Benefits of active listening during 3D sound localization.

In everyday life, sound localization entails more than just the extraction and processing of auditory cues. When determining sound position in three dimensions, the brain also considers the available visual information (e.g., visual cues to sound position) and resolves perceptual ambiguities through active listening behavior (e.g., spontaneous head movements while listening). Here, we examined to what extent spontaneous head movements improve sound localization in 3D-azimuth, elevation, and depth-by comparing static vs. active listening postures. To this aim, we developed a novel approach to sound localization based on sounds delivered in the environment, brought into alignment thanks to a VR system. Our system proved effective for the delivery of sounds at predetermined and repeatable positions in 3D space, without imposing a physically constrained posture, and with minimal training. In addition, it allowed measuring participant behavior (hand, head and eye position) in real time. We report that active listening improved 3D sound localization, primarily by ameliorating accuracy and variability of responses in azimuth and elevation. The more participants made spontaneous head movements, the better was their 3D sound localization performance. Thus, we provide proof of concept of a novel approach to the study of spatial hearing, with potentials for clinical and industrial applications.

Embodiment into a robot increases its acceptability.

Recent studies have shown how embodiment induced by multisensory bodily interactions between individuals can positively change social attitudes (closeness, empathy, racial biases). Here we use a simple neuroscience-inspired procedure to beam our human subjects into one of two distinct robots and demonstrate how this can readily increase acceptability and social closeness to that robot. Participants wore a Head Mounted Display tracking their head movements and displaying the 3D visual scene taken from the eyes of a robot which was positioned in front of a mirror and piloted by the subjects' head movements. As a result, participants saw themselves as a robot. When participant' and robot's head movements were correlated, participants felt that they were incorporated into the robot with a sense of agency. Critically, the robot they embodied was judged more likeable and socially closer. Remarkably, we found that the beaming experience with correlated head movements and corresponding sensation of embodiment and social proximity, was independent of robots' humanoid's appearance. These findings not only reveal the ease of body-swapping, via visual-motor synchrony, into robots that do not share any clear human resemblance, but they may also pave a new way to make our future robotic helpers socially acceptable.

Effect of prism adaptation on left dichotic listening deficit in neglect patients: glasses to hear better?

Unilateral neglect is a disabling syndrome frequently observed following right hemisphere brain damage. Symptoms range from visuo-motor impairments through to deficient visuo-spatial imagery, but impairment can also affect the auditory modality. A short period of adaptation to a rightward prismatic shift of the visual field is known to improve a wide range of hemispatial neglect symptoms, including visuo-manual tasks, mental imagery, postural imbalance, visuo-verbal measures and number bisection. The aim of the present study was to assess whether the beneficial effects of prism adaptation may generalize to auditory manifestations of neglect. Auditory extinction, whose clinical manifestations are independent of the sensory modalities engaged in visuo-manual adaptation, was examined in neglect patients before and after prism adaptation. Two separate groups of neglect patients (all of whom exhibited left auditory extinction) underwent prism adaptation: one group (n = 6) received a classical prism treatment ('Prism' group), the other group (n = 6) was submitted to the same procedure, but wore neutral glasses creating no optical shift (placebo 'Control' group). Auditory extinction was assessed by means of a dichotic listening task performed three times: prior to prism exposure (pre-test), upon prism removal (0 h post-test) and 2 h later (2 h post-test). The total number of correct responses, the lateralization index (detection asymmetry between the two ears) and the number of left-right fusion errors were analysed. Our results demonstrate that prism adaptation can improve left auditory extinction, thus revealing transfer of benefit to a sensory modality that is orthogonal to the visual, proprioceptive and motor modalities directly implicated in the visuo-motor adaptive process. The observed benefit was specific to the detection asymmetry between the two ears and did not affect the total number of responses. This indicates a specific effect of prism adaptation on lateralized processes rather than on general arousal. Our results suggest that the effects of prism adaptation can extend to unexposed sensory systems. The bottom-up approach of visuo-motor adaptation appears to interact with higher order brain functions related to multisensory integration and can have beneficial effects on sensory processing in different modalities. These findings should stimulate the development of therapeutic approaches aimed at bypassing the affected sensory processing modality by adapting other sensory modalities.

Action-specific remapping of peripersonal space.

