Neuronal modulation of auditory attention by informative and uninformative spatial cues

Mixed emotions to social situations: An fMRI investigation

BACKGROUND

Neuroscience research has generally studied emotions each taken in isolation. However, mixed emotional states (e.g., the co-occurrence of amusement and disgust, or sadness and pleasure) are common in everyday life. Psychophysiological and behavioral evidence suggests that mixed emotions may have response profiles that are distinguishable from their constituent emotions. Yet, the brain bases of mixed emotions remain unresolved.

METHODS

We recruited 38 healthy adults who viewed short, validated film clips, eliciting either positive (amusing), negative (disgusting), neutral, or mixed (a mix of amusement and disgust) emotional states, while brain activity was assessed by functional magnetic resonance imaging (fMRI). We assessed mixed emotions in two ways: first by comparing neural reactivity to ambiguous (mixed) with that to unambiguous (positive and negative) film clips and second by conducting parametric analyses to measure neural reactivity with respect to individual emotional states. We thus obtained self-reports of amusement and disgust after each clip and computed a minimum feeling score (shared minimum of amusement and disgust) to quantify mixed emotional feelings.

RESULTS

Both analyses revealed a network of the posterior cingulate (PCC), medial superior parietal lobe (SPL)/precuneus, and parieto-occipital sulcus to be involved in ambiguous contexts eliciting mixed emotions.

CONCLUSION

Our results are the first to shed light on the dedicated neural processes involved in dynamic social ambiguity processing. They suggest both higher-order (SPL) and lower-order (PCC) processes may be needed to process emotionally complex social scenes.

Involuntary Orienting and Conflict Resolution during Auditory Attention: The Role of Ventral and Dorsal Streams

Selective attention to sound object features such as pitch and location is associated with enhanced brain activity in ventral and dorsal streams, respectively. We examined the role of these pathways in involuntary orienting and conflict resolution using fMRI. Participants were presented with two tones that may, or may not, share the same nonspatial (frequency) or spatial (location) auditory features. In separate blocks of trials, participants were asked to attend to sound frequency or sound location and ignore the change in the task-irrelevant feature. In both attend-frequency and attend-location tasks, RTs were slower when the task-irrelevant feature changed than when it stayed the same (involuntary orienting). This behavioral cost coincided with enhanced activity in the pFC and superior temporal gyrus. Conflict resolution was examined by comparing situations where the change in stimulus features was congruent (both features changed) and incongruent (only one feature changed). Participants were slower and less accurate for incongruent than congruent sound features. This congruency effect was associated with enhanced activity in the pFC and was greater in the right superior temporal gyrus and medial frontal cortex during the attend-location task than during the attend-frequency task. Together, these findings do not support a strict division of "labor" into ventral and dorsal streams but rather suggest interactions between these pathways in situations involving changes in task-irrelevant sound feature and conflict resolution. These findings also validate the Test of Attention in Listening task by revealing distinct neural correlates for involuntary orienting and conflict resolution.

Specific Visual Subregions of TPJ Mediate Reorienting of Spatial Attention

The temporo-parietal junction (TPJ) has been associated with various cognitive and social functions, and is critical for attentional reorienting. Attention affects early visual processing. Neuroimaging studies dealing with such processes have thus far concentrated on striate and extrastriate areas. Here, we investigated whether attention orienting or reorienting modulate activity in visually driven TPJ subregions. For each observer we identified 3 visually responsive subregions within TPJ: 2 bilateral (vTPJant and vTPJpost) and 1 right lateralized (vTPJcent). Cortical activity in these subregions was measured using fMRI while observers performed a 2-alternative forced-choice orientation discrimination task. Covert spatial endogenous (voluntary) or exogenous (involuntary) attention was manipulated using either a central or a peripheral cue with task, stimuli and observers constant. Both endogenous and exogenous attention increased activity for invalidly cued trials in right vTPJpost; only endogenous attention increased activity for invalidly cued trials in left vTPJpost and in right vTPJcent; and neither type of attention modulated either right or left vTPJant. These results demonstrate that vTPJpost and vTPJcent mediate the reorientation of covert attention to task relevant stimuli, thus playing a critical role in visual attention. These findings reveal a differential reorienting cortical response after observers' attention has been oriented to a given location voluntarily or involuntarily.

From Behavioral Facilitation to Inhibition: The Neuronal Correlates of the Orienting and Reorienting of Auditory Attention

Successful adaptive behavior relies on the ability to automatically (bottom-up) orient attention to different locations in the environment. This results in a biphasic pattern in which reaction times (RT) are faster for stimuli that occur in the same spatial location (valid) for the first few hundred milliseconds, which is termed facilitation. This is followed by faster RT for stimuli that appear in novel locations (invalid) after longer delays, termed inhibition of return. The neuronal areas and networks involved in the transition between states of facilitation and inhibition remain poorly understood, especially for auditory stimuli. Functional magnetic resonance imaging (fMRI) data were therefore collected in a large sample of healthy volunteers (N = 52) at four separate auditory stimulus onset asynchronies (SOAs; 200, 400, 600, and 800 ms). Behavioral results indicated that facilitation (valid RT < invalid RT) occurred at the 200 ms SOA, with inhibition of return (valid RT > invalid RT) present at the three longer SOAs. fMRI results showed several brain areas varying their activation as a function of SOA, including bilateral superior temporal gyrus, anterior thalamus, cuneus, dorsal anterior cingulate gyrus, and right ventrolateral prefrontal cortex (VLPFC)/anterior insula. Right VLPFC was active during a behavioral state of facilitation, and its activation (invalid – valid trials) further correlated with behavioral reorienting at the 200 ms delay. These results suggest that right VLPFC plays a critical role when auditory attention must be quickly deployed or redeployed, demanding heightened cognitive and inhibitory control. In contrast to previous work, the ventral and dorsal frontoparietal attention networks were both active during valid and invalid trials across SOAs. These results suggest that the dorsal and ventral networks may not be as specialized during bottom-up auditory orienting as has been previously reported during visual orienting.

Supramodal executive control of attention

The human attentional system can be subdivided into three functional networks of alerting, orienting, and executive control. Although these networks have been extensively studied in the visuospatial modality, whether the same mechanisms are deployed across different sensory modalities remains unclear. In this study we used the attention network test for the visuospatial modality, in addition to two auditory variants with spatial and frequency manipulations to examine cross-modal correlations between network functions. Results showed that among the visual and auditory tasks, the effects of executive control, but not effects of alerting and orienting, were significantly correlated. These findings suggest that while alerting and orienting functions rely more upon modality-specific processes, the executive control of attention coordinates complex behavior via supramodal mechanisms.

A multimodal approach for determining brain networks by jointly modeling functional and structural connectivity

Recent innovations in neuroimaging technology have provided opportunities for researchers to investigate connectivity in the human brain by examining the anatomical circuitry as well as functional relationships between brain regions. Existing statistical approaches for connectivity generally examine resting-state or task-related functional connectivity (FC) between brain regions or separately examine structural linkages. As a means to determine brain networks, we present a unified Bayesian framework for analyzing FC utilizing the knowledge of associated structural connections, which extends an approach by Patel et al. (2006a) that considers only functional data. We introduce an FC measure that rests upon assessments of functional coherence between regional brain activity identified from functional magnetic resonance imaging (fMRI) data. Our structural connectivity (SC) information is drawn from diffusion tensor imaging (DTI) data, which is used to quantify probabilities of SC between brain regions. We formulate a prior distribution for FC that depends upon the probability of SC between brain regions, with this dependence adhering to structural-functional links revealed by our fMRI and DTI data. We further characterize the functional hierarchy of functionally connected brain regions by defining an ascendancy measure that compares the marginal probabilities of elevated activity between regions. In addition, we describe topological properties of the network, which is composed of connected region pairs, by performing graph theoretic analyses. We demonstrate the use of our Bayesian model using fMRI and DTI data from a study of auditory processing. We further illustrate the advantages of our method by comparisons to methods that only incorporate functional information.

