Asymmetric learning transfer between imagined viewer- and object-rotations: Evidence of a hierarchical organization of spatial reference frames

Neural resources subserving spatial processing in either egocentric or allocentric reference frames are, at least partly, dissociated. However, it is unclear whether these two types of representations are independent or whether they interact. We investigated this question using a learning transfer paradigm. The experiment and material were designed so that they could be used in a clinical setting. Here, we tested healthy subjects in an imagined viewer-rotation task and an imagined object-rotation task. The order of the tasks was counterbalanced across subjects. The results showed that subjects who did the viewer-rotation task first had fewer errors and shorter latencies of response in the object-rotation task, whereas subjects who did the object-rotation task first had little if any advantage in the viewer-rotation task. In other words, the results revealed an asymmetric learning transfer between tasks, which suggests that spatial representations are hierarchically organized. Specifically, the results indicate that the viewer-rotation task engaged allocentric representations and egocentric representations, whereas the object-rotation task engaged only egocentric representations.     

A Survey on Driving in Clients With Mental Health Disorders

Few studies have explored driving issues in adult mental health. In this pilot study, 48 drivers were compared to 24 participants who had ceased driving, on their clinical and driving characteristics. Driving-related services offered to them were also documented. Participants who had stopped driving were more likely to be in-patients on antipsychotic or several medications. A third of the participants reported negative effects of their illness and/or medications on driving. Psychiatrists and occupational therapists offered assessments and recommendations related to fitness to drive to 30% of their clients using complementary approaches. This survey indicates that few drivers with mental health disorders receive driving-related services. More evidence-based practice guidelines are needed.     

Knee muscle contributions to joint rotational stiffness

The purpose of this paper was to investigate total joint rotational stiffness (JRS) and relative muscle contributions to JRS with varying extensor moment demands. It was hypothesized that greater co-activation of the flexors at lower levels of moment would result in greater JRS, relative to moment demands. It was also hypothesized that the flexors would have greater relative JRS contributions at lower moment levels. Twelve male participants generated isometric extensor moments about the knee at varying intensities, during plateau and ramping (up and down) conditions. Electromyography was used to estimate individual muscle forces, which were used to calculate JRS about three orthogonal axes. Orthogonal trend analysis revealed a linear relationship (p<.001) between moment and JRS, about all axes. The vastus lateralis provided the greatest JRS about all axes. Of the flexors, the semimembranosis provided the most JRS about the flexion/extension (FE) and axial (AX) axes. However, while most muscle activity increased linearly, the gastrocnemious lateral (GL) had an interaction between condition and moment. Despite an extensor moment, the GL had minor contributions about the FE axis (1.2%), and it was postulated that this increase in activation was to stabilize about the VV axis, where its contribution was as high as 18.9%.     

Atypical Hemispheric Specialization in Intellectual Deficiency

In order to determine the relation between hemispheric specialization for language and intellectual deficiency, two groups of lower-IQ subjects were compared to normal-IQ controls on word-dichotic listening tasks. Two conditions in which stimuli differed by their level of phonological complexity were used. Normal controls showed the expected right-ear advantage in both conditions. Moreover, they showed a greater magnitude of ear difference on the condition requiring higher-order phonological processing. In the mentally deficient group, almost half the subjects exhibited a left-ear advantage and they showed no difference between the two conditions in terms of the magnitude of ear difference. These results point to the presence of atypical hemispheric specialization in mentally deficient subjects.     

Shades of disengagement: high school dropouts speak out

The purpose of this study was to describe how dropouts navigate their educational journeys. Eighty dropouts participated to individual interviews which were recorded and transcribed. The data analysis yielded three broad categories in answering the research question. Setting the stage in the family and the school, the dropouts described their teetering between in and out of school contexts and proceeded to explain how they ended their educational journey. For 20 dropouts, family turmoil represented a pervasive force negatively influencing their schooling. For 24 dropouts, problems in school set the stage for dropping out. Teetering represented juggling strategies to prolongand to sabotage the journey, while the end of the journey occurred as a result of a pivotal moment (48%) or a gradual fade out (52%) from the school context.

Risk and protective factors for urban African-American youth

The present study investigated risk and resilience processes in a sample of urban African-American youth. Risk and protective factors were assessed across ecological levels including individual, family and community. Both externalizing and internalizing symptomatology were included as measures of child adjustment. Youth and parental reports as well as various methods, such as the Experience Sampling Method, were used to capture the daily experiences of the adolescents from different perspectives. Poverty, hassles, and exposure to violence predicted higher rates of externalizing and internalizing symptoms. Individual and family protective variables emerged as powerful sources of resilience. An inner sense of confidence and helpful family support were associated with reductions in the deleterious effects of community poverty. Two main patterns, protective-stabilizing and overwhelming-risk, seemed to characterize most of the risk by protective factor interactions. The present findings are important for understanding the complex experiences of urban youth and furthering the literature on sources of risk and protection for African-Americans.     

