under shallow task conditions (Experiment 3). We conclude that when iconic gesture fragments and speech are in synchrony, their interaction is more or less automatic. When they are not, more controlled, active memory processes are necessary to be able to combine the gesture fragment and speech context in such a way that the homonym is disambiguated correctly.