The neural basis of implicit learning of task-irrelevant Chinese tonal sequence

The present study sought to investigate the neural basis of implicit learning of task-irrelevant perceptual sequence. A novel SRT task, the serial syllable identification task (SSI task), was used in which the participants were asked to recognize which one of two Chinese syllables was presented. The tones of the syllables were irrelevant to the task but followed an underlying structured sequence. Participants were scanned while they performed the SSI task. Results showed that, at the behavioral level, faster RTs for the sequential material indicated that task-irrelevant sequence knowledge could be learned. In the subsequent prediction test of knowledge of the tonal cues using subjective measures, we found that the knowledge was obtained unconsciously. At the neural level, the left caudate, bilateral hippocampus and bilateral superior parietal lobule were engaged during the sequence condition relative to the random condition. Further analyses revealed that greater learning-related activation (relative to random) in the right caudate nucleus, bilateral hippocampus and left superior parietal lobule were found during the second half of the training phase compared with the first half. When people reported that they were guessing, the magnitude of the right hippocampus and left superior parietal lobule activations was positively related to the accuracy of prediction test, which was significantly better than chance. Together, the present results indicated that the caudate, hippocampus and superior parietal lobule played critical roles in the implicit perceptual sequence learning even when the perceptual features were task irrelevant.

Top-down controlled and bottom-up triggered orienting of auditory attention to pitch activate overlapping brain networks

A number of previous studies have suggested segregated networks of brain areas for top-down controlled and bottom-up triggered orienting of visual attention. However, the corresponding networks involved in auditory attention remain less studied. Our participants attended selectively to a tone stream with either a lower pitch or higher pitch in order to respond to infrequent changes in duration of attended tones. The participants were also required to shift their attention from one stream to the other when guided by a visual arrow cue. In addition to these top-down controlled cued attention shifts, infrequent task-irrelevant louder tones occurred in both streams to trigger attention in a bottom-up manner. Both cued shifts and louder tones were associated with enhanced activity in the superior temporal gyrus and sulcus, temporo-parietal junction, superior parietal lobule, inferior and middle frontal gyri, frontal eye field, supplementary motor area, and anterior cingulate gyrus. Thus, the present findings suggest that in the auditory modality, unlike in vision, top-down controlled and bottom-up triggered attention activate largely the same cortical networks. Comparison of the present results with our previous results from a similar experiment on spatial auditory attention suggests that fronto-parietal networks of attention to location or pitch overlap substantially. However, the auditory areas in the anterior superior temporal cortex might have a more important role in attention to the pitch than location of sounds. This article is part of a Special Issue entitled SI: Prediction and Attention.

Functional connectivity of dorsal and ventral frontoparietal seed regions during auditory orienting

Our ability to refocus auditory attention is vital for even the most routine day-to-day activities. Shifts in auditory attention can be initiated "voluntarily," or triggered "involuntarily" by unexpected novel sound events. Here we employed psychophysiological interaction (PPI) analyses of auditory functional MRI data, to compare functional connectivity patterns of distinct frontoparietal cortex regions during cued voluntary vs. novelty-driven involuntary auditory attention shifting. Overall, our frontoparietal seed regions exhibited significant PPI increases with auditory cortex (AC) areas during both cued and novelty-driven orienting. However, significant positive PPI patterns associated with voluntary auditory attention (cue>novel task regressor), but mostly absent in analyses emphasizing involuntary orienting (novel>cue task regressor), were observed with seeds within the frontal eye fields (FEF), superior parietal lobule (SPL), and right supramarginal gyri (SMG). In contrast, significant positive PPIs associated selectively with involuntary orienting were observed between ACs and seeds within the bilateral anterior interior frontal gyri (IFG), left posterior IFG, SMG, and posterior cingulate cortices (PCC). We also found indices of lateralization of different attention networks: PPI increases selective to voluntary attention occurred primarily within right-hemispheric regions, whereas those related to involuntary orienting were more frequent with left-hemisphere seeds. In conclusion, despite certain similarities in PPI patterns across conditions, the more dorsal aspects of right frontoparietal cortex demonstrated wider connectivity during cued/voluntary attention shifting, whereas certain left ventral frontoparietal seeds were more widely connected during novelty-triggered/involuntary orienting. Our findings provide partial support for distinct attention networks for voluntary and involuntary auditory attention.

