Perceived standing position after reduction of foot-pressure sensation by cooling the sole

We investigated the influence of the reduction of foot-pressure sensation by cooling the sole of the foot, at 1 degree C for 30 or 40 minutes, on the perception of standing position varied in the anteroposterior direction. The subjects were 16 healthy undergraduates. Firstly, for 4 of the subjects, cooling the sole of the foot decreased sensory information from the mechanoreceptors in the sole, by testing for an increase in the threshold for two-point discrepancy discrimination on the sole of the foot and for the disappearance of postural change with vibration to the sole. Next, the perception of standing position was measured by reproduction of a given standing reference position involving forward or backward leaning under both normal and cooled conditions of the feet. Standing position was varied in relation to the location of the center of foot pressure, defined as distance from the heel in percentage of the length of the foot. The reference positions, representing various locations of the center of foot pressure, were set at 10% increments from 20% to 80% of the length of the foot. With eyes closed, the subject first experienced the reference position and then attempted to reproduce it. The mean location of the center of foot pressure in the quiet standing posture was 45.7%. At the 40%, 50%, and 60% reference positions, those closest to quiet standing, absolute errors of reproduction were significantly larger than at other reference positions in both the normal and the cooled conditions. They were significantly larger in the cooled than in the normal condition. The 50% and 60% reference positions were reproduced significantly further forward in the cooled than in the normal condition. These results may be explained as due to an absence of marked changes in sensory information from both muscular activity and foot pressure when moving to reference positions close to the quiet standing posture.     

Regional brain activity during face and word discrimination: simultaneous recording of event-related potentials and positron emission tomography

In order to clarify the brain mechanisms involved in the recognition of faces, words, and figures, spatiotemporal analyses were carried out with event-related potentials (ERPs) and positron emission tomography (PET) in normal subjects. In the first experiment, we analyzed the ERPs of eight normal subjects under a passive habituation paradigm using pictures of faces and letters. In the second experiment, regional cerebral blood flow (rCBF) measured using PET was obtained simultaneously with the ERP recordings during a continuous performance task (CPT) in 12 normal subjects. This required the active discrimination of famous people's faces, meaningful words consisting of two Japanese hiragana characters, and simple geometric figures. There were similar deflections in the global field power (GFP) in the first 200 ms of the passive and active tasks, regardless of type of stimuli. This suggests a common time course in the visual information processing mechanisms during the preattentive stage. Mesiotemporal activity, dominant on the right, was seen during the face discrimination task in both the PET results and the ERP topographies. In the word task, activity that was clearly dominant on the left was observed at around a 160 ms latency in the posteriotemporal region of the ERP topography and this again coincided well with the PET data. The spatiotemporal resolution of the analyses was improved by combining PET and topographic ERP studies, and this provided additional neurophysiological information concerning cognitive processing.     

Respecting autonomy in difficult medical settings: a questionnaire study in Japan

Some people in Japan are still comfortable with the paternalistic role of doctors, but others wish that their own decisions would receive a greater amount of respect. A total of 747 students of universities and colleges and 114 parents of these students participated in a questionnaire survey. Most of the participants thought that autonomy should be respected in situations involving death with dignity and euthanasia, whereas it should not be respected in attempted suicide and involuntary admission of individuals with mental illness. A cluster analysis revealed that the participants could be divided into the following groups: aid in dying advocates (n=577), complete libertarians (n=109), protectors of the mentally ill (n=90), complete paternalists (n=29), and questionables (n=27). The assertion of independence score of the Scale for Independent and Interdependent Construal of the Self showed a significant difference among the 5 clusters. These findings suggest that the traditional paternalistic relationship between doctor and patient is undergoing a gradual transformation in Japan.     

Schizotypal personality traits and prediction of one's own movements in motor control: what causes an abnormal sense of agency?

Background. Positive schizophrenic symptoms, especially passivity phenomena, including auditory hallucinations, may be caused by an abnormal sense of agency, which people with schizotypal personality traits also tend to exhibit. A sense of agency asserts that it is oneself who is causing or generating an action. It is possible that this abnormal sense of self-agency is attributable to the abnormal prediction of one’s own movements in motor control. Method. We conducted an experiment using the “disappeared cursor” paradigm in which non-clinical, healthy participants were required to click on a target using an invisible mouse cursor. Prediction error was defined as the distance between the target and the click point. Results. The results showed that schizotypal personality traits, but not depressive or anxious traits, were correlated with deficits in predicting movements of the subjects’ left hand. In particular, auditory hallucination proneness had the strongest relationship with movement prediction error. In this report, we also discuss the error tendency (overestimations or underestimations of one’s own movements). Conclusions. This finding is in accordance with the idea that passivity phenomena or proneness may be caused by the abnormal prediction of one’s own actions or movements.     

The relationship between the sense of self-agency and schizotypal personality traits

People with schizotypal traits may possess abnormal self-awareness, particularly with regard to their sense of self-agency, that is, the sense that it is oneself who is causing or generating an action. Participants in Experiments 1A (N = 11), 1B (N = 12), and 2 (N = 20) moved a mouse device and viewed resultant feedback, which was biased either temporally or spatially. They then judged whether there was a bias or whether they felt they had moved the cursor on their own. The authors found, for the 1st time, that a sense of self-agency can be experienced even if some degree of temporal bias is perceived. Furthermore, they determined that highly schizotypal people have an abnormal (weaker) sense of self-agency.