Catarina Mendonça

The effect of instruction to synchronize over step frequency while walking with auditory cues on a treadmill

Walking to a pacing stimulus has proven useful in motor rehabilitation, and it has been suggested that spontaneous synchronization could be preferable to intentional synchronization. But it is still unclear if the paced walking effect can occur spontaneously, or if intentionality plays a role. The aim of this work is to analyze the effect of sound pacing on gait with and without instruction to synchronize, and with different rhythmic auditory cues, while walking on a treadmill. Firstly, the baseline step frequency while walking on a treadmill was determined for all participants, followed by experimental sessions with both music and footstep sound cues. Participants were split into two groups, with one being instructed to synchronize their gait to the auditory stimuli, and the other being simply told to walk. Individual auditory cues were generated for each participant: for each trial, cues were provided at the participants baseline walking frequency, at 5% and 10% above baseline, and at 5% and 10% below baseline. This studys major finding was the role of intention on synchronization, given that only the instructed group synchronized their gait with the auditory cues. No differences were found between the effects of step or music stimuli on step frequency. In conclusion, without intention or cues that direct the individuals attention, spontaneous gait synchronization does not occur during treadmill walking.

Predicting auditory space calibration from recent multisensory experience

Multisensory experience can lead to auditory space recalibration. After exposure to discrepant audiovisual stimulation, sound percepts are displaced in space, in the direction of the previous visual stimulation. This study focuses on identifying the factors in recent sensory experience leading to such auditory space shifts. Sequences of five audiovisual pairs were presented, each randomly congruent or discrepant in space. Each sequence was followed by a single auditory trial and two visual trials. In each trial, participants had to identify the perceived stimuli positions. We found that auditory localization is shifted during audiovisual discrepant trials and during subsequent auditory trials, suggesting a recalibration effect. Time did not lead to greater recalibration effects. The last audiovisual trial affects the subsequent auditory shift the most. The number of discrepant trials in a sequence, and the number of consecutive trials in sequence, also correlated with the subsequent auditory shift. To estimate the individual contribution of previously presented trials to the recalibration effect, a best-fitting model was developed to predict the shift in a linear weighted combination of stimulus features: (1) whether matching or discrepant trials occurred in the sequence, (2) total number of discrepant trials, and (3) maximum number of consecutive discrepant trials, (4) whether the last trial was discrepant or not. The selected model consists of a function including as properties the type of stimulus of the last audiovisual sequence trial and the overall probability of mismatching trials in sequence.

Noise abatement and traffic safety: The trade-off of quieter engines and pavements on vehicle detection

Road traffic sounds are a major source of noise pollution in urban areas. But recent developments such as low noise pavements and hybrid/electric engine vehicles cast an optimistic outlook over such an environmental problem. However, it can be argued that engine, tire, and road noise could be relevant sources of information to avoid road traffic conflicts and accidents. In this paper, we analyze the potential trade-offs of traffic-noise abatement approaches in an experimental study, focusing for the first time on the impact and interaction of relevant factors such as pavement type, vehicle type, listeners age, and background noise, on vehicle detection levels. Results reveal that vehicle and pavement type significantly affect vehicle detection. Age is a significant factor, as both younger and older people exhibit lower detection levels of incoming vehicles. Low noise pavements combined with all-electric and hybrid vehicles might pose a severe threat to the safety of vulnerable road users. All factors interact simultaneously, and vehicle detection is best predicted by the loudness signal-to-noise ratio.

Depth Cues and Perceived Audiovisual Synchrony of Biological Motion

Background Due to their different propagation times, visual and auditory signals from external events arrive at the human sensory receptors with a disparate delay. This delay consistently varies with distance, but, despite such variability, most events are perceived as synchronic. There is, however, contradictory data and claims regarding the existence of compensatory mechanisms for distance in simultaneity judgments. Principal Findings In this paper we have used familiar audiovisual events – a visual walker and footstep sounds – and manipulated the number of depth cues. In a simultaneity judgment task we presented a large range of stimulus onset asynchronies corresponding to distances of up to 35 meters. We found an effect of distance over the simultaneity estimates, with greater distances requiring larger stimulus onset asynchronies, and vision always leading. This effect was stronger when both visual and auditory cues were present but was interestingly not found when depth cues were impoverished. Significance These findings reveal that there should be an internal mechanism to compensate for audiovisual delays, which critically depends on the depth information available.

Auditory localization by subjects with unilateral tinnitus

Tinnitus is associated with changes in neural activity. How such alterations impact the localization ability of subjects with tinnitus remains largely unexplored. In this study, subjects with self-reported unilateral tinnitus were compared to subjects with matching hearing loss at high frequencies and to normal-hearing subjects in horizontal and vertical plane localization tasks. Subjects were asked to localize a pink noise source either alone or over background noise. Results showed some degree of difference between subjects with tinnitus and subjects with normal hearing in horizontal plane localization, which was exacerbated by background noise. However, this difference could be explained by different hearing sensitivities between groups. In vertical plane localization there was no difference between groups in the binaural listening condition, but in monaural listening the tinnitus group localized significantly worse with the tinnitus ear. This effect remained when accounting for differences in hearing sensitivity. It is concluded that tinnitus may degrade auditory localization ability, but this effect is for the most part due to the associated levels of hearing loss. More detailed studies are needed to fully disentangle the effects of hearing loss and tinnitus.

