101 resultados para Perception Transduction


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In the genus Petunia, distinct pollination syndromes may have evolved in association with bee-visitation (P. integrifolia spp.) or hawk moth-visitation (P. axillaris spp). We investigated the extent of congruence between floral fragrance and olfactory perception of the hawk moth Manduca sexta. Hawk moth pollinated P. axillaris releases high levels of several compounds compared to the bee-pollinated P. integrifolia that releases benzaldehyde almost exclusively. The three dominating compounds in P. axillaris were benzaldehyde, benzyl alcohol and methyl benzoate. In P. axillaris, benzenoids showed a circadian rhythm with an emission peak at night, which was absent from P. integrifolia. These characters were highly conserved among different P. axillaris subspecies and P. axillaris accessions, with some differences in fragrance composition. Electroantennogram (EAG) recordings using flower-blends of different wild Petunia species on female M. sexta antennae showed that P. axillaris odours elicited stronger responses than P. integrifolia odours. EAG responses were highest to the three dominating compounds in the P. axillaris flower odours. Further, EAG responses to odour-samples collected from P. axillaris flowers confirmed that odours collected at night evoked stronger responses from M. sexta than odours collected during the day. These results show that timing of odour emissions by P. axillaris is in tune with nocturnal hawk moth activity and that flower-volatile composition is adapted to the antennal perception of these pollinators.

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Auxin is of vital importance in virtually every aspect of plant growth and development, yet, even after almost a century of intense study, major gaps in our knowledge of its synthesis, distribution, perception, and signal transduction remain. One unique property of auxin is its polar transport, which in many well-documented cases is a critical part of its mode of action. Auxin is actively transported through the action of both influx and efflux carriers. Inhibition of polar transport by the efflux inhibitor N-1-naphthylphthalamic acid (NPA) causes a complete cessation of leaf initiation, a defect that can be reversed by local application of the auxin, indole-3-acetic acid (IAA), to the responsive zone of the shoot apical meristem. In this study, we address the role of the auxin influx carrier in the positioning and outgrowth of leaf primordia at the shoot apical meristem of tomato. By using a combination of transport inhibitors and synthetic auxins, we demonstrate that interference with auxin influx has little effect on organ formation as such, but prevents proper localization of leaf primordia. These results suggest the existence of functional auxin concentration gradients in the shoot apical meristem that are actively set up and maintained by the action of efflux and influx carriers. We propose a model in which efflux carriers control auxin delivery to the shoot apical meristem, whereas influx and efflux carriers regulate auxin distribution within the meristem.

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THE INFLUENCE of combat sport practice on behaviour, attitude, personality and other factors was, and still remains, a research topic of great interest as well as conflicting points of view. Findings are as yet inconclusive since a direct or causal effect is difficult to establish and other factors external to the individual, such as the instructor’s coaching style, also need to be taken into consideration. Furthermore, the wide range of disciplines pertaining to the category combat sports differ from each other on a number of characteristics, such as the extent of physical contact or competition rules, and in fact, attempts have been made to distinguish between various sub-types (e.g. Trulson, 1986). A common distinction made is that between the traditional martial arts, which place emphasis on the art’s philosophy, its traditions and hierarchy (e.g. traditional karate, aikido) and the modern (or Western) combat sports (e.g. boxing, Mixed Martial Arts). An ongoing debate exists about the potential positive and/or negative influence of combat sport practice in comparison to other sport disciplines that do not include this element of fighting and direct aggression. On the one hand, combat sports have been presented by some researchers and sport practitioners as a means of promoting positive social and individual behavior, such as in Theeboom, De Knop and Wylleman’s (2008) evaluation of a martial arts Programme for socially disadvantaged youths in Belgium. Results revealed a positive effect of this project; however, it also highlighted the crucial role played by the instructors or leaders of such programmes. In another intervention using martial arts, Trulson (1986) reported a positive effect of a six month traditional martial art (Korean Tae Kwon Do) intervention with male juvenile delinquents including a reduction in aggressiveness and anxiety, thus confirming the positive influence of such an activity. Nevertheless, this effect was not observed in the other group participating in a modern Adaptation of this martial art led by the same instructor, where the philosophical aspect of this discipline was not emphasised. Moreover, an opposite effect was ascertained in this case where an increased tendency towards delinquency was reported. These results support the distinction between the various types of combat sports together with the way this sport is presented and taught by the instructor.

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Most previous neurophysiological studies evoked emotions by presenting visual stimuli. Models of the emotion circuits in the brain have for the most part ignored emotions arising from musical stimuli. To our knowledge, this is the first emotion brain study which examined the influence of visual and musical stimuli on brain processing. Highly arousing pictures of the International Affective Picture System and classical musical excerpts were chosen to evoke the three basic emotions of happiness, sadness and fear. The emotional stimuli modalities were presented for 70 s either alone or combined (congruent) in a counterbalanced and random order. Electroencephalogram (EEG) Alpha-Power-Density, which is inversely related to neural electrical activity, in 30 scalp electrodes from 24 right-handed healthy female subjects, was recorded. In addition, heart rate (HR), skin conductance responses (SCR), respiration, temperature and psychometrical ratings were collected. Results showed that the experienced quality of the presented emotions was most accurate in the combined conditions, intermediate in the picture conditions and lowest in the sound conditions. Furthermore, both the psychometrical ratings and the physiological involvement measurements (SCR, HR, Respiration) were significantly increased in the combined and sound conditions compared to the picture conditions. Finally, repeated measures ANOVA revealed the largest Alpha-Power-Density for the sound conditions, intermediate for the picture conditions, and lowest for the combined conditions, indicating the strongest activation in the combined conditions in a distributed emotion and arousal network comprising frontal, temporal, parietal and occipital neural structures. Summing up, these findings demonstrate that music can markedly enhance the emotional experience evoked by affective pictures.

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Strategies of cognitive control are helpful in reducing anxiety experienced during anticipation of unpleasant or potentially unpleasant events. We investigated the associated cerebral information processing underlying the use of a specific cognitive control strategy during the anticipation of affect-laden events. Using functional magnetic resonance imaging, we examined differential brain activity during anticipation of events of unknown and negative emotional valence in a group of eighteen healthy subjects that used a cognitive control strategy, similar to "reality checking" as used in psychotherapy, compared with a group of sixteen subjects that did not exert cognitive control. While expecting unpleasant stimuli, the "cognitive control" group showed higher activity in left medial and dorsolateral prefrontal cortex areas but reduced activity in the left extended amygdala, pulvinar/lateral geniculate nucleus and fusiform gyrus. Cognitive control during the "unknown" expectation was associated with reduced amygdalar activity as well and further with reduced insular and thalamic activity. The amygdala activations associated with cognitive control correlated negatively with the reappraisal scores of an emotion regulation questionnaire. The results indicate that cognitive control of particularly unpleasant emotions is associated with elevated prefrontal cortex activity that may serve to attenuate emotion processing in for instance amygdala, and, notably, in perception related brain areas.

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Traditionnellement un monde d’homme, la politique fonctionne encore aujourd’hui selon des règles faites par et pour les hommes. Malgré cet univers hostile à la gente féminine, les femmes sont entrées en politique dès que les pays leurs ont accordés les droits politiques. Toujours minoritaire, les femmes se sont aujourd’hui faites une place dans les parlements et gouvernements du monde. L’augmentation de la proportion de femmes dans les instances politiques laisse supposer qu’être une femme ne constitue pas obligatoirement un handicap en politique. Ce livre s’intéresse à ce changement de signification du genre féminin en politique et montre, à l’exemple de la Suisse, comment les membres de l’élite politique perçoivent le rôle du genre dans les affaires publiques. Cette étude s’adresse à toute personne intéressée par les rapports de genre dans le monde du pouvoir.