The role of the right temporoparietal junction in attention and social interaction as revealed by ALE meta-analysis

The right temporoparietal junction (rTPJ) is frequently associated with different capacities that to shift attention to unexpected stimuli (reorienting of attention) and to understand others' (false) mental state [theory of mind (ToM), typically represented by false belief tasks]. Competing hypotheses either suggest the rTPJ representing a unitary region involved in separate cognitive functions or consisting of subregions subserving distinct processes. We conducted activation likelihood estimation (ALE) meta-analyses to test these hypotheses. A conjunction analysis across ALE meta-analyses delineating regions consistently recruited by reorienting of attention and false belief studies revealed the anterior rTPJ, suggesting an overarching role of this specific region. Moreover, the anatomical difference analysis unravelled the posterior rTPJ as higher converging in false belief compared with reorienting of attention tasks. This supports the concept of an exclusive role of the posterior rTPJ in the social domain. These results were complemented by meta-analytic connectivity mapping (MACM) and resting-state functional connectivity (RSFC) analysis to investigate whole-brain connectivity patterns in task-constrained and task-free brain states. This allowed for detailing the functional separation of the anterior and posterior rTPJ. The combination of MACM and RSFC mapping showed that the posterior rTPJ has connectivity patterns with typical ToM regions, whereas the anterior part of rTPJ co-activates with the attentional network. Taken together, our data suggest that rTPJ contains two functionally fractionated subregions: while posterior rTPJ seems exclusively involved in the social domain, anterior rTPJ is involved in both, attention and ToM, conceivably indicating an attentional shifting role of this region.

Lateralized parietotemporal oscillatory phase synchronization during auditory selective attention

Based on the infamous left-lateralized neglect syndrome, one might hypothesize that the dominating right parietal cortex has a bilateral representation of space, whereas the left parietal cortex represents only the contralateral right hemispace. Whether this principle applies to human auditory attention is not yet fully clear. Here, we explicitly tested the differences in cross-hemispheric functional coupling between the intraparietal sulcus (IPS) and auditory cortex (AC) using combined magnetoencephalography (MEG), EEG, and functional MRI (fMRI). Inter-regional pairwise phase consistency (PPC) was analyzed from data obtained during dichotic auditory selective attention task, where subjects were in 10-s trials cued to attend to sounds presented to one ear and to ignore sounds presented in the opposite ear. Using MEG/EEG/fMRI source modeling, parietotemporal PPC patterns were (a) mapped between all AC locations vs. IPS seeds and (b) analyzed between four anatomically defined AC regions-of-interest (ROI) vs. IPS seeds. Consistent with our hypothesis, stronger cross-hemispheric PPC was observed between the right IPS and left AC for attended right-ear sounds, as compared to PPC between the left IPS and right AC for attended left-ear sounds. In the mapping analyses, these differences emerged at 7-13Hz, i.e., at the theta to alpha frequency bands, and peaked in Heschl's gyrus and lateral posterior non-primary ACs. The ROI analysis revealed similarly lateralized differences also in the beta and lower theta bands. Taken together, our results support the view that the right parietal cortex dominates auditory spatial attention.

