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The most common form of synaesthesia is grapheme-colour synaesthesia. However, rarer forms of synaesthesia also exist, such as word-gustatory and olfactory-gustatory synaesthesia, whereby a word or smell will induce a specific. In this study we describe a single individual (LJ) who experiences a concurrent olfactory stimulus when presented with congruent visual images. For some visual stimuli, he perceives a strong and automatic olfactory percept, which has existed throughout his life. In this study, we explore whether his experiences are a new form of synaesthesia or simply vivid imagery. Unlike other forms of synaesthesia, the concurrent odour is congruent to the visual inducer. For example, a photograph of dress shoes will elicit the smell of leather. We presented LJ and several control participants with 75 images of everyday objects. Their task was to indicate the strength of any perceived odours induced by the visual images. LJ rated several of the images as inducing a concurrent odour, while controls did not have any such percept. Images that LJ reported as inducing the strongest odours were used, along with colour-matched control images, in the context of an fMRI experiment. Participants were given a one-back task to maintain attention. A block-design odour localizer was presented to localize the piriform cortex (primary olfactory cortex). We found an increased BOLD response in the piriform cortex for the odour-inducing images compared to the control images in LJ. There was no difference in BOLD response between these two stimulus types in the control participants. A subsequent olfactory imagery task did not elicit enhanced activity in the piriform cortex in LJ, suggesting his perceptual experiences may not be based on olfactory imagery. [ABSTRACT FROM AUTHOR]

The processing of visual and haptic inputs, occurring either separately or jointly, is crucial for everyday-life object recognition, and has been a focus of recent neuroimaging research. Previously, visuohaptic convergence has been mostly investigated with matching-task paradigms. However, much less is known about visuohaptic convergence in the absence of additional task demands. We conducted two functional magnetic resonance imaging experiments in which subjects actively touched and/or viewed unfamiliar object stimuli without any additional task demands. In addition, we performed two control experiments with audiovisual and audiohaptic stimulation to examine the specificity of the observed visuohaptic convergence effects. We found robust visuohaptic convergence in bilateral lateral occipital cortex and anterior cerebellum. In contrast, neither the anterior cerebellum nor the lateral occipital cortex showed any involvement in audiovisual or audiohaptic convergence, indicating that multisensory convergence in these regions is specifically geared to visual and haptic inputs. These data suggest that in humans the lateral occipital cortex and the anterior cerebellum play an important role in visuohaptic processing even in the absence of additional task demands. [ABSTRACT FROM AUTHOR]

In complex natural environments, auditory and visual information often have to be processed simultaneously. Previous functional magnetic resonance imaging (fMRI) studies focused on the spatial localization of brain areas involved in audiovisual (AV) information processing, but the temporal characteristics of AV information flow in these regions remained unclear. In this study, we used fMRI and a novel information-theoretic approach to study the flow of AV sensory information. Subjects passively perceived sounds and images of objects presented either alone or simultaneously. Applying the measure of mutual information, we computed for each voxel the latency in which the blood oxygenation level-dependent signal had the highest information content about the preceding stimulus. The results indicate that, after AV stimulation, the earliest informative activity occurs in right Heschl's gyrus, left primary visual cortex, and the posterior portion of the superior temporal gyrus, which is known as a region involved in object-related AV integration. Informative activity in the anterior portion of superior temporal gyrus, middle temporal gyrus, right occipital cortex, and inferior frontal cortex was found at a later latency. Moreover, AV presentation resulted in shorter latencies in multiple cortical areas compared with isolated auditory or visual presentation. The results provide evidence for bottom-up processing from primary sensory areas into higher association areas during AV integration in humans and suggest that AV presentation shortens processing time in early sensory cortices. [ABSTRACT FROM AUTHOR]

The cortical integration of auditory and visual features is crucial for efficient object recognition. Previous studies have shown that audiovisual (AV) integration is affected by where and when auditory and visual features occur. However, because relatively little is known about the impact of what is integrated, we here investigated the impact of semantic congruency and object familiarity on the neural correlates of AV integration. We used functional magnetic resonance imaging to identify regions involved in the integration of both (congruent and incongruent) familiar animal sounds and images and of arbitrary combinations of unfamiliar artificial sounds and object images. Unfamiliar object images and sounds were integrated in the inferior frontal cortex (IFC), possibly reflecting learning of novel AV associations. Integration of familiar, but semantically incongruent combinations also correlated with IFC activation and additionally involved the posterior superior temporal sulcus (pSTS). For highly familiar semantically congruent AV pairings, we again found AV integration effects in pSTS and additionally in superior temporal gyrus. These findings demonstrate that the neural correlates of object-related AV integration reflect both semantic congruency and familiarity of the integrated sounds and images. [ABSTRACT FROM AUTHOR]

Abstract: Research on the psychological and neuronal underpinnings of addiction has concentrated mostly on affective, motivational, learning, and executive processes and the brain regions subserving these functions. In contrast, sensory and motor aspects of addiction have largely been neglected even though they may be highly relevant for the development and preservation of addiction. The aim of the present review is to emphasize the significance of sensory and motor processes for the better understanding and treatment of addiction. We focus on research investigating substance-related addictions and on brain imaging studies in humans that have assessed the contribution of cortical and cerebellar systems to sensory and motor mechanisms of addiction. Activations of sensory and motor brain regions in response to drug-associated cues can predict relapse and correlate with craving, severity of dependence and automatized behavioral reactions towards drug-related stimuli. We propose a model of how sensory and motor processes might be involved in the different stages of addiction. [Copyright &y& Elsevier]

Visuo-haptic integration contributes essentially to object shape recognition. Although there has been a considerable advance in elucidating the neural underpinnings of multisensory perception, it is still unclear whether seeing an object and exploring it with the dominant hand elicits the same brain response as compared to the non-dominant hand. Using fMRI to measure brain activation in right-handed participants, we found that for both left- and right-hand stimulation the left lateral occipital complex (LOC) and anterior cerebellum (aCER) were involved in visuo-haptic integration of familiar objects. These two brain regions were then further investigated in another study, where unfamiliar, novel objects were presented to a different group of right-handers. Here the left LOC and aCER were more strongly activated by bimodal than unimodal stimuli only when the left but not the right hand was used. A direct comparison indicated that the multisensory gain of the fMRI activation was significantly higher for the left than the right hand. These findings are in line with the principle of “inverse effectiveness”, implying that processing of bimodally presented stimuli is particularly enhanced when the unimodal stimuli are weak. This applies also when right-handed subjects see and simultaneously touch unfamiliar objects with their non-dominant left hand. Thus, the fMRI signal in the left LOC and aCER induced by visuo-haptic stimulation is dependent on which hand was employed for haptic exploration. [ABSTRACT FROM AUTHOR]