Multisensory Enhancement Research Articles

Deactivation of Association Cortices Disrupted the Congruence of Visual and Auditory Receptive Fields in Superior Colliculus Neurons.

Physiological and behavioral studies in cats show that corticotectal inputs play a critical role in the information-processing capabilities of neurons in the deeper layers of the superior colliculus (SC). Among them, the sensory inputs from functionally related associational cortices are especially critical for SC multisensory integration. However, the underlying mechanism supporting this influence is still unclear. Here, results demonstrate that deactivation of relevant cortices can both dislocate SC visual and auditory spatial receptive fields (RFs) and decrease their overall size, resulting in reduced alignment. Further analysis demonstrated that this RF separation is significantly correlated with the decrement of neurons' multisensory enhancement and is most pronounced in low stimulus intensity conditions. In addition, cortical deactivation could influence the degree of stimulus effectiveness, thereby illustrating the means by which higher order cortices may modify the multisensory activity of SC.

Multisensory Enhancements with Unconscious Visual Stimuli in Posterior Cortical Atrophy

Multisensory Enhancements with Unconscious Visual Stimuli in Posterior Cortical Atrophy

Augmenting sensorimotor control using "goal-aware" vibrotactile stimulation during reaching and manipulation behaviors.

We describe two sets of experiments that examine the ability of vibrotactile encoding of simple position error and combined object states (calculated from an optimal controller) to enhance performance of reaching and manipulation tasks in healthy human adults. The goal of the first experiment (tracking) was to follow a moving target with a cursor on a computer screen. Visual and/or vibrotactile cues were provided in this experiment, and vibrotactile feedback was redundant with visual feedback in that it did not encode any information above and beyond what was already available via vision. After only 10minutes of practice using vibrotactile feedback to guide performance, subjects tracked the moving target with response latency and movement accuracy values approaching those observed under visually guided reaching. Unlike previous reports on multisensory enhancement, combining vibrotactile and visual feedback of performance errors conferred neither positive nor negative effects on task performance. In the second experiment (balancing), vibrotactile feedback encoded a corrective motor command as a linear combination of object states (derived from a linear-quadratic regulator implementing a trade-off between kinematic and energetic performance) to teach subjects how to balance a simulated inverted pendulum. Here, the tactile feedback signal differed from visual feedback in that it provided information that was not readily available from visual feedback alone. Immediately after applying this novel "goal-aware" vibrotactile feedback, time to failure was improved by a factor of three. Additionally, the effect of vibrotactile training persisted after the feedback was removed. These results suggest that vibrotactile encoding of appropriate combinations of state information may be an effective form of augmented sensory feedback that can be applied, among other purposes, to compensate for lost or compromised proprioception as commonly observed, for example, in stroke survivors.

Temporal Cortex Activation to Audiovisual Speech in Normal-Hearing and Cochlear Implant Users Measured with Functional Near-Infrared Spectroscopy.

Background: Speech understanding may rely not only on auditory, but also on visual information. Non-invasive functional neuroimaging techniques can expose the neural processes underlying the integration of multisensory processes required for speech understanding in humans. Nevertheless, noise (from functional MRI, fMRI) limits the usefulness in auditory experiments, and electromagnetic artifacts caused by electronic implants worn by subjects can severely distort the scans (EEG, fMRI). Therefore, we assessed audio-visual activation of temporal cortex with a silent, optical neuroimaging technique: functional near-infrared spectroscopy (fNIRS).Methods: We studied temporal cortical activation as represented by concentration changes of oxy- and deoxy-hemoglobin in four, easy-to-apply fNIRS optical channels of 33 normal-hearing adult subjects and five post-lingually deaf cochlear implant (CI) users in response to supra-threshold unisensory auditory and visual, as well as to congruent auditory-visual speech stimuli.Results: Activation effects were not visible from single fNIRS channels. However, by discounting physiological noise through reference channel subtraction (RCS), auditory, visual and audiovisual (AV) speech stimuli evoked concentration changes for all sensory modalities in both cohorts (p < 0.001). Auditory stimulation evoked larger concentration changes than visual stimuli (p < 0.001). A saturation effect was observed for the AV condition.Conclusions: Physiological, systemic noise can be removed from fNIRS signals by RCS. The observed multisensory enhancement of an auditory cortical channel can be plausibly described by a simple addition of the auditory and visual signals with saturation.

