PsySuite: An android application designed to perform multimodal psychophysical testing.

In behavioral sciences, there is growing concern about the inflation of false-positive rates due to the amount of under-powered studies that have been shared in the past years. While problematic, having the possibility to recruit (lots of) participants (for a lot of time) is realistically not achievable for many research facilities. Factors that hinder the reaching of optimal sample sizes are, to name but a few, research costs, participants' availability and commitment, and logistics. We challenge these issues by introducing PsySuite, an Android app designed to foster a remote approach to multimodal behavioral testing. To validate PsySuite, we first evaluated its ability to generate stimuli appropriate to rigorous psychophysical testing, measuring both the app's accuracy (i.e., stimuli's onset, offset, and multimodal simultaneity) and precision (i.e., the stability of a given pattern across trials), using two different smartphone models. We then evaluated PsySuite's ability to replicate perceptual performances obtained using a classic psychophysical paradigm, comparing sample data collected with the app against those measured via a PC-based setup. Our results showed that PsySuite could accurately reproduce stimuli with a minimum duration of 7 ms, 17 ms, and 30 ms for the auditory, visual, and tactile modalities, respectively, and that perceptual performances obtained with PsySuite were consistent with the perceptual behavior observed using the classical setup. Combined with the high accessibility inherently supported by PsySuite, here we ought to share the app to further boost psychophysical research, aiming at setting it to a cheap, user-friendly, and portable level.

Computational modeling of human multisensory spatial representation by a neural architecture.

Our brain constantly combines sensory information in unitary percept to build coherent representations of the environment. Even though this process could appear smooth, integrating sensory inputs from various sensory modalities must overcome several computational issues, such as recoding and statistical inferences problems. Following these assumptions, we developed a neural architecture replicating humans' ability to use audiovisual spatial representations. We considered the well-known ventriloquist illusion as a benchmark to evaluate its phenomenological plausibility. Our model closely replicated human perceptual behavior, proving a truthful approximation of the brain's ability to develop audiovisual spatial representations. Considering its ability to model audiovisual performance in a spatial localization task, we release our model in conjunction with the dataset we recorded for its validation. We believe it will be a powerful tool to model and better understand multisensory integration processes in experimental and rehabilitation environments.

Deaf individuals use compensatory strategies to estimate visual time events.

Temporal perception is so profoundly linked to hearing that congenitally and early deaf individuals appear to experience visual temporal impairments. However, most studies investigated visual temporal perception in deaf individuals using static stimuli, while ecological objects with which we interact in everyday life often move across space and time. Given that deafness does not impact spatial metric representations, we hypothesize that, while the temporal perception of static stimuli is altered after early hearing loss, it can be enhanced by providing additional, ecologically relevant information. To evaluate our hypothesis, deaf and hearing participants were tested using an oddball-like visual temporal task. In such a task, participants had to temporally discriminate a Target embedded in a series of static stimuli, whose spatiotemporal structure was dynamically manipulated during the presentation. Our results highlighted that deaf participants could not successfully discriminate the Target's duration when only temporal information was manipulated, while their temporal sensitivity significantly improved when coherent spatiotemporal information was displayed. Our findings suggest that deaf individuals might develop compensatory strategies based on other visual, non-temporal features to estimate external time events.

The development of adaptation aftereffects in the vibrotactile domain.

Sensory adaptation is a feature-specific modulation of neural responses and is potentially fundamental to maximizing perceptual sensitivity. Despite its function being unclear, it has been hypothesized that sensory adaptation modifies the neurons' response codes, increasing the ability to process sensory signals on a larger scale. To better understand how such flexibility of our brain is possible, we investigated the effect of high- and low-frequency vibrotactile adaptation on perceived tactile temporal frequency during childhood, a time known for the brain to experience varying levels of plasticity. We tested tactile temporal frequency discrimination thresholds in both children and adults before and after tactile adaptation. Our results demonstrate that sensory adaptation does not consistently change perceived tactile temporal frequency in younger children as it does in adults, as adult-like trends begin to emerge at around 8 years of age but consolidate only in 10-year-old children. The absence of adaptation aftereffects suggests that, under certain conditions, sensory history does not affect perception in younger children in a similar way to adults. Surprisingly, younger children proved to be less flexible in modulating neural responses after prolonged exposure to an adapting stimulus, a tendency conflicting with the high plasticity levels the brain experiences during the early stages of life. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Distortions of visual time induced by motor adaptation.

As perception of time is fundamental for action planning and execution, we investigated how action distorts the perception of visual duration. Participants adapted to tapping in midair for a few seconds, either slowly or quickly, then judged the relative duration of 2 drifting gratings, 1 spatially coincident with the tapped region and the other in the opposite field. Fast tapping decreased apparent duration in the tapping region while slow tapping increased it. The effect was spatially specific in external (not body-centered) coordinates, occurring within a 10° region centered on the tapping hand. Within this space, motor adaptation similarly distorts visual numerosity, suggesting common mechanisms for number and time. However, motor adaptation did not affect the perception of speed, a lower level visual property, suggesting that the interactions were at a high level of processing. These results reinforce studies that suggest that visual time perception is coupled with action and suggest the existence of multiple local visuomotor clocks. (PsycInfo Database Record (c) 2020 APA, all rights reserved).