Switching auditory attention using spatial and non-spatial features recruits different cortical networks

Switching attention between different stimuli of interest based on particular task demands is important in many everyday settings. In audition in particular, switching attention between different speakers of interest that are talking concurrently is often necessary for effective communication. Recently, it has been shown by multiple studies that auditory selective attention suppresses the representation of unwanted streams in auditory cortical areas in favor of the target stream of interest. However, the neural processing that guides this selective attention process is not well understood. Here we investigated the cortical mechanisms involved in switching attention based on two different types of auditory features. By combining magneto- and electro-encephalography (M-EEG) with an anatomical MRI constraint, we examined the cortical dynamics involved in switching auditory attention based on either spatial or pitch features. We designed a paradigm where listeners were cued in the beginning of each trial to switch or maintain attention halfway through the presentation of concurrent target and masker streams. By allowing listeners time to switch during a gap in the continuous target and masker stimuli, we were able to isolate the mechanisms involved in endogenous, top-down attention switching. Our results show a double dissociation between the involvement of right temporoparietal junction (RTPJ) and the left inferior parietal supramarginal part (LIPSP) in tasks requiring listeners to switch attention based on space and pitch features, respectively, suggesting that switching attention based on these features involves at least partially separate processes or behavioral strategies.

Rethinking the role of the rTPJ in attention and social cognition in light of the opposing domains hypothesis: findings from an ALE-based meta-analysis and resting-state functional connectivity

The right temporo-parietal junction (rTPJ) has been associated with two apparently disparate functional roles: in attention and in social cognition. According to one account, the rTPJ initiates a “circuit-breaking” signal that interrupts ongoing attentional processes, effectively reorienting attention. It is argued this primary function of the rTPJ has been extended beyond attention, through a process of evolutionarily cooption, to play a role in social cognition. We propose an alternative account, according to which the capacity for social cognition depends on a network which is both distinct from and in tension with brain areas involved in focused attention and target detection: the default mode network (DMN). Theory characterizing the rTPJ based on the area's purported role in reorienting may be falsely guided by the co-occurrence of two distinct effects in contiguous regions: activation of the supramarginal gyrus (SMG), associated with its functional role in target detection; and the transient release, during spatial reorienting, of suppression of the angular gyrus (AG) associated with focused attention. Findings based on meta-analysis and resting functional connectivity are presented which support this alternative account. We find distinct regions, possessing anti-correlated patterns of resting connectivity, associated with social reasoning (AG) and target detection (SMG) at the rTPJ. The locus for reorienting was spatially intermediate between the AG and SMG and showed a pattern of connectivity with similarities to social reasoning and target detection seeds. These findings highlight a general methodological concern for brain imaging. Given evidence that certain tasks not only activate some areas but also suppress activity in other areas, it is suggested that researchers need to distinguish two distinct putative mechanisms, either of which may produce an increase in activity in a brain area: functional engagement in the task vs. release of suppression.

Using neuroimaging to understand the cortical mechanisms of auditory selective attention

Over the last four decades, a range of different neuroimaging tools have been used to study human auditory attention, spanning from classic event-related potential studies using electroencephalography to modern multimodal imaging approaches (e.g., combining anatomical information based on magnetic resonance imaging with magneto- and electroencephalography). This review begins by exploring the different strengths and limitations inherent to different neuroimaging methods, and then outlines some common behavioral paradigms that have been adopted to study auditory attention. We argue that in order to design a neuroimaging experiment that produces interpretable, unambiguous results, the experimenter must not only have a deep appreciation of the imaging technique employed, but also a sophisticated understanding of perception and behavior. Only with the proper caveats in mind can one begin to infer how the cortex supports a human in solving the "cocktail party" problem. This article is part of a Special Issue entitled Human Auditory Neuroimaging.

