1,721,085 research outputs found
Mechanisms of top-down visual spatial attention: computational and behavioral investigations
Full text linkThis thesis examines the mechanisms underlying visual spatial attention. In particular I focused on top-‐down or voluntary attention, namely the ability to select relevant information and discard the irrelevant according to our goals. Given the limited processing resources of the human brain, which does not allow to process all the available information to the same degree, the ability to correctly allocate processing resources is fundamental for the accomplishment of most everyday tasks. The cost of misoriented attention is that we could miss some relevant information, with potentially serious consequences.
In the first study (chapter 2) I will address the issue of the neural substrates of visual spatial attention: what are the neural mechanisms that allow the deployment of visual spatial attention? According to the premotor theory orienting attention to a location in space is equivalent to planning an eye movement to the same location, an idea strongly supported by neuroimaging and neurophysiological evidence. Accordingly, in this study I will present a model that can account for several attentional effects without requiring additional mechanisms separate from the circuits that perform sensorimotor transformations for eye movements. Moreover, it includes a mechanism that allows, within the framework of the premotor theory, to explain dissociations between attention and eye movements that may be invoked to disprove it. In the second model presented (chapter 3) I will further investigate the computational mechanisms underlying sensorimotor transformations. Specifically I will show that a representation in which the amplitude of visual responses is modulated by postural signal is both efficient and plausible, emerging also in a neural network model trained through unsupervised learning (i.e., using only signals locally available at the neuron level). Ultimately this result gives additional support to the approach adopted in the first model.
Next, I will present a series of behavioral studies: in the first (chapter 4) I will show that spatial constancy of attention (i.e., the ability to sustain attention at a spatial location across eye movements) is dependent on some properties of the image, namely the presence of continuous visual landmarks at the attended locations. Importantly, this finding helps resolve contrasts between several recent results. In the second behavioral study (chapter 5), I will investigate an often neglected aspect of spatial cueing paradigms, probably the most widely used technique in studies of covert attention: the role of cue predictivity (i.e. the extent to which the spatial cue correctly indicates the location where the target stimulus will appear). Results show that, independently of participant’s awareness, changes

in predictivity result in changes in spatial validity effects, and that reliable shifts of attention can take place also in the absence of a predictive cue. In sum the results question the appropriateness of using predictive cues for delineating pure voluntary shifts of spatial attention. Finally, in the last study I will use a psychophysiological measure, the diameter of the eye’s pupil, to investigate intensive aspects of attention. Event-‐related pupil dilations accurately mirrored changes in visuospatial awareness induced by a dual-‐task manipulation that consumed attentional resources. Moreover, results of the primary spatial monitoring task revealed a significant rightward bias, indicated by a greater proportion of missed targets in the left hemifield. Interestingly this result mimics the extinction to double simultaneous stimulation (i.e., the failure to respond to a stimulus when it is presented simultaneously with another stimulus) which is often found in patients with unilateral brain damage.
Overall, these studies present an emerging picture of attention as a complex mechanism that even in its volitional aspects is modulated by other non-‐volitional factors, both external and internal to the individua
The regulation of social touch and interpersonal distance during human-avatar social interactions.
No full textNonverbal behaviors, defined as “communication effected by mean other than words” (Knapp et al., 2014), have a deep impact on the process and outcome of our social interactions (Mehrabian & Wiener, 1967). According to the embodied cognition framework, mental processes, including high-level social and cognitive representations, are situated and embodied in our physical experiences (Barsalou, 2008; Niedenthal et al., 2005). The embodiment of social cognition constitutes the basis of social interaction: bodily-motor cues (such as facial expression, gestures, body posture, and movement) are in a reciprocal relationship (circular causality; Haken, 1977) with mental processes (affects, emotions, motivation, attitudes; Tschacher, Giersch, & Friston, 2017). Liking and attitudes toward the other are expressed primarily by nonverbal channels, often in an automatic fashion (Vogeley & Bente, 2010). On the other hand, embodied cues, such as interpersonal touch, can result in a change of attitudes toward the other person and the whole social category that him/her represents (Seger et al., 2014). This thesis aims to advance the understanding of two nonverbal behaviors that constitute the core of embodied intersubjectivity (Csordas, 2008), namely the regulation of social touch and interpersonal distance, capitalizing on the Virtual Reality (VR) technology. Indeed, the investigation of the bidirectional relationship between nonverbal behaviors and attitudes, and its physiological and neural underpinnings, has been limited by the lack of either naturalistic interactions and/or experimental control that VR can partially overcome (Pan & Hamilton, 2018). Here we aimed at developing a new paradigm to study social and intimate vicarious touch from an embodied perspective and investigate the role of affiliative and self-protective motives affecting the regulation of interpersonal distance toward virtual avatars
Vicarious touch in Immersive Virtual Reality
No full textSocial touch is an important tool to communicate emotions but it’s still unclear how it could promote and maintain social bonds between individuals. Immersive Virtual Reality offers unprecedented opportunities to explore the effect of somatosensory stimuli (like pain and touch) even when they are not actually delivered. We found that the the mere observation of touch kinematics delivered on a first person perspective embodied avatar causes different behavioural and psychophysiological reactions according to the gender of the participant, the gender of the toucher and the area touched .The vicarious experience in virtual reality allows to address more directly a delicate issue that can otherwise be explored only through imagination).
