Biomedical subjects

Pío Tudela

Publications and source records attributed to Pío Tudela.

11 recordsLinked to original sources

PubMed2006

Temporal attention enhances early visual processing: a review and new evidence from event-related potentials.

Two fundamental cognitive functions, selective attention and processing of time, have been simultaneously explored in recent studies of temporal orienting of attention. A temporal-orienting procedure may consist of a temporal analogue to the Posner's paradigm, such that symbolic cues indicate the most probable moment for target arrival. Behavioral measures suggest that performance is improved for events appearing at expected vs. unexpected moments. However, there is no agreement on the locus of stimulus processing at which temporal attention operates. Thus, it remains unclear whether early perceptual or just late motor processes can be modulated. This article reviews current ERP research on temporal orienting, with an emphasis on factors that might determine the modulation of temporal orienting at early stages of processing. We conclude that: First, late components (N2 and P300) are consistently modulated by temporal orienting, which suggests attentional preparation of decision and/or motor processes. Second, early components (e.g., N1) seem to be modulated only when the task is highly demanding in perceptual processing. Hence, we conducted an ERP experiment which aimed to observe a modulation of early visual processing by using a perceptually demanding task, such as letter discrimination. The results show, for the first time, that targets appearing at attended moments elicited a larger P1 component than unattended targets. Moreover, temporal attention modulated the amplitude and latency of N2 and P300 components. This suggests that temporal orienting of attention not only modulates late motor processing, but also early visual processing when perceptually demanding tasks are used.

Acoustic Stimulation↗

PubMed2006

Selective temporal attention enhances the temporal resolution of visual perception: Evidence from a temporal order judgment task.

We investigated whether attending to a particular point in time affects temporal resolution in a task in which participants judged which of two visual stimuli had been presented first. The results showed that temporal resolution can be improved by attending to the relevant moment as indicated by the temporal cue. This novel finding is discussed in terms of the differential effects of spatial and temporal attention on temporal resolution.

Attention↗

PubMed2005

The attentional mechanism of temporal orienting: determinants and attributes.

A review of traditional research on preparation and foreperiod has identified strategic (endogenous) and automatic (exogenous) factors probably involved in endogenous temporal-orienting experiments, such as the type of task, the way by which temporal expectancy is manipulated, the probability of target occurrence and automatic sequential effects, yet their combined impact had not been investigated. These factors were manipulated within the same temporal-orienting procedure, in which a temporal cue indicated that the target could appear after an interval of either 400 or 1,400 ms. We observed faster reaction times for validly versus invalidly cued targets, that is, endogenous temporal-orienting effects. The main results were that the probability of target occurrence (catch-trial proportion) modulated temporal orienting, such that the attentional effects at the short interval were independent of catch trials, whereas at the long interval the effects were only observed when catch trials were present. In contrast, the interval duration of the previous trial (i.e., exogenous sequential effects) did not influence endogenous temporal orienting. A flexible and endogenous mechanism of attentional orienting in time can account for these results. Despite the contribution of other factors, the use of predictive temporal cues was sufficient to yield attentional facilitation based on temporal expectancy.

Attention↗

PubMed2005

Modulations among the alerting, orienting and executive control networks.

This paper reports a series of experiments that were carried out in order to study the attentional system. Three networks make up this system, and each of them specializes in particular processes. The executive control network specializes in control processes, such as conflict resolution or detection of errors; the orienting network directs the processing system to the source of input and enhances its processing; the alerting network prepares the system for a fast response by maintaining an adequate level of activation in the cognitive system. Recently, Fan and collaborators [J Cogn Neurosci 14(3):340-347, 2002] designed a task to measure the efficiency of each network. We modified Fan's task to test the influences among the networks. We found that the executive control network is inhibited by the alerting network, whereas the orienting network raises the efficiency of the executive control network (Experiment 1). We also found that the alerting network influences the orienting network by speeding up its time course function (Experiment 2). Results were replicated in a third experiment, proving the effects to be stable over time, participants and experimental context, and to be potentially important as a tool for neuropsychological assessment.

Acoustic Stimulation↗

PubMed2005

Two brain pathways for attended and ignored words.

The dependency of word processing on spare attentional resources has been debated for several decades. Recent research in the study of selective attention has emphasized the role of task load in determining the fate of ignored information. In parallel to behavioral evidence, neuroimaging data show that the activation generated by unattended stimuli is eliminated in task-relevant brain regions during high attentional load tasks. We conducted an fMRI experiment to explore how word encoding proceeds in a high load situation. Participants saw a rapid series of stimuli consisting of overlapping drawings and letter strings (words or nonwords). In different blocks, task instructions directed attention to either the drawings or the letters, and subjects responded to immediate repetition of items in the attended dimension. To look at the effect of attention on word processing, we compared brain activations for words and nonwords under the two attentional conditions. As compared to nonwords, word stimuli drove responses in left frontal, left temporal and parietal areas when letters were attended. However, although the behavioral measures suggested that ignored words were not analyzed when drawings were attended, a comparison of ignored words to ignored nonwords indicated the involvement of several regions including left insula, right cerebellum and bilateral pulvinar. Interestingly, word-specific activations found when attended and ignored words were compared showed no anatomical overlap, suggesting a change in processing pathways for attended and ignored words presented in a high attentional load task.

