Transfer of Motor Learning Engages Specific Neural Substrates During Motor Memory Consolidation Dependent on the Practice Structure

The authors investigated how brain activity during motor-memory consolidation contributes to transfer of learning to novel versions of a motor skill following distinct practice structures. They used 1 Hz repetitive Transcranial Magnetic Stimulation (rTMS) immediately after constant or variable practice of an arm movement skill to interfere with primary motor cortex (M1) or dorsolateral prefrontal cortex (DLPFC). The effect of interference was assessed through skill performance on two transfer targets: one within and one outside the range of practiced movement parameters for the variable practice group. For the control (no rTMS) group, variable practice benefited delayed transfer performance more than constant practice. The rTMS effect on delayed transfer performance differed for the two transfer targets. For the within-range target, rTMS interference had no significant affect on the delayed transfer after either practice structure. However, for the outside-range target, rTMS interference to DLPFC but not M1 attenuated delayed transfer benefit following variable practice. Additionally, for the outside-range target, rTMS interference to M1 but not DLPFC attenuated delayed transfer following constant practice. This suggests that variable practice may promote reliance on DLPFC for memory consolidation associated with outside-range transfer of learning, whereas constant practice may promote reliance on M1 for consolidation and long-term transfer.     

A Dual Process Account of Coarticulation in Motor Skill Acquisition

Many tasks, such as typing a password, are decomposed into a sequence of subtasks that can be accomplished in many ways. Behavior that accomplishes subtasks in ways that are influenced by the overall task is often described as “skilled” and exhibits coarticulation. Many accounts of coarticulation use search methods that are informed by representations of objectives that define skilled. While they aid in describing the strategies the nervous system may follow, they are computationally complex and may be difficult to attribute to brain structures. Here, the authors present a biologically- inspired account whereby skilled behavior is developed through 2 simple processes: (a) a corrective process that ensures that each subtask is accomplished, but does not do so skillfully and (b) a reinforcement learning process that finds better movements using trial and error search that is not informed by representations of any objectives. We implement our account as a computational model controlling a simulated two-armed kinematic “robot” that must hit a sequence of goals with its hands. Behavior displays coarticulation in terms of which hand was chosen, how the corresponding arm was used, and how the other arm was used, suggesting that the account can participate in the development of skilled behavior.     

Knowledge About Hand Shaping and Knowledge About Objects

Our two experiments investigated associations between cognitive representations of objects and hand-shape categories. Hand configurations were partitioned according to prehensility and the size of the contacting surface, resulting in the classes: pinch, poke, palm, and clench. Experiment 1 elicited object names in response to configuration-name cues, provided ratings of the relevance of each configuration to a set of objects, and probed for the functions determining such relevance. Cueing with a configuration class elicited an associated object category with substantial intersubject agreement, and vice versa. Both the object categories and the functions associated with the four hand-configuration classes differed substantially, although the same object could be associated to some extent with multiple configurations, given variations in function. Experiment 2 elicited the names of hand-configuration classes in response to unfamiliar forms, which varied systematically in depth and the size of the projecting picture-plane surface. The modal response, response time, and degree of intersubject agreement were directly related to these variables. These structural variables, however, did not adequately predict shaping responses to real objects, as ascertained from Experiment 1. The results have implications for cognitive representation of motor categories and hand shaping in response to objects.     

Context-Dependent Learning in People With Parkinson's Disease

Context-dependent learning is a phenomenon in which people demonstrate superior performance in the context in which they originally learned a skill but perform less well in a novel context. This study investigated context-dependent learning in people with Parkinson's disease (PD) and age-matched nondisabled adults. All participants practiced 3 finger sequences, each embedded within a unique context (colors and locations on a computer screen). One day after practice, the participants were tested either under the sequence-context associations remained the same as during practice, or the sequence-context associations were changed (SWITCH). Compared with nondisabled adults, people with PD demonstrated significantly greater decrement in performance (especially movement time) under the SWITCH condition, suggesting that individuals with PD are more context dependent than nondisabled adults.     

The Force/Force-Variability Relationship Under Controlled Temporal Conditions

Previously, an inverted U relationship between force and force variability was demonstrated in both static and dynamic responses. Recent research suggests that the inverted U function may be due to a lack of control of the temporal aspects of the response. To investigate this hypothesis, we examined the relationship between force and force variability in rapid movements under controlled temporal conditions. Subjects (N = 4) made rapid reversal responses with a horizontal lever (using elbow flexion and extension) such that the time to reversal (160 ms) and the distance to reversal (45°) were held constant in each of six load conditions (either 0, .260, .520, .780,1.040, or 1.560 kg added to the lever). When time to reversal and time to peak acceleration were held constant, a curvilinear relationship between force and force variability resulted, suggesting that the inverted U function is related to control of the temporal aspects of the response.     

Communal Versus Individual Learning of a Math-Estimation Task: African American Children and the Culture of Learning Contexts

The authors compared the performance of 78 African American 5th-grade students who studied a math-estimation task in one of two learning contexts. Learning contexts differed in the degree to which they afforded the expression of communalism. ANCOVA confirmed that posttest performance was best for students who studied in the high communal-learning context. The findings support A. W. Boykin's (1994) contention that the cultural context of learning can be a critical mediator of children's performance.     

Preference for Sex of Child Among Primiparous Women

Primiparous American women (N = 140) were questioned during their third trimester concerning their choice of sex of offspring and their willingness to use sex preselection techniques (if available). Eighty-two women expressed no preference for sex of offspring; of the remaining 58, 33 chose girls and 25 chose boys. Of the 26 women who indicated they would have used preselection technology, 13 chose boys and 13 chose girls. Fifty-three percent of the sample indicated they would not have used preselection techniques; 29% were undecided. These results were at variance with earlier studies that indicated a consistent choice of male firstborns, especially in nonpregnant samples. The discrepancy is discussed in terms of a move from boy preference to no preference and a gradual weakening of societal bias against women.     

Adolescents' Reactions to the Evacuation of the Sinai Settlements: A Longitudinal Study

This study investigated psychological reactions of adolescents to a severe stress situation—the evacuation of the Sinai settlements. The research focused on emotional reactions of anxiety and anger to this stress situation. Two central problems were investigated: (a) The intensity of the emotional responses of anxiety and anger of the adolescents to the stress situation, before and after the evacuation, and (b) the impact of three intervening variables on these emotional reactions—cognitive perception of the political situation, family functioning, and personality characteristics. Data for this study were collected in a regional high school in Israel from 418 pupils in 9th through 12th grades. Seventy-eight of the pupils lived in the Yamit area. Measurements were obtained at three points in time: 6 weeks and 1 week before the evacuation and 2 months after it. The results supported the predicted trend that adolescents in the Yamit group before the evacuation would score higher on state anxiety and state anger than would those in the comparison group. Two months after the evacuation there was a significant drop in those scores. The trait measures remained stable in both groups and no significant differences were found between the two groups on these scores. Concerning the impact of the three intervening variables on the intensity of the state emotional responses, the results did not support any of the hypotheses.     

Index to Volume 122

I examined the impact of first names on ratings of physical attractiveness as judged by British undergraduate subjects using male and female full-face pictures presented on photographic slides. The photographs were identified with attractive names, unattractive names, or without any name indicated. Subjects rated the stimulus figures for physical attractiveness. Names accounted for approximately 6% of the variance in subjects' ratings of physical attractiveness. This effect was highly significant for pictures of women (p < .001), but nonsignificant for pictures of men (p > .05).