Jonathan G. Hakun

Do brain activation changes persist in athletes with a history of multiple concussions who are asymptomatic

Primary objective: To evaluate brain activation patterns of asymptomatic athletes with a history of two or more concussions. Research design: A paired case-control design was used to evaluate brain activation patterns during cognitive performance in 14 athletes with a history of two or more concussions and 14 age- and sex-matched controls with no previous concussion. Methods and procedures: Percentage Blood-Oxygen-Level-Dependent (BOLD) change during an N-back working memory task was assessed in all participants. Performance on the Trail-Making Test Form A and B, Symbol-Digit Modalities Test and the Immediate Post-concussion Assessment and Cognitive Test (ImPACT) was also compared between groups. Main results: As expected, brain regions activated during the performance of the N-back were equivalent between groups. The groups performed similarly on the neurocognitive measures. The history of concussion group was less accurate than controls on the 1-, 2- and 3-back conditions of the N-back. Conclusions: Following the complete resolution of symptoms, a history of two or more concussions is not associated with changes in regional brain activation during the performance of working memory task. Compensatory brain activation may only persist during the typically brief time athletes experience symptoms following concussion.

Cognitive control: Preparation of task switching components

Task performance often improves when tasks can be prepared in advance. However, the mechanisms that support advance preparation are highly debated. Proceeding under the hypothesis that switch-specific neural activation during advance preparation is the hallmark of controlled processing, this study investigates the behavioral and neural effects of component preparation during task-switching. Toward this end, fMRI was used to observe neural activity during preparation of response rules (RULE task) compared to preparation of stimulus set (PERCEPTUAL task). We predicted that switch-specific activation would be observed for RULE and PERCEPTUAL switching when component preparation was isolated from target-related activation. The results indicated that preparation for both tasks was supported by common regions of activation; however preparation for switches of response rule was supported by switch-specific activation of the anterior cingulate (ACC) and left lateral prefrontal cortex (LPFC). Shift-cost was also eradicated in this condition with enough preparation time, and was associated with an increase in ACC activation. Switches of stimulus set were not marked by specific neural activity during the preparation interval. While the amount of preparation time affected overall performance, PERCEPTUAL task switches did not benefit more from preparation time than task repeats. It was concluded that response rules can be reconfigured pre-target due to the support of ACC-LPFC activation, where preparation of stimulus sets is supported by a general type of configuration common to both components.

Functional specialization of the left ventral parietal cortex in working memory

The function of the ventral parietal cortex (VPC) is subject to much debate. Many studies suggest a lateralization of function in the VPC, with the left hemisphere facilitating verbal working memory and the right subserving stimulus-driven attention. However, many attentional tasks elicit activity in the VPC bilaterally. To elucidate the potential divides across the VPC in function, we assessed the pattern of activity in the VPC bilaterally across two tasks that require different demands, an oddball attentional task with low working memory demands and a working memory task. An anterior region of the VPC was bilaterally active during novel targets in the oddball task and during retrieval in WM, while more posterior regions of the VPC displayed dissociable functions in the left and right hemisphere, with the left being active during the encoding and retrieval of WM, but not during the oddball task and the right showing the reverse pattern. These results suggest that bilateral regions of the anterior VPC subserve non-mnemonic processes, such as stimulus-driven attention during WM retrieval and oddball detection. The left posterior VPC may be important for speech-related processing important for both working memory and perception, while the right hemisphere is more lateralized for attention.

Influence of Social Factors on Student Satisfaction Among College Students With Disabilities

A significant body of research on student retention reflects that social and environmental factors influence continued enrollment in postsecondary education and academic success. Yet, for students with disabilities, more emphasis is placed on accommodations, access, and support services without sufficient attention to the social aspect of the student experience. In this study, we investigated belonging as a primary contