ABSTRACT
Miraculin, the extract of miracle fruit (Richadella dulcifica or Synsepalum dulcificum), is a taste‐modifying protein, its effect consisting in a temporary and almost complete replacement of ...sour taste with sweet taste. Despite psychophysical investigations were carried out in the past, very little is known about the effect of this molecule on taste interactions. We investigated the changes induced by miraculin on the gustatory sensations evoked by isolated tastants (citric acid, caffeine, NaCl and sucrose) and by binary and trinary mixtures that included a sour tastant (citric acid). We confirmed the effects of miraculin on citric acid, both as a single tastant and in mixtures. In mixtures including a salty tastant, the “illusory sweetness” induced by miraculin significantly reduced saltiness. Variable effects were shown on the perception of bitterness, although mostly in the direction of bitterness suppression. Finally, contrary to previous results, miraculin added sweetness in mixtures that included a sweet tastant.
PRATICAL APPLICATIONS
The taste‐modifying protein miraculin has been known since long time due to its surprising property of transforming sourness into sweetness. Here, we put at test the properties of miraculin in mixtures, proving that its sweetness‐inducing effect has an impact also on saltiness and bitterness, provided that the mixture includes a sour tastant (citric acid). In all mixtures containing NaCl (sour‐salty, sour‐salty‐bitter and sour‐salty‐sweet), saltiness was significantly reduced, suggesting a suppressive interaction between miraculin‐induced sweetness and NaCl. Similarly, although less strongly, the bitterness (of caffeine) was suppressed in two mixtures out of three (sour‐bitter and sour‐bitter‐sweet).
Flexible and adaptive behavior requires the ability to contextually stop inappropriate actions and select the right one as quickly as possible. Recently, it has been proposed that three brain ...regions, i.e., the inferior frontal gyrus (iFg), the anterior insula (aIns), and the anterior intraparietal sulcus (aIPs), play an important role in several processing phases of perceptual decision tasks, especially in the preparation, perception and action phases, respectively. However, little is known about hemispheric differences in the activation of these three areas during the transition from perception to action. Many studies have examined how people prepare to stop upcoming responses through both proactive and reactive inhibitory control. Although inhibitory control has been associated with activity in the right prefrontal cortex (PFC), we have previously reported that, during a discriminative response task performed with the right hand, we observed: 1) a bilateral activity in the iFg during the preparation phase, and 2) a left dominant activity in the aIns and aIPs during the transition from perception to action, i.e., the so-called stimulus-response mapping. To clarify the hemispheric dominance of these processes, we combined the high temporal resolution of event-related potentials (ERPs) with the high spatial resolution of event-related functional magnetic resonance imaging (fMRI) while participants performed a discriminative response task (DRT) and a simple response task (SRT) using their non-dominant left hand. We confirmed that proactive inhibitory control originates in the iFg: its activity started one second before the stimulus onset and was released concomitantly to the stimulus appearance. Most importantly, we confirmed the presence of a bilateral iFg activity that seems to reflect a bilateral proactive control rather than a right-hemisphere dominance or a stronger control of the hemisphere contralateral to the responding hand. Further, we observed a stronger activation of the left aIns and a right-lateralized activation of the aIPs reflecting left-hemisphere dominance for stimulus-response mapping finalized to response execution and a contralateral-hand parietal premotor activity, respectively.
•Proactive inhibitory control originates in the iFg.•iFg activity reflects bilateral proactive control.•Left aIns activity reflects stimulus-response mapping for response execution.•Contralateral aIPs contributes to motor response planning.
Xenomelia is a rare condition characterized by a persistent and intense desire for amputation of one or more healthy limbs. Some frequent clinical manifestations suggest the involvement of distinct ...neural substrates. Specifically, recent aetiopathological hypotheses about xenomelia propose a neurodevelopmental origin, highlighting the putative contribution of the right parietal lobe and right insula, known to subserve the construction of a coherent representation of the body as a whole. This literature review is aimed at analysing relevant findings about structural and functional brain correlates of xenomelia, focusing on the identification of key regions and their hemispheric distribution. Finally, implications about the potential link between xenomelia and phylogenetic development of the right parietal lobe are discussed. Despite a certain degree of heterogeneity and the spatial extension of networks involved, signs of partial right-sided lateralization of cortical nodes and left-sided lateralization of subcortical nodes emerged. Indeed, some areas-rsPL, riPL, PMC and rInsula-have been consistently found altered in xenomelia. In conclusion, the presence of both structural and functional multi-layered brain abnormalities in xenomelia suggests a multifactorial aetiology; however, as the prevalence of correlational studies, causal relationships remain to be investigated.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, FSPLJ, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The event-related potential (ERP) literature described two error-related brain activities: the error-related negativity (Ne/ERN) and the error positivity (Pe), peaking immediately after the erroneous ...response. ERP studies on error processing adopted a response-locked approach, thus, the question about the activities preceding the error is still open. In the present study, we tested the hypothesis that the activities preceding the false alarms (FA) are different from those occurring in the correct (responded or inhibited) trials. To this aim, we studied a sample of 36 Go/No-go performers, adopting a stimulus-locked segmentation also including the pre-motor brain activities. Present results showed that neither pre-stimulus nor perceptual activities explain why we commit FA. In contrast, we observed condition-related differences in two pre-response components: the fronto-central N2 and the prefrontal positivity (pP), respectively peaking at 250ms and 310ms after the stimulus onset. The N2 amplitude of FA was identical to that recorded in No-go trials, and larger than Hits. Because the new findings challenge the previous interpretations on the N2, a new perspective is discussed. On the other hand, the pP in the FA trials was larger than No-go and smaller than Go, suggesting an erroneous processing at the stimulus-response mapping level: because this stage triggers the response execution, we concluded that the neural processes underlying the pP were mainly responsible for the subsequent error commission. Finally, sLORETA source analyses of the post-error potentials extended previous findings indicating, for the first time in the ERP literature, the right anterior insula as Pe generator.