Voluntary eye movements direct attention on the mental number space
No full textGrowing evidence suggests that orienting visual attention in space can influence the processing of numerical magnitude, with leftward orienting speeding up the processing of small numbers relative to larger ones and the converse for rightward orienting. The manipulation of eye movements is a convenient way to direct visuospatial attention, but several aspects of the complex relationship between eye movements, attention orienting and number processing remain unexplored. In a previous study, we observed that inducing involuntary, reflexive eye movements by means of optokinetic stimulation affected number processing only when numerical magnitude was task relevant (i.e. during magnitude comparison, but not during parity judgment; Ranzini et al. in J Cogn Psychol 27, 459–470, (2015). Here, we investigated whether processing of task-irrelevant numerical magnitude can be modulated by voluntary eye movements, and whether the type of eye movements (smooth pursuit vs. saccades) would influence this interaction. Participants tracked with their gaze a dot while listening to a digit. The numerical task was to indicate whether the digit was odd or even through non-spatial, verbal responses. The dot could move leftward or rightward either continuously, allowing tracking by smooth pursuit eye movements, or in discrete steps across a series of adjacent locations, triggering a sequence of saccades. Both smooth pursuit and saccadic eye movements similarly affected number processing and modulated response times for large numbers as a function of direction of motion. These findings suggest that voluntary eye movements redirect attention in mental number space and highlight that eye movements should play a key factor in the investigation of number–space interactions.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Heterosexual, gay, and lesbian people’s reactivity to virtual caresses on their embodied avatars’ taboo zones
Full text linkEmbodying an artificial agent through immersive virtual reality (IVR) may lead to feeling vicariously somatosensory stimuli on one’s body which are in fact never delivered. To explore whether vicarious touch in IVR reflects the basic individual and social features of real-life interpersonal interactions we tested heterosexual men/women and gay men/lesbian women reacting subjectively and physiologically to the observation of a gender-matched virtual body being touched on intimate taboo zones (like genitalia) by male and female avatars. All participants rated as most erogenous caresses on their embodied avatar taboo zones. Crucially, heterosexual men/women and gay men/lesbian women rated as most erogenous taboo touches delivered by their opposite and same gender avatar, respectively. Skin conductance was maximal when taboo touches were delivered by female avatars. Our study shows that IVR may trigger realistic experiences and ultimately allow the direct exploration of sensitive societal and individual issues that can otherwise be explored only through imagination
Visual perspective and body ownership modulate vicarious pain and touch: A systematic review
No full text: We conducted a systematic review investigating the influence of visual perspective and body ownership (BO) on vicarious brain resonance and vicarious sensations during the observation of pain and touch. Indeed, the way in which brain reactivity and the phenomenological experience can be modulated by blurring the bodily boundaries of self-other distinction is still unclear. We screened Scopus and WebOfScience, and identified 31 articles, published from 2000 to 2022. Results show that assuming an egocentric perspective enhances vicarious resonance and vicarious sensations. Studies on synaesthetes suggest that vicarious conscious experiences are associated with an increased tendency to embody fake body parts, even in the absence of congruent multisensory stimulation. Moreover, immersive virtual reality studies show that the type of embodied virtual body can affect high-order sensations such as appropriateness, unpleasantness, and erogeneity, associated with the touched body part and the toucher's social identity. We conclude that perspective plays a key role in the resonance with others' pain and touch, and full-BO over virtual avatars allows investigation of complex aspects of pain and touch perception which would not be possible in reality
Right ventricular strain as a novel approach to analyze right ventricular performance in patients with heart failure
No full textSpeckle tracking echocardiography (STE) has recently applied as imaging technique to accurately evaluate right ventricular (RV) function. STE provides a non-Doppler, angle-independent and objective quantification of RV myocardial deformation. Data regarding feasibility, accuracy and clinical applications of RV strain are rapidly gathering, especially in the setting of heart failure patients. This review describes the fundamental concepts of RV-STE and discusses its emerging clinical applications, focusing on the useful of this technique in the clinical management of patients with advanced heart failure
Pupil dilation reveals top-down attentional load during spatial monitoring
Full text linkIt has long been known that the diameter of human pupil enlarges with increasing effort during the execution of a task. This has been observed not only for purely mechanical effort but also for mental effort, as for example the computation of arithmetic problems with different levels of difficulty. Here we show that pupil dilation reflects changes in visuospatial awareness induced by attentional load during multi-tasking. In the single-task condition, participants had to report the position of lateralized, briefly presented, masked visual targets ("right", "left", or "both" sides). In the multitasking conditions, participants also performed additional tasks, either visual or auditory, to increase the attentional load. Sensory stimulation was kept constant across all conditions to rule out the influence of low-level factors. Results show that event-related pupil dilation strikingly increased with task demands, mirroring a concurrent decrease in visuospatial awareness. Importantly, pupil dilation significantly differed between two dual-task conditions that required to process the same number of stimuli but yielded differed levels of accuracy (difficulty). In contrast, pupil dilation did not differ between two conditions which were equally challenging but differed both in the modality of the dual task (auditory vs. visual) and in the number of stimuli to be attended. We conclude that pupil dilation genuinely reflects the top-down allocation of supramodal attentional resources
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