A conceptual framework for the assessment of brand congruent sensory modalities

Companies wishing to engage in multisensory marketing by adding previously unused sensory modalities to their brands need to ask how their brand identity translates into these unoccupied modalities. Identifying brand identity congruent sensory modalities in a unisensory fashion is not helpful as multisensory interaction effects change their meaning. Furthermore, existing sensory evaluation techniques do not meet the requirements of marketing managers to serve this purpose. This article addresses this gap by first analysing a multisensory marketing strategy of adding previously unused sensory modalities to an existing brand. Theory supports this strategy, because it enhances the recognition, evaluation and memory of the brand and lets the brand profit from multisensory enhancement. Paramount for this strategy to work is to guarantee the congruency between the newly added sensory modalities with the existing ones of the brand and the brand personality. Therefore, as a second goal, this article proposes a conceptual framework to assess the congruency of sensory modalities in a multisensory semantic context. A three-step process is presented that draws on evaluation techniques used to assess congruency in psychology and the sensory evaluation of food.

Multisensory interactions between vestibular, visual and somatosensory signals.

Vestibular inputs are constantly processed and integrated with signals from other sensory modalities, such as vision and touch. The multiply-connected nature of vestibular cortical anatomy led us to investigate whether vestibular signals could participate in a multi-way interaction with visual and somatosensory perception. We used signal detection methods to identify whether vestibular stimulation might interact with both visual and somatosensory events in a detection task. Participants were instructed to detect near-threshold somatosensory stimuli that were delivered to the left index finger in one half of experimental trials. A visual signal occurred close to the finger in half of the trials, independent of somatosensory stimuli. A novel Near infrared caloric vestibular stimulus (NirCVS) was used to artificially activate the vestibular organs. Sham stimulations were used to control for non-specific effects of NirCVS. We found that both visual and vestibular events increased somatosensory sensitivity. Critically, we found no evidence for supra-additive multisensory enhancement when both visual and vestibular signals were administered together: in fact, we found a trend towards sub-additive interaction. The results are compatible with a vestibular role in somatosensory gain regulation.

Deconstructing multisensory enhancement in detection.

The mechanisms responsible for the integration of sensory information from different modalities have become a topic of intense interest in psychophysics and neuroscience. Many authors now claim that early, sensory-based cross-modal convergence improves performance in detection tasks. An important strand of supporting evidence for this claim is based on statistical models such as the Pythagorean model or the probabilistic summation model. These models establish statistical benchmarks representing the best predicted performance under the assumption that there are no interactions between the two sensory paths. Following this logic, when observed detection performances surpass the predictions of these models, it is often inferred that such improvement indicates cross-modal convergence. We present a theoretical analyses scrutinizing some of these models and the statistical criteria most frequently used to infer early cross-modal interactions during detection tasks. Our current analysis shows how some common misinterpretations of these models lead to their inadequate use and, in turn, to contradictory results and misleading conclusions. To further illustrate the latter point, we introduce a model that accounts for detection performances in multimodal detection tasks but for which surpassing of the Pythagorean or probabilistic summation benchmark can be explained without resorting to early cross-modal interactions. Finally, we report three experiments that put our theoretical interpretation to the test and further propose how to adequately measure multimodal interactions in audiotactile detection tasks.

Multisensory and modality specific processing of visual speech in different regions of the premotor cortex.

Behavioral and neuroimaging studies have demonstrated that brain regions involved with speech production also support speech perception, especially under degraded conditions. The premotor cortex (PMC) has been shown to be active during both observation and execution of action (“Mirror System” properties), and may facilitate speech perception by mapping unimodal and multimodal sensory features onto articulatory speech gestures. For this functional magnetic resonance imaging (fMRI) study, participants identified vowels produced by a speaker in audio-visual (saw the speaker's articulating face and heard her voice), visual only (only saw the speaker's articulating face), and audio only (only heard the speaker's voice) conditions with varying audio signal-to-noise ratios in order to determine the regions of the PMC involved with multisensory and modality specific processing of visual speech gestures. The task was designed so that identification could be made with a high level of accuracy from visual only stimuli to control for task difficulty and differences in intelligibility. The results of the functional magnetic resonance imaging (fMRI) analysis for visual only and audio-visual conditions showed overlapping activity in inferior frontal gyrus and PMC. The left ventral inferior premotor cortex (PMvi) showed properties of multimodal (audio-visual) enhancement with a degraded auditory signal. The left inferior parietal lobule and right cerebellum also showed these properties. The left ventral superior and dorsal premotor cortex (PMvs/PMd) did not show this multisensory enhancement effect, but there was greater activity for the visual only over audio-visual conditions in these areas. The results suggest that the inferior regions of the ventral premotor cortex are involved with integrating multisensory information, whereas, more superior and dorsal regions of the PMC are involved with mapping unimodal (in this case visual) sensory features of the speech signal with articulatory speech gestures.

