Biomedical subjects

Hiroshi Kadota

Publications and source records attributed to Hiroshi Kadota.

4 recordsLinked to original sources

PubMed2004

Time-series pattern changes related to movement rate in synchronized human tapping.

We investigated the effect of movement rate on the time-series properties of human synchronization errors by applying power spectrum analysis and detrended fluctuation analysis (DFA). Participants were required to execute a finger-tapping task with their right index finger in synchrony with periodic sounds under seven conditions of movement rates ranging from 1 to 4 Hz and separated by 0.5 Hz. At slow movement rates (1 and 1.5 Hz), the power spectrum of the synchronization errors flattened in the low-frequency portion, resulting in short-range correlation. At fast movement rates (from 2 to 4 Hz), on the other hand, the time series of the timing errors exhibited a 1/fbeta-type long-range correlation. These results indicate that the movement rate has an effect on the temporal coordination pattern in the human timing control mechanism. We inferred that this change in the coordination pattern reflects the transition between different states in human synchronization movements with an external signal.

Adult↗

PubMed2004

1/f-type fluctuation in human visuomotor transformation.

In the absence of vision of the limb, movements toward a visual target exhibit substantial errors which are considered to originate mainly in the visuomotor transformation process. To determine the time-dependent property of human visuomotor transformation, we investigated the error sequences in movements toward visual target using scaling analyses. When subjects could see their controlling limb, the error sequences could not be distinguished from a random sequence. On the other hand, when the controlling limb was invisible, the error sequences were not random in order, but exhibited 1/f-type time correlation. This finding that the variation in human visuomotor transformation shows 1/f-type fluctuation provides a significant index for mathematical modeling and system identification in human visuomotor control.

Adult↗

PubMed2004

Selective activation and deactivation of the human brain structures between speeded and precisely timed tapping responses to identical visual stimulus: an fMRI study.

We investigated the difference between brain activities in speeded and precisely timed responses to identical visual stimulus using fMRI. Stimulus used was a row of seven light-emitting diodes (LEDs) lightened up one after another with constant speed within a trial but with various speeds between trials. Subjects were asked to execute finger-thumb tapping with the right hand in response to the onset of the first LED light in the reaction time (RT) task and in anticipation of the onset of the last (i.e., seventh) LED light in the timing task. In control condition, they were asked to passively view the stimulus without motor response. Results showed that various movement-related areas including contralateral cingulate motor cortex were commonly activated for both tasks relative to the control condition, suggesting these structures are involved in general perception and response execution rather than specific function for speeded or precisely timed responses. In the RT task, the presupplementary motor area extending to the cingulate sulcus was activated more strongly than in the timing task probably to focus attention to the onset of the first LED light unpredictably presented after random foreperiods. The lateral occipital area extending to the temporo-parieto-occipital junction was activated more strongly in the timing task than in the RT task; the same area was deactivated in the RT task relative to the control condition. Auditory-related areas were also deactivated in the both tasks. This inter- and intramodal task-specific modification including deactivation underscores significance of the context for perception and action and can have an important role in dexterous or skilled performance.

Adult↗

PubMed2002

Sequential muscle activity and its functional role in the upper extremity and trunk during overarm throwing.

The proximal-to-distal segmental sequence has been identified in many sports activities, including baseball pitching and ball kicking. However, proximal-to-distal sequential muscle activity has not been identified. The aims of this study were to establish whether sequential muscle activity does occur and, if it does, to determine its functional role. We recorded surface electromyograms (EMGs) for 17 muscles from the upper extremity and abdomen during overarm throwing and detected the onset and peak times as indices of muscle activity. The following electromyographic properties were commonly identified in the participants. First, sequential muscle activity was observed from the scapular protractors to the shoulder horizontal flexors and from the shoulder horizontal flexors to the elbow extensor, but not from the elbow extensor to the wrist flexor or forearm pronator. Secondly, the external oblique contralateral to the throwing arm became activated before the ipsilateral external oblique. This sequence is considered to be very effective for the generation of high force and energy in the trunk. Thirdly, the ipsilateral external oblique began its activity almost at foot strike. Finally, the main activity of the rectus abdominis appeared just before the point of release.

Abdominal Muscles↗