Audiovisual Integration in Apraxia of Speech: EEG Evidence for Processing Differences

Speech perception is a unique audiovisual experience in part because timing of the speech signal is influenced by simultaneous overlapping gestures in coarticulation. Apraxia of speech (AOS) is a motor planning disorder that impairs coarticulation. Imaging studies show that brain regions damaged in AOS are critical to audiovisual speech perception. Although AOS is a motor planning disorder, individuals with AOS may have a disruption to the perceptual system for speech gestures. To evaluate this hypothesis we investigated audiovisual mismatch negativity (MMN) brain responses in adults with damage to Broca’s area (n =5) compared to a healthy age-matched comparison group (n = 5). We utilized the McGurk effect, in which incongruent auditory and visual information alters perception. Participants viewed videos of a speaker articulating the syllable /ba/ (standard) for 80% trials and /ga/ (deviant) for 20% of the trials while the auditory stimulus /ba/ remained consistent throughout. Responses to this McGurk audiovisual condition were compared to an inverse McGurk audiovisual condition in which the visual stimulus remained constant while the auditory stimulus changed, and a visual-only condition without sound to control for evoked activity from changes to the visual stimulus. Incongruent McGurk deviants elicited an MMN over left hemisphere electrodes in the comparison group, while the AOS group exhibited a later, attention-based response, a P300. The AOS group similarly responded to inverse McGurk deviants, which do not require fusion of the percept, with a P300 response, indicating that auditory and visual aspects of the incongruent McGurk deviants were not integrated. In the visual-only control condition, the AOS group showed a left-lateralized MMN, suggesting greater influence of visual processing when confronted with conflicting multisensory information compared to the comparison group. Overall, the comparison group’s responses were indicative of early and automatic audiovisual integration of incongruent McGurk percepts while the responses of the AOS group showed contributions of both attentional and visual processing. The timing of the response in the AOS group was correlated with speech production characteristics of apraxia, as well as performance on taxing motor speech tasks. Results of this study support the hypothesis that AOS is a disorder beyond motor planning, with implications for higher-level linguistic and cognitive systems

Intratumoral Delivery of MDNA55, an Interleukin-4 Receptor Targeted Immunotherapy, by MRI-Guided Convective Delivery for the Treatment of Recurrent Glioblastoma

https://digitalcommons.psjhealth.org/other_pubs/1047/thumbnail.jp

Audiovisual Integration in Apraxia of Speech: EEG Evidence for Processing Differences

Speech perception is a unique audiovisual experience in part because timing of the speech signal is influenced by simultaneous overlapping gestures in coarticulation. Apraxia of speech (AOS) is a motor planning disorder that impairs coarticulation. Imaging studies show that brain regions damaged in AOS are critical to audiovisual speech perception. Although AOS is a motor planning disorder, individuals with AOS may have a disruption to the perceptual system for speech gestures. To evaluate this hypothesis we investigated audiovisual mismatch negativity (MMN) brain responses in adults with damage to Broca’s area (n =5) compared to a healthy age-matched comparison group (n = 5). We utilized the McGurk effect, in which incongruent auditory and visual information alters perception. Participants viewed videos of a speaker articulating the syllable /ba/ (standard) for 80% trials and /ga/ (deviant) for 20% of the trials while the auditory stimulus /ba/ remained consistent throughout. Responses to this McGurk audiovisual condition were compared to an inverse McGurk audiovisual condition in which the visual stimulus remained constant while the auditory stimulus changed, and a visual-only condition without sound to control for evoked activity from changes to the visual stimulus. Incongruent McGurk deviants elicited an MMN over left hemisphere electrodes in the comparison group, while the AOS group exhibited a later, attention-based response, a P300. The AOS group similarly responded to inverse McGurk deviants, which do not require fusion of the percept, with a P300 response, indicating that auditory and visual aspects of the incongruent McGurk deviants were not integrated. In the visual-only control condition, the AOS group showed a left-lateralized MMN, suggesting greater influence of visual processing when confronted with conflicting multisensory information compared to the comparison group. Overall, the comparison group’s responses were indicative of early and automatic audiovisual integration of incongruent McGurk percepts while the responses of the AOS group showed contributions of both attentional and visual processing. The timing of the response in the AOS group was correlated with speech production characteristics of apraxia, as well as performance on taxing motor speech tasks. Results of this study support the hypothesis that AOS is a disorder beyond motor planning, with implications for higher-level linguistic and cognitive systems

