Biomedical subjects

Massimo Turatto

Publications and source records attributed to Massimo Turatto.

11 recordsLinked to original sources

PubMed2005

Change perception using visual transients: object substitution and deletion.

In three experiments we studied change detection and identification when no extraneous transients were present in the image at the time of change. Each image consisted of 12 different objects, sorted by color into three different levels of probability of change. In Experiment 1, change of one object was detected and identified frequently in objects having the highest probability of change (central interest), which we hypothesize were mainly visited by attention. Changes in other objects with a lower probability of change (marginal interest), however, although detected efficiently were unlikely to be identified. Identification improved for less attended objects if the changed stimulus simply disappeared, allowing visual persistence to hold information about the object until attention could be shifted to it (Experiment 2). Contrary to previous findings showing that response times (RTs) for luminance change detection in a multi-element display are not altered by attention, we found changes in objects of central interest to be detected faster than in objects of marginal interest when objects' identity was to be held in working memory. However, no differences in RTs emerged in the same change detection task when objects' identity was not stored in working memory (Experiment 3).

Adult↗

PubMed2005

Rare stimuli or rare changes: what really matters for the brain?

Previous research has demonstrated that the electric brain response to changes consists of a negative deflection with a latency of 200 ms post-stimulus. Two different hypotheses, namely the mismatch and the rareness accounts, have been invoked to explain this electrocortical response. In the present study, this negative component emerged only for visual changes caused by the presentation of rare stimuli, documenting a precise brain response to rareness, and not to change per se. Crucially, no specific electrophysiological marker was evident when the change was rare, but consisted of stimuli frequently seen. Hence, we suggest that changes are preferentially processed by the brain only when they involve the occurrence of new and rare stimuli.

Adult↗

PubMed2005

Crossmodal object-based attention: auditory objects affect visual processing.

According to the object-based view, visual attention can be deployed to "objects" or perceptual units, regardless of spatial locations. Recently, however, the notion of object has also been extended to the auditory domain, with some authors suggesting possible interactions between visual and auditory objects. Here we show that task-irrelevant auditory objects may affect the deployment of visual attention, providing evidence that crossmodal links can also occur at an object-based level. Hence, in addition to the well documented control of visual objects over what we hear, our findings demonstrate that, in some cases, auditory objects can affect visual processing.

Affect↗

PubMed2004

The role of the right dorsolateral prefrontal cortex in visual change awareness.

Recently, the neural correlates of change detection vs change blindness have been investigated using fMRI. Results revealed that conscious perception of change is associated with enhanced activity in a neural network comprising the parietal (bilateral) and right dorsolateral prefrontal (DLPF) cortex. Here, by means of repetitive transcranial magnetic stimulation (rTMS), we unveil the causal role of the right DLPF cortex in perceiving changes. When rTMS was applied to this area, change perception was impaired as compared to left DLPF rTMS and sham stimulation. This result is important as it shows, for the first time, that conscious change perception is associated with normal activity in the right DLPF cortex. Our findings are in agreement with a recent view emphasizing the role of frontal areas, in addition to classical ventral and dorsal pathways, in visual awareness.

Adult↗

PubMed2004

Inhibition of return in microsaccades.

Inhibition of return (IOR) is the term used to describe the phenomenon whereby stimuli appearing at recently attended locations are reacted to less efficiently than stimuli appearing at locations that have not yet been attended. In the present study, we employed a typical IOR paradigm with peripheral uninformative cues while participants maintained their eyes at fixation. Eye position was monitored at a high sampling rate (500 Hz) in order to detect miniature eye movements called microsaccades, which have been shown to be crucial for avoiding disappearance of visual image. However, recent studies have demonstrated a close relationship between covert endogenous attentional shifts and the direction of microsaccades. Here, we demonstrate that the direction of microsaccades can be biased away from the peripheral location occupied by a salient, although task-irrelevant, visual signal. Because microsaccades are known not to be under conscious control, our results suggest strong links between IOR and unconscious oculomotor programming.

Adult↗

PubMed2004

Foreground-background segmentation and attention: a change blindness study.

One of the most debated questions in visual attention research is what factors affect the deployment of attention in the visual scene? Segmentation processes are influential factors, providing candidate objects for further attentional selection, and the relevant literature has concentrated on how figure-ground segmentation mechanisms influence visual attention. However, another crucial process, namely foreground-background segmentation, seems to have been neglected. By using a change blindness paradigm, we explored whether attention is preferentially allocated to the foreground elements or to the background ones. The results indicated that unless attention was voluntarily deployed to the background, large changes in the color of its elements remained unnoticed. In contrast, minor changes in the foreground elements were promptly reported. Differences in change blindness between the two regions of the display indicate that attention is, by default, biased toward the foreground elements. This also supports the phenomenal observations made by Gestaltists, who demonstrated the greater salience of the foreground than the background.

Adult↗

PubMed2004

The role of the magnocellular and parvocellular systems in the redundant target effect.