Modeling the perception of audiovisual distance: Bayesian causal inference and other models

Studies of audiovisual perception of distance are rare. Here, visual and auditory cue interactions in distance are tested against several multisensory models, including a modified causal inference model. In this causal inference model predictions of estimate distributions are included. In our study, the audiovisual perception of distance was overall better explained by Bayesian causal inference than by other traditional models, such as sensory dominance and mandatory integration, and no interaction. Causal inference resolved with probability matching yielded the best fit to the data. Finally, we propose that sensory weights can also be estimated from causal inference. The analysis of the sensory weights allows us to obtain windows within which there is an interaction between the audiovisual stimuli. We find that the visual stimulus always contributes by more than 80% to the perception of visual distance. The visual stimulus also contributes by more than 50% to the perception of auditory distance, but only within a mobile window of interaction, which ranges from 1 to 4 m.

Reproducing Reality: Multimodal Contributions in Natural Scene Discrimination

Most research on multisensory processing focuses on impoverished stimuli and simple tasks. In consequence, very little is known about the sensory contributions in the perception of real environments. Here, we presented 23 participants with paired comparison tasks, where natural scenes were discriminated in three perceptually meaningful attributes: movement, openness, and noisiness. The goal was to assess the auditory and visual modality contributions in scene discrimination with short (≤500ms) natural scene exposures. The scenes were reproduced in an immersive audiovisual environment with 3D sound and surrounding visuals. Movement and openness were found to be mainly visual attributes with some input from auditory information. In some scenes, the auditory system was able to derive information about movement and openness that was comparable with audiovisual condition already after 500ms stimulation. Noisiness was mainly auditory, but visual information was found to have a facilitatory role in a few scenes. The sensory weights were highly imbalanced in favor of the stronger modality, but the weaker modality was able to affect the bimodal estimate in some scenes.

The Man With the Swollen Tongue

Eosinophilia is defined as an elevation of the eosinophil count above 0.5 × 10 9 /L and it can be further classified in mild, moderate or severe according to blood eosinophil count. It is important to recognize the combination of eosinophilia and symptoms caused by eosinophils in order to make the correct diagnostic workup, so that distinction between secondary, primary and idiopathic forms can be made. The authors present a case of a 72-year-old man with asthma diagnosed during adulthood. He had a history of diarrhea for the last 9 months already investigated with abdominal imaging and colonoscopy and interpreted as a pancolitis of undetermined etiology. He presented to the emergency department complaining of a swollen tongue in the last 2 weeks. His laboratory studies showed leukocytosis and eosinophilia with a negative HIV antibody test. CT scan of the head and neck revealed diffuse thickening of the intrinsic muscles of the tongue. As for the chest CT, it showed right and left upper lobe patchy opacities. Biopsies of the regions affected (tongue, small intestine and colon) showed abundant infiltration by polymorphonuclear eosinophils. The cytoplasmic anti-neutrophil cytoplasmic antibody (C-ANCA) was elevated and, according to the clinical and laboratory data described before, the patient was diagnosed with Churg-Strauss syndrome (CSS). Treatment with corticosteroids and cyclophosphamide led to complete remission of symptoms and eosinophilia. Clinicians must be aware of eosinophil-associated disease, an entity that refers to a wide spectrum of disorders but in which eosinophils play a central role. Eosinophilic granulomatosis with polyangiitis (EGPA), formerly known as CSS, is a rare systemic vasculitis and a better understanding of the disease is still needed. J Med Cases. 2016;7(12):543-546 doi: https://doi.org/10.14740/jmc2677w

Content or reproduction: Natural scene perception in immersive and non-immersive reproduction setups

In this work the effect of reproduction setup on the perception of natural scene attributes was studied. Discrimination of reproduced real-world scenes in movement, openness and noisiness was inspected between an immersive large reproduction setup and a non-immersive small reproduction setup. The results show decreased sensitivity for movement discrimination and increased sensitivity for noisiness discrimination when using the large setup, and content dependent effects for openness discrimination. The results have implications on future content descriptors and quality evaluation in large-screen systems and spatial audio setups.

Reflection orders and auditory distance

The perception of sound distance has been sparsely studied so far. It is assumed to depend on familiar loudness, reverberation, sound spectrum, and parallax, but most of these factors have never been carefully addressed. Reverberation has been mostly analyzed in terms of ratio between direct and indirect sound, and total duration. Here we were interested in assessing the impact of each reflection order on distance localization. We compared sound source discrimination at an intermediate and at a distant location with direct sound only, one, two, three, and four reflection orders in a 2AFC task. At the intermediate distances, normalized psychophysical curves reveal no differentiation between direct sound and up to three reflection orders, but sounds with four reflection orders have significantly lower thresholds. For the distant sources, sounds with four reflection orders yielded the best discrimination slopes, but there was also a clear benefit for sounds with three reflection orders. We discuss the result...