Papers by Roberto Dell'Acqua
Participants had to determine the orientation of a segment inside a target color circle among oth... more Participants had to determine the orientation of a segment inside a target color circle among other gray distractor circles. The target circle was either red or green and was accompanied in the display by a distractor in the other color. To dissociate event-related potentials of target and distractor processing, one of them was on the vertical meridian and the other in a lateral position. In Experiment 1, the target color was indicated on a per-trial basis and, in Experiment 2, on a per-block basis. The results revealed the N2pc elicited by red targets had an earlier latency relative to the N2pc elicited by green targets. Contralateral responses of positive polarity linked to distractor inhibition were found only with red lateral distractors. The results suggest that the choice of colors to distinguish targets from distractors may play a role in visual search performance and in the functional characterization of event-related lateralizations.
Acqua, " Long-term continuous monitoring of the preterm brain with diffuse optical tomography and... more Acqua, " Long-term continuous monitoring of the preterm brain with diffuse optical tomography and electroencephalography: a technical note on cap manufacturing, " Neurophoton. 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 electroen-cephalography 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.
Using the event-related potential (ERP) approach, we tracked the time-course of white participant... more Using the event-related potential (ERP) approach, we tracked the time-course of white participants empathic reactions to white (own-race) and black (other-race) faces displayed in a painful condition (i.e. with a needle penetrating the skin) and in a nonpainful condition (i.e. with Q-tip touching the skin). In a 280-340 ms time-window, neural responses to the pain of own-race individuals under needle penetration conditions were amplified relative to neural responses to the pain of other-race individuals displayed under analogous conditions. This ERP reaction to pain, whose source was localized in the inferior frontal gyrus, correlated with the empathic concern ratings of the Interpersonal Reactivity Index questionnaire. In a 400-750 ms time-window, the difference between neural reactions to the pain of own-race individuals, localized in the middle frontal gyrus and other-race individuals, localized in the temporoparietal junction was reduced to nil. These findings support a functional, neural and temporal distinction between two sequential processing stages underlying empathy, namely, a race-biased stage of pain sharing/mirroring followed by a race-unbiased stage of cognitive evaluation of pain.
Neurophotonics, 2016
Diffuse optical tomography (DOT) has recently proved useful for detecting whole-brain oxygenation... more 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.
We measured electroencephalographic activity during visual search of a target object among object... more 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 postcue 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.
Visual short-term memory has a very limited storage capacity of about three objects. Some stages ... more Visual short-term memory has a very limited storage capacity of about three objects. Some stages of categorization and decision making appear also to have very sharp capacity limitations, sometimes as low as one representation. Early visual processing, on the other ...
Frontiers in Psychology, 2010
We used the event-related potential (ERP) approach combined with a subtraction technique to explo... more We used the event-related potential (ERP) approach combined with a subtraction technique to explore the timecourse of activation of semantic and phonological representations in the pictureword interference paradigm. Subjects were exposed to to-be-named pictures superimposed on to-be-ignored semantically related, phonologically related, or unrelated words, and distinct ERP waveforms were generated time-locked to these different classes of stimuli. Difference ERP waveforms were generated in the semantic condition and in the phonological condition by subtracting ERP activity associated with unrelated picture-word stimuli from ERP activity associated with related picture-word stimuli. We measured both latency and amplitude of these difference ERP waveforms in a pre-articulatory time-window. The behavioral results showed standard interference effects in the semantic condition, and facilitatory effects in the phonological condition. The ERP results indicated a bimodal distribution of semantic effects, characterized by the extremely rapid onset (at about 100 ms) of a primary component followed by a later, distinct, component. Phonological effects in ERPs were characterized by components with later onsets and distinct scalp topography of ERP sources relative to semantic ERP components. Regression analyses revealed a covariation between semantic and phonological behavioral effect sizes and ERP component amplitudes, and no covariation between the behavioral effects and ERP component latency. The early effect of semantic distractors is thought to reflect very fast access to semantic representations from picture stimuli modulating on-going orthographic processing of distractor words.
Brain Research, 2007
A rapid serial visual presentation technique was used to display sequentially two targets, T1 and... more A rapid serial visual presentation technique was used to display sequentially two targets, T1 and T2, and monitor P3 amplitude and latency variations associated with the attentional blink (AB) effect. A red T1 digit was embedded on each trial in a sequence of black letters. T2 was either masked by a trailing stimulus or not masked. T1 had to be identified on a proportion of trials, or ignored in other trials. T2 was the black letter 'E' on 20% of the trials, or any other non-'E' black letter in the other 80% of the trials. A delayed 'E' detection task was required at the end of each trial. An AB was observed when T1 had to be reported and T2 was masked. The AB effect was associated with a sizable amplitude reduction of the P3 component time locked to T2 onset. When T2 was not masked, no AB or P3 amplitude variations were observed. When T1 had to be reported, a delayed P3 peak latency was observed at short compared to long T1-T2 intervals. No effect of T1-T2 interval was observed on the T2-locked P3 peak latency when T1 could be ignored. Taken together these findings provide converging evidence in support of temporal attention models bridging behavior and electrophysiology that postulate a direct link between the cause of the AB effect and the sources of both amplitude and latency variations in the T2-locked P3 component. a v a i l a b l e a t w w w. s c i e n c e d i r e c t . c o m w w w. e l s e v i e r. c o m / l o c a t e / b r a i n r e s
Brain Research, 2007
In order to investigate the interplay between visuo-spatial attention and central attention, we v... more In order to investigate the interplay between visuo-spatial attention and central attention, we varied the relative probability (25% vs. 75%) of the responses to lateralized targets in an attentional blink paradigm. When the first target was associated with a less probable response, we observed a larger attentional blink, that is, a general reduction in accuracy for the second target. The efficiency of deployment of spatial attention to the second target was also reduced as a function of the response frequency for the first target. Both the N2pc, an event-related potential (ERP) associated with the deployment of attention in visual space, and the SPCN (sustained posterior contralateral negativity), an ERP associated with the maintenance of information in visual short-term memory, time-locked to T2 were significantly reduced when the first target was associated with a less frequent response.
Journal of Cognitive Neuroscience, 2010
■ Does the capacity of visual short-term memory ( VSTM) depend on the complexity of the objects r... more ■ Does the capacity of visual short-term memory ( VSTM) depend on the complexity of the objects represented in memory? Although some previous findings indicated lower capacity for more complex stimuli, other results suggest that complexity effects arise during retrieval (due to errors in the comparison process with what is in memory) that is not related to storage limitations of VSTM, per se. We used ERPs to track neuronal activity specifically related to retention in VSTM by measuring the sustained posterior contralateral negativity during a change detection task (which required detecting if an item was changed between a memory and a test array). The sustained posterior contralateral negativity, during the retention interval, was larger for complex objects than for simple objects, suggesting that neurons mediating VSTM needed to work harder to maintain more complex objects. This, in turn, is consistent with the view that VSTM capacity depends on complexity. ■
European Journal of Cognitive Psychology, 2006
We studied attentional control mechanisms using electrophysiological methods, focusing on the N2p... more We studied attentional control mechanisms using electrophysiological methods, focusing on the N2pc event-related potential (ERP), to track the moment-bymoment deployment of visual spatial attention. Two digits (T 1 and T 2 , both red or both green, and masked, were embedded in a rapid serial visual presentation of letter distractors with an SOA of 200 ms or 800 ms. T 1 was at fixation, whereas T 2 was 38 to the left or right of fixation and presented with a concurrent equiluminant distractor digit in a different colour. T 1 and T 2 were reported in one block of trials, and only T 2 in another block (order counterbalanced). Accuracy for T 2 was lower at short SOA than at long SOA when both T1 and T2 were reported, suggesting an attentional blink (AB) effect. It was difficult to ignore T 1 because T 1 had the same colour as T 2 , producing a large deficit in T 2 accuracy at short SOA in the control condition. The amplitude of the N2pc ERP component was attenuated in the short-SOA condition relative to the long-SOA condition, both in the experimental and the control conditions, suggesting that T 1 involuntarily captured visual spatial attention and that while attention was deployed on T 1 , the processing of T 2 was significantly impaired.
