Navegando por Autor "GAWRYSZEWSKI, Luiz de Gonzaga"

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Manual responses to visual stimuli: early and late facilitatory effects due to the offset of a peripheral cue
(2003) PINHEIRO, Walter Machado; GAWRYSZEWSKI, Luiz de Gonzaga; PEREIRA JÚNIOR, Antônio
Manual and saccadic reaction times (MRTs and SRTs) are reduced when a warning signal precedes the onset of a target. The decreasing on SRTs observed after the offset of a fixation point has been called the gap effect. Different theories have been proposed to explain it. According to some authors, the offset also allows the saccadic system to generate a separate population of SRTs, the express saccades. Nevertheless there is no agreement about the influence of the offset of a peripheral stimulus on MRT. In two experiments we tested the effects of a peripheral visual offset used as preparatory signal on MRTs to a target after variable intervals. We found a reduction on MRT at short (200-300 ms) and long (1300-2000 ms) intervals after the peripheral offset. MRT distribution shifted toward short latencies, which sometimes formed a separate population. Since MRTs obtained at long intervals were affected by the introduction of catch trials, while MRTs at short intervals were not, we propose that two different mechanisms are involved in the decreasing of MRTs: warning and temporal expectancy. Our data support the hypothesis that the temporal component involved with the preparatory stages for motor responses can be shared by saccadic movements and key press responses, allowing the reduction on motor latencies after the visual offset in the gap paradigm. Our data corroborate the three components model for the gap effect. In our view, the question of the existence or not of a gap effect for manual responses is essentially conceptual.
Acesso aberto (Open Access)
Mental rotation of anthropoid hands: a chronometric study
(2007-03) GAWRYSZEWSKI, Luiz de Gonzaga; SANTOS, Caren Francisca Silva dos; SILVA, Júlio César Santos; LAMEIRA, Allan Pablo do Nascimento; PEREIRA JÚNIOR, Antônio
It has been shown that mental rotation of objects and human body parts is processed differently in the human brain. But what about body parts belonging to other primates? Does our brain process this information like any other object or does it instead maximize the structural similarities with our homologous body parts? We tried to answer this question by measuring the manual reaction time (MRT) of human participants discriminating the handedness of drawings representing the hands of four anthropoid primates (orangutan, chimpanzee, gorilla, and human). Twenty-four right-handed volunteers (13 males and 11 females) were instructed to judge the handedness of a hand drawing in palm view by pressing a left/right key. The orientation of hand drawings varied from 0º (fingers upwards) to 90º lateral (fingers pointing away from the midline), 180º (fingers downwards) and 90º medial (finger towards the midline). The results showed an effect of rotation angle (F(3, 69) = 19.57, P < 0.001), but not of hand identity, on MRTs. Moreover, for all hand drawings, a medial rotation elicited shorter MRTs than a lateral rotation (960 and 1169 ms, respectively, P < 0.05). This result has been previously observed for drawings of the human hand and related to biomechanical constraints of movement performance. Our findings indicate that anthropoid hands are essentially equivalent stimuli for handedness recognition. Since the task involves mentally simulating the posture and rotation of the hands, we wondered if "mirror neurons" could be involved in establishing the motor equivalence between the stimuli and the participants' own hands.
Acesso aberto (Open Access)
Postura da mão e imagética motora: um estudo sobre reconhecimento de partes do corpo
(2008-10) LAMEIRA, Allan Pablo do Nascimento; SILVA, Sabrina Guimarães; FERREIRA, Fernanda Maciel; Lima, LV; PEREIRA JÚNIOR, Antônio; GAWRYSZEWSKI, Luiz de Gonzaga
Objective: Recognition of body parts activates specifi c somatosensory representations in a way that is similar to motor imagery. These representations are implicitly activated to compare the body with the stimulus. In the present study, we investigate the infl uence of proprioceptive information relating to body posture on the recognition of body parts (hands). It proposes that this task could be used for rehabilitation of neurological patients. Methods: Ten right-handed volunteers participated in this experiment. The task was to recognize the handedness of drawings of a hand that were presented in different perspectives and several orientations. For drawings of a right hand, the volunteers pressed the right key, and for drawings of a left hand, they pressed the left key. The volunteers underwent two sessions: one with their hands in a prone posture and the other with their hands in a supine posture. Results: The manual reaction time was longer for perspectives and orientations for which the real movement was diffi cult to achieve. This showed that, during the task, motor representations were activated to compare the body with the stimulus. Furthermore, the subject’s posture had an infl uence in relation to specifi c perspectives and orientations. Conclusions: These results showed that motor representations are activated to compare the body with the stimulus, and that the position of the hand infl uences this resonance between the stimulus and the body part.