Biomedical subjects

L E Ribeiro-do-Valle

Publications and source records attributed to L E Ribeiro-do-Valle.

10 recordsLinked to original sources

PubMed2006

Control of attention by a peripheral visual cue depends on whether the target is difficult to discriminate.

The influence of a peripheral cue represented by a gray ring on responsivity to a subsequent target varies. When a vertical line inside a ring was a go target and a white small ring inside a ring was a no-go target, reaction time was shorter at the same location relative to a different location. However, no reaction time difference between the two locations occurred when a white cross inside the ring, instead of the white vertical line inside the ring, was the go target. We investigated whether this last finding was due to a forward masking influence of the cue, a requirement of low attention for the discrimination or a lack of attention mobilization by the cue. In Experiment 1, the intensity of the cue was reduced in an attempt to reduce forward masking. In Experiment 2, the vertical line and the cross were presented in the same block of trials so as to be dealt with a common attentional strategy. In Experiments 3 and 4, the no-go target was a 45 masculine rotated cross inside a ring to increase the difficulty of the discrimination. No evidence was obtained that the cross was forward masked by the cue nor that it demanded less attention to be discriminated from the small ring. There was a facilitation of responsivity by the cue when the small ring was replaced by the rotated cross. The results suggest that when the discrimination to be performed is too easy the cue does not mobilize attention.

Adult↗

PubMed2004

Relative contribution of expectancy and immediate arousal to the facilitatory effect of an auditory accessory stimulus.

An auditory stimulus speeds up a digital response to a subsequent visual stimulus. This facilitatory effect has been related to the expectancy and the immediate arousal that would be caused by the accessory stimulus. The present study examined the relative contribution of these two influences. In a first and a third experiment a simple reaction time task was used. In a second and fourth experiment a go/no-go reaction time task was used. In each of these experiments, the accessory stimulus preceded the target stimulus by 200 ms for one group of male and female volunteers (GFix). For another group of similar volunteers (GVar) the accessory stimulus preceded the target stimulus by 200 ms in 25% of the trials, by 1000 ms in 25% of the trials and was not followed by the target stimulus in 50% of the trials (Experiments 1a and 1b) or preceded the target stimulus by 200 ms in 6% of the trials and by 1000 ms in 94% of the trials (Experiments 2a and 2b). There was a facilitatory effect of the accessory stimulus for GFix in the four experiments. There was also a facilitatory effect of the accessory stimulus at the 200-ms stimulus onset asynchrony for GVar in Experiments 1a and 1b but not in Experiments 2a and 2b. The facilitatory effects observed were larger in the go/no-go task than in the simple task. Taken together, these results suggest that expectancy is much more important than immediate arousal for the improvement of performance caused by an accessory stimulus.

Acoustic Stimulation↗

PubMed2004

Experimental context modulates warning signal effects.

Previous studies have shown that saccadic eye responses but not manual responses were sensitive to the kind of warning signal used, with visual onsets producing longer saccadic latencies compared to visual offsets. The aim of the present study was to determine the effects of distinct warning signals on manual latencies and to test the premise that the onset interference, in fact, does not occur for manual responses. A second objective was to determine if the magnitude of the warning effects could be modulated by contextual procedures. Three experimental conditions based on the kind of warning signal used (visual onset, visual offset and auditory warning) were run in two different contexts (blocked and non-blocked). Eighteen participants were asked to respond to the imperative stimulus that would occur some milliseconds (0, 250, 500 or 750 ms) after the warning signal. The experiment consisted in three experimental sessions of 240 trials, where all the variables were counterbalanced. The data showed that visual onsets produced longer manual latencies than visual offsets in the non-blocked context (275 vs 261 ms; P < 0.001). This interference was obtained, however, only for short intervals between the warning and the stimulus, and was abolished when the blocked context was used (256 vs 255 ms; P = 0.789). These results are discussed in terms of bottom-up and top-down interactions, mainly those related to the role of attentional processing in cancelling out competitive interactions and suppressive influences of a distractor on the relevant stimulus.