An event-related FMRI study of exogenous orienting across vision and audition

The orienting of attention to the spatial location of sensory stimuli in one modality based on sensory stimuli presented in another modality (i.e., cross-modal orienting) is a common mechanism for controlling attentional shifts. The neuronal mechanisms of top-down cross-modal orienting have been studied extensively. However, the neuronal substrates of bottom-up audio-visual cross-modal spatial orienting remain to be elucidated. Therefore, behavioral and event-related functional magnetic resonance imaging (FMRI) data were collected while healthy volunteers (N = 26) performed a spatial cross-modal localization task modeled after the Posner cuing paradigm. Behavioral results indicated that although both visual and auditory cues were effective in producing bottom-up shifts of cross-modal spatial attention, reorienting effects were greater for the visual cues condition. Statistically significant evidence of inhibition of return was not observed for either condition. Functional results also indicated that visual cues with auditory targets resulted in greater activation within ventral and dorsal frontoparietal attention networks, visual and auditory "where" streams, primary auditory cortex, and thalamus during reorienting across both short and long stimulus onset asynchronys. In contrast, no areas of unique activation were associated with reorienting following auditory cues with visual targets. In summary, current results question whether audio-visual cross-modal orienting is supramodal in nature, suggesting rather that the initial modality of cue presentation heavily influences both behavioral and functional results. In the context of localization tasks, reorienting effects accompanied by the activation of the frontoparietal reorienting network are more robust for visual cues with auditory targets than for auditory cues with visual targets.

The cortical dynamics underlying effective switching of auditory spatial attention

Successful rapid deployment of attention to relevant sensory stimuli is critical for survival. In a complex environment, attention can be captured by salient events or be deployed volitionally. Furthermore, when multiple events are of interest concurrently, effective interaction with one's surroundings hinges on efficient top-down control of shifting attention. It has been hypothesized that two separate cortical networks coordinate attention shifts across multiple modalities. However, the cortical dynamics of these networks and their behavioral relevance to switching of auditory attention are unknown. Here we show that the strength of each subject's right temporoparietal junction (RTPJ, part of the ventral network) activation was highly correlated with their behavioral performance in an auditory task. We also provide evidence that the recruitment of the RTPJ likely precedes the right frontal eye fields (FEF; participating in both the dorsal and ventral networks) and middle frontal gyrus (MFG) by around 100 ms when subjects switch their auditory spatial attention.

Brain networks of novelty-driven involuntary and cued voluntary auditory attention shifting

In everyday life, we need a capacity to flexibly shift attention between alternative sound sources. However, relatively little work has been done to elucidate the mechanisms of attention shifting in the auditory domain. Here, we used a mixed event-related/sparse-sampling fMRI approach to investigate this essential cognitive function. In each 10-sec trial, subjects were instructed to wait for an auditory "cue" signaling the location where a subsequent "target" sound was likely to be presented. The target was occasionally replaced by an unexpected "novel" sound in the uncued ear, to trigger involuntary attention shifting. To maximize the attention effects, cues, targets, and novels were embedded within dichotic 800-Hz vs. 1500-Hz pure-tone "standard" trains. The sound of clustered fMRI acquisition (starting at t = 7.82 sec) served as a controlled trial-end signal. Our approach revealed notable activation differences between the conditions. Cued voluntary attention shifting activated the superior intra--parietal sulcus (IPS), whereas novelty-triggered involuntary orienting activated the inferior IPS and certain subareas of the precuneus. Clearly more widespread activations were observed during voluntary than involuntary orienting in the premotor cortex, including the frontal eye fields. Moreover, we found -evidence for a frontoinsular-cingular attentional control network, consisting of the anterior insula, inferior frontal cortex, and medial frontal cortices, which were activated during both target discrimination and voluntary attention shifting. Finally, novels and targets activated much wider areas of superior temporal auditory cortices than shifting cues.

