The Perception of Integrated Events in Autism Spectrum Disorders: The Role of Semantic Relatedness and Timing

AbstractAutism Spectrum Disorders (ASD) has been associated with impaired multisensory processing, however research on the topic has been inconclusive. For instance, research on the synchrony perception of complex stimuli has shown that children with ASD have impaired integration of audiovisual speech (e.g., a woman counting or telling a story) but normal non speech integration (e.g., a ball moving through a series of plastic ramps and cliffs; Bebko et al., 2006), while research on adult ASD patients has shown impaired integration for both speech (e.g., syllables) and non speech events (e.g., flash-beeps, handclap; de Boer- Schellekens et al., 2013). Studies utilizing simple stimuli and illusory paradigms such as the double-flash illusion have suggested that individuals with ASD exhibit an extended temporal integration window as compared to healthy participants (Foss-Feig et al., 2010; Kwakye et al., 2011), while others have shown no such effect (e.g., Van der Smagt et al., 2007). It is as yet unclear, therefore, whether or not individuals with ASD have impaired integration mechanisms and whether this impairment is due to the stimuli presented (simple vs. complex; social vs. non social), the population used (adult vs. children, severity of symptoms), and/or the tasks utilized (e.g., preferential looking paradigm vs. temporal order judgments). Additionally, it is as yet unclear whether individuals with ASD are impaired in terms of timing or binding per se (e.g., Freeman et al., 2013). In order to elucidate this issue, we aim to further examine the nature of these deficits through a well-formed group of children with similar symptom severity and two types of tasks. Initially, using a reaction time (RT) task, we will assess the audiovisual integration capabilities of children with ASD as compared to typically developing (TD) children without the involvement of timing (i.e., no timing differences will be introduced). According to the ‘unity effect’, a multisensory event is perceived as an integrated multisensory event (rather than multiple unimodal events) when signals are present close in time and space and due to other factors (e.g., informational relatedness; e.g., Vatakis & Spence, 2007). In the RT experiment, therefore, we will not modulate space and time, but informational relatedness. Specifically, participants will be asked to complete speeded detection of two targets. The targets will be audiovisual, visual, and auditory and for the audiovisual cases the steams will be presented in congruent and incongruent format.Subsequently, the same group of individuals will be tested in a simultaneity judgment (SJ) task where the temporal window of integration will be assessed. The SJ task will target the evaluation of temporal processing. For both tasks, three types of stimuli will be used: a) simple stimuli in order to minimize the meaningful context (Bien et al., 2013), b) stimuli with emotional context depicted through human faces in order to assess ASD processing of facial social stimuli, and c) stimuli with emotional context using body expressions (instead of faces). The use of the RT and SJ tasks we allow the evaluation of the interaction of multisensory integration and synchrony perception in ASD as well as the role of stimulus type (semantic vs. non semantic, social vs. non social) in multisensory processing

Crossmodal Binding Rivalry: An Alternative Hypothesis for the Double Flash Illusion

AbstractExtensive research on multisensory processing has established that temporal and/or spatial proximity of sensory information lead to the percept of a unified multisensory event, both at a behavioral and neuronal level (e.g., Stein, Huneycutt, & Meredith, 1988). Binding of multiple sensory inputs has also been demonstrated for stimuli presented with a certain degree of temporal disparity (e.g., Vatakis & Spence, 2010). A classical example of crossmodal interaction is the well-known sound induced flash illusion (SIFI; whereby a brief flash paired with two auditory beeps is actually perceived as two distinct flashes; Shams, Kamitani, & Shimojo, 2000). SIFI is considered an example of auditory dominance, where auditory stimulation modulates visual perception for audiovisual presentations that fall within the temporal window of integration. Studies on the SIFI (Andersen, Tiipana, & Sams, 2004; Shams, Kamitani, & Shimojo, 2002) have shown diminished performance in 1 flash-2 beeps (SIFI illusion) and 2 flash-1 beep presentations (considered different from SIFI but as yet not elucidated), while the performance in 1 flash-1 beep is excellent. That is, the close in time-space presence of 2 versus 1 input from different sensory modalities affects participant performance, while this is not the case for presentations of equal number of sensory stimulus inputs. We claim that the diminished performance in 1 flash-2 beeps and 2 flash-1 beep conditions are not two different illusions but they both represent examples of the crossmodal binding rivalry between the unequal number of sensory inputs presented. That is, presentations of multiple sensory inputs in close spatial and temporal proximity lead to a rivalry between the sensory inputs that are to be integrated. This rivalry will be weaker or stronger depending on a number of findings related to multisensory integration.As has been previously shown, a unified multisensory percept is more robust if the visual input is presented slightly before or in synchrony with the auditory input (Keetels & Vroomen, 2012; van Wassenhove, Grant, & Poeppel, 2007; Vatakis & Spence, 2007, 2008). In cases where the auditory input precedes the visual, binding is weaker leading to a less integrated percept. Moreover, binding is highly dependent on timing with temporally proximal presentations taking precedence over distal presentations (e.g., Vatakis & Spence, 2010). Thus, presentations of asynchronous stimuli even if presented within the temporal window of integration represent binding types of different strength with synchronous presentations being the ones leading to higher binding. These findings drive our crossmodal binding rivalry hypothesis and we support that the rivalry between the unequal number of sensory inputs will vary according to their binding robustness. So, for inputs where the visual is in synchrony or leading the auditory input, the binding is robust leading to a stronger rivalry with the spare stimulus. This rivalry results to a lower percent of illusory percepts and slower reaction times. On the other hand, if the binding between the auditory and visual inputs is weak, then the rivalry between them and the spare stimulus is less intense, thus resulting in quicker responding and higher illusory experiences. Generally, during illusion conditions, we expect to have slower reaction times than in conditions with equal number of visual and auditory inputs and in bimodal conditions (equal number of inputs) more accurate responses than in unimodal conditions.We have tested directly the rivalry hypothesis by utilizing the classical SIFI but with multiple timing presentations (never tested before in one experimental set-up). More specifically, we have used 0, 25, 50, and 100ms onset asynchronies of auditory beep before and after the visual flash. Illusion conditions and test conditions were intermixed in order to avoid biased responding (in terms of the number of flashes) and to be sure that the task is not too difficult for the participants to carry out. The proposed project will allow us to evaluate the rivalry hypothesis for multiple audiovisual inputs, which will provide a common explanation for both 1 flash-2 beeps and 2 flash-1 beep presentations, while at the same time it will allow the revisiting of the role of auditory dominance in the double flash illusion

Time Distortions in Mind

Time Distortions in Mind brings together current research on temporal processing in clinical populations to elucidate the interdependence between perturbations in timing and disturbances in the mind and brain. For the student, the scientist, and the stepping-stone for further research

Assisted spatial navigation: new directions

Blockchain technology brings new possibilities in assisted spatial navigation. Decentralized map building enables collaboration between users around the world, while providing researchers with a common reference map for extending the capabilities of navigational systems towards more intuitive and accurate landmark navigation assistance. Research on landmark navigation has been mainly focused on the visual characteristics of landmarks. Human behavior, however, has systematically been shown to be enhanced in the presence of multisensory unified events. We propose, therefore, the enhancement of spatial assisted navigation by utilizing landmarks that are multisensory and semantically congruent. Further, our research will provide insights in terms of the auditory parameters that could be combined with a given visual landmark, so as to facilitate landmark retrieval algorithms and user satisfaction during assisted spatial navigation

Timing and Time Perception: Procedures, Measures, and Applications

Timing and Time Perception: Procedures, Measures, and Applications is a one-of-a-kind, collective effort to present the most utilized and known methods on timing and time perception. Specifically, it covers methods and analysis on circadian timing, synchrony perception, reaction/response time, time estimation, and alternative methods for clinical/developmental research. The book includes experimental protocols, programming code, and sample results and the content ranges from very introductory to more advanced so as to cover the needs of both junior and senior researchers. We hope that this will be the first step in future efforts to document experimental methods and analysis both in a theoretical and in a practical manner

Viral complementation allows HIV-1 replication without integration

<p>Abstract</p> <p>Background</p> <p>The integration of HIV-1 DNA into cellular chromatin is required for high levels of viral gene expression and for the production of new virions. However, the majority of HIV-1 DNA remains unintegrated and is generally considered a replicative dead-end. A limited amount of early gene expression from unintegrated DNA has been reported, but viral replication does not proceed further in cells which contain only unintegrated DNA. Multiple infection of cells is common, and cells that are productively infected with an integrated provirus frequently also contain unintegrated HIV-1 DNA. Here we examine the influence of an integrated provirus on unintegrated HIV-1 DNA (uDNA).</p> <p>Results</p> <p>We employed reporter viruses and quantitative real time PCR to examine gene expression and virus replication during coinfection with integrating and non-integrating HIV-1. Most cells which contained only uDNA displayed no detected expression from fluorescent reporter genes inserted into early (Rev-independent) and late (Rev-dependent) locations in the HIV-1 genome. Coinfection with an integrated provirus resulted in a several fold increase in the number of cells displaying uDNA early gene expression and efficiently drove uDNA into late gene expression. We found that coinfection generates virions which package and deliver uDNA-derived genomes into cells; in this way uDNA completes its replication cycle by viral complementation. uDNA-derived genomes undergo recombination with the integrated provirus-derived genomes during second round infection.</p> <p>Conclusion</p> <p>This novel mode of retroviral replication allows survival of viruses which would otherwise be lost because of a failure to integrate, amplifies the effective amount of cellular coinfection, increases the replicating HIV-1 gene pool, and enhances the opportunity for diversification through errors of polymerization and recombination.</p

BSAVA Formulary: Your questions answered

A new edition of the BSAVA Small Animal Formulary has been published. Ian Ramsey explains what is in and what is out of this new version

Overlapping but Divergent Neural Correlates Underpinning Audiovisual Synchrony and Temporal Order Judgments

Multisensory processing is a core perceptual capability, and the need to understand its neural bases provides a fundamental problem in the study of brain function. Both synchrony and temporal order judgments are commonly used to investigate synchrony perception between different sensory cues and multisensory perception in general. However, extensive behavioral evidence indicates that these tasks do not measure identical perceptual processes. Here we used functional magnetic resonance imaging to investigate how behavioral differences between the tasks are instantiated as neural differences. As these neural differences could manifest at either the sustained (task/state-related) and/or transient (event-related) levels of processing, a mixed block/event-related design was used to investigate the neural response of both time-scales. Clear differences in both sustained and transient BOLD responses were observed between the two tasks, consistent with behavioral differences indeed arising from overlapping but divergent neural mechanisms. Temporal order judgments, but not synchrony judgments, required transient activation in several left hemisphere regions, which may reflect increased task demands caused by an extra stage of processing. Our results highlight that multisensory integration mechanisms can be task dependent, which, in particular, has implications for the study of atypical temporal processing in clinical populations