Adolescent↗

PubMed2001

The early facilitatory effect of a peripheral spatially noninformative prime stimulus depends on target stimulus features.

We investigated the dependency of the early facilitatory effect of a prime stimulus (S1) on the physical characteristics of the target stimulus (S2). A go-no go reaction time paradigm was used. The S1 was a gray ring and the S2s were a white vertical line, a white horizontal line, a white cross and a white small ring, all inside a white ring with the same dimensions as the S1. S1 onset-S2 onset asynchrony was 100 ms. The stimuli appeared randomly in any one of the quadrants of a monitor screen. The S2 could occur at the same position as the S1 or at a different one. We observed a strong facilitatory effect when the vertical line or the horizontal line was the go stimulus and no effect when the cross was the go stimulus. These results show that the features of the target stimulus can be decisive for the appearance of the facilitatory effect of a peripheral spatially noninformative prime stimulus.

Adult↗

PubMed2001

Behavioral correlates of the activity of serotonergic and non-serotonergic neurons in caudal raphe nuclei.

We investigated the behavioral correlates of the activity of serotonergic and non-serotonergic neurons in the nucleus raphe pallidus (NRP) and nucleus raphe obscurus (NRO) of unanesthetized and unrestrained cats. The animals were implanted with electrodes for recording single unit activity, parietal oscillographic activity, and splenius, digastric and masseter electromyographic activities. They were tested along the waking-sleep cycle, during sensory stimulation and during drinking behavior. The discharge of the serotonergic neurons decreased progressively from quiet waking to slow wave sleep and to fast wave sleep. Ten different patterns of relative discharge across the three states were observed for the non-serotonergic neurons. Several non-serotonergic neurons showed cyclic discharge fluctuations related to respiration during one, two or all three states. While serotonergic neurons were usually unresponsive to the sensory stimuli used, many non-serotonergic neurons responded to these stimuli. Several non-serotonergic neurons showed a phasic relationship with splenius muscle activity during auditory stimulation. One serotonergic neuron showed a tonic relationship with digastric muscle activity during drinking behavior. A few non-serotonergic neurons exhibited a tonic relationship with digastric and/or masseter muscle activity during this behavior. Many non-serotonergic neurons exhibited a phasic relationship with these muscle activities, also during this behavior. These results suggest that the serotonergic neurons in the NRP and NRO constitute a relatively homogeneous population from a functional point of view, while the non-serotonergic neurons form groups with considerable functional specificity. The data support the idea that the NRP and NRO are implicated in the control of somatic motor output.

Animals↗

PubMed1998

Gap effect and reaction time distribution: simple vs choice manual responses.

It is well known that saccadic reaction times (SRT) are reduced when the target is preceded by the offset of the fixation point (FP)--the gap effect. Some authors have proposed that the FP offset also allows the saccadic system to generate a separate population of SRT, the express saccades. Nevertheless, there is no agreement as to whether the gap effect and express responses are also present for manual reaction times (MRT). We tested the gap effect and the MRT distribution in two different conditions, i.e., simple and choice MRT. In the choice MRT condition, subjects need to identify the side of the stimulus and to select the appropriate response, while in the simple MRT these stages are not necessary. We report that the gap effect was present in both conditions (22 ms for choice MRT condition; 15 ms for simple MRT condition), but, when analyzing the MRT distributions, we did not find any clear evidence for express manual responses. The main difference in MRT distribution between simple and choice conditions was a shift towards shorter values for simple MRT.

Adult↗

PubMed1997

Serotonergic neurons in the caudal raphe nuclei discharge in association with activity of masticatory muscles.