Activation of Right Ventral Prefrontal Cortex Using a Predictive Cue during Visual Spatial Orienting of Attentional Processes: An fMRI Study

Visual spatial orienting of attention can be investigated with location-cueing paradigms in which a cue provides correct information about the location of the upcoming target. Target detection is facilitated when the target appears at the expected cued location. In this study, we examined the brain activation of the spatial orienting response based on attentional "benefits." During an fMRI experiment, two types of attentional tasks were used. Both predictive and nonpredictive cues were used and followed by an upcoming target. Behavioral data showed a faster reaction time with the predictive cue when compared with that of the nonpredictive cue. The fMRI results of these two tasks were compared, whereby isolated brain areas activated when the targets appeared at the attended position after a specific spatial expectation was induced by the cue were compared with when equivalent targets appeared after no spatial expectation was induced by the cue. The results showed that the right ventral prefrontal cortex was activated to a similar degree as the dorsal frontoparietal spatial attentional network.

Auditory orienting and inhibition of return in schizophrenia: a functional magnetic resonance imaging study

Patients with schizophrenia (SP) exhibit deficits in both attentional reorienting and inhibition of return (IOR) during visual tasks. However, it is currently unknown whether these deficits are supramodal in nature and how these deficits relate to other domains of cognitive dysfunction. In addition, the neuronal correlates of this pathological orienting response have not been investigated in either the visual or auditory modality. Therefore, 30 SP and 30 healthy controls (HC) were evaluated with an extensive clinical protocol and functional magnetic resonance imaging (fMRI) during an auditory cuing paradigm. SP exhibited both increased costs and delayed IOR during auditory orienting, suggesting a prolonged interval for attentional disengagement from cued locations. Moreover, a delay in the development of IOR was associated with cognitive deficits on formal neuropsychological testing in the domains of attention/inhibition and working memory. Event-related fMRI showed the characteristic activation of a frontoparietal network (invalid trials>valid trials), but there were no differences in functional activation between patients and HC during either attentional reorienting or IOR. Current results suggest that orienting deficits are supramodal in nature in SP, and are related to higher-order cognitive deficits that directly interfere with day-to-day functioning.

Current perspectives and methods in studying neural mechanisms of multisensory interactions

In the past decade neuroscience has witnessed major advances in the field of multisensory interactions. A large body of research has revealed several new types of cross-sensory interactions. In addition, multisensory interactions have been reported at temporal and spatial system levels previously thought of as strictly unimodal. We review the findings that have led to the current broad consensus that most, if not all, higher, as well as lower level neural processes are in some form multisensory. We continue by outlining the progress that has been made in identifying the functional significance of different types of interactions, for example, in subserving stimulus binding and enhancement of perceptual certainty. Finally, we provide a critical introduction to cutting edge methods from bayes optimal integration to multivoxel pattern analysis as applied to multisensory research at different system levels.

Brain networks of bottom-up triggered and top-down controlled shifting of auditory attention

During functional magnetic resonance imaging (fMRI), our participants selectively attended to tone streams at the left or right, and occasionally shifted their attention from one stream to another as guided by a centrally presented visual cue. Duration changes in the to-be-attended stream served as targets. Loudness deviating tones (LDTs) occurred infrequently in both streams to catch attention in a bottom-up manner, as indicated by their effects on reaction times to targets. LDTs activated the right temporo-parietal junction (TPJ), posterior parts of the left inferior/middle frontal gyrus (IFG/MFG), ventromedial parts of the superior parietal lobule (SPL), and left frontal eye field/premotor cortex (FEF/PMC). In addition, LDTs in the to-be-ignored sound stream were associated with enhanced activity in the ventromedial prefrontal cortex (VMPFC) possibly related to evaluation of the distracting event. Top-down controlled cue-guided attention shifts (CASs) activated bilateral areas in the SPL, intraparietal sulcus (IPS), FEF/PMC, TPJ, IFG/MFG, and cingulate/medial frontal gyrus, and crus I/II of the cerebellum. Thus, our results suggest that in audition top-down controlled and bottom-up triggered shifting of attention activate largely overlapping temporo-parietal, superior parietal and frontal areas. As the IPS, superior parts of the SPL, and crus I/II were activated specifically by top-down controlled attention shifts, and the VMPFC was specifically activated by bottom-up triggered attention shifts, our results also suggest some differences between auditory top-down controlled and bottom-up triggered shifting of attention.