Biomedical subjects

Luis Carretié

Publications and source records attributed to Luis Carretié.

11 recordsLinked to original sources

PubMed2006

An electrophysiological study on the interaction between emotional content and spatial frequency of visual stimuli.

Previous studies suggest that the magnocellular pathway, a visual processing system that rapidly provides low spatial frequency information to fast-responding structures such as the amygdala, is more involved in the processing of emotional facial expressions than the parvocellular pathway (which conveys all spatial frequencies). The present experiment explored the spatio-temporal characteristics of the spatial frequency modulation of affect-related neural processing, as well as its generalizability to non-facial stimuli. To that aim, the event-related potentials (ERPs) elicited by low-pass filtered (i.e., high spatial frequencies are eliminated) and intact non-facial emotional images were recorded from 31 participants using a 60-electrode array. The earliest significant effect of spatial frequency was observed at 135 ms from stimulus onset: N135 component of the ERPs. In line with previous studies, the origin of N135 was localized at secondary visual areas for low-pass filtered stimuli and at primary areas for intact stimuli. Importantly, this component showed an interaction between spatial frequency and emotional content: within low-pass filtered pictures, negative stimuli elicited the highest N135 amplitudes. By contrast, within intact stimuli, neutral pictures were those eliciting the highest amplitudes. These results suggest that high spatial frequencies are not essential for the initial affect-related processing of visual stimuli, which would mainly rely on low spatial frequency visual information. According to present data, high spatial frequencies would come into play later on.

Adult↗

PubMed2006

Neural response to sustained affective visual stimulation using an indirect task.

Event-related potentials were recorded from 30 subjects using sustained stimulation and an indirect task, two strategies which facilitate affective responses that are complete and free of cognitive interference. Stimuli were of three types: pleasant, unpleasant and neutral. A three-phase pattern was found. The first phase, an amplitude increase in response to negative stimuli higher than to neutral and pleasant stimuli, was produced at 160 ms after stimulus onset, the prefrontal cortex being the origin of this phase. The second phase, characterized by maximal amplitudes in response to positive stimuli, was produced at 400 ms, originating in the visual cortex. Finally, the third phase, another amplitude increase in response to negative stimuli, was produced at 680 ms, and its source was located in the left precentral gyrus. Present data show that the cortical response to sustained emotional visual stimulation presented within indirect tasks provides information on attention-, motivation- and motor-related biases that complement information obtained under other experimental conditions.

Adult↗

PubMed2005

Cortical response to subjectively unconscious danger.

Cortical involvement in the evolution-favored automatic reaction to danger was studied. Electrical neural activity was recorded from 31 subjects, reporting fear of spiders, at 60 scalp locations. Visual stimuli containing spiders (negative elements) or, alternatively, nonnegative elements were presented to subjects, though they were unaware of their presence: a concurrent visual detection task using consciously perceived targets was administered. Spatial and temporal principal component analyses were employed to define and quantify, in a reliable manner, the main components of the neuroelectrical response to unconscious stimuli, and a source localization algorithm provided information on their neural origin. Results indicated that around 150 ms after stimulus onset, ventromedial prefrontal areas previously reported as responding rapidly to danger-related (conscious) stimuli were activated by unconsciously perceived spiders more markedly than by nonnegative unconscious stimuli. Subsequently, around 500 ms after stimulus onset, activation of the posterior cingulate and visual association cortices increased in this same direction. These data support previous results indicating that the ventromedial prefrontal cortex is involved in the top-down regulation of attention (through its capability to modulate the activity of posterior cortices in charge of visual processing) and that it automatically facilitates danger processing.

Adult↗

PubMed2005

Neural activity associated with metaphor comprehension: spatial analysis.