•The motor error is accounted by erroneous stimulus–response mapping.•The pP component predicts the motor error 80ms before its execution.•New interpretations are provided about the modulation of the N2 component.•sLORETA indicated the right anterior insula as Pe generator.
•Future events are anticipated by endogenous motor, cognitive and sensory processes.•The prefrontal negativity (pN) reflects temporal orienting, like the CNV.•Left pIPS plays a crucial role in ...temporal orienting supported by external cues.•Task learning is detected at the level of frontal areas with external cues.
Prediction about event timing plays a leading role in organizing and optimizing behavior. We recorded anticipatory brain activities and evaluated whether temporal orienting processes are reflected by the novel prefrontal negative (pN) component, as already shown for the contingent negative variation (CNV). Fourteen young healthy participants underwent EEG and fMRI recordings in separate sessions; they were asked to perform a Go/No-Go task in which temporal orienting was manipulated: the external condition (a visual display indicating the time of stimulus onset) and the internal condition (time information not provided). In both conditions, the source of the pN was localized in the pars opercularis of the iFg; the source of the CNV was localized in the supplementary motor area and cingulate motor area, as expected. Anticipatory activity was also found in the occipital-parietal cortex. Time on task EEG analysis showed a marked learning effect in the internal condition, while the effect was minor in the external condition. In fMRI, the two conditions had a similar pattern; similarities and differences of results obtained with the two techniques are discussed. Overall, data are consistent with the view that the pN reflects a proactive cognitive control, including temporal orienting.
Under normal circumstances, different inner- and outer-body sources are integrated to form coherent and accurate mental experiences of the state of the body, leading to the phenomenon of corporeal ...awareness. How these processes are affected by changes in inner and outer inputs to the body remains unclear. Here, we aim to present empirical evidence in which people with a massive sensory and motor disconnection may continue to experience feelings of general body state awareness without complete control of their inner and outer states. In these clinical populations, the activity of the neural structures subserving inner and outer body processing can be manipulated and tuned by means of body illusions that are usually based on multisensory stimulation. We suggest that a multisensory therapeutic approach could be adopted in the context of therapies for patients suffering from deafferentation and deefferentation. In this way, these individuals could regain a more complete feeling and control of the sensations they experience, which vary widely depending on their neurological condition.
Referred phantom sensations are frequently reported following a peripheral injury. However, very few cases describe such sensations of the ear, and it remains unclear how the aural nerve territory ...can be remapped to one specific peripheral nerve region. We report on a patient with brachial plexus avulsion who underwent sensory testing and was asked to report the location of the stimulated site and any other sensations experienced. The patient spontaneously described the sensation of his arm being separate from his body. Despite visual input, he felt that his fist was closed, with his thumb pointing inward. Importantly, he felt clear and reproducible sensations from the affected arm when the ipsilateral ear was touched. These referred sensations were noted just 15 days after sustaining the injury. The arm nerve territory was systematically remapped to a specific aural nerve territory by applying both manual and electrical stimulation. Stimulation of the external ear, which is innervated by the vagus nerve, showed high spatial specificity for the dorsal and volar skin surfaces of the limb, and clearly delineated digits. Somatosensory-evoked potentials indicated that cortical adaptation in the somatosensory stream transferred a spatially organized map of the limb to the skin of the outer ear. This referral of sensations to the ear, as distinct from the face, provides evidence of highly specific topographical reorganization of the central nervous system following peripheral injury. Rapid map changes in the phantom sensation to the ear as a function of stimulation of vagus nerve suggest that the reorganization process can occur in cortex rather than in the brainstem.
Objective: The aim of the present study was to investigate the cortical correlates of the intraindividual coefficient of variation (ICV) in a go/no-go task, focusing on the prefrontal cortex (PFC) ...contribution and evaluating both pre- and poststimulus brain activity. Method: We recorded event-related potentials (ERPs) in 40 subjects, arranged a posteriori in 2 groups on the basis of their ICV values. By this method, we formed the consistent (low ICV; n = 20) and inconsistent (high ICV; n = 20) group: the age, speed, and accuracy performance of the 2 groups were matched. Results: The prestimulus anticipatory PFC activity, as reflected by the prefrontal negativity (pN) wave, and the poststimulus P3 component were larger in the consistent than in the inconsistent group. In contrast, no differences were observed between groups in the brain activities associated to motor preparation and early sensory processing. Conclusions: Data are interpreted as an enhanced top-down control in consistent performers, likely characterized by a greater sustained attention on the task.
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