Movements Of Others Research Articles

The parietal role in the sense of self-ownership with temporal discrepancy between visual and proprioceptive feedbacks

One hypothesis on how we recognize an image of, for example, an arm as our own is through the co-occurrence of multiple sensory feedbacks, especially visual and proprioceptive feedbacks, in this process. It has been suggested that the parietal lobe is the region where proprioceptive and visual information of one's own body is integrated. This study investigated parietal cortical activity during a visual-proprioceptive synchrony judgment task in which visual feedback of the subjects' own passively moving hand was delayed. The subjects were required to judge whether or not there was a delay between the proprioceptive and visual feedbacks. Parietal cortical activity, which was measured using a 48-channel near-infrared spectroscopy (NIRS) apparatus, appeared to be modulated by the length of the delay between the visual and proprioceptive feedbacks. The bilateral superior/middle parietal areas were involved in experiencing the synchrony between the visual and proprioceptive feedbacks, whereas the right inferior parietal areas were strongly activated when discrepancy between the two feedbacks was detected. We postulate that the superior portion of the parietal lobe is essential for maintaining one's own body image, while the right inferior portion is involved in detecting movements of others.

The human temporal lobe integrates facial form and motion: evidence from fMRI and ERP studies

Physiological studies in humans and monkeys indicate that the posterior temporal cortex is active when viewing the movements of others. Here we tested the premise that this region integrates form and motion information by presenting both natural and line-drawn displays of moving faces and motion controls where motion was continuously presented in the same part of the visual field. The cortex in and near the STS and on the fusiform gyrus (FG) responded to both types of face stimuli, but not to the controls, in a functional magnetic resonance imaging study in 10 normal subjects. The response in the STS to both types of facial motion was equal in magnitude, whereas in the FG the natural image of the face produced a significantly greater response than that of the line-drawn face. In a subsequent recording session, the electrical activity of the brain was recorded in the same subjects to the same activation task. Significantly larger event-related potentials (ERPs) to both types of moving faces were observed over the posterior temporal scalp compared to the motion controls at around 200 ms postmotion onset. Taken together, these data suggest that regions of temporal cortex actively integrate form and motion information—a process largely independent of low-level visual processes such as changes in local luminance and contrast.

Impaired Mirror-Image Imitation in Asperger and High-Functioning Autistic Subjects

Imitation is crucial for proper development of social and communicative skills. Here, we argue that, based on an error analysis of a behavioral imitation task, adult Asperger and high-functioning autistic subjects suffer from an intriguing deficit of imitation: they lack the natural preference for imitation in a mirror-image fashion. The imitation task consisted of a simple movement sequence of putting a pen with the left or right hand into a green or a blue cup using one of two possible grips. The subjects were asked to imitate the experimenter's hand movements either using the crossed hand (e.g., the subject's right hand corresponding to the experimenter's right hand) for imitation or to imitate as if looking in a mirror (e.g., the subject's left hand corresponding to the experimenter's right hand). When people normally view other persons face-to-face, they prefer to imitate as in a mirror [1, 2], and observation of mirror-image-like movements speeds up performance in nonimitative tasks [3, 4]. However, our autistic subjects, defective in social cognition, did not profit from mirror-image movements of others. These results provide a new insight into the difficulties that autistic subjects face in viewing and understanding actions of others.

THE VISUAL PERCEPTION OF HUMAN LOCOMOTION

To function adeptly within our environment, we must perceive and interpret the movements of others. What mechanisms underlie our exquisite visual sensitivity to human m ovement? To address this question, a set of psychophysical studies was conducted to ascertain the temporal characteristics of the visual perception of human locomotion. Subjects viewed a computer-generated point-light walker presented within a mask under conditions of apparent motion. The temporal delay between the display frames as well as the motion characteristics of the mask were varied. With sufficiently long trial durations, performance in a direction discrimination task remained fairly constant across inter-stimulus interval (ISI) when the walker was presented within a random motion mask but increased with ISI when the mask motion duplicated the motion of the walker. This pattern of results suggests that both low-level and high-level visual analyses are involved in the visual perception of human locomotion. These findings are discussed in relation to recent neurophysiological data suggesting that the visual perception of human movement may involve a functional linkage between the visual and motor systems.

CINE-MICROGRAPHIC STUDIES ON DICENTRIC CHROMOSOMES.

The behavior during mitosis of SR (sister reunion) bridges and other types of dicentric anaphase bridges was analysed. The endosperm of Haemanthus katharinae was used as material, and 16 mm time-lapse cine-film was analysed frame by frame. Most observations concern anaphase and telophase. The bridges break or are stretched and their variation in behavior depends on the length of the bridge and the stage when it is stretched. Breakage in anaphase is due to the pulling action of the kinetochores, while breakage in telophase is due to phragmoplast activity and a formation of a cell plate. The kinetochore movements of the dicentrics are usually, but not always, slowed down when the bridges stretch up to when the bridges have broken. Whether the movement of the kinetochores is slowed down or not depends mostly on the metaphase position of the kinetochore relative to the equator. A retarded movement of one kinetochore influences the movements of others in its close neighborhood while kinetochores situated further away are not influenced at all. In cells with many short bridges whole groups of chromosomes are retarded and the formation of a restitution nucleus follows. The formation of a restitution nucleus may also result from the existence of numerous bridges causing failure of phragmoplast formation. The contraction of the bridges during telophase pulls the two parts of the restitution nucleus together and contributes to maintain their connection.