Peripersonal space processing in monkeys' brain relies on visuo-tactile neurons activated by objects near, not touching, the animal's skin. Multisensory interplay in peripersonal space is now well documented also in humans, in brain damaged patients presenting cross-modal extinction as well as in healthy subjects and typically takes the form of stronger visuo-tactile interactions in peripersonal than far space. We recently showed in healthy humans the existence of a functional link between voluntary object-oriented actions (Grasping) and the multisensory coding of the space around us (as indexed by visual-tactile interaction). Here, we investigated whether performing different actions towards the same object implies differential modulations of peripersonal space. Healthy subjects were asked to either grasp or point towards a target object. In addition, they discriminated whether tactile stimuli were delivered on their right index finger (up), or thumb (down), while ignoring visual distractors. Visuo-tactile interaction was probed in baseline Static conditions (before the movement) and in dynamic conditions (action onset and execution). Results showed that, compared to the Static baseline both actions similarly strengthened visuo-tactile interaction at the action onset, when Grasping and Pointing were kinematically indistinguishable. Crucially, Grasping induced further enhancement than Pointing in the execution phase, i.e., when the two actions kinematically diverged. These findings reveal that performing actions induce a continuous remapping of the multisensory peripersonal space as a function of on-line sensory-motor requirements, thus supporting the hypothesis of a role for peripersonal space in the motor control of voluntary actions.

Deficit of auditory space perception in patients with visuospatial neglect.

There have been many studies of visuospatial neglect, but fewer studies of neglect in relation with other sensory modalities. In the present study we investigate the performance of six right brain damaged (RBD) patients with left visual neglect and six RBD patients without neglect in an auditory spatial task. Previous work on sound localisation in neglect patients adopted measure of sound localisation based on directional motor responses (e.g., pointing to sounds) or judgement of sound position with respect to the body midline (auditory midline task). However, these measures might be influenced by non-auditory biases related with motor and egocentric components. Here we adopted a perceptual measure of sound localisation, consisting in a verbal judgement of the relative position (same or different) of two sequentially presented sounds. This task was performed in a visual and in a blindfolded condition. The results revealed that sound localisation performance of visuospatial neglect patients was severely impaired with respect to that of RBD controls, especially when sounds originated in contralesional hemispace. In such condition, neglect patients were always unable to discriminate the relative position of the two sounds. No difference in performance emerged as a function of the visual condition in either group. These results demonstrate a perceptual deficit of sound localisation in patients with visuospatial neglect, suggesting that the spatial deficits of these patients can arise multimodally for the same portion of external space.

Auditory peripersonal space in humans: a case of auditory-tactile extinction.

Animal experiments have shown that the spatial correspondence between auditory and tactile receptive fields of ventral pre-motor neurons provides a map of auditory peripersonal space around the head. This allows neurons to localize a near sound with respect to the head. In the present study, we demonstrated the existence of an auditory peripersonal space around the head in humans. In a right-brain damaged patient with tactile extinction, a sound delivered near the ipsilesional side of the head extinguished a tactile stimulus delivered to the contralesional side of the head (cross-modal auditory-tactile extinction). In contrast, when an auditory stimulus was presented far from the head, cross-modal extinction was dramatically reduced. This spatially specific cross-modal extinction was found only when a complex sound like a white noise burst was presented; pure tones did not produce spatially specific cross-modal extinction. These results show a high degree of functional similarity between the characteristics of the auditory peripersonal space representation in humans and monkeys. This similarity suggests that analogous physiological substrates might be responsible for coding this multisensory integrated representation of peripersonal space in human and non-human primates.

Ventriloquism in patients with unilateral visual neglect.

Can visual stimuli that go undetected, because they are presented in the extinguished region of neglect patients' visual field, nevertheless shift in their direction the apparent location of simultaneous sounds (the well-known 'ventriloquist effect')? This issue was examined using a situation in which each trial involved the simultaneous presentation of a tone over loudspeakers, together with a bright square area on either the left, the right or both sides of fixation. Participants were required to report the presence of squares, and indicate by hand pointing the apparent location of the tone. Five patients with left hemineglect consistently failed to detect the left square, either presented alone or together with another square on the right. Nevertheless, on bimodal trials with a single undetected square to the left, their sound localization was significantly shifted in the direction of that undetected square. By contrast, in bimodal trials with either a single square on the right or a square on each side, their sound localization showed only small and non-significant shifts. This particular result might be due to a combination of low discrimination of lateral sound deviations with variable individual strategies triggered by conscious detection of the right square. The important finding is the crossmodal bias produced by the undetected left visual distractors. It provides a new example of implicit processing of inputs affected by unilateral visual neglect, and on the other hand is consistent with earlier demonstrations of the automaticity of crossmodal bias.

Left tactile extinction following visual stimulation of a rubber hand.

