Biomedical subjects

Veronica Mazza

Publications and source records attributed to Veronica Mazza.

8 recordsLinked to original sources

PubMed2006

How automatic are audiovisual links in exogenous spatial attention?

Three experiments on healthy humans investigated the degree of automaticity of crossmodal spatial attention shifts by assessing the intentionality criterion. We used the orthogonal cuing paradigm in which a lateralized cue, either visual or auditory was followed by a unimodal or crossmodal target that occurred at the same or opposite side. In all experiments, the cue was always uninformative as to target location. In Experiment 1, where both side and modality of targets were unpredictable, we found faster discriminations for visual targets following uninformative auditory cues on the same side. This result was replicated in Experiment 2, where target side was blocked and participants could orient attention in advance toward the appropriate side, and in Experiment 3, where they were additionally informed about target modality. Our results suggest that this sort of crossmodal orienting is automatic because it occurred even when participants were provided with detailed information about the target to prevent uninformative auditory cues from orienting attention. This is consistent with the notion that peripheral auditory stimuli are very powerful in capturing visual attention.

Adolescent↗

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↗

PubMed2005

Electrophysiological correlates of change detection.

To identify electrophysiological correlates of change detection, event-related brain potentials (ERPs) were recorded while participants monitored displays containing four faces in order to detect a face identity change across successive displays. Successful change detection was mirrored by an N2pc component at posterior electrodes contralateral to the side of a change, suggesting close links between conscious change detection and attention. ERPs on undetected-change trials differed from detected-change and no-change trials. We suggest that short-latency ERP differences between these trial types reflect trial-by-trial fluctuations in advance task preparation, whereas differences in the P3 time range are due to variations in the duration of perceptual and decision-related processing. Overall, these findings demonstrate that ERPs are a useful tool for dissociating processes underlying change blindness and change detection.

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

Electrophysiological correlates of stimulus-driven multiplication facts retrieval.

We investigated ERPs elicited by stimulus-driven retrieval of arithmetic facts related to multiplication. To this purpose, we recorded the electrophysiological activity from the scalp of participants while they were performing a number-matching task. Crucially, arithmetic was task-irrelevant within this paradigm, because participants were simply to physically compare a cue composed of two one- or two-digit numbers and a single probe number. In line with past literature, behavioral data showed that, in non-matching trials, participants were significantly slower and/or less accurate to respond when the probe number was the product of the two numbers in the cue compared to when the probe number was arithmetically unrelated (i.e., neutral) to those numbers (interference effect). Consistent with recent findings on ERPs and task-relevant arithmetic facts retrieval, we showed that the interference effect resulted in a modulation of the amplitude of an N400-like ERP component, with neutral probes generating relatively more negativity than product probes. The observed dissociation between behavioral data and ERP measures is interpreted as evidence of activation spreading in the lexicon of arithmetic facts, because alternative accounts that rely on strategic factors such as expectancy or semantic matching would have predicted the two measures to show a converging trend.

Adult↗

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↗