Roberto Dell’Acqua

Naming times and standardized norms for the italian PD/DPSS set of 266 pictures: Direct comparisons with American, English, French, and Spanish published databases

The present study provides Italian normative measures for 266 line drawings belonging to the new set of pictures developed by Lotto, Dell’Acqua, and Job (in press). The pictures have been standardized on the following measures: number of letters, number of syllables, name frequency, within-category typicality, familiarity, age of acquisition, name agreement, and naming time. In addition to providing the measures, the present study focuses on indirect and direct comparisons (i.e., correlations) of the present norms with databases provided by comparable studies in Italian (in which normative data were collected with Snodgrass & Vanderwart’s set of pictures; Nisi, Longoni, & Snodgrass, 2000), in British English (Barry, Morrison, & Ellis, 1997), in American English (Snodgrass & Vanderwart, 1980; Snodgrass & Yuditsky, 1996), in French (Alario & Ferrand, 1999), and in Spanish (Sanfeliu & Fernandez, 1996).

Orienting attention to objects in visual short-term memory

We measured electroencephalographic activity during visual search of a target object among objects available to perception or among objects held in visual short-term memory (VSTM). For perceptual search, a single shape was shown first (pre-cue) followed by a search-array, and the task was to decide whether the pre-cue was or was not in the search-array. For search of VSTM, a search-array was shown first followed by a single shape (post-cue), and the task was to decide whether the post-cue was or was not in the previously displayed search-array. We focused on early lateralized electrical brain activity over posterior and temporal areas time-locked to search-arrays in pre-cue trials and to post-cues in post-cue trials. In Experiment 1, search-arrays were composed of two lateralized shapes, displayed in the upper/lower two quadrants of the monitor. In Experiment 2, search-arrays were composed of four shapes, displayed at the corners of an imaginary square centered on fixation. In pre-cue trials, we observed an N2pc of about equal amplitude and latency for search-arrays composed of two or four shapes. In post-cue trials, we observed N2pc-like activity with search-arrays composed of two shapes, that was however substantially attenuated with search-arrays composed of four shapes. For many aspects, attending to a perceptual object was functionally and neurally analogous to attending to an object held in VSTM, suggesting that spatial selective attention biases search of objects during both ongoing perception and retention.

Selective influence of second target exposure duration and Task1 load effects in the attentional blink phenomenon

The purpose of the experiments was to constrain the locus of interference in the attentional blink (AB) paradigm. Two visual stimuli, T1 and T2, were shown 300 msec apart, and each was followed by a mask. T1 was an “H,” an “S,” an “ &, ” or a blank field; T2 consisted of five letters. In Task1, blank fields and & characters could be ignored, whereas Hs and Ss had to be identified and reported. Task2 was always to report as many letters as possible from T2. Task2 performance was lower when T1 had to be reported, as expected from the attentional blink phenomenon (AB). The exposure duration of T2 was also manipulated. More letters could be reported as exposure duration was increased. However, this effect was additive with manipulations of Task1 processing load that produced the AB effect. Log-linear analyses assuming that effects of T2 exposure duration and Task1 load effects occur at functionally distinct stages of processing provided satisfactory fits to the results, suggesting that none of the AB effect occurs as early as those of T2 exposure duration. The results suggest that the locus of the AB effect is later than the stage(s) of processing affected by exposure duration.

Cross-modal attentional deficits in processing tactile stimulation

In order to substantiate recent theorization on the possible links between the causes of the attentional blink and the psychological refractory period phenomena (e.g., Jolicoeur, 1999a), four experiments are reported in which two target stimuli, T1 and T2, were presented in different modalities at varying stimulus onset asynchronies (SOAs), with each stimulus being associated with a distinct task, Task1 and Task2. In Experiment 1, T1 was a tone, and Task1 was a speeded vocal response based on pitch. T2 was a brief press applied to either of two distal fingerpads, and Task2 was a speeded manual response based on tactile stimulus location. In Experiment 2, the same T1 as that used in Experiment 1 was presented, and in Task1 the subject either made a speeded vocal response based on pitch or ignored T1. T2 was a masked tactile stimulation, and Task2 was an unspeeded manual discrimination of the tactile stimulation location. This Task2 was maintained in Experiments 3 and 4. The auditory T1 was replaced with a white digit embedded in a rapid serial visualization presentation of a stream of black letters, and in Task1 the subject either made an unspeeded decision based on T1 identity or ignored T1. In all the experiments, the results showed an SOA-locked impairment in Task2. As SOA was decreased, reaction times in the speeded Task2 of Experiment 1 increased, and accuracy in the unspeeded Task2 of Experiments 2–4 decreased. The SOA-locked impairment was almost eliminated when T1 could be ignored or was absent. The results are discussed in terms of central processing limitations as the cause of such effects.

Electrophysiological evidence of enhanced cortical activity in the human brain during visual curve tracing.

ERPs were recorded while participants performed a curve tracing task in which they had to identify the end point of a target curve presented among three other distractor curves. Differential activation associated with the side of the target curve was found in the form of a sustained posterior contralateral negativity (SPCN). This contralateral brain activity suggests covert attention was deployed to the target curve during performance of the tracing task. The amplitude of the SPCN varied according to the hypothesized curve-tracing process, depending on whether the start and end locations of the target curve were above to below the horizontal midline, or the opposite, and this detailed analysis of the results provided evidence supporting the spread-of-attention model of curve tracing. These results represent the first neurophysiological investigation of brain activity reflecting visual curve tracing in humans.