Though neuropsychological data indicate that the right hemisphere (RH) plays a major role in metaphor processing, other studies suggest that, at least during some phases of this processing, a RH advantage may not exist. The present study explores, through a temporally agile neural signal--the event-related potentials (ERPs)--, and through source-localization algorithms applied to ERP recordings, whether the crucial phase of metaphor comprehension presents or not a RH advantage. Participants (n=24) were submitted to a S1-S2 experimental paradigm. S1 consisted of visually presented metaphoric sentences (e.g., "Green lung of the city"), followed by S2, which consisted of words that could (i.e., "Park") or could not (i.e., "Semaphore") be defined by S1. ERPs elicited by S2 were analyzed using temporal principal component analysis (tPCA) and source-localization algorithms. These analyses revealed that metaphorically related S2 words showed significantly higher N400 amplitudes than non-related S2 words. Source-localization algorithms showed differential activity between the two S2 conditions in the right middle/superior temporal areas. These results support the existence of an important RH contribution to (at least) one phase of metaphor processing and, furthermore, implicate the temporal cortex with respect to that contribution.

Adult↗

PubMed2005

Higher-order activity beyond the word level: cortical dynamics of simple transitive sentence comprehension.

Slow electrophysiological effects, which fluctuate throughout the course of a sentence, independent of transient responses to individual words, have been reported. However, this type of activity has scarcely been studied, and with only limited use of electrophysiological information, so that the brain areas in which these variations originate have not been clearly identified. To improve this state of affairs, a principal component analysis and a modern source analysis algorithm (LORETA) were applied to the slow activity underlying transitive sentence reading. Four components explained 97.3% of the variance. Of key interest was a slow variation that occurred throughout the entire sentence but peaked with the appearance of the verb. The main solution for this component was localized in prefrontal and temporal regions presumably involved in semantic sentence processing. This constitutes empirical evidence for cortical activity--related to semantic processes thought to be involved in thematic role assignment--developing throughout the sentence but presenting a conspicuous maximum with the appearance of the verb. This finding also highlights the central role of verb information in the understanding of transitive sentences.

Adult↗

PubMed2004

The influence of emotional context on attention in anxious subjects: neurophysiological correlates.

Several studies have shown the influence of threatening context on level of attention to target environmental stimuli. The present experiment explored the possibility that this influence of aversive context is particularly strong in anxious subjects, due to their known attentional bias towards negative information. Event-related potentials, that provide a direct index of attention-related cerebral processing, were recorded in 27 participants selected from a larger sample of 250, as a function of their trait anxiety scores (14 high, 13 low). State anxiety was also measured in selected subjects. Several contexts were presented: positive, negative, relaxing and neutral, and participants were instructed to attend, within these contexts, to a series of auditory stimuli. Threatening context triggered an increase in attention to these auditory stimuli only in conditions of high state anxiety, this increase being reflected in the greater amplitude of the P2 component, which is related to attentional processes. There were no significant differences in relation to trait anxiety. Data show that threatening context and high level of state anxiety in combination increase the quantity of attentional resources directed to the environment.

Acoustic Stimulation↗

PubMed2004

Automatic attention to emotional stimuli: neural correlates.

We investigated the capability of emotional and nonemotional visual stimulation to capture automatic attention, an aspect of the interaction between cognitive and emotional processes that has received scant attention from researchers. Event-related potentials were recorded from 37 subjects using a 60-electrode array, and were submitted to temporal and spatial principal component analyses to detect and quantify the main components, and to source localization software (LORETA) to determine their spatial origin. Stimuli capturing automatic attention were of three types: emotionally positive, emotionally negative, and nonemotional pictures. Results suggest that initially (P1: 105 msec after stimulus), automatic attention is captured by negative pictures, and not by positive or nonemotional ones. Later (P2: 180 msec), automatic attention remains captured by negative pictures, but also by positive ones. Finally (N2: 240 msec), attention is captured only by positive and nonemotional stimuli. Anatomically, this sequence is characterized by decreasing activation of the visual association cortex (VAC) and by the growing involvement, from dorsal to ventral areas, of the anterior cingulate cortex (ACC). Analyses suggest that the ACC and not the VAC is responsible for experimental effects described above. Intensity, latency, and location of neural activity related to automatic attention thus depend clearly on the stimulus emotional content and on its associated biological importance.

Adult↗

PubMed2004

Voltage-based versus factor score-based source localization analyses of electrophysiological brain activity: a comparison.