Visual-somatosensory integration and balance: evidence for psychophysical integrative differences in aging.

Research detailing multisensory integration (MSI) processes in aging and their association with clinically relevant outcomes is virtually non-existent. To our knowledge, the relationship between MSI and balance has not been well-established in aging. Given known alterations in unisensory processing with increasing age, the aims of the current study were to determine differential behavioral patterns of MSI in aging and investigate whether MSI was significantly associated with balance and fall-risk. Seventy healthy older adults (M = 75 years; 58% female) participated in the current study. Participants were instructed to make speeded responses to visual, somatosensory, and visual-somatosensory (VS) stimuli. Based on reaction times (RTs) to all stimuli, participants were classified into one of two groups (MSI or NO MSI), depending on their MSI RT benefit. Static balance was assessed using mean unipedal stance time. Overall, results revealed that RTs to VS stimuli were significantly shorter than those elicited to constituent unisensory conditions. Further, the current experimental design afforded differential patterns of multisensory processing, with 75% of the elderly sample demonstrating multisensory enhancements. Interestingly, 25% of older adults did not demonstrate multisensory RT facilitation; a finding that was attributed to extremely fast RTs overall and specifically in response to somatosensory inputs. Individuals in the NO MSI group maintained significantly better unipedal stance times and reported less falls, compared to elders in the MSI group. This study reveals the existence of differential patterns of multisensory processing in aging, while describing the clinical translational value of MSI enhancements in predicting balance and falls risk.

Color Selectivity of the Spatial Congruency Effect: Evidence from the Focused Attention Paradigm

ABSTRACT The multisensory response enhancement (MRE), occurring when the response to a visual target integrated with a spatially congruent sound is stronger than the response to the visual target alone, is believed to be mediated by the superior colliculus (SC) (Stein & Meredith, 1993). Here, we used a focused attention paradigm to show that the spatial congruency effect occurs with red (SC-effective) but not blue (SC-ineffective) visual stimuli, when presented with spatially congruent sounds. To isolate the chromatic component of SC-ineffective targets and to demonstrate the selectivity of the spatial congruency effect we used the random luminance modulation technique (Experiment 1) and the tritanopic technique (Experiment 2). Our results indicate that the spatial congruency effect does not require the distribution of attention over different sensory modalities and provide correlational evidence that the SC mediates the effect.

Spatio-temporal measures of electrophysiological correlates for behavioral multisensory enhancement during visual, auditory and somatosensory stimulation: A behavioral and ERP study

Multisensory enhancement, as a facilitation phenomenon, is responsible for superior behavioral performance when an individual is responding to cross-modal versus modality-specific stimuli. However, the event-related potential (ERP) counterparts of behavioral multisensory enhancement are not well known. We recorded ERPs and behavioral data from 14 healthy volunteers with three types of target stimuli (modality-specific, bimodal, and trimodal) to examine the spatio-temporal electrophysiological characteristics of multisensory enhancement by comparing behavioral data with ERPs. We found a strong correlation between P3 latency and behavioral performance in terms of reaction time (RT) (R = 0.98, P <0.001), suggesting that P3 latency constitutes a temporal measure of behavioral multisensory enhancement. In addition, a fast RT and short P3 latency were found when comparing the modality-specific visual target with the modality-specific auditory and somatosensory targets. Our results indicate that behavioral multisensory enhancement can be identified by the latency and source distribution of the P3 component. These findings may advance our understanding of the neuronal mechanisms of multisensory enhancement.