Cross-modal integration in the brain is related to phonological awareness only in typical readers, not in those with reading difficulty

Fluent reading requires successfully mapping between visual orthographic and auditory phonological representations and is thus an intrinsically cross-modal process, though reading difficulty has often been characterized as a phonological deficit. However, recent evidence suggests that orthographic information influences phonological processing in typical developing (TD) readers, but that this effect may be blunted in those with reading difficulty (RD), suggesting that the core deficit underlying reading difficulties may be a failure to integrate orthographic and phonological information. Twenty-six (13 TD and 13 RD) children between 8 and 13 years of age participated in a functional magnetic resonance imaging (fMRI) experiment designed to assess the role of phonemic awareness in cross-modal processing. Participants completed a rhyme judgment task for word pairs presented unimodally (auditory only) and cross-modally (auditory followed by visual). For typically developing children, correlations between elision and neural activation were found for the cross-modal but not unimodal task, whereas in children with RD, no correlation was found. The results suggest that elision taps both phonemic awareness and cross-modal integration in typically developing readers, and that these processes are decoupled in children with reading difficulty

Carpaccio’s Original Painting Installation in the Scuola Dalmata: Where and Why

The original installation of Vittore Carpaccio’s narra­tive paintings in the Scuola Dalmata has long been assumed to have been in the upper chapter hall, following the practice used in other Venetian confraternities (Scuole). Studies and observations dur­ing the recent conservation campaign of the canvases have led to a new hypothesis that Carpaccio may very well have instead placed his paintings on the ground floor, as we see them today, due to a heated dispute with the Priory of the Order of Saint John of Jerusalem over the control of the upstairs premises

Neural Correlates of Modality-Sensitive Deviance Detection in the Audiovisual Oddball Paradigm

The McGurk effect, an incongruent pairing of visual /ga/–acoustic /ba/, creates a fusion illusion /da/ and is the cornerstone of research in audiovisual speech perception. Combination illusions occur given reversal of the input modalities—auditory /ga/-visual /ba/, and percept /bga/. A robust literature shows that fusion illusions in an oddball paradigm evoke a mismatch negativity (MMN) in the auditory cortex, in absence of changes to acoustic stimuli. We compared fusion and combination illusions in a passive oddball paradigm to further examine the influence of visual and auditory aspects of incongruent speech stimuli on the audiovisual MMN. Participants viewed videos under two audiovisual illusion conditions: fusion with visual aspect of the stimulus changing, and combination with auditory aspect of the stimulus changing, as well as two unimodal auditory- and visual-only conditions. Fusion and combination deviants exerted similar influence in generating congruency predictions with significant differences between standards and deviants in the N100 time window. Presence of the MMN in early and late time windows differentiated fusion from combination deviants. When the visual signal changes, a new percept is created, but when the visual is held constant and the auditory changes, the response is suppressed, evoking a later MMN. In alignment with models of predictive processing in audiovisual speech perception, we interpreted our results to indicate that visual information can both predict and suppress auditory speech perception

Superimposition of ten NAD⁺ docking poses in the TcSIR2rp1 productive (A) and non-productive (B) forms.

<p>NAD⁺ molecules are represented in brown-capped sticks. Protein structures are represented as ribbons and colored in dark pink and green representing the TcSIR2rp1 productive and non-productive form, respectively. Pocket surfaces were generated with MOE (MOE 2012.10; Chemical Computing Group, Montreal, Canada) and are colored in gray.</p

PLP scores for the anti-trypanosomal compounds docked into <i>Tc</i>SIR2rp1 and <i>Tc</i>SIR2rp3 productive forms.

<p>The compounds selected from the virtual screening for structural inspections are reported in bold.</p