In close analogy with neurophysiological findings in monkeys, neuropsychological studies have shown that the human brain constructs visual maps of space surrounding different body parts. In right-brain-damaged patients with tactile extinction, the existence of a visual peripersonal space centred on the hand has been demonstrated by showing that cross-modal visual-tactile extinction is segregated mainly in the space near the hand. That is, tactile stimuli on the contralesional hand are extinguished more consistently by visual stimuli presented near the ipsilesional hand than those presented far from it. Here, we report the first evidence in humans that this hand-centred visual peripersonal space can be coded in relation to a seen rubber replica of the hand, as if it were a real hand. In patients with left tactile extinction, a visual stimulus presented near a seen right rubber hand induced strong cross-modal visual-tactile extinction, similar to that obtained by presenting the same visual stimulus near the patient's right hand. Critically, this specific cross-modal effect was evident when subjects saw the rubber hand as having a plausible posture relative to their own body (i.e. when it was aligned with the subject's right shoulder). In contrast, cross-modal extinction was strongly reduced when the seen rubber hand was arranged in an implausible posture (i. e. misaligned with respect to the subject's right shoulder). We suggest that this phenomenon is due to the dominance of vision over proprioception: the system coding peripersonal space can be 'deceived' by the vision of a fake hand, provided that its appearance looks plausible with respect to the subject's body.

Crossmodal links between vision and touch in covert endogenous spatial attention.

The authors report a series of 6 experiments investigating crossmodal links between vision and touch in covert endogenous spatial attention. When participants were informed that visual and tactile targets were more likely on 1 side than the other, speeded discrimination responses (continuous vs. pulsed, Experiments 1 and 2; or up vs. down, Experiment 3) for targets in both modalities were significantly faster on the expected side, even though target modality was entirely unpredictable. When participants expected a target on a particular side in just one modality, corresponding shifts of covert attention also took place in the other modality, as evidenced by faster elevation judgments on that side (Experiment 4). Larger attentional effects were found when directing visual and tactile attention to the same position rather than to different positions (Experiment 5). A final study with crossed hands revealed that these visuotactile links in spatial attention apply to common positions in external space.

Reappraising the apparent costs of attending to two separate visual objects.

Support for object-based accounts of visual attention has been drawn from several different types of effect. One effect is found when observers try to restrict their attention to a particular region of a display. Other regions belonging to the same object are often selected as well, suggesting that attention spreads spatially over entire objects. Another effect is found when judging two visual attributes; performance is often less efficient when the attributes belong to separate objects rather than both belonging to a single object. This latter effect has been taken to imply that only one segmented object can be attended at a time. However, it may instead merely be a variant of the first effect. If, as we assume here, attention spreads to task-irrelevant regions of relevant objects, it will encompass a larger spatial region and more information when judging attributes of two objects rather than one. Here we compared judging one versus two objects, while manipulating whether the two objects occupied a wider extent than the single object condition (as in previous work), or not. Costs were found for judging two objects versus one only when together they occupied a wider spatial extent. We conclude that reported difficulties in attending two objects may be due to attention spreading across the entire spatial extent of objects when judging their parts, rather than a fixed inability to process more than object at a time.

Visual capture of touch: out-of-the-body experiences with rubber gloves.

When the apparent visual location of a body part conflicts with its veridical location, vision can dominate proprioception and kinesthesia. In this article, we show that vision can capture tactile localization. Participants discriminated the location of vibrotactile stimuli (upper, at the index finger, vs. lower, at the thumb), while ignoring distractor lights that could independently be upper or lower. Such tactile discriminations were slowed when the distractor light was incongruent with the tactile target (e.g., an upper light during lower touch) rather than congruent, especially when the lights appeared near the stimulated hand. The hands were occluded under a table, with all distractor lights above the table. The effect of the distractor lights increased when rubber hands were placed on the table, "holding" the distractor lights, but only when the rubber hands were spatially aligned with the participant's own hands. In this aligned situation, participants were more likely to report the illusion of feeling touch at the rubber hands. Such visual capture of touch appears cognitively impenetrable.

Are perception and action affected differently by the Titchener circles illusion?

In the present study, we investigated the effects of the Titchener circles illusion in perception and action. In this illusion, two identical discs can be perceived as being different in size when one is surrounded by an annulus of smaller circles and the other is surrounded by an annulus of larger circles. This classic size-contrast illusion, known as Ebbinghaus or Titchener Circles Illusion, has a strong perceptual effect. By contrast, it has recently been demonstrated that when subjects are required to pick up one of the discs, their grip aperture during reaching is largely appropriate to the size of the target. This result has been considered as evidence of a clear dissociation between visual perception and visuomotor behaviour in the intact human brain. In this study, we suggest and investigate an alternative explanation for these results. We argue that, in a previous study, while perception was subjected to the simultaneous influence of the large and small circles displays, in the grasping task only the annulus of circles surrounding the target object was influential. We tested this hypothesis by requiring 18 subjects to perceptually estimate and grasp a disc centred in a single annulus of Titchener circles. The results showed that both the perceptual estimation and the hand shaping while grasping the disc were similarly influenced by the illusion. Moreover, the stronger the perceptual illusion, the greater the effect on the grip scaling. We discuss the results as evidence of an interaction between the functional pathways for perception and action in the intact human brain.

Neuropsychological evidence of the functional integration of visual, auditory and proprioceptive spatial maps.