Exploring the geometric and mechanical characteristics of the spine musculature to provide rotational stiffness to two spine joints in the neutral posture

Joint stiffness is inherently linked to both performance and injury. Muscular activation is the predominant provider of stiffness to the lumbar spine, and is essential to ensure optimal spine performance. The purpose of the current paper was to examine the potential of the trunk muscles to provide rotational joint stiffness at two spine joints in the neutral posture, and to demonstrate the sensitivity of this stiffening potential to various muscle orientation and stiffness assumptions. Two separate anatomical models were utilized to analyze the muscular contributions to the 3-dimensional rotational stiffness about each of the L1-L2 and L4-L5 spine joints. Total muscular stiffening potentials, for both joints in each anatomical model, were found to be highest about the global lateral bend axis, and lowest about the global axial twist axis. The stiffening potential was found to depend highly on both the assumed muscle stiffness coefficient (q value) and the moment arm of the muscle about the joint in question. Analyses of spine stiffness were found to be greatly affected by both the anatomical representation of the surrounding musculature and the selection of the q value in the determination of muscular stiffness. Inappropriate choices of either of these factors could lead to errors in stiffness and subsequently stability estimates, and in the interpretation and possible clinical recommendations stemming from such estimates.     

Contributions of the dorsal hippocampus and the dorsal subiculum to processing of idiothetic information and spatial memory

It is well established that the dorsal hippocampal formation is crucial for spatial memory in rats. However, little is known about the distinct functions of the dorsal hippocampus and the dorsal subiculum. To examine the role of the dorsal hippocampus and the dorsal subiculum, Long-Evans rats with excitotoxic lesions (NMDA) of the dorsal hippocampus (DH), the dorsal subiculum (DS), or both (DHDS), and controls were trained on a nonmatching-to-place task. Then, to identify the strategy used by each group, they were tested on the same task in the dark with the T-maze being rotated between the sample and the test runs. In the light, rats with combined lesions were impaired. In the dark, groups DH, DS, and controls performed near chance level except in trials without rotation, suggesting the use of a sense of direction. The same rats were trained on a radial-arm maze task. In the light, where proximal visual cues were accessible, combined lesions affected performance whereas in the dark, it was impaired by all lesions. This experiment demonstrated that the dorsal subiculum and the dorsal hippocampus play a crucial role in processing idiothetic information and/or in maintenance of this information in memory.     

Learning at the breast: preference formation for an artificial scent and its attraction against the odor of maternal milk

Human newborns are known to display spontaneous attraction to the odor of human milk. This study aimed to assess whether the positive response to human milk odor can be explained by nursing-related learning, and whether it can be easily reassigned to a novel odor associated with nursing. Infants were exposed or not to a novel odor (camomile, Ca) during nursing, and tested on day 3-4 for their preference for camomile in comparison with either a scentless control (Exp. 1), a scented control (Exp. 2), or maternal milk (Exp. 3). Prior experience with Ca modified the newborns' responses. While the Ca odor became more attractive than a scented control in the Ca-exposed group, the Ca-non-exposed group did not differentiate either stimulus. In Exp. 3, the Ca-non-exposed group preferred the milk odor to the Ca odor, whereas the Ca-exposed group displayed on average equal attraction to both stimuli. Thus, a novel odor can be learned at the breast, and gain similar attractive power than the odor of mother's milk. In sum, reinforcements related with the early episodes of breastfeeding mediate the rapid development of novel odor preferences in human infants.     

Subject-Verb Agreement in Children and Adults: Serial or Hierarchical Processing?

Two processes, serial and hierarchical, are generally opposed to account for grammatical encoding in language production. In a developmental perspective, the question addressed here is whether the subject-verb agreement during writing is computed serially, once the words are linearly ordered in the sentence, or hierarchically, as soon as the number features are determined in a hierarchical frame. Adults and children from 3rd to 5th grades were requested to listen to sentences with built-in prepositional phrases or relative clauses and to transcribe them as quickly as possible. A serial hypothesis assumes that subject-verb agreement errors should be equally frequent with both preambles because each has the same length separating the subject head noun and the main verb. Conversely, according to a hierarchical view, errors should be more frequent with a prepositional phrase because the syntactic distance between the subject and the verb is greater than with a relative clause. The results revealed a main effect of the preamble manipulated in 5th graders and adults, but not in 3rd graders. These data were in favor of a hierarchical processing in older writers and a serial one in younger children. However, in 3rd grade, we assumed that the potential serial account was a result of the resource constraint on writing more than of a real serial processing of the agreement.