Biomedical subjects

Carles Escera

Publications and source records attributed to Carles Escera.

15 recordsLinked to original sources

PubMed2006

Impaired duration mismatch negativity in developmental dyslexia.

A mismatch negativity event-related potential protocol was administered to dyslexic children and their respective controls to test whether a specific auditory deficit concerning phonetic processing or a lower level auditory processing deficit was present in developmental dyslexia. Three different contrast conditions were explored, including nonphonological sounds, contrasted in pitch and duration, and phonemes. Mismatch negativity amplitudes differed significantly between groups in the duration condition, whereas no differences were found in the frequency and phoneme conditions. Moreover, the dyslexic children had delayed mismatch negativity latencies in the three contrast conditions. Our results suggest a deficit in low-level auditory discrimination in dyslexic children, in particular when detecting stimulus duration, and support the rapid auditory processing theory of dyslexia.

Acoustic Stimulation↗

PubMed2006

The effect of age on involuntary capture of attention by irrelevant sounds: a test of the frontal hypothesis of aging.

The aim of this study was to examine the effects of aging on the involuntary capture of attention by irrelevant sounds (distraction) and the use of these sounds as warning cues (alertness) in an oddball paradigm. We compared the performance of older and younger participants on a well-characterized auditory-visual distraction task. Based on the dissociations observed in aging between attentional processes sustained by the anterior and posterior attentional networks, our prediction was that distraction by irrelevant novel sounds would be stronger in older adults than in young adults while both groups would be equally able to use sound as an alert to prepare for upcoming stimuli. The results confirmed both predictions: there was a larger distraction effect in the older participants, but the alert effect was equivalent in both groups. These results give support to the frontal hypothesis of aging [Raz, N. (2000). Aging of the brain and its impact on cognitive performance: integration of structural and functional finding. In F.I.M. Craik & T.A. Salthouse (Eds.) Handbook of aging and cognition (pp. 1-90). Mahwah, NJ: Erlbaum; West, R. (1996). An application of prefrontal cortex function theory to cognitive aging. Psychological Bulletin, 120, 272-292].

Acoustic Stimulation↗

PubMed2006

Problem size effect and processing strategies in mental arithmetic.

We investigated the event-related brain potentials elicited by arithmetical operations whose solution requires direct memory retrieval or non-retrieval strategies. The problem size effect--the increment in reaction time for arithmetical problems with large operands--appears to be due to the selective use of non-retrieval procedures, and studies with event-related potentials have demonstrated an amplitude modulation of a late positive slow wave (range between 400-800 ms) related to the problem size effect. Two arithmetic operations (additions and subtractions) and three levels of problem size (adding or subtracting 2, 4 or 6) were used. We found an amplitude modulation of the late positive slow wave in subtractions, where non-retrieval procedures are mainly used. This amplitude modulation was not evident in additions, where direct retrieval strategies are believed to be used. Our results suggest that the problem size effect is related to non-retrieval procedures of calculation.

Adult↗

PubMed2006

Task switching and novelty processing activate a common neural network for cognitive control.

The abrupt onset of a novel event captures attention away from, and disrupts, ongoing task performance. Less obvious is that intentional task switching compares with novelty-induced behavioral distraction. Here we explore the hypothesis that intentional task switching and attentional capture by a novel distracter both activate a common neural network involved in processing contextual novelty [Barcelo, F., Periáñez, J. A., & Knight, R. T. Think differently: A brain orienting response to task novelty. NeuroReport, 13, 1887-1892, 2002.]. Event-related potentials were recorded in two task-cueing paradigms while 16 subjects sorted cards following either two (color or shape; two-task condition) or three (color, shape, or number; three-task condition) rules of action. Each card was preceded by a familiar tone cueing the subject either to switch or to repeat the previous rule. Novel sound distracters were interspersed in one of two blocks of trials in each condition. Both novel sounds and task-switch cues impaired responses to the following visual target. Novel sounds elicited novelty P3 potentials with their usual peak latency and frontal-central scalp distribution. Familiar tonal switch cues in the three- and two-task conditions elicited brain potentials with a similar latency and morphology as the novelty P3, but with relatively smaller amplitudes over frontal scalp regions. Covariance and principal component analyses revealed a sustained frontal negative potential that was distorting concurrent novelty P3 activity to the tonal switch cues. When this frontal negativity was statistically removed, P3 potentials to novel sounds and task-switch cues showed similar scalp topographies. The degree of activation in the novelty P3 network seemed to be a function of the information (entropy) conveyed by the eliciting stimulus for response selection, over and above its relative novelty, probability of occurrence, task relevance, or feedback value. We conclude that novelty P3 reflects transient activation in a neural network involved in updating task set information for goal-directed action selection and might thus constitute one key element in a central bottleneck for attentional control.