Psychological Research, 2006
A test of whether patients suffering from a severe closed-head injury (CHI) were affected by disp... more A test of whether patients suffering from a severe closed-head injury (CHI) were affected by disproportionate dual-task costs compared to those of healthy control participants was carried out through a direct comparison of CHI effects on dual-task (psychological refractory period, or PRP) performance and on singletask performance. In the dual-task condition of the present experiment, independent choice-responses were required to two sequential stimuli presented at a variable stimulus onset asynchrony (SOA). A significant delay of the reaction time (RT) to the second stimulus was reported by both CHI patients and controls at short (SOA) compared to long SOA, i.e., a PRP effect. The PRP effect was more pronounced for CHI patients than controls. In the single-task condition, a single choiceresponse was required to a stimulus presented in isolation. The RT produced by CHI patients in the singletask paradigm was longer than the RT produced by controls. CHI effects on dual-task performance and on single-task performance were compared following (1) their transformation into Cohen's ds, and (2) the application of a correction algorithm taking into account the different reliability of single-task and dual-task measures. The analysis of Cohen's ds revealed that CHI effects on performance were, if anything, smaller in the dual-task condition than in the single-task condition. The results imply that CHI patient's slower responding in single-and dual-task performance reflects a single common cause-slowing of the central processing.
European Journal of Cognitive Psychology, 2006
Brief tactile presses stimulated the index and middle fingers of the right and left hands. The st... more Brief tactile presses stimulated the index and middle fingers of the right and left hands. The stimulation on each hand consisted of a triplet of presses. Each triplet was composed of a brief press to one finger (e.g., the middle finger), followed by a brief press to the other finger (e.g., the index finger), and by a final simultaneous press to both fingers of a given hand. With equal probability, a triplet could begin with the index or middle finger, and either 360 ms or 800 ms later another triplet stimulated fingers on the other hand. The task was to indicate which finger was stimulated first in each triplet. In four experiments, response accuracy to the second triplet revealed an attentional blink in taction, that is, responses were less accurate at the short triplet Átriplet interval than at the long triplet Átriplet interval. This effect was substantially reduced when the first triplet could be ignored.
Psychophysiology, 2006
A variant of the rapid serial visual presentation paradigm was used to display sequentially two l... more A variant of the rapid serial visual presentation paradigm was used to display sequentially two lateral sequences of stimuli, one to the left and one to the right of fixation, embedding two pairs of target stimuli, T1 and T2. T1 was composed of a pair of alphanumeric characters, and subjects had either to ignore T1 or to encode T1 for a delayed response. T2 was a lateral square of a prespecified color. The square had a small gap in one side, and the task for this stimulus was to report which side had the gap. When subjects were required to ignore T1, the T2-locked ERP produced a clear N2pc, that is, a greater negativity at electrode sites contralateral to the position occupied by T2. This N2pc was followed by a sustained posterior contralateral negativity (SPCN). When subjects were required to monitor T1 in addition to T2, both the N2pc and the SPCN components amplitude depended on the difficulty of the task associated with T1. If T1 was composed of digits that had to be encoded for a delayed same/different judgment, both the N2pc and the SPCN components were entirely suppressed. Although attenuated, such components were present when T1 was composed of a pair of symbols that subjects could disregard. The results suggest that a set of mechanisms subserving the allocation of attention in the spatial domain, resulting in the N2pc, suffer significant interference from concurrent cognitive operations required to encode information into visual short-term memory.
Psychophysiology, 2013
Early event-related potential (ERP) hemispheric asymmetries recorded at occipitoparietal sites ar... more Early event-related potential (ERP) hemispheric asymmetries recorded at occipitoparietal sites are usually observed following the sudden onset of a lateral peripheral stimulus. This is usually reflected in an onset-locked larger N1 over the posterior contralateral hemisphere relative to the ipsilateral hemisphere, an early ERP asymmetry labeled N1pc. When the peripheral sudden onset is followed by a central stimulus, or by a bilaterally balanced visual array of stimuli, these events evoke a reversed N1pc, that is, a larger N1 over the hemisphere ipsilateral to the peripheral sudden onset. This N1pc reversal has been taken as evidence for a remapping of the visual space from an absolute, retinally based frame of reference to a relative, attentionally based frame of reference that codes the spatial positions of objects relative to the peripheral sudden onset, rather than relative to the fovea. Here, we pit the reference frame-remapping account against an alternative account based on reduced neural reactivity following the peripheral sudden onset. In three experiments, we varied the spatial location of an object relative to a preceding sudden onset, and tested the opposite predictions generated by the frame-remapping and the reduced neural reactivity accounts. Taken together, the results from the present experiments were consistent with the reduced neural reactivity account and inconsistent with the frame-remapping account.
Psychological Research, 2006
We used electrophysiological methods to track the deployment of visual spatial attention while ob... more We used electrophysiological methods to track the deployment of visual spatial attention while observers were engaged in concurrent central attentional processing, using a variant of the attentional blink paradigm. Two visual targets (T1, T2) were presented at a stimulus onset asynchrony of either 200 ms or 800 ms. T1 was a white digit among white letters presented on a dark background using rapid serial visual presentation at fixation. T2 was another digit that was presented to the left or right of fixation simultaneously with a distractor digit in the opposite visual field, each followed by a pattern mask. In each T2 display, one digit was red and one was green. Half of the subjects reported the red digit and ignored the green one, whereas the other half reported the green digit and ignored the red one. T1 and T2 were reported in one block of trials, and only T2 in another block (order counterbalanced across subjects). Accuracy of report of T2 was lower at short SOA than at long SOA when both T1 and T2 were reported, but was similar across SOA when only T2 was reported. The electrophysiological results focused on the N2pc component, which was used as an index of the locus of spatial attention. N2pc was reduced in amplitude when subjects reported T1, and particularly so at the short SOA. The results suggest that attention to T1 interfered with the deployment of visual spatial attention to T2.
Social Cognitive and Affective Neuroscience, 2012
We tested the ability of white participants to encode and retain over a brief period of time info... more We tested the ability of white participants to encode and retain over a brief period of time information about the identity of white and black people, using faces as stimuli in a standard change detection task and tracking neural activity using electroencephalography. Neural responses recorded over the posterior parietal cortex reflecting visual working memory activity increased in amplitude as a function of the number of faces that had to be maintained in memory. Critically, these memory-related neural responses varied as a function of participants implicit racial prejudice toward black people. High-prejudiced participants encoded black people faces with a lower degree of precision compared to low-prejudiced participants, suggesting that the class of mental operations affected by implicit racial prejudice includes basic cognitive mechanisms underpinning the encoding and maintenance of faces visual representations in visual working memory.
Vision Research, 2003
When two target stimuli (T1 and T2) are presented sequentially within half a second of each other... more When two target stimuli (T1 and T2) are presented sequentially within half a second of each other, identification accuracy is often poor for T2. This phenomenon, known as attentional blink (AB), can be observed generally only if the stimulus terminating the presentation of T2 acts as an interruption mask. Recent evidence suggests that even four small dots surrounding a target item can exert masking effects, provided the target onset occurs at an unattended spatial location. In order to test whether an AB could be observed under conditions of four-dot masking of T2, five rapid serial visual presentation streams of letters were synchronously displayed on each trial of the present experiment. T1 and T2 were digits presented at unpredictable locations and unpredictable temporal intervals. T2 was followed by either a blank field, a letter, or four-dots. No AB was observed when T2 was not masked, but robust and equally sized ABs were observed when T2 was followed by both the letter mask and the four-dots.
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Papers by Roberto Dell'Acqua