The Effects of Feature Type on Semantic Priming of Picture Naming in Normal Speakers

The aim of this study was to investigate the roles of features on conceptual activation.  A picture naming paradigm was employed to measure speech reaction time (SRT) during feature-to-concept activation.  Forty-seven older adults completed the priming task twice with an ISI of 200msec and 600msec. Results indicate that regardless of semantic category, distinctive feature primes resulted in the fastest SRT compared to shared features, combined distinctive and shared features, and neutral primes.  The results indicate that as stated in the Conceptual Structure Account (Tyler & Moss, 2001; Taylor et al., 2007) distinctive features have a privileged role in concept activation

Bayesian longitudinal tensor response regression for modeling neuroplasticity

A major interest in longitudinal neuroimaging studies involves investigating voxel-level neuroplasticity due to treatment and other factors across visits. However, traditional voxel-wise methods are beset with several pitfalls, which can compromise the accuracy of these approaches. We propose a novel Bayesian tensor response regression approach for longitudinal imaging data, which pools information across spatially-distributed voxels to infer significant changes while adjusting for covariates. The proposed method, which is implemented using Markov chain Monte Carlo (MCMC) sampling, utilizes low-rank decomposition to reduce dimensionality and preserve spatial configurations of voxels when estimating coefficients. It also enables feature selection via joint credible regions which respect the shape of the posterior distributions for more accurate inference. In addition to group level inferences, the method is able to infer individual-level neuroplasticity, allowing for examination of personalized disease or recovery trajectories. The advantages of the proposed approach in terms of prediction and feature selection over voxel-wise regression are highlighted via extensive simulation studies. Subsequently, we apply the approach to a longitudinal Aphasia dataset consisting of task functional MRI images from a group of subjects who were administered either a control intervention or intention treatment at baseline and were followed up over subsequent visits. Our analysis revealed that while the control therapy showed long-term increases in brain activity, the intention treatment produced predominantly short-term changes, both of which were concentrated in distinct localized regions. In contrast, the voxel-wise regression failed to detect any significant neuroplasticity after multiplicity adjustments, which is biologically implausible and implies lack of power.Comment: 28 pages, 8 figures, 6 table

Self-reported Physical Activity and Objective Aerobic Fitness: Differential Associations with Gray Matter Density in Healthy Aging

Aerobic fitness (AF) and self-reported physical activity (srPA) do not represent the same construct. However, many exercise and brain aging studies interchangeably use AF and srPA measures, which may be problematic with regards to how these metrics are associated with brain outcomes, such as morphology. If AF and PA measures captured the same phenomena, regional brain volumes associated with these measures should directly overlap. This study employed the general linear model to examine the differential association between objectively-measured AF (treadmill assessment) and srPA (questionnaire) with gray matter density (GMd) in 29 cognitively unimpaired community- dwelling older adults using voxel based morphometry. The results show significant regional variance in terms of GMd when comparing AF and srPA as predictors. Higher AF was associated with greater GMd in the cerebellum only, while srPA displayed positive associations with GMd in occipito-temporal, left perisylvian, and frontal regions after correcting for age. Importantly, only AF level, and not srPA, modified the relationship between age and GMd, such that higher levels of AF were associated with increased GMd in older age, while decreased GMd was seen in those with lower AF as a function of age. These results support existing literature suggesting that both AF and PA exert beneficial effects on GMd, but only AF served as a buffer against age-related GMd loss. Furthermore, these results highlight the need for use of objective PA measurement and comparability of tools across studies, since results vary dependent upon the measures used and whether these are objective or subjective in nature

Neural Signatures of Semantic and Phonemic Fluency in Young and Old Adults

As we age, our ability to select and produce words changes, yet we know little about the underlying neural substrate of word-finding difficulties in old adults. The present study was designed to elucidate changes in specific frontally mediated retrieval processes involved in word-finding difficulties associated with advanced age. We implemented two overt verbal (semantic and phonemic) fluency tasks during functional magnetic resonance imaging and compared brain activity patterns of old and young adults. Performance during the phonemic task was comparable for both age-groups and mirrored by strongly left lateralized (frontal) activity patterns. On the other hand, a significant drop of performance during the semantic task in the older goup was accompanied by additional right (inferior and middle) frontal activity, which was negatively correlated with performance. Moreover, the younger group recruited different subportions of the left inferior frontal gyrus for both fluency tasks, while the older participants failed to show this distinction. Thus, functional integrity and efficient recruitment of left frontal language areas seems to be critical for successful word-retrieval in old age

Multi-modal Treatment of Phonological Alexia: Behavioral and Pilot fMRI Outcomes

Post-stroke phonological alexia is characterized by impaired reading of pseudowords, with relatively intact reading or orthographically irregular words. We conducted a single-subject repeated-probe research study of a multi-modal treatment of phonological processing and reading skills in five adults with phonological alexia. Based on the phonological deficit hypothesis, treatment tasks involved training written and verbal phonological skills. Visual inspection of repeated-probe graphs and standardized test scores provided evidence of improved phonological processing and real word reading skills for only some participants. One participant’s Pilot fMRI of overt pseudoword reading and pseudoword repeating exhibited perilesional and right-hemisphere neural reorganization

Aging, Aerobic Activity and Interhemispheric Communication

Recent studies have shown that during unimanual motor tasks, aging adults show bilateral recruitment of primary motor cortex (M1), while younger adults show a suppression of the ipsilateral motor cortex. Additional work has indicated that increased bilateral M1 recruitment in older adults may be deleterious when performing some motor tasks. However, higher levels of physical fitness are associated with improved dexterity and fitness may mitigate the loss of both inhibitory and excitatory communication in aging adults. The goal of this study was to assess dexterity and interhemispheric motor communication in physically fit and sedentary middle-age (40–60 years) right handed participants using tests of hand deftness and transcranial magnetic stimulation (TMS). To behaviorally assess the influence of interhemispheric communication on motor performance, participants also perform the coin rotation deftness task while maintaining pinch force with the opposite hand (bimanual condition). We correlated these behavioral measures with the ipsilateral silent period using TMS to assess interhemispheric inhibition. Our results show that the middle-aged adults who were physically fit had better dexterity of their right hand (finger tapping and peg-board). When performing the coin rotation task the fit group had no between hand differences, but the sedentary group’s left hand performance was inferior to the their right hand. We found that better dexterity correlated with ipsilateral silent period duration (greater inhibition) thereby supporting the postulate that fitness improves interhemispheric motor communication

Effects of a 12-Week Aerobic Spin Intervention on Resting State Networks in Previously Sedentary Older Adults

Objective: We have previously demonstrated that aerobic exercise improves upper extremity motor function concurrent with changes in motor cortical activity using task-based functional magnetic resonance imaging (fMRI). However, it is currently unknown how a 12-week aerobic exercise intervention affects resting-state functional connectivity (rsFC) in motor networks. Previous work has shown that over a 6-month or 1-year exercise intervention, older individuals show increased resting state connectivity of the default mode network and the sensorimotor network (Voss et al., 2010b; Flodin et al., 2017). However, the effects of shorter-term 12-week exercise interventions on functional connectivity have received less attention.Method: Thirty-seven sedentary right-handed older adults were randomized to either a 12-week aerobic, spin cycling exercise group or a 12-week balance-toning exercise group. Resting state functional magnetic resonance images were acquired in sessions PRE/POST interventions. We applied seed-based correlation analysis to left and right primary motor cortices (L-M1 and R-M1) and anterior default mode network (aDMN) to test changes in rsFC between groups after the intervention. In addition, we performed a regression analysis predicting connectivity changes PRE/POST intervention across all participants as a function of time spent in aerobic training zone regardless of group assignment.Results: Seeding from L-M1, we found that participants in the cycling group had a greater PRE/POST change in rsFC in aDMN as compared to the balance group. When accounting for time in aerobic HR zone, we found increased heart rate workload was positively associated with increased change of rsFC between motor networks and aDMN. Interestingly, L-M1 to aDMN connectivity changes were also related to motor behavior changes in both groups. Respective of M1 laterality, comparisons of all participants from PRE to POST showed a reduction in the extent of bilateral M1 connectivity after the interventions with increased connectivity in dominant M1.Conclusion: A 12-week physical activity intervention can change rsFC between primary motor regions and default mode network areas, which may be associated with improved motor performance. The decrease in connectivity between L-M1 and R-M1 post-intervention may represent a functional consolidation to the dominant M1.Topic Areas: Neuroimaging, Aging

Work-worlds colliding: Self-reflexivity, power and emotion in organizational ethnography

While organizational ethnographers have embraced the concept of self-reflexivity, problems remain. In this article we argue that the prevalent assumption that self-reflexivity is the sole responsibility of the individual researcher limits its scope for understanding organizations. To address this, we propose an innovative method of collective reflection that is inspired by ideas from cultural and feminist anthropology. The value of this method is illustrated through an analysis of two ethnographic case studies, involving a ‘pair interview’ method. This collective approach surfaced self-reflexive accounts, in which aspects of the research encounter that still tend to be downplayed within organizational ethnographies, including emotion, intersubjectivity and the operation of power dynamics, were allowed to emerge. The approach also facilitated a second contribution through the conceptualization of organizational ethnography as a unique endeavour that represents a collision between one ‘world of work’: the university, with a second: the researched organization. We find that this ‘collision’ exacerbates the emotionality of ethnographic research, highlighting the refusal of ‘researched’ organizations to be domesticated by the specific norms of academia. Our article concludes by drawing out implications for the practice of self-reflexivity within organizational ethnography