Acoustic Stimulation↗

PubMed2005

Abnormal speech sound representation in persistent developmental stuttering.

OBJECTIVES: To determine whether adults with persistent developmental stuttering (PDS) have auditory perceptual deficits. METHODS: The authors compared the mismatch negativity (MMN) event-related brain potential elicited to simple tone (frequency and duration) and phonetic contrasts in a sample of PDS subjects with that recorded in a sample of paired fluent control subjects. RESULTS: Subjects with developmental stuttering had normal MMN to simple tone contrasts but a significant supratemporal left-lateralized enhancement of this electrophysiologic response to phonetic contrasts. In addition, the enhanced MMN correlated positively with speech disfluency as self-rated by the subjects. CONCLUSIONS: Individuals with persistent developmental stuttering have abnormal permanent traces for speech sounds, and their abnormal speech sound representation may underlie their speech disorder. The link between abnormal speech neural traces of the auditory cortex and speech disfluency supports the relevance of speech perception mechanisms to speech production.

Acoustic Stimulation↗

PubMed2005

Auditory event-related potentials as a function of abstract change magnitude.

Event-related potentials were recorded in healthy volunteers to test the accuracy of the human brain to extract, preattentively, auditory abstract rules. The abstract rule was determined by the frequency relationship between two pure tones forming a pair. The standard pairs had identical tone frequency, whereas the deviant pairs had the second tone two, four, six or eight musical steps higher or lower in frequency than the first one. All abstract changes elicited mismatch negativity, which was not affected by the magnitude of change. However, the subsequent P3a increased as a function of the magnitude of the abstract change. These results suggest that mismatch negativity detects violations of abstract rules, and the amount of violation is analyzed in subsequent stages of auditory processing.

Acoustic Stimulation↗

PubMed2005

Problem size effect in additions and subtractions: an event-related potential study.

The psychophysiological basis of problem size effect in the arithmetical processing of additions and subtractions was studied with event-related brain potentials (ERP). Subjects were presented sequences of seven numbers, and ERPs elicited to the sixth number were analyzed. Two variables were manipulated: operation type (addition and subtraction) and problem size (by adding or subtracting 2, 3 or 4). Results showed two phases in the ERP pattern: an early phase, appearing to reflect automatic processing involved in stimulus identification, and a positive slow wave, believed to be a computing indicator of the subsequent calculation. The amplitude of this positive slow wave was modulated by the problem size (the more problem size, the larger the amplitude), suggesting that the amplitude of this slow wave indexes the activation of the cerebral network underlying problem size effect.

Adult↗

PubMed2005

A kind of auditory 'primitive intelligence' already present at birth.

'Primitive intelligence' in audition refers to the capacity of the auditory system to adaptatively model the acoustic regularity and react neurophysiologically to violations of such regularity, thus supporting the ability to predict future auditory events. In the present study, event-related brain potentials to pairs of tones were recorded in 11 human newborns to determine the infants' ability to extract an abstract acoustic rule, the direction of a frequency change. Most of the pairs (standard, P = 0.875) were of ascending frequency (i.e. the second tone higher than the first), while the remaining pairs (deviant, P = 0.125) were of descending frequency (the second tone being lower). Their frequencies varied among seven levels to prevent discrimination between standard and deviant pairs on the basis of absolute frequencies. We found that event-related brain potentials to deviant pairs differed in amplitude from those to standard pairs at 50-450 ms from the onset of the second tone of a pair, indicating the infants' ability to represent the abstract rule. This finding suggests the early ontogenetic origin of 'primitive intelligence' in audition that eventually may form a prerequisite for later language acquisition.

Acoustic Stimulation↗

PubMed2004

Effects of auditory distraction on electrophysiological brain activity and performance in children aged 8-13 years.

Distractibility was investigated in three age groups of children (8-9, 10-11, and 12-13 years) with event-related brain potentials (ERPs) and performance measures in a forced-choice visual task. Distraction was reflected by increased reaction times (RTs) and decreased performance accuracy in the visual discrimination task following presentation of unexpected novel sounds. The amplitude of the late portion of the P3a elicited by novel sounds was largest for the youngest group and showed a centrally dominant scalp distribution and smallest for the oldest group with a frontal scalp distribution. A frontally dominant late negativity (LN) that was largest in the youngest group followed the P3a. Correlation between the RT increase caused by the distracting novel sounds and the amplitude of the LN elicited by these sounds suggested that the LN is associated with the degree of attention engaged by the distracting sounds.