Cellular and Synaptic Architecture of Multisensory Integration in the Mouse Neocortex

Multisensory integration (MI) is crucial for sensory processing, but it is unclear how MI is organized in cortical microcircuits. Whole-cell recordings in a mouse visuotactile area located between primary visual and somatosensory cortices revealed that spike responses were less bimodal than synaptic responses but displayed larger multisensory enhancement. MI was layer and cell type specific, with multisensory enhancement being rare in the major class of inhibitory interneurons and in the output infragranular layers. Optogenetic manipulation of parvalbumin-positive interneuron activity revealed that the scarce MI of interneurons enables MI in neighboring pyramids. Finally, single-cell resolution calcium imaging revealed a gradual merging of modalities: unisensory neurons had higher densities toward the borders of the primary cortices, but were located in unimodal clusters in the middle of the cortical area. These findings reveal the role of different neuronal subcircuits in the synaptic process of MI in the rodent parietal cortex.

Verbal and novel multisensory associative learning in adults

To date, few studies have focused on the behavioural differences between the learning of multisensory auditory-visual and intra-modal associations. More specifically, the relative benefits of novel auditory-visual and verbal-visual associations for learning have not been directly compared. In Experiment 1, 20 adult volunteers completed three paired associate learning tasks: non-verbal novel auditory-visual (novel-AV), verbal-visual (verbal-AV; using pseudowords), and visual-visual (shape-VV). Participants were directed to make a motor response to matching novel and arbitrarily related stimulus pairs. Feedback was provided to facilitate trial and error learning. The results of Signal Detection Theory analyses suggested a multisensory enhancement of learning, with significantly higher discriminability measures (d-prime) in both the novel-AV and verbal-AV tasks than the shape-VV task. Motor reaction times were also significantly faster during the verbal-AV task than during the non-verbal learning tasks. Experiment 2 (n = 12) used a forced-choice discrimination paradigm to assess whether a difference in unisensory stimulus discriminability could account for the learning trends in Experiment 1. Participants were significantly slower at discriminating unisensory pseudowords than the novel sounds and visual shapes, which was notable given that these stimuli produced superior learning. Together the findings suggest that verbal information has an added enhancing effect on multisensory associative learning in adults

Neuromodulation of Early Multisensory Interactions in the Visual Cortex

Merging information derived from different sensory channels allows the brain to amplify minimal signals to reduce their ambiguity, thereby improving the ability of orienting to, detecting, and identifying environmental events. Although multisensory interactions have been mostly ascribed to the activity of higher-order heteromodal areas, multisensory convergence may arise even in primary sensory-specific areas located very early along the cortical processing stream. In three experiments, we investigated early multisensory interactions in lower-level visual areas, by using a novel approach, based on the coupling of behavioral stimulation with two noninvasive brain stimulation techniques, namely, TMS and transcranial direct current stimulation (tDCS). First, we showed that redundant multisensory stimuli can increase visual cortical excitability, as measured by means of phosphene induction by occipital TMS; such physiological enhancement is followed by a behavioral facilitation through the amplification of signal intensity in sensory-specific visual areas. The more sensory inputs are combined (i.e., trimodal vs. bimodal stimuli), the greater are the benefits on phosphene perception. Second, neuroelectrical activity changes induced by tDCS in the temporal and in the parietal cortices, but not in the occipital cortex, can further boost the multisensory enhancement of visual cortical excitability, by increasing the auditory and tactile inputs from temporal and parietal regions, respectively, to lower-level visual areas.

Verbal and novel multisensory associative learning in adults

To date, few studies have focused on the behavioural differences between the learning of multisensory auditory-visual and intra-modal associations. More specifically, the relative benefits of novel auditory-visual and verbal-visual associations for learning have not been directly compared. In Experiment 1, 20 adult volunteers completed three paired associate learning tasks: non-verbal novel auditory-visual (novel-AV), verbal-visual (verbal-AV; using pseudowords), and visual-visual (shape-VV). Participants were directed to make a motor response to matching novel and arbitrarily related stimulus pairs. Feedback was provided to facilitate trial and error learning. The results of Signal Detection Theory analyses suggested a multisensory enhancement of learning, with significantly higher discriminability measures (d-prime) in both the novel-AV and verbal-AV tasks than the shape-VV task. Motor reaction times were also significantly faster during the verbal-AV task than during the non-verbal learning tasks. Experiment 2 (n = 12) used a forced-choice discrimination paradigm to assess whether a difference in unisensory stimulus discriminability could account for the learning trends in Experiment 1. Participants were significantly slower at discriminating unisensory pseudowords than the novel sounds and visual shapes, which was notable given that these stimuli produced superior learning. Together the findings suggest that verbal information has an added enhancing effect on multisensory associative learning in adults.