The redundant target effect (RTE) consists in the speeding of reaction time with single versus multiple targets and can be explained either by a neural coactivation or by a race model. To try to understand the role of the magnocellular and parvocellular systems in the determination of the RTE we carried out three experiments using onset or feature singletons. The former are likely to be mainly processed by the magnocellular system while the latter are mainly processed by the parvocellular system. In experiment 1 we found an RTE both when the target (red disk) was presented in isolation and when it was surrounded by equiluminant green distractors. Thus, the RTE occurred both with onset and feature singletons. However, with the former, the RTE could be accounted for by neural coactivation while with the latter it could be accounted for by a probabilistic explanation. In experiment 2 we tried to ascertain the role of distractors in yielding a probabilistic RTE: we used either targets in isolation or surrounded by distractors of lower luminance and found an RTE that could be explained by neural coactivation for both kinds of targets. This ruled out an effect of distractors per se in determining a probabilistic RTE. Finally, in experiment 3 we used targets of lower luminance than either the background or the distractors. We found that the RTE could be accounted for by neural coactivation with targets alone while it was probabilistic with distractors. Overall, these results show that stimuli presumably processed by the magnocellular system yield redundancy gains that result from a neural coactivation mechanism. In contrast, stimuli presumably processed by the parvocellular system are compatible with a probabilistic redundancy gain.

Adult↗

PubMed2004

Stimulus-driven attentional capture: An empirical comparison of display-size and distance methods.

Four experiments examined attentional capture by colour as assessed by two different investigative methods. Subjects performed a visual search task for a vertical-target line embedded among tilted-distractor lines, presented inside 4, 8, or 12 coloured discs. Interestingly, when the colour singleton was task irrelevant, and data were analysed by means of the display-size method combined with the zero-slope criterion, no evidence for attentional capture by colour was found. However, when data were analysed by means of the distance method, which consists of monitoring the spatial relationship between the target and the singleton, results showed that the target was found faster and/or more accurately when it was inside the singleton than when it was in a nonsingleton location. This provided evidence for a stimulus-driven attentional capture. In addition, the application of signal detection methodology showed that attentional capture, as revealed by the distance method, resulted from a perceptual modulation at the singleton location, rather than from a criterion shift. We conclude that, at least with the kind of stimuli used here, the display-size method combined with the zero-slope criterion is less than ideal for investigating how static discontinuities can affect the automatic deployment of visual attention.

Adult↗

PubMed2003

Space-independent modality-driven attentional capture in auditory, tactile and visual systems.

Extending previous evidence for attentional shifts across auditory and visual modalities without the confound of the two modalities originating at different locations (Turatto et al. 2002), we investigated attention shifts between auditory and tactile modalities, and between tactile and visual modalities. Two stimuli (S1 and S2), either in the same or in different modalities, were delivered from the same spatial source and were separated by a variable temporal gap. S1 was task irrelevant, whereas S2 required a speeded discrimination. Results showed that modality switching is detrimental independently of the stimulated modality as long as the temporal lag between S1 and S2 is short enough that there is not time to switch attention before S2 is delivered. We observed automatic, modality-driven, attentional capture, with ipsimodal trials leading to faster response times than crossmodal trials. The present results cannot be accounted for by spatial artifacts, response priming or criterion shifts, and are interpreted as the consequence of a space-independent attentional shift across sensory modalities.

Acoustic Stimulation↗

PubMed2002

Looking without seeing the background change: electrophysiological correlates of change detection versus change blindness.

Two experiments document that conceptual knowledge influences 3-year-olds' extension of novel words. In Experiment 1, when objects were described as having conceptual properties typical of artifacts, children extended novel labels for these objects on the basis of shape alone. When the very same objects were described as having conceptual properties typical of animate kinds, children extended novel labels for these objects on the basis of both shape and texture. Moreover, providing a salient perceptual cue (Experiment 2) did not interfere with children's reliance on conceptual information in extending novel words: when an object with eyes was labeled with a novel word in the context of a story describing the object as an artifact, children extended the label on the basis of shape alone (i.e. as though the object were an artifact). These results, which challenge directly the position that 'dumb attentional mechanisms' can account for word learning, stand as evidence for the central role of conceptual information in mapping words to meaning.

Adult↗

PubMed2002

Nonspatial attentional shifts between audition and vision.

This study investigated nonspatial shifts of attention between visual and auditory modalities. The authors provide evidence that the modality of a stimulus (S1) affected the processing of a subsequent stimulus (S2) depending on whether they shared the same modality. For both vision and audition, the onset of S1 summoned attention exogenously to its modality, causing a delay in processing S2 in a different modality. That undermines the notion that auditory stimuli have a stronger and more automatic alerting effect than visual stimuli (M. I. Posner, M. J. Nissen, & R. M. Klein, 1976). The results are consistent with other recent studies showing cross-modal attentional limitation. The authors suggest that such cross-modal limitation can be produced by simply presenting S1 and S2 in different modalities and that central processing mechanisms are also, at least partially, modality dependent.

Adult↗