Movement refractoriness: The influence of response structure and speed

In the first experiment, refractoriness of a primary arm swing was studied using two movement speeds and three secondary responses (reversal, contralateral and ipsilateral thumb-lift). Pre-movement inter-stimulus intervals were 100, 200 or 300 msec and response-stimulus intervals ranged from zero to 200 msec. Accelerometers provided kinematic data. The second experiment repeated the reversal condition with the addition of EMG analysis.The prediction that the maximal speed condition would show a general intensification of control processes, and thus less refractoriness as compared to submaximal speed, was upheld for all response conditions. The findings also supported the prediction that the pattern of refractoriness depends on the functional relationships of the muscles concerned.The EMG analysis revealed that while the sequencing of muscle action was unchanged with movement speed, its phasing characterized the shifts in response metrics. The overall findings emphasize the need to view the refractoriness phenomenon in the context of anatomical and mechanical consequences of force changes in controlling limb movement as they interact with intentional command.     

Some effects of congenital spasticity on fundamental frequency

5 normal speakers and 5 speakers with congenital upper motor-neuron damage repeatedly spoke a three-work sentence stressing the first, second, or third words. Fundamental frequency was measured for each word and over each sentence. Analysis showed that the spastics' mean fundamental frequency was significantly higher than the normals', regardless of utterance. Also, spastics were more restricted in their prosodic maneuvering above this average fundamental frequency. Despite this finding, the spastics were capable of producing consistent stress patterns with normal variability.     

A nonsequential approach to the study of operant renewal: a reverse translation

ABA renewal is a model of treatment relapse that describes the recurrence of severe problem behavior when behavior learned in one context (e.g., home; A) and treated in a separate context (e.g., clinic; B) reemerges when the original context is reintroduced (A). However, in the typical environment and during the usual course of treatment for severe problem behavior, the target behavior is exposed to the baseline context periodically (e.g., the child returns home after several hours in a clinic setting). Due to the difficulty of studying what effect this may have on treatment relapse during ABA renewal in a strictly applied investigation, we developed a human‐laboratory translation to study renewal in a nonsequential manner. Using undergraduate students as subjects, we directly compared levels of recurrence using the standard ABA renewal procedure and a modified nonsequential ACA procedure, one modeled from the typical course of treatment for problem behavior. Both methods produced renewal at comparable levels, and patterns during nonsequential ACA renewal were similar to those during sequential ABA renewal. We discuss the implications of these findings in the framework of treatment for severe problem behavior.