Integration of Bimodal Looming Signals through Neuronal Coherence in the Temporal Lobe

Abstract

The ability to integrate information across multiple sensory systems offers several behavioral advantages, from quicker reaction times and more accurate responses to better detection and more robust learning. At the neural level, multisensory integration requires large-scale interactions between different brain regions--the convergence of information from separate sensory modalities, represented by distinct neuronal populations. The interactions between these neuronal populations must be fast and flexible, so that behaviorally relevant signals belonging to the same object or event can be immediately integrated and integration of unrelated signals can be prevented. Looming signals are a particular class of signals that are behaviorally relevant for animals and that occur in both the auditory and visual domain. These signals indicate the rapid approach of objects and provide highly salient warning cues about impending impact. We show here that multisensory integration of auditory and visual looming signals may be mediated by functional interactions between auditory cortex and the superior temporal sulcus, two areas involved in integrating behaviorally relevant auditory-visual signals. Audiovisual looming signals elicited increased gamma-band coherence between these areas, relative to unimodal or receding-motion signals. This suggests that the neocortex uses fast, flexible intercortical interactions to mediate multisensory integration.

Multidimensional processing of dynamic sounds: more than meets the ear

“…In audiovisual processing, this law suggests that redundant information from an irrelevant modality can benefit the perception of the target signal to the extent that the target signal is weak in the first place. Previous studies have shown that sounds with rising amplitude evoke greater neural responses than do falling sounds (Maier, Chandrasekaran & Ghazanfar, 2008;Maier & Ghazanfar, 2007), consistent with our finding of faster and more accurate detection of rising sounds across conditions. Given that processing of falling sounds was relatively inferior to processing of rising sounds, inverse effectiveness would predict a greater facilitation of detection for falling sounds when congruent cross-modal cues are available.…”

“…Looming sounds (typically, an increase in amplitude) can serve as a warning of impending contact (Bach, Schachinger, Neuhoff, Esposito, Di Salle, Lehmann & Seifritz, 2008;Ghazanfar, Neuhoff & Logothetis, 2002) and are more likely to speed up responses, bias attention and change distance estimates (Ghazanfar et al, 2002;Maier et al, 2004;Neuhoff, 1998Neuhoff, , 2001, and induce stronger neural activation than are receding or constant sounds (Bach et al, 2008;Maier et al, 2008;Maier & Ghazanfar, 2007;Seifritz et al, 2002). Although frequency spectrum, reverberant energy, and interaural differences also vary with sound motion in depth (Hall & Moore, 2003;Zahorik, 2002), modulating sound amplitude is sufficient to produce the response biases associated with looming sounds (Bach, Neuhoff, Perrig & Seifritz, 2009) and activate cortical areas known to respond to auditory motion (Seifritz, Neuhoff, Bilecen, Scheffler, Mustovic, Schachinger & Di Salle, 2002).…”

Auditory–Visual Multisensory Interactions in Humans: Timing, Topography, Directionality, and Sources

“…Multisensory stimulation appears to result in more extensive functional coupling between primary auditory and visual cortices as well as pSTS. Similar findings have been reported in studies of macaque monkeys Maier et al, 2008;. Recordings in these studies were limited to auditory regions and STS (no electrodes were implanted in visual cortices), Nonetheless, these studies showed there to be functional coupling between auditory cortex and the STS in the theta and beta frequency bands of the local field potential as well as between auditory belt regions and the STS at higher gamma frequencies above 50 Hz Maier et al, 2008).…”

Category-selective phase coding in the superior temporal sulcus

“…These results add to the growing body of literature on coding stimulus attributes by assignment to different oscillatory phases (15)(16)(17)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39) (16). Much of the existing literature focuses on invertebrate and hippocampal circuits, demonstrating proof of coding principle; however, more recently phase coding has been observed in V1 for visual stimuli (15,16) and in the prefrontal cortex (PFC) for item order during working memory (17).…”