Is object recognition automatic

A new paradigm is proposed that involves a simple judgment on an object’s perceptual feature that is independent of object identity. Subjects were required to categorize as vertical or horizontal the main axis of elongation of an object picture. Both fake and real-world objects were presented, and a graphical manipulation was applied to their shapes so that the canonical elongation of the real-world objects was incongruent with the elongation of their shapes after the manipulation. The results showed an influence of the identity of the objects on the perceptual task in the form of a cost in judging the elongation of the incongruent real-world objects. The results are taken as evidence for automatic activation of objects’ stored representations. A “horse-race” model of the influence of these representations on the perceptual task is proposed in the final section of the article.

The attentional blink freezes spatial attention allocation to targets, not distractors: Evidence from human electrophysiology

Previous work found a significant reduction of the amplitude of the N2pc ERP component during the attentional blink in response to lateral visual targets, suggesting that the allocation of attention to visual targets is impaired during the attentional blink. Recent theorizing on the processes reflected by the N2pc suggests the possibility of distinct sets of neural mechanisms underlying its generation, one responsible for target activation, and one for distractor inhibition. To disentangle whether either or both of these mechanisms are impaired during the attentional blink, an RSVP sequence of circles, equidistant from fixation was used. The first target frame (T1) contained the same repeated target colour circle and target whereas the second target frame (T2) contained a distractor colour singleton as well as a target colour singleton. Only the target or only the distractor was presented at a lateral position; the other singleton was presented on the vertical midline so as not to elicit any event-related lateralization. Impaired T2 report accuracy at a short stimulus-onset asynchrony (SOA) was accompanied by a significant delay of the N2pc to lateral T2 targets when compared to a long SOA condition. No such delay was found when the lateralized stimulus was a distractor, suggesting that the attentional blink impacts attention allocation to targets, not distractors. We also observed a lateralized component earlier than the N2pc, a posterior contralateral positivity (Ppc) that did not depend on T1-T2 SOA and that was elicited by both lateral targets and distractors. We conclude that, contrary to N2pc, the Ppc likely reflects activity of bottom-up mechanisms responding unselectively to asymmetrical visual displays.

The attentional blink within and across the hemispheres: Evidence from a patient with a complete section of the corpus callosum

The attentional blink (AB) refers to an impairment in the report of a second target (T2) if it closely follows the presentation of a first target (T1) in a rapid serial visual presentation (RSVP), when both targets must be reported. In the present study, a modified AB paradigm was used in which targets could appear in any of four simultaneous RSVP streams, one in each quadrant of the visual field. In half of the trials, T1 and T2 were displayed in the same visual hemifield (either left or right) and, in the other half, T1 and T2 were displayed in different visual hemifields. Using this paradigm with both neurologically intact individuals and a split-brain patient, we sought to investigate (1) possible hemispheric asymmetries in attentional processes, and (2) whether the AB would be reduced when targets are displayed in different visual hemifields. A comparable AB was found for both neurologically intact individuals and the split-brain patient, with no significant variations due to whether targets were displayed in the same or in different hemifields. A left hemisphere advantage in the processing of same and different hemifield targets was observed only in the split-brain patient.

The SNARC effect is not a unitary phenomenon

Models of the spatial–numerical association of response codes (SNARC) effect—faster responses to small numbers using left effectors, and the converse for large numbers—diverge substantially in localizing the root cause of this effect along the numbers’ processing chain. One class of models ascribes the cause of the SNARC effect to the inherently spatial nature of the semantic representation of numerical magnitude. A different class of models ascribes the effect’s cause to the processing dynamics taking place during response selection. To disentangle these opposing views, we devised a paradigm combining magnitude comparison and stimulus–response switching in order to monitor modulations of the SNARC effect while concurrently tapping both semantic and response-related processing stages. We observed that the SNARC effect varied nonlinearly as a function of both manipulated factors, a result that can hardly be reconciled with a unitary cause of the SNARC effect.

Long-term continuous monitoring of the preterm brain with diffuse optical tomography and electroencephalography: a technical note on cap manufacturing.

Abstract. Diffuse optical tomography (DOT) has recently proved useful for detecting whole-brain oxygenation changes in preterm and term newborns’ brains. The data recording phase in prior explorations was limited up to a maximum of a couple of hours, a time dictated by the need to minimize skin damage caused by the protracted contact with optode holders and interference with concomitant clinical/nursing procedures. In an attempt to extend the data recording phase, we developed a new custom-made cap for multimodal DOT and electroencephalography acquisitions for the neonatal population. The cap was tested on a preterm neonate (28 weeks gestation) for a 7-day continuous monitoring period. The cap was well tolerated by the neonate, who did not suffer any evident discomfort and/or skin damage. Montage and data acquisition using our cap was operated by an attending nurse with no difficulty. DOT data quality was remarkable, with an average of 92% of reliable channels, characterized by the clear presence of the heartbeat in most of them.