The COGs (context, object, and goals) in multisensory processing

Our understanding of how perception operates in real-world environments has been substantially advanced by studying both multisensory processes and “top-down” control processes influencing sensory processing via activity from higher-order brain areas, such as attention, memory, and expectations. As the two topics have been traditionally studied separately, the mechanisms orchestrating real-world multisensory processing remain unclear. Past work has revealed that the observer’s goals gate the influence of many multisensory processes on brain and behavioural responses, whereas some other multisensory processes might occur independently of these goals. Consequently, other forms of top-down control beyond goal dependence are necessary to explain the full range of multisensory effects currently reported at the brain and the cognitive level. These forms of control include sensitivity to stimulus context as well as the detection of matches (or lack thereof) between a multisensory stimulus and categorical attributes of naturalistic objects (e.g. tools, animals). In this review we discuss and integrate the existing findings that demonstrate the importance of such goal-, object- and context-based top-down control over multisensory processing. We then put forward a few principles emerging from this literature review with respect to the mechanisms underlying multisensory processing and discuss their possible broader implications

Switching to the rubber hand

Inducing the rubber hand illusion (RHI) requires that participants look at an imitation hand while it is stroked in synchrony with their occluded biological hand. Previous explanations of the RHI have emphasized multisensory integration, and excluded higher cognitive functions. We investigated the relationship between the RHI and higher cognitive functions by experimentally testing task switch (as measured by switch cost) and mind wandering (as measured by SART score); we also included a questionnaire for attentional control that comprises two subscales, attention-shift and attention-focus. To assess experience of RHI, the Botvinick and Cohen (1998) questionnaire was used and illusion onset time was recorded. Our results indicate that rapidity of onset reliably indicates illusion strength. Regression analysis revealed that participants evincing less switch cost and higher attention-shift scores had faster RHI onset times, and that those with higher attention-shift scores experienced the RHI more vividly. These results suggest that the multi-sensory hypothesis is not sufficient to explain the illusion: higher cognitive functions should be taken into account when explaining variation in the experience of ownership for the rubber hand

Dissociable neural correlates of multisensory coherence and selective attention

Previous work has demonstrated that performance in an auditory selective attention task can be enhanced or impaired, depending on whether a task-irrelevant visual stimulus is temporally coherent with a target auditory stream or with a competing distractor. However, it remains unclear how audiovisual (AV) temporal coherence and auditory selective attention interact at the neurophysiological level. Here, we measured neural activity using electroencephalography (EEG) while human participants (men and women) performed an auditory selective attention task, detecting deviants in a target audio stream. The amplitude envelope of the two competing auditory streams changed independently, while the radius of a visual disc was manipulated to control the audiovisual coherence. Analysis of the neural responses to the sound envelope demonstrated that auditory responses were enhanced independently of the attentional condition: both target and masker stream responses were enhanced when temporally coherent with the visual stimulus. In contrast, attention enhanced the event-related response (ERP) evoked by the transient deviants, independently of AV coherence. Finally, in an exploratory analysis, we identified a spatiotemporal component of ERP, in which temporal coherence enhanced the deviant-evoked responses only in the unattended stream. These results provide evidence for dissociable neural signatures of bottom-up (coherence) and top-down (attention) effects in AV object formation.Significance StatementTemporal coherence between auditory stimuli and task-irrelevant visual stimuli can enhance behavioral performance in auditory selective attention tasks. However, how audiovisual temporal coherence and attention interact at the neural level has not been established. Here, we measured EEG during a behavioral task designed to independently manipulate AV coherence and auditory selective attention. While some auditory features (sound envelope) could be coherent with visual stimuli, other features (timbre) were independent of visual stimuli. We find that audiovisual integration can be observed independently of attention for sound envelopes temporally coherent with visual stimuli, while the neural responses to unexpected timbre changes are most strongly modulated by attention. Our results provide evidence for dissociable neural mechanisms of bottom-up (coherence) and top-down (attention) effects on AV object formation

Neural Architecture of Hunger-Dependent Multisensory Decision Making in C. elegans

Little is known about how animals integrate multiple sensory inputs in natural environments to balance avoidance of danger with approach to things of value. Furthermore, the mechanistic link between internal physiological state and threat-reward decision making remains poorly understood. Here we confronted C. elegans worms with the decision whether to cross a hyperosmotic barrier presenting the threat of desiccation to reach a source of food odor. We identified a specific interneuron that controls this decision via top-down extrasynaptic aminergic potentiation of the primary osmosensory neurons to increase their sensitivity to the barrier. We also establish that food deprivation increases the worm's willingness to cross the dangerous barrier by suppressing this pathway. These studies reveal a potentially general neural circuit architecture for internal state control of threat-reward decision making

Cross-Modality Dysfunction between the Visual and Olfactory Systems in Parkinson’s Disease

Cross-modality in function is a fundamental ability in humans and is closely associated with the basic functions. Several studies have demonstrated that vision strongly influences other senses such as hearing, touch, taste, and smell. However, the dysfunction in this cross-modality caused by disease, is poorly understood. In addition to evidence that Parkinson’s disease (PD) impairs various cognitive functions including olfaction, a recent study showed that olfactory function is unaffected by visual information in patients with PD. This finding suggests that the link between vision and olfaction is underactive in PD. This chapter reviews the cross-modal dysfunction and dwells on the possibility of a novel precursor assessment for PD

Time Distortions in Mind

Time Distortions in Mind brings together current research on temporal processing in clinical populations to elucidate the interdependence between perturbations in timing and disturbances in the mind and brain. For the student, the scientist, and the stepping-stone for further research. Readership: An excellent reference for the student and the scientist interested in aspects of temporal processing and abnormal psychology

Time Distortions in Mind

Time Distortions in Mind brings together current research on temporal processing in clinical populations to elucidate the interdependence between perturbations in timing and disturbances in the mind and brain. For the student, the scientist, and the stepping-stone for further research

Hippocampal temporal-parietal junction interaction in the production of psychotic symptoms: a framework for understanding the schizophrenic syndrome

A framework is described for understanding the schizophrenic syndrome at the brain systems level. It is hypothesized that over-activation of dynamic gesture and social perceptual processes in the temporal-parietal occipital junction (TPJ), posterior superior temporal sulcus (PSTS) and surrounding regions produce the syndrome (including positive and negative symptoms, their prevalence, prodromal signs, and cognitive deficits). Hippocampal system hyper-activity and atrophy have been consistently found in schizophrenia. Hippocampal activity is highly correlated with activity in the TPJ and may be a source of over-excitation of the TPJ and surrounding regions. Strong evidence for this comes from in-vivo recordings in humans during psychotic episodes. Many positive symptoms of schizophrenia can be reframed as the erroneous sense of a presence or other who is observing, acting, speaking, or controlling; these qualia are similar to those evoked during abnormal activation of the TPJ. The TPJ and PSTS play a key role in the perception (and production) of dynamic social, emotional, and attentional gestures for the self and others (e.g., body/face/eye gestures, audiovisual speech and prosody, and social attentional gestures such as eye gaze). The single cell representation of dynamic gestures is multimodal (auditory, visual, tactile), matching the predominant hallucinatory categories in schizophrenia. Inherent in the single cell perceptual signal of dynamic gesture representations is a computation of intention, agency, and anticipation or expectancy (for the self and others). Stimulation of the TPJ resulting in activation of the self representation has been shown to result a feeling of a presence or multiple presences (due to heautoscopy) and also bizarre tactile experiences. Neurons in the TPJ are also tuned, or biased to detect threat related emotions. Abnormal over-activation in this system could produce the conscious hallucination of a voice (audiovisual speech), a person or a touch. Over-activation could interfere with attentional/emotional gesture perception and production (negative symptoms). It could produce the unconscious feeling of being watched, followed, or of a social situation unfolding along with accompanying abnormal perception of intent and agency (delusions). Abnormal activity in the TPJ would also be predicted to create several cognitive disturbances that are characteristic of schizophrenia, including abnormalities in attention, predictive social processing, working memory, and a bias to erroneously perceive threat