Adolescent↗

PubMed2003

Effects of temporal encoding on auditory object formation: a mismatch negativity study.

Analysis of auditory scene relies on the appropriate division of the sensory input into meaningful events. The auditory system uses a sequential grouping strategy to segregate different acoustic events in the time domain. As a result of grouping, the organization of sound is expected to include acoustic events spanning different scales of time. It is unclear, however, at which moment the central auditory system begins to introduce changes in the neural representation of the auditory scene as a result of grouping different information units into a larger acoustic event. The present set of experiments examines this issue by using the mismatch negativity (MMN) component of event-related potentials. The MMN is elicited in response to changes in the previously registered auditory regularity whether or not the subject's attention is focused on the auditory stimuli. By presenting three consecutive pairs of alternating tones in serial stimulus trains, we found that across-train repetitions of the tone elicited the MMN with inter-train intervals up to 240 ms. Beyond this interval, only within-train repetitions of the tone elicited the MMN, suggesting that pairs of tones were bound together into a single acoustic event (i.e., train of six tones) within a temporal window not much longer than 240 ms. Furthermore, a different pattern of responses was seen depending on the position of the deviant event within the train and the frequency distance between the alternating tones. These results suggest that grouping discrete auditory inputs may introduce changes in the neural representation of the auditory scene by applying rules to sounds spanning larger temporal scales.

Acoustic Stimulation↗

PubMed2003

Spatiotemporal dynamics of the auditory novelty-P3 event-related brain potential.

The spatiotemporal dynamics of the cerebral network involved in novelty processing was studied by means of scalp current density (SCD) analysis of the novelty P3 (nP3) event-related brain potential (ERP). ERPs were recorded from 30 scalp electrodes at the occurrence of novel unpredictable environmental sounds during the performance of a visual discrimination task. Increased SCD was observed at left frontotemporal (FT3), bilateral temporoparietal (TP3 and TP4) and prefrontal locations (F8-F4 and F7-F3), suggesting novelty-P3 generators located in the left auditory cortex, and bilaterally in temporoparietal and prefrontal association regions. Additional increased SCD was found at a central location (Cz) and at superior parietal locations (P3-Pz-P4). The SCD of the nP3 was therefore generated at three successive, partially overlapping, stages of neuroelectric activation. At the central location, SCD started to be significant before the onset of the nP3 waveform, contributing solely to its early phase. At temporoparietal and left frontotemporal locations, nP3 electrophysiological activity was characterized by sustained current density, starting at about 210 ms and continuing during the full latency range of the response, including its early and late phases. At its late phase, the nP3 was characterized by sharp phasic current density at prefrontal and superior parietal locations, starting at about 290 ms and vanishing at around 385 ms. Taken together, these results provide the first evidence of the cerebral spatio-temporal dynamics underlying novelty processing.

Acoustic Stimulation↗

PubMed2003

Electrophysiological evidence of abnormal activation of the cerebral network of involuntary attention in alcoholism.

OBJECTIVE: Increased distractibility is a common impairment in alcoholism, but objective evidence has remained elusive. Here, a task designed to investigate with event-related brain potentials (ERPs) the neural mechanism underlying distraction was used to show abnormal involuntary orienting of attention in chronic alcoholism. METHODS: Fifteen alcoholics and 17 matched healthy controls were instructed to ignore auditory stimuli while concentrating in the discrimination of immediately following visual stimuli. The auditory sequences contained repetitive standard tones occasionally replaced by deviant tones of slightly higher frequency, or by complex novel sounds. RESULTS: Deviant tones and novel sounds distracted visual performance, i.e. increased reaction time to visual stimuli, similarly in patients and controls. Compared to controls, however, alcoholics showed ERP abnormalities, i.e. enhanced P3a amplitudes over the left frontal region, and a positive posterior deflection instead of the frontally distributed reorienting negativity (RON). CONCLUSIONS: The enhanced P3a to novelty and subsequent positive wave instead of RON in alcoholics suggests encoding into working memory of task-irrelevant auditory events and provides neurophysiological markers of impaired involuntary attention mechanisms in chronic alcoholism.

Acoustic Stimulation↗

PubMed2003

Attention capture by auditory significant stimuli: semantic analysis follows attention switching.