Adult↗

PubMed2005

Inattentional amnesia to words in a high attentional load task.

We investigated the dependence of visual word processes on attention by examining event-related potential (ERP) responses as subjects viewed words while their attention was engaged by a concurrent highly demanding task. We used a paradigm from a previous functional magnetic resonance imaging (fMRI) experiment [Rees, G., Russel, C., Frith, C. D., & Driver, J. Inattentional blindness vs. inattentional amnesia for fixated but ignored words. Science, 286, 2504-2506, 1999] in which participants attended either to drawings or to overlapping letters (words or nonwords) presented at a fast rate. Although previous fMRI results supported the notion that word processing was obliterated by attention withdrawal, the current electrophysiological results demonstrated that visual words are processed even under conditions in which attentional resources are engaged in a different task that does not involve reading. In two experiments, ERPs for attended words versus nonwords differed in the left frontal, left posterior, and medial scalp locations. However, in contrast to the previous fMRI results, ERPs responded differentially to ignored words and consonant strings in several regions. These results suggest that fMRI and ERPs may have differential sensitivity to some forms of neural activation. Moreover, they provide evidence to restore the notion that the brain analyzes words even when attention is tied to another dimension.

Adult↗

PubMed2005

Attentional preparation based on temporal expectancy modulates processing at the perceptual level.

Research that uses simple response time tasks and neuroimaging has emphasized that attentional preparation based on temporal expectancy modulates processing at motor levels. A novel approach was taken to study whether the temporal orienting of attention can also modulate perceptual processing. A temporal-cuing paradigm was used together with a rapid serial visual presentation procedure, in order to maximize the processing demands of perceptual analysis. Signal detection theory was applied in order to examine whether temporal orienting affects processes related to perceptual sensitivity or to response criterion (indexed by d' and beta measures, respectively). If temporal orienting implies perceptual preparation, we would expect to observe an increase in perceptual sensitivity (d') when a target appeared at expected, rather than unexpected, time intervals. Indeed, our behavioral results opened the possibility that focusing attention on time intervals not only enhances motor processing, as has been shown by previous research, but also might improve perceptual processing.

Attention↗

PubMed2004

The three attentional networks: on their independence and interactions.

The present investigation was aimed to the study of the three attentional networks (Alerting, Orienting, and Executive Function) and their interactions. A modification of the task developed by Fan, McCandliss, Sommer, Raz, and Posner (2002) was used, in which a cost and benefit paradigm was combined with a flanker task and an alerting signal. We obtained significant interactions as predicted. The alerting network seemed to inhibit the executive function network (a larger flanker-congruency effect was found on trials where an alerting signal had been previously presented). The orienting network influenced the executive function network in a positive way (the flanker effect was smaller for cued than for uncued trials). Finally, alertness increased orienting (the cueing effect was bigger after the alerting signal). This last result, taken together with previous findings, points to an influence in the sense of a faster orienting under alertness, rather than a larger one. These results offer new insight into the functioning of the attentional system.

Adolescent↗

PubMed2004

Endogenous temporal orienting of attention in detection and discrimination tasks.

Endogenous temporal-orienting effects were studied using a cuing paradigm in which the cue indicated the time interval during which the target was most likely to appear. Temporal-orienting effects were defined by lower reaction times (RTs) when there was a match between the temporal expectancy for a target (early or late) and the time interval during which the target actually appeared than when they mismatched. Temporal-orienting effects were found for both early and late expectancies with a detection task in Experiment 1. However, catch trials were decisive in whether temporal-orienting effects were observed in the early-expectancy condition. No temporal-orienting effects were found in the discrimination task. In Experiments 2A and 2B, temporal-orienting effects were observed in the discrimination task; however, they were larger when temporal expectancy was manipulated between blocks, rather than within blocks.

Attention↗

PubMed2003

High density ERP indices of conscious and unconscious semantic priming.

The existence of differential brain mechanisms of conscious and unconscious processing is a matter of debate nowadays. The present experiment explores whether conscious and unconscious semantic priming in a lexical decision task at a long prime-target stimulus onset asynchrony (SOA) correlate with overlapping or different event related potential (ERP) effects. Results show that the N400 effect, which appeared when words were consciously perceived, completely disappeared when primes were masked at a level where the ability of participants to detect the prime was near chance. Instead, a rather different set of ERP effects was found to index unconscious semantic priming. This suggests that the processes at the basis of conscious and unconscious semantic analyses can under some circumstances be rather different. Moreover, our results support the notion that conscious and unconscious processes are at least partially separable in the brain.

Adult↗

PubMed2002

Priming and interference effects can be dissociated in the Stroop task: new evidence in favor of the automaticity of word recognition.

Recently, Besner, Stolz, and Boutilier (1997) showed that by coloring a single letter instead of the whole word, Stroop interference is reduced or even eliminated, a result that is at odds with the widely accepted assumption that word recognition is automatic. In a replication of the Besner et al. study, we computed priming effects in addition to the standard Stroop interference. Interference results replicated those of Besner et al. Also, negative priming in the all-letter-colored condition and positive priming in the single-letter-colored condition were obtained. Priming findings demonstrate that word processing can take place in the absence of interference effects. These results support the view of automatic processing of words in the Stroop task and call for priming as a more appropriate measure of word processing than interference.

Automatism↗