Seeing and feeling for self and other: Proprioceptive spatial location determines multisensory enhancement of touch

We have investigated the relation between visuo-tactile interactions and the self-other distinction. In the Visual Enhancement of Touch (VET) effect, non-informative vision of one’s own hand improves tactile spatial perception. Previous studies suggested that looking at another person’s hand could also enhance tactile perception, but did not systematically investigate the basis of this effect. In Experiment 1 we manipulated the spatial location where one’s own or another person’s hand was seen. Viewing one’s own hand enhanced tactile orientation discrimination relative to viewing a neutral object, but only when the visual image of the hand was spatially aligned with the actual location of the participant’s unseen hand, as signaled by proprioception. In contrast, viewing another person’s hand produced enhanced tactile perception irrespective of spatial location.In Experiment 2, we used a multisensory stimulation technique, known as Visual Remapping of Touch (VRT), to reduce the spatial misalignment between the visual and proprioceptive locations of the hand. Participants saw an image of their own hand being touched at the same time as the tactile stimulation, which reduces perceived misalignment. This spatial adaptation procedure caused the VET effect to return. Our results suggest that multisensory modulation of touch depends on a representation of one’s own body that is fundamentally spatial in nature. In contrast, representation of others is free from this spatial constraint.

Developmental Trends in the Enhancements of Multisensory Object Processing in Presence of Distractors

Event Abstract Back to Event Developmental Trends in the Enhancements of Multisensory Object Processing in Presence of Distractors Harriet C. Downing1, Ayla Barutchu1, 2, 3 and Sheila G. Crewther1* 1 La Trobe University, Psychological Science, Australia 2 Deakin University, Psychology, Australia 3 Florey Institute of Neuroscience and Mental Health, University of Melbourne, Australia Human survival depends on the ability to effectively discriminate relevant signals both auditory and visual (e.g. threats) from noise in the environment. However, although this ability to discriminate auditory and visual target objects from distractors is partly dependent on experience, its developmental trajectory is unknown. Thus this study aimed to investigate developmental changes in 9-year-old (N = 18) and 11-year-old (N = 20) children, adolescents (N = 19) and adults (N = 22), using an audiovisual discrimination task with uni- and multisensory distractors. Target objects consisted of a bird, a cat or a dog, and for any given target animal, with the other animals acting as distractors. The results indicate that audiovisual reaction times (RTs) were significantly slower with visual and audiovisual distractors, although all groups continued to demonstrate multisensory motor enhancements irrespective of distractor condition. Developmentally, adolescents recorded faster motor responses and greater multisensory enhancements than children. Interestingly, while adolescents’ demonstrated immature multisensory enhancements in the presence of visual and audiovisual distractors, they showed adult or near-adult performances with no distractor and with auditory distractor conditions alone. It was concluded that multisensory processes continue to mature throughout adolescence with visual distractors being more detrimental to performance than auditory. Acknowledgements Australia Research Council grant, ARC DP0985837 to SGC. The research was also funded by La Trobe University, School of Psychological Science, Faculty of Science, Technology and Engineering postgraduate research funding to HCD. We would like to acknowledge the following contributors: Russell Beaton, Technical Officer, La Trobe University, technical assistance; Dallas Johnson, Sound Engineer, Mnemonic Audio, creation of sound files; Dr Ben C Ong, Senior Lecturer, La Trobe University, discuss Keywords: multisensory, audiovisual, facilitation, Interaction, distractors, development, Children, adolescents, adults Conference: ACNS-2013 Australasian Cognitive Neuroscience Society Conference, Clayton, Melbourne, Australia, 28 Nov - 1 Dec, 2013. Presentation Type: Poster Topic: Sensation and Perception Citation: Downing HC, Barutchu A and Crewther SG (2013). Developmental Trends in the Enhancements of Multisensory Object Processing in Presence of Distractors. Conference Abstract: ACNS-2013 Australasian Cognitive Neuroscience Society Conference. doi: 10.3389/conf.fnhum.2013.212.00090 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 28 Sep 2013; Published Online: 25 Nov 2013. * Correspondence: Prof. Sheila G Crewther, La Trobe University, Psychological Science, Melbourne, Victoria, 3086, Australia, s.crewther@latrobe.edu.au Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Harriet C Downing Ayla Barutchu Sheila G Crewther Google Harriet C Downing Ayla Barutchu Sheila G Crewther Google Scholar Harriet C Downing Ayla Barutchu Sheila G Crewther PubMed Harriet C Downing Ayla Barutchu Sheila G Crewther Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Audio-Visual Detection Benefits in the Rat