Event-related potentials (ERPs) were recorded from the scalp to investigate a long-standing controversy in auditory attention research, namely when the 'breakthrough of the unattended' takes place in the human brain. Nine subjects classified visual stimuli appearing 300 ms after task-irrelevant standard tones (80%, i.e. P = 0.8) or novel sounds (20%, i.e. P = 0.2) into odd/even categories. After the recording session, subjects scored the novel sounds as to whether they had any particular meaning (identifiable) or were perceived as a burst of noise (non-identifiable), and performance and ERPs were analysed according to this classification. A control condition, in which the visual stimuli were presented with no sounds, showed that subjects covertly monitored the task-irrelevant sounds during visual task-performance, and a further condition, in which the auditory and visual stimuli appeared regardless of each other, made it possible to trace the processing of the distracters during allocation of attention outside the auditory environment. Results yielded identical N1-enhancement for the two types of novel sounds, indicating similar attention switching triggered to these two types of unexpected sounds. However, there was a stronger orientating of attention towards identifiable novel sounds, as indicated both by behavioural distraction and by larger novelty-P3. Furthermore, this stronger orientating of attention was due to the sounds being contingent on the visual stimuli, as no increase in novelty-P3 to identifiable novel sounds was observed in the control condition, in which the sounds occurred outside the attentional set. Therefore, provided that the N1-enhancement reflects a call for focal attention, and novelty-P3 the effective orientating of attention towards the eliciting sounds, the present results suggest that semantic analysis of significant sounds occurs after a transitory switch of attention towards the eliciting stimuli. Moreover, as the novelty-P3 increase in amplitude was observed only when subjects covertly monitored the sounds, the present data suggest that semantic analysis of irrelevant sounds depends on the top-down cognitive influences of the attentional set.

Acoustic Stimulation↗

PubMed2002

ERPs and behavioural indices of long-term preattentive and attentive deficits after closed head injury.

Attentional deficits are often reported even years after sustaining a closed head injury (CHI). Disturbance of cognitive attentional functions following CHI has been documented in both behavioural and event-related brain potential (ERP) studies. Recently, the possibility that the sequelae of CHI extend to preattentive processes of attention has been pointed out. We used a paradigm that makes it possible to assess simultaneously the processing of relevant information and involuntary mechanisms of attention to gain further insight in this matter. Eleven patients with CHI greater than 1 year post-trauma and 14 age-matched control subjects were engaged in the performance of a continuous visual reaction time (RT) discrimination task while ignoring streams of auditory task-irrelevant stimuli. The main characteristic in the paradigm was that all visual stimuli were shortly preceded by an auditory stimulus, which could be a repeated (90%) or a different (deviant) tone. We measured performance on the discrimination task, and ERP indices of preattentive (mismatch negativity MMN) and attentive information processing (P1, N165, P3b). In relation to control subjects, CHI patients showed an attenuation of the MMN evoked by the deviant-tone. In response to the visual stimuli, CHI patients showed a delay of P1, and a reduction of the N165 and P3b components. Moreover, they had slower RT and missed more responses in a visual discrimination task. These results indicate both preattentive and attentive deficits, which is consistent with the typical diffuse axonal injury (DAI) resulting after CHI.

Adult↗

PubMed2002

An electrophysiological and behavioral investigation of involuntary attention towards auditory frequency, duration and intensity changes.

We measured behavior and event-related brain potentials (ERPs) in 12 subjects performing on an audio-visual distraction paradigm to investigate the cerebral mechanisms of involuntary attention towards stimulus changes in the acoustic environment. Subjects classified odd/even numbers presented on a computer screen 300 ms after the occurrence of a task-irrelevant auditory stimulus, by pressing the corresponding response button. Auditory stimuli were standard tones (600 Hz, 200 ms, 85 dB; P=0.8) or deviant tones (P=0.2), these differing from the standard either in frequency (700 Hz), duration (50 ms) or intensity (79 dB), in separate blocks. In comparison to performance to visual stimuli following the standard tones, reaction time increased by 24 ms (F(1,11)=10.91, P<0.01) and hit rate decreased by 4.6% (F(1,11)=35.47, P<0.001) to visual stimuli following the deviant tones, indicating behavioral distraction. ERPs revealed the mismatch negativity (MMN) elicited to deviant tones, which was larger for the duration deviant than for the frequency and intensity deviants (F(2,22)=19.43, P<0.001, epsilon =0.83), and which had different scalp distribution for all three deviant conditions (F(16,176)=2.40, P<0.05, epsilon =0.12). As the shorter duration and softer intensity deviant tones were unlikely to engage fresh neurons responding to their specific physical features, the present results indicate that a genuine change detection mechanism is involved in triggering attention switching towards sound changes, and suggest a largely distributed neural network of the auditory cortex underlying such involuntary attention switching.

Acoustic Stimulation↗