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Biomedical subjects

S E Lea

Publications and source records attributed to S E Lea.

7 recordsLinked to original sources
PubMed1999

Inescapable shock-induced potentiation of morphine analgesia in rats: sites of action.

Inescapable shock (IS) enhances analgesia to systemic morphine (MOR) 24 hr later. IS activates serotonin neurons in the dorsal raphe nucleus (DRN), rendering them hyperexcitable. These studies tested whether IS potentiates the analgesic effect of MOR microinjected in the DRN, as predicted by this hypothesis. To test site specificity, the effect of previous IS was examined on MOR microinjected lateral to the DRN and into 2 other sites that support MOR analgesia, the nucleus raphe magnus (NRM) and spinal cord. Twenty-four hours after IS, potentiated analgesia was observed after 0.5 microg MOR microinjected into, but not lateral to, the DRN. Potentiated analgesia was also observed after NRM (1.0 microg) and spinal cord (3.0 microg) MOR microinjections. These data suggest that IS-induced excitability changes within the DRN synergize with opiates microinjected in other analgesia areas and that this potentiates the responses to opiates 24 hr after IS.

Analgesia↗
PubMed1997

Inescapable shock-induced potentiation of morphine analgesia.

Exposure to various stressors potentiates nociceptive and nonnociceptive responses to morphine. These phenomena have received little study despite their seeming generality and importance for understanding analgesia and opiate action. The present experiments characterize inescapable shock (IS)-induced potentiation of morphine analgesia. Rats were exposed to IS, equal escapable shocks (ESs), or restraint (control). Potentiation of analgesia (tail-flick [TF] test and hotplate test) was observed only in rats given IS 24 or 48 hr earlier, in agreement with previously reported learned-helplessness effects. Finally, no change in tail temperature or motor function was found that could be inaccurately interpreted as analgesia. The relevance of these findings to stressor-induced enhancement of morphine analgesia and potential substrates of IS effects are discussed.

Analgesics, Opioid↗
PubMed1996

Perception of emotion from dynamic point-light displays represented in dance.

It is well known that biological motion, as produced by point-light displays on a human body, gives a good representation of the represented body-eg its gender and the nature of the task which it is engaged in. The question is whether it is possible to judge the emotional state of a human body from motion information alone. An ability to make this kind of judgment may imply that people are able to perceive emotion from patterns of movement without having to compute the detailed shape first. Subjects were shown brief video clips of two trained dancers (one male, one female). The dancers were aiming to convey the following emotions: fear, anger, grief, joy, surprise, and disgust. The video clips portrayed fully lit scenes and point-light scenes, with thirteen small points of light attached to the body of each dancer. Half the stimuli were presented the right way up, while half were inverted. The subjects' task was to judge which emotion was being portrayed. Full-body clips gave good recognition of emotionality (88% correct), but the results for upright biological-motion displays were also significantly above chance (63% correct). Inversion of the display reduced biological-motion (but not full-body) performance to close to chance but still significantly above chance. A space-time analysis of the motion of the points of light was carried out, and was related to the discriminability of the different emotions. Biological-motion displays, which convey no information while static, are able to give a rich description of the subject matter, including the ability to judge emotional state. This ability is disrupted when the image is inverted.

Analysis of Variance↗
PubMed1994

Visual perception of intentional motion.

A series of experiments were performed to investigate how motion sequences provide information about the intentional structure of moving figures or actors. Observers had to detect simulations of biologically meaningful motion within a set of moving letters. In the first two experiments a factorial design was used, with type of instruction as a between-subject factor and six movement parameters (number of items, speed and directness of target and distractors, and 'relentlessness' of target movement) as within-subject factor; in the final two experiments, the visibility of the goal towards which the target moved and the use of a tracking movement to distinguish the target were varied. In such displays search time increases with increasing number of stimuli. It was found that (a) the more direct the motion, the more likely it was to be interpreted as intentional; (b) intentional motion was much easier to detect when the target moved faster than the distractors than when it moved more slowly; (c) recognition of intentionality was impaired but not abolished if the goal towards which the target was moving was invisible; and (d) participants did not report intentional movement when the target was distinguished by brightness rather than the manner in which it moved. We argue that the perception of intentionality is strongly related to observers' use of conceptual knowledge, which in turn is activated by particular combinations of features. This supports a process model, in which intentionality is seen as the result of a conceptual integration of objective visual features.

Animals↗
PubMed1980

Coding processes in normal and learning-disabled children: evidence for modality-specific pathways to the cognitive system.

In Experiment 1, normal 10-yr.-olds and 10-yr.-olds diagnosed as learning disabled (LD) were presented with items in visual and auditory modalities for free and cued recall. The LD children had deficits in auditory and/or visual memory. Recall by LD children was worse than for nonimpaired peers only on tasks in the impaired modality, and on cued recall the deficit was confined to recall given a semantic category cue: Recall given perceptual cues was unimpaired. In Experiment 2, presentation-time tasks were used to create a bias toward either perceptual or semantic encoding. The semantic-encoding task removed the modality-specific deficit between LD children and controls. We conclude that deficits in semantically cued recall for children with only one impaired modality had their origins at presentation time. The most parsimonious explanation of these results involves separate pathways linking the auditory and visual modalities to the semantic system.

Child↗