Human psychophysical studies have described multisensory perceptual benefits such as enhanced detection rates and faster reaction times in great detail. However, the neural circuits and mechanism underlying multisensory integration remain difficult to study in the primate brain. While rodents offer the advantage of a range of experimental methodologies to study the neural basis of multisensory processing, rodent studies are still limited due to the small number of available multisensory protocols. We here demonstrate the feasibility of an audio-visual stimulus detection task for rats, in which the animals detect lateralized uni- and multi-sensory stimuli in a two-response forced choice paradigm. We show that animals reliably learn and perform this task. Reaction times were significantly faster and behavioral performance levels higher in multisensory compared to unisensory conditions. This benefit was strongest for dim visual targets, in agreement with classical patterns of multisensory integration, and was specific to task-informative sounds, while uninformative sounds speeded reaction times with little costs for detection performance. Importantly, multisensory benefits for stimulus detection and reaction times appeared at different levels of task proficiency and training experience, suggesting distinct mechanisms inducing these two multisensory benefits. Our results demonstrate behavioral multisensory enhancement in rats in analogy to behavioral patterns known from other species, such as humans. In addition, our paradigm enriches the set of behavioral tasks on which future studies can rely, for example to combine behavioral measurements with imaging or pharmacological studies in the behaving animal or to study changes of integration properties in disease models.

Multisensory Decision-Making in Rats and Humans

We report a novel multisensory decision task designed to encourage subjects to combine information across both time and sensory modalities. We presented subjects, humans and rats, with multisensory event streams, consisting of a series of brief auditory and/or visual events. Subjects made judgments about whether the event rate of these streams was high or low. We have three main findings. First, we report that subjects can combine multisensory information over time to improve judgments about whether a fluctuating rate is high or low. Importantly, the improvement we observed was frequently close to, or better than, the statistically optimal prediction. Second, we found that subjects showed a clear multisensory enhancement both when the inputs in each modality were redundant and when they provided independent evidence about the rate. This latter finding suggests a model where event rates are estimated separately for each modality and fused at a later stage. Finally, because a similar multisensory enhancement was observed in both humans and rats, we conclude that the ability to optimally exploit sequentially presented multisensory information is not restricted to a particular species.

Predicting multisensory enhancement in neuronal responses

The most dramatic physiological example of multisensory integration is response enhancement, where the integration of concordant signals across multiple sensory modalities leads to a larger and more reliable response. In the model system of the superior colliculus, the largest enhancements (often greater than the predicted sum) are observed when the individual signals being combined are weak. This principle conforms to expectations based on signal detection theory, and also as expected, enhancement is not uniform throughout any response. Typically it is greatest near its onset, when the unisensory inputs are at their weakest (Initial Response Enhancement, see Rowland et al., 2007; Rowland and Stein, 2008). Despite the general accuracy of this heuristic, however, there is a substantial amount of variance in the degree of observed enhancement at all levels of responsiveness. This observation appears to violate standard Bayesian predictions that are based on overall response magnitude. Aside from statistical noise, a possible explanation is that individual neurons in the dataset are calibrated to different ‘computational modes’. An alternative hypothesis is that the amount of enhancement is influenced greatly by response properties other than magnitude, specifically, the temporal profile of the response. The present analysis advances the latter hypothesis. We present a mechanistic framework that explains these findings and extends the standard Bayesian approach to generate an accurate prediction for the multisensory response profile given known unisensory response profiles. These predictions offer a ‘null hypothesis’ that can be used to quantify the circumstances and timing of anomalies in the integrative processes in different experimental conditions; for example, when it is developing under different conditions, or when it is disrupted by experimental or surgical intervention at any stage of life.