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Bimanual finger tapping: effects of frequency and auditory information on timing consistency and coordination
No full textThe authors' goal in this study was to probe the basis for an earlier, unexpected finding that preferred-frequency finger tapping tends to have higher frequencies and to be less stable for in-phase than for antiphase tasks. In follow-up experiments, 3 protocols were employed: a preferred-frequency replication in both coordination modes, a metronome-driven matching of the preferred frequencies to each of the coordination modes, and a frequency scaling of both modes. The original findings were affirmed for preferred frequency. Tapping to a metronome had a differential effect on in-phase and antiphase: A more stable coupling across frequencies was exhibited during in-phase. Under frequency scaling, the antiphase pattern decomposed at lower frequencies than did in-phase, but no phase transitions were observed. The loss of stable coordination in both modes was attended by sudden increases in frequency differences between fingers and by phase wandering. The emergence of those effects is discussed in light of asymmetric modifications to the Haken-Kelso-Bunz model (H. Haken, J. A. S. Kelso, & H. Bunz, 1985) and the task constraints of tappin
The effect of nonspecific task constraints on quadrupedal locomotion: II. Joint kinematics
No full textThe effects of directional and postural constraints on preferred speed quadrupedal gait patterns were studied by comparing responses to four hand-foot crawling tasks: forward and backward prone (FP and BP) and forward and backward supine (FS and BS). A central question was whether the task dynamics evident at the end-effector level also appear at the joint effector system level. Timing of reversals in each limb's proximal effector system joints was shown to be related to the functional role (propulsion or reaching) of the limb. Within joints, task constraint changes strongly tended to affect reversal times, and time-reversed directional comparisons tended to show "mirroring" responses. Peak reaching positions were also closely associated with forelimb touchdowns and interlimb coordination. Discussion centers on task function, task dynamics, and their influence on effector system behavio
A note on time-frequency analysis of finger tapping
No full textFinger tapping involves 3 important features: time, spatial amplitude, and frequency. In classical analysis, investigators examine timing parameters; in spectral analysis, they examine frequency parameters. Both types of analysis are based on stationary tap information. The authors propose that time-frequency analysis is a useful tool for analyzing nonstationary finger tapping. They describe the method and give examples of frequency modulation, age difference, and speed transition that demonstrate additional insights one can gain by using this analysi
Individual differences and similarities in the stability, timing consistency, and natural frequency of rhythmic coordinated actions
No full textUnder preferred speed conditions, 15 adults undertook bimanual in-phase and antiphase tapping, clapping, galloping, galloping while clapping, and crawling on their hands and feet. We measured stability of interlimb coordination (standard deviation of mean interlimb relative phasing), single limb timing consistency (coefficient of variation of mean single limb cycle durations), and natural limb frequency. Pearson product-moment correlations among tasks established that only the natural limb frequencies were significantly correlated (specifically among gross motor actions in which larger contributions of inertial loads contribute to natural frequencies). Intraclass correlations were high for tasks, meaning that within each task, all participants performed similarly. Thus, only frequency has a tendency to show a common time-based process within a participant, but common time-based processes exist between participant
Dual-finger preferred-speed tapping: effects of coordination mode and anatomical finger and limb pairings
No full textInterlimb and interfinger coordination were examined on a dual-finger tapping paradigm in which 16 subjects performed at preferred frequencies. Three bimanual finger combinations, in random order (2 index; 2 middle; and 1 index and 1 middle), were performed in in-phase and antiphase coordination modes, in addition to 1 unimanual combination (antiphase index middle). Relative phase means were within 3% accuracy for all conditions. A lower tapping frequency was found in all antiphase vs. in-phase conditions, accompanied by lower phasing variability and lower intrafinger consistency in the antiphase. When frequency was changed from the preferred rate, the 2 coordination modes became more alike in variability and, within the same frequency range, demonstrated no significant differences. The bimanual mixed-fingers tapping tended to have significantly lower phasing values (a small fixed point drift) and higher tapping frequencies than the symmetric conditions. The unimanual task was similar to all other antiphase conditions. Changes in preferred frequency with different coordination modes may be related to differing perceptual informational constraints. Current models addressing natural frequencies of coupled oscillators do not account for the present dat
The effect of nonspecific task constraints on quadrupedal locomotion: I. Interlimb coordination
No full textThe present study examined the effect of nonspecific task constraints on the multilimb coordination task of preferred-speed crawling. Adult subjects undertook three trials each of the following randomly ordered conditions: forward prone (FP), backward supine (BS), backward prone (BP) and forward supine (FS). Subjects adopted specific coordinative solutions consistent with task-related function rather than anatomical specification. The patterns were relatively stable, with BP being least stable. Across conditions, subjects changed their velocity in a predictable order that corresponded to the various constraints. These velocity changes were largely attributable to stride length adjustments and not limb frequency. Within a condition, neither velocity nor anthropometrics appeared to influence the coordinative solution. Overall, rather large differences were found in coordinative solutions, possibly owing to the nature of the tasks and/or individual searching strategies. The results were interpretable within a dynamic approach to coordination and support the idea that coordination is functionally rather than anatomically determine
Intracortical inhibition and facilitation with unilateral dominant, unilateral nondominant and bilateral movement tasks in left- and right-handed adults
No full textPurposeTo investigate intracortical inhibition and facilitation in response to unilateral dominant, nondominant and bilateral biceps activation and short-term upper extremity training in right- and left-handed adults.MethodsPaired-pulse transcranial magnetic stimulation was used to measure intracortical excitability in motor dominant and nondominant cortices of 26 nondisabled adults. Neural facilitation and inhibition were measured in each hemisphere during unilateral dominant, nondominant and bilateral arm activation and after training in each condition.ResultsNo differences were seen between right- and left-handed subjects. Intracortical facilitation and decreased inhibition were seen in each hemisphere with unilateral activation/training of contralateral muscles and bilateral muscle activation/training. Persistent intracortical inhibition was seen in each hemisphere with ipsilateral muscle activation/training. Inhibition was greater in the nondominant hemisphere during dominant hemisphere activation (dominant arm contraction).ConclusionStrongly dominant individuals show no difference in intracortical responses given handedness. Intracortical activity with unilateral and bilateral arm activation and short-term training differs based on hemispheric dominance, with the motor dominant hemisphere exerting a larger inhibitory influence over the nondominant hemisphere. Bilateral activation and training have a disinhibitory effect in both dominant and nondominant hemispheres
Improved hemiparetic muscle activation in treadmill versus overground walking
No full textObjective: treadmill training is a promising tool for retraining gait after stroke. The treadmill induces an immediate shift toward symmetry and longer paretic stance times due to altered muscle activation (active) or the motorized belt (passive). The authors investigated vastus lateralis and medial hamstrings activation differences between treadmill and overground walking in participants with stroke.Methods: vastus lateralis and medial hamstrings surface electromyography was recorded during velocity-matched overground and treadmill walking in 19 chronically hemiparetic subjects. Variables from ensemble averages of electromyography included burst onset and offset times (% cycle), duration (% cycle), integrated amplitude (mV.% cycle), and onset relative to foot strike (% cycle). Conditions were compared using paired t-tests (alpha = 0.05).Results: paretic vastus lateralis onset occurred earlier in the treadmill condition (overground: 47.1%, treadmill: 41.9%, P = 0.01). For nonparetic vastus lateralis in the treadmill condition, onset occurred later (overground: 85.2%, treadmill: 87.6%, P = 0.09), offset occurred earlier (overground: 54.7%, treadmill: 47.8%, P = 0.03), duration was shorter (overground: 69.1%, treadmill: 61.2%, P = 0.01), and integrated amplitude was lower (overground: 14.1, treadmill: 10.6, P = 0.05). Within limbs, paretic vastus lateralis onset occurred earlier relative to paretic foot strike. Nonparetic vastus lateralis onset occurred later relative to nonparetic foot strike.Conclusions: treadmill walking induces immediate changes in vastus lateralis, but not medial ham-strings, activation patterns. These alterations (earlier paretic vastus lateralis onset and later nonparetic vastus lateralis onset) during treadmill versus overground walking parallel the increased symmetry in gait patternin
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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