We infer the functional integration of the visual, auditory and proprioceptive spatial maps from the behaviour of a patient (G.A.) with left visual neglect, i.e. a derangement of visual space representation. G.A. was required to point manually to left, centre or right acoustic stimuli, under visual control or blindfolded, with the responding hand (left or right) located either on the left, centre or right space. G.A.'s manual pointing responses to left auditory stimuli were strongly influenced by the visual spatial information and by the proprioceptive spatial information related to the position of the responding effector. In the visual control condition, when the patient performed the task with the left effector located on the left, pointing responses to left auditory stimuli were shifted towards the right intact visual space. In contrast, when the visual spatial information was rendered less salient, i.e. in the blindfolded condition, and the effector was again located on the left, manual pointing responses were confined to the previously ignored left space. These findings are consistent with the view that the acoustic representation is modulated by the impaired visual representation and by the proprioceptive spatial map related to the position of the responding effector.

Moving around objects and recognizing them.

This research concerned the use of mental rotation in recognizing rotated objects. Instead of the classic Shepard's paradigm in which subjects were still while observing rotated objects, here subjects had to move (or imagine moving) around stationary three-dimensional objects put in the middle of the trajectory. Thus, depending on the viewing positions, such objects were seen under six different perspectives (from 30 degrees to 180 degrees). The latter task has been thought to be closer to everyday life in which we obtain information regarding objects from their spatial properties. The results do not follow the classic rules of mental rotation of an object predicting a linear increase of the time needed to recognize distorted objects as a function of their angular displacement. They also differ from data in the literature about spatial imagery showing that access to spatial information is facilitated more when people actually move through a path than when they imagine moving. A probable explanation of this difference from the literature is discussed in relation to the particular involvement of the body in the experimental task.

[Diagnostic use of the mathematical model of nonlinear regression in the interpretation of the crystalline bilirubin loading test in Gilbert's syndrome]. / Applicabilità diagnostica del modello matematico di regressione non lineare per l'interpretazione del test da carico con bilirubina cristallina nella sindrome di Gilbert.

The results of a study conducted both on subjects affected by constitutional hyperbilirubinaemia (Gilbert's syndrome) and healthy subjects using the charge test with crystalline bilirubin are presented. The parameters which are involved in bilirubin kinetics were established by means of non linear regression methods (the Marquardt method). 19 Gilbert syndrome patients and 12 normal control subjects were studied. Important parameters readily applicable to clinical and diagnostic evaluation of subjects suffering from familial cholemia were identified.

[Abdominal ultrasonography in the staging and follow-up of malignant lymphomas]. / Ruolo della ecotomografia addominale nello staging e nel follow-up dei linfomi maligni.

During the period September 1980-June 1984, abdominal US was performed by the authors on 103 patients with confirmed malignant lymphomas. The results indicate US has accuracy comparable to that of lymphography for lymph node enlargement; furthermore, US has the added advantages of being able to demonstrate mesenteric, renal hilar and other abdominal lymph nodes that are not commonly filled with contrast medium during lymphography. For these reasons, US is now frequently used in the diagnosis and staging of malignant lymphomas as well as for following up the results of therapy.(US = ultrasonography)

[Comparative diagnostic value of echography and oral radiologic examination of the gallbladder in relation to surgical findings]. / Valore diagnostico comparato dell'ecografia e dell'esame radiologico per os della colecisti al vaglio chirurgico.

For nearly 60 years, since it was introduced by Graham and Cole (1924), oral cholecystography (OCG) has been used as the imaging technique of choice in investigation of gallbladder disorders. Recently, the future of OCG has come into doubt, principally as a result of ultrasonography, with the advent of high-resolution real-time scanning. Stones are seen as echoes within the lumen of the gallbladder and are associated with an acoustic shadow, findings which are highly specific. On this basis, to evaluate the accuracy of ultrasonography in detecting cholelithiasis, the A. have performed by real-time cholecystosonography 60 patients with not diagnostic OCG in a group of 546 patients affected by gallbladder diseases. Our results have confirmed that sonography revealed 4 normal gallbladders, 51 gallstones and 1 primary gallbladder cancer, with 5 cases of false positive. The true false negative rate has been difficult to determine, as surgery is usually not performed after a negative study. The accuracy of cholecystosonography for gallstone diagnosis was found to be 88,1% for all three Crade's categories.

[Value and limits of echography and abdominal lymphography in malignant lymphomas]. / Valori e limiti dell'ecografia e della linfografia addominale nei linfomi maligni.

Diagnostic results obtained by echography and lymphography in the study of abdominal lymphoglandular involvement in patients with lymphomas are compared. The data indicate that while lymphography is more revealing, the two examinations should be used together in staging. Echography, on the other hand, should be used for long-term surveillance, once the lymphographic contrast medium has been absorbed.