There is a dense serotonergic projection from nucleus raphe pallidus and nucleus raphe obscurus to the trigeminal motors nucleus and serotonin exerts a strong facilitatory action on the trigeminal motoneurons. Some serotonergic neurons in these caudal raphe nuclei increase their discharged during feeding. The objective of the present study was to investigate the possibility that the activity of these serotonergic neurons is related to activity of masticatory muscles. Cats were implanted with microelectrodes and gross electrodes. Caudal raphe single neuron activity, electrocorticographic activity, and splenius, digastric and masseter electromyographic activities were recorded during active behaviors (feeding and grooming), during quiet waking and during sleep. Seven presumed serotonergic neurons were identified. These neurons showed a long duration action potential (> 2.0 msec) and discharged slowly (2-7 Hz) and very regularly (interspike interval coefficient of variation < 0.3) during quiet waking. The activity of these neurons decreased remarkably during fast wave sleep (78-100%). Six of these neurons showed tonic changes in their activity positively related to digastric and/or masseter muscles activity but not to splenius muscle activity during waking. These data are consistent with the hypothesis that serotonergic neurons in the caudal raphe nuclei play an important role in the control of jaw movements.

Animals↗

PubMed1991

Facilitation of masseter EMG and masseteric (jaw-closure) reflex by serotonin in behaving cats.

The trigeminal motor nucleus (MoV) contains the somata of the motoneurons that control jaw position and jaw movements. This nucleus is of neurochemical interest because it receives a dense serotonergic input. We examined the effects of application of serotonin or fluoxetine, a serotonin reuptake blocker, into this nucleus on the spontaneous or reflex (jaw-closure) electrical activity of the masseter muscle in behaving cats. Serotonin produced a clearcut enhancement of both spontaneous and reflex activities. This action was attenuated by previous systemic injection of the serotonin receptor antagonist methysergide. The effect was mimicked to a certain extent by fluoxetine. These data provide evidence that the serotonergic input to MoV exerts a general facilitatory influence on masseter motoneurons activity.

Animals↗

PubMed1987

Absence of complete internasal-interocular transfer of habituation of exploratory behavior in rats.

Normal, blind, anosmic, and unilaterally blind and contralaterally anosmic albino rats were submitted to unilateral peripheral sensory (olfactory and/or visual) occlusion and observed in an initially unfamiliar arena. Next day, either the same sensory periphery (control subjects) or the contralateral one (experimental subjects) was occluded and a new observation in the arena was made. The duration of the exploratory behavior of control and experimental subjects, on each occasion, was compared. There was not a complete internasal-interocular transfer of long-term habituation of exploratory behavior, either when olfaction and vision were suppressed on opposite sides or when they were suppressed on the same side, but there was a complete internasal transfer of this habituation in blind animals and a complete interocular transfer of this habituation in anosmic animals. These results suggest that long-term habituation of the exploratory behavior elicited by one olfactory and one visual periphery activation and that of the exploratory behavior elicited by the other olfactory and the other visual periphery activation depend upon different representations of the stimulatory situation in the central nervous system. These representations would, however, have only a small number of elements which are not shared.

Animals↗

PubMed1986

Internasal and interocular transfers of habituation of exploratory behavior.

Albino rats were individually placed in an unfamiliar arena and their exploratory behavior was recorded for 1 h on two consecutive days. Subjects that were tested with the right (left) nostril occluded and retested with the left (right) nostril occluded explored the arena for the same period of time as subjects that were tested and retested with the right (left) nostril occluded, in both sessions. Subjects without one olfactory bulb that were tested with the contralateral nostril occluded and retested with the ipsilateral nostril occluded explored as subjects without one olfactory bulb that were tested and retested with the ipsilateral nostril occluded, in both sessions. Subjects that were tested with the right (left) eyelids sutured and retested with the left (right) eyelids sutured explored for the same time in the test session as subjects that were tested with the right and the left eyelids sutured and retested with the right or the left eyelids sutured and subjects that were tested and retested with the right (left) eyelids sutured. In the retest session, the first group of subjects explored for less time than the second and for the same time as the third one. A complete internasal transfer of habituation of exploratory behavior probably occurred. There was a complete interocular transfer of habituation of exploratory behavior. This indicates that there is no developed specification of the side of peripheral origin of the visual information in the neural representation of the stimulatory situation responsible for habituation of exploratory behavior.

Animals↗