Biomedical subjects

F Valle-Inclán

Publications and source records attributed to F Valle-Inclán.

8 recordsLinked to original sources

PubMed1999

Early visual processing during binocular rivalry studied with visual evoked potentials.

Visual evoked potentials (VEPs) were recorded to probes presented to the dominant and suppressed eyes in a binocular rivalry paradigm. Probes presented to the suppressed eye interrupted the current dominance phase and produced a P300-like deflection (400-700 ms). Probes delivered to the dominant eye increased the duration of the current dominance phase. VEPs to these probes included an endogenous component that overlapped the early exogenous components. The early endogenous component (rivalry-related potential, RRP) started as early as 70 ms and had a broad centroparietooccipital distribution.

Adult↗

PubMed1999

Accessory stimulus effects on response selection: does arousal speed decision making?

When an intense but task-irrelevant "accessory" stimulus accompanies the imperative stimulus in a choice reaction task, reaction times (RTs) are facilitated. In a similar previous study (Hackley & Valle-Inclán, 1998), we showed that this effect is not due to a reduction of the interval from onset of the lateralized readiness potential (LRP) until movement onset. In the present study, the RT task was modified to move a portion of the response selection stage into this time interval. The interval remained invariant, indicating that this late phase of the response selection process is not speeded by accessory stimulation. However, we observed amplitude modulation of the LRP on no-go trials in a condition with three alternative responses. This finding suggests that an earlier phase of response selection is influenced by accessory stimulation. In addition, a novel dependent measure was introduced to event-related potential research--the latency of spontaneous, post-trial blinking.

Acoustic Stimulation↗

PubMed1999

Prevalence of pregnancy and postpartum thyroid dysfunction in a homogeneous population of Spain.

To determine the prevalence of pregnancy and postpartum thyroid dysfunction in the Spanish population, 691 women divided into six cohorts were studied. Biochemical hypothyroidism was observed in 9.4%, 4.4%, 1.9%, 4.6% and 4.8% at the first trimester of pregnancy, at delivery and at the second, fourth and sixth to twelfth postpartum months, respectively. Biochemical hyperthyroidism was observed in 6.7%, 0.8%, 1.9%, 4.6% and 2.4% in the same cohorts of subjects. Thyroiditis was observed in 4%, 0%, 0.6%, 6.2% and 7.3% in the cohorts studied. No depression or psychological alterations were detected either in pregnancy or in the postpartum period. Our data suggest that if screening for thyroid dysfunction is to be recommended in the postpartum period, this must be based on biochemical parameters.

Autoantibodies↗

PubMed1998

Automatic alerting does not speed late motoric processes in a reaction-time task.

When an irrelevant 'accessory' stimulus is presented at about the same time as the imperative signal in a choice reaction time-task, the latency of the voluntary response is markedly reduced. The most prominent cognitive theories agree that this effect is attributable to a brief surge in arousal ('automatic alerting'), but they disagree over whether the facilitation is localized to a late, low-level motoric process or to an earlier stage, the process of orienting to and then perceptually categorizing the reaction stimulus. To test these alternative hypotheses, we used the onset of the lateralized readiness potential (a movement-related brain potential) as a temporal landmark to partition mean reaction time into two time segments. The first segment included the time required to perceive the visual stimulus and decide which hand to react with; the second included only motoric processes. Presentation of an irrelevant acoustic stimulus shortened the first interval but had no effect on the second. We therefore rejected the motoric hypothesis.

Auditory Perception↗

PubMed1998

Effects of a negative visual hypnotic hallucination on ERPs and reaction times.

The study of changes in ERPs provoked by negative hypnotic hallucinations has thus far yielded contradictory results. Most previous studies have failed to separate specific changes in the processing of the hallucinated stimuli from non-specific changes in arousal due to hypnosis. The present study addresses this issue with the combination of two experimental effects in the task designed to test the hallucination: the noise-compatibility effect and the Simon effect. A choice reaction task was used in which targets appearing at either side of a screen were defined by color and were accompanied by irrelevant noise, and a negative hallucination suggestion was given for noise stimuli. Four highly hypnotizable subjects performed the task on two separate occasions, with and without the suggestion. Increases in reaction times and P300 latencies were found as a function of noise and spatial stimulus-response (SR) incompatibility (Simon effect). Suggestion decreased the response times for all types of trials non-significantly, and it decreased significantly those of left-hand responses. On the other hand, suggestion reduced the increase in P300 latencies in noise-incompatible trials, but did not influence the Simon effect. This result indicates a specific effect of suggestion in the processing of hallucinated stimuli, which is consistent with the hallucinatory experience reported by the subjects.

Adult↗

PubMed1998

On the automaticity of ipsilateral response activation in the Simon effect.

The effects on performance of unattended stimulus-response spatial relationships in choice reaction time tasks (i.e., the Simon effect) have been attributed to automatic activation of the response ipsilateral to stimulus location. We tested this assumption using the lateralized readiness potential (LRP). The response key labels changed randomly from trial to trial and were presented either 400 ms before (immediate-reaction trials) or 400 ms after (delayed-reaction trials) stimulus. The critical test for the automatic activation hypothesis was on delayed-reaction trials, in which LRP deflections were expected in the interval between stimulus and response-key labels. Contrary to this prediction, there were no LRP signs of response activation within that interval.

Adult↗

PubMed1996

The locus of interference in the Simon effect: an ERP study.

The Simon effect was studied using ERPs and the lateralized readiness potential (LRP). In Experiment 1, visual stimuli requiring left or right hand responses were presented at either side of fixation. In Experiment 2, the empty side was occupied by a distractor. Spatial S-R incompatibility delayed P300 latency in both experiments, as predicted by perceptual interference accounts of the Simon effect. However, the LRP results were not conclusive. The lateralized presentation of visual stimuli (Experiment 1) or targets (Experiment 2) produced a posterior ERP hemispheric asymmetry that spread to central electrodes and obscured the early development of the LRP. Experiment 3 avoided the problem by presenting the stimuli in the vertical meridian, and the LRP showed signs of incorrect response preparation in incompatible trials, in agreement with response-interference models. Both perceptual and response interference may be present in the Simon effect.

Adult↗

PubMedDate not supplied

The Simon effect and its reversal studied with event-related potentials.

The Simon effect (slower RT when stimulus and response locations do not match, stimulus location being irrelevant) and its reversal, were investigated using P300 latency and motor-related potentials. Stimuli were one of two colors, and response keys were two buttons with color labels that changed randomly in every trial. Depending on the stimulus-response (S-R) mapping instructions, subjects pressed the same-color key or the alternate-color key. Behavioral measures showed a Simon effect in same- and a reverse Simon effect in alternate-color mapping contradicting the display-control arrangement correspondence and the S-S compatibility, as explanations for the reverse Simon effect. P300 latencies followed the same pattern as RT, i.e. they were influenced by the S-R mapping, suggesting that this measure does not index the duration of the stimulus evaluation, but response selection processes. The motor-related potentials demonstrated response activation based on stimulus location, also supporting response- interference interpretations of the Simon effect.

Acoustic Stimulation↗