RESUMO
Multimodal integration is crucial for human interaction, in particular for social communication, which relies on integrating information from various sensory modalities. Recently a third visual pathway specialized in social perception was proposed, which includes the right superior temporal sulcus (STS) playing a key role in processing socially relevant cues and high-level social perception. Importantly, it has also recently been proposed that the left STS contributes to audiovisual integration of speech processing. In this article, we propose that brain areas along the right STS that support multimodal integration for social perception and cognition can be considered homologs to those in the left, language-dominant hemisphere, sustaining multimodal integration of speech and semantic concepts fundamental for social communication. Emphasizing the significance of the left STS in multimodal integration and associated processes such as multimodal attention to socially relevant stimuli, we underscore its potential relevance in comprehending neurodevelopmental conditions characterized by challenges in social communication such as autism spectrum disorder (ASD). Further research into this left lateral processing stream holds the promise of enhancing our understanding of social communication in both typical development and ASD, which may lead to more effective interventions that could improve the quality of life for individuals with atypical neurodevelopment.
Assuntos
Cognição Social , Percepção da Fala , Lobo Temporal , Humanos , Lobo Temporal/fisiologia , Lobo Temporal/fisiopatologia , Percepção da Fala/fisiologia , Percepção Social , Transtorno Autístico/fisiopatologia , Transtorno Autístico/psicologia , Lateralidade Funcional/fisiologiaRESUMO
Selective attentional biases arising from one sensory modality manifest in others. The effects of visuospatial attention, important in visual object perception, are unclear in the auditory domain during audiovisual (AV) scene processing. We investigate temporal and spatial factors that underlie such transfer neurally. Auditory encoding of random tone pips in AV scenes was addressed via a temporal response function model (TRF) of participants' electroencephalogram (N = 30). The spatially uninformative pips were associated with spatially distributed visual contrast reversals ("flips"), through asynchronous probabilistic AV temporal onset distributions. Participants deployed visuospatial selection on these AV stimuli to perform a task. A late (~300 ms) cross-modal influence over the neural representation of pips was found in the original and a replication study (N = 21). Transfer depended on selected visual input being (i) presented during or shortly after a related sound, in relatively limited temporal distributions (<165 ms); (ii) positioned across limited (1:4) visual foreground to background ratios. Neural encoding of auditory input, as a function of visual input, was largest at visual foreground quadrant sectors and lowest at locations opposite to the target. The results indicate that ongoing neural representations of sounds incorporate visuospatial attributes for auditory stream segregation, as cross-modal transfer conveys information that specifies the identity of multisensory signals. A potential mechanism is by enhancing or recalibrating the tuning properties of the auditory populations that represent them as objects. The results account for the dynamic evolution under visual attention of multisensory integration, specifying critical latencies at which relevant cortical networks operate.
RESUMO
La magnetoencefalografía es una técnica de neuroimagen no invasiva que mide, con gran exactitud temporal, los campos magnéticos en la superficie de la cabeza producidos por corrientes neuronales en regiones cerebrales. Esta técnica es sumamente útil en la investigación básica y clínica, porque además permite ubicar el origen de la actividad neural en el cerebro. En esta revisión se abordan aspectos básicos de la biofísica del método y se discuten los hallazgos sobre procesos como la percepción del habla, la atención auditiva y la integración de la información visual y auditiva, que son importantes en la investigación. Igualmente, se ilustran sus ventajas, sus limitaciones y las nuevas tendencias en la investigación con magnetoencefalografía.
Magnetoencephalography is a noninvasive imaging technique that measures the magnetic fields on the surface of the head --produced by neuronal currents in brain regions -- and provides highly accurate temporal information. Magnetoencephalography is extremely useful in basic and clinical research as it can also locate the sources of neural activity in the brain. This review chiefly approaches biophysics-related aspects of the method; findings are also discussed on issues such as speech perception, auditory attention and integration of visual-auditory information, which are quintessential in this type of research. Lastly, this review discusses the benefits and limitations of magnetoencephalography and outlines new trends in research with this technique.