Though, traditionally, electrophysiological recordings have been limited to provide temporal information on neural activity, the development of mathematical algorithms capable of solving the inverse problem is facilitating, in recent years, the access to spatial information (i.e., on the origin of neural activation). This study explored a new strategy in order to increase the reliability of inverse problem solutions: applying these algorithms on factor scores (and not on voltages), a parameter that can be defined as "clean amplitude". Factor scores derive from Principal Component Analysis (PCA) applied to event-related potentials (ERPs). The main advantage of PCA is its capability to extract and quantify ERP components free of the influence of adjacent or subjacent components. The LORETA algorithm for source localization was applied on peak voltage, average voltage and factor scores for the motor potential recorded from 25 subjects, who had to repeatedly press a button with their right hand. The solutions given by LORETA in these three modalities were compared. The motor potential, a negative wave that begins just before any voluntary movement and is centrally distributed in the scalp, is particularly useful to the scope of this study, since its origin is known: contralateral motor cortex. Results show that the three modalities (peak voltage, mean voltage and factor scores) provided the same main focus (left motor cortex), though the "cleanest" solution (i.e., the main focus was more salient with respect to other secondary, noisy foci) was achieved by the factor score-based LORETA.

Adolescent↗

PubMed2004

Valence-related vigilance biases in anxiety studied through event-related potentials.

INTRODUCTION: Behavioral experiments on reaction time indicate that anxious subjects' vigilance-related attention is biased towards threatening words, though direct data on cerebral activity associated to this bias are conspicuously scarce. METHODS: In the present study, event-related potentials (ERPs) were recorded from 30 subjects, grouped according to their scores in trait and state anxiety questionnaires. The specific role of the arousal and valence content of the stimulation in the vigilance bias was investigated by blocking the arousal content. Stimulation with high biological significance was employed. An S1 (sound)-S2 (emotional picture) task ensured that subjects were vigilant towards positive, negative or control (neutral) images. RESULTS: Only subjects presenting high state scores and high state-trait combination scores showed significantly higher amplitudes in the Early Contingent Negative Variation during vigilance towards negative stimuli. This ERP component typically appears between S1 and S2 and reflects the intensity of vigilance. CONCLUSIONS: ERP activity detects cerebral indices that confirm the presence of valence-related vigilance biases in anxiety.

Adult↗

PubMed2003

Cerebral patterns of attentional habituation to emotional visual stimuli.

Attentional habituation in response to emotional stimuli, an aspect of the interaction between cognitive and emotional processes that has received scant attention, was investigated. Event-related potentials were recorded using a 60-electrode array from 25 participants who attended to 120 presentations of three different picture types: emotionally negative (S-), positive (S+), and neutral (SO). The affective content of the stimulation was assessed, through questionnaires, by the participants themselves. N1 showed different patterns of habituation as a function of the stimulation: amplitudes indicated that S- was more resistant to habituation than SO and S+. This pattern, which reflects a greater capacity of S- to attract and maintain the participant's attention, is interpreted as a manifestation of the "negativity bias," a phenomenon that reflects an evolution-favored set of mechanisms that facilitate a rapid and intense response to aversive events.

Adult↗

PubMed2002

The recognition potential and repetition effects.

The recognition potential (RP) is an electrical brain response peaking at 250 ms that appears when subjects view meaningful stimuli. Previous RP research was conducted in experimental conditions in which repetition effects could not be totally ruled out as influencing the generation of the RP response. The present study aims to elucidate whether repetition effects affect the topography and waveform of this component. For this purpose semantically correct, orthographically correct, strings of random letters, control and background stimuli were presented to 20 subjects following the rapid stream stimulation procedure and without repetition of any test stimulus. As previously, the RP showed its maximal amplitude at the PO7 electrode. It showed sensitivity to all levels of lexical processing, its response being maximal for semantically correct stimuli, and its topographical distribution was similar for all types of stimulus. Direct statistical comparisons with the data of a previous study where repetition effects could not be disregarded were performed, confirming the similarity between the results obtained in both experiments. The neural generators of the RP were placed again, as in previous studies, within the lingual gyrus. Although repetition effects have been reported to affect other semantic-related components such as the N400, they do not seem to affect either the topography or the waveform of the RP.

Adult↗