Biomedical subjects

A Garcia-Colera

Publications and source records attributed to A Garcia-Colera.

4 recordsLinked to original sources

PubMed1989

Force transition control within a movement sequence in Parkinson's disease.

An experiment was performed which examined movement planning and force transition control in six patients with Parkinson's disease (PD) during a sequence of five finger taps at either a fast (200 ms) or slow (600 ms) temporal speed. The patients acted as their own controls and performed finger taps under three task conditions: (1) where all taps had to be of the same force intensity: no stress; (2) where it was known that one of the taps had to be executed with an augmented force: stress simple reaction time (SRT); and (3) where it was not known prior to initiation which one of the taps was to be more forcefully produced: stress choice reaction time (CRT). Reaction time data revealed a between-condition effect where stress SRT was faster than stress CRT and no stress was faster than both. Under both speed conditions, the interval after the stressed tap was profoundly lengthened. It was found that the lengthening was due to increases in both lift and dwell times for the slow tapping rate. In contrast, at the fast tapping rate, proportionately more of the interval increase was due to the increase in lift time. These findings suggest that patients with Parkinson's disease, when performing under a motor program mode, have difficulty in initiating a sequence and making a transition to lighter force levels after a stressed tap.

Aged↗

PubMed1988

Distributed planning of movement sequences.

Three experiments are reported that examine whether fast finger-tapping sequences are entirely planned before execution starts (advance planning), or if they can be started while planning is still under way (distributed planning). Subjects performed finger tapping sequences of three to eight taps at a high rate, under both simple and 2-choice reaction time (RT) conditions. The sequences differed in the location of an accentuated element within them. The RT to choose between sequences with different accent locations progressively decreased as an inverse function of the time-distance between the initial tap and the first point at which the alternative sequences differed. The shortening in choice reaction time (CRT) was never accompanied by noticeable changes in the inter-response times or force patterns of the tapping sequences. The RT to initiate sequences with accent location known beforehand (SRT condition) showed, in two of three experiments, a weak decreasing trend as the accentuated tap shifted away from the beginning of the sequence. The SRT results suggest a possible predominance of advance planning when the same sequence is repeated over a series of trials. The CRT results are taken as evidence that planning of the sequence beyond the unpredictable tap could be distributed before and after sequence initiation. Several factors are discussed that may influence the balance between planning in advance of, and planning in parallel with, sequence execution.

Journal Article↗

PubMed1984

On controlling force and time in rhythmic movement sequences: the effect of stress location.

Accentuation involves modulation of motor intensity. It differentiates a movement from others within a motor sequence. Does the serial position of the accent characterize the whole sequence as a particular response? How are the control of time and force coordinated in the motor sequence? Subjects produced sequences of four fingertaps on a key. Time of onset and force of each tap were recorded. Tapping rate was imposed by a string of four clicks delivered at 180-msec intervals before each trial. A flashed digit served as go signal. It indicated to the subject which of the four taps had to be tapped stronger (stress +) or weaker (stress -) than all the others. These conditions were run in separate series. Reaction time (RT) of the sequence increased when the number of equally likely locations of the stress increased from 2 to 4. RT was also longer under the stress - than under the stress + condition. Tapping intervals were longer before and after the stressed tap than elsewhere in the series. The first and last intervals tended to be longer than the second one. These effects were the same under both stress conditions. The RT data indicate that the motor sequence is identified as a particular response before it starts. Timing is partly force-independent, but is modulated by central processes that control force.

Attention↗

PubMedDate not supplied

Movement specification time with age.

An experiment is reported which localizes and compares movement specification times between three age groups, young (18-25 yrs.), middle (40-50 yrs.), and elderly (65-75 yrs.), in order to assess whether movement planning processes are partially responsible for the commonly observed slowing of response initiation time in the elderly. A movement precuing paradigm was used in which 24 subjects (8/age group) received either no, partial, or complete movement task information prior to the imperative response signal. The results established that the elderly had slower reaction times, movement times, information transmission rates and more errors. While the results indicated that the elderly could use precue information to prepare an upcoming movement, their specification times for arm, direction, and extent were markedly slower. The data are interpreted as providing evidence that part of the slowing in reaction time observed in the elderly is due to the increased time required to specify a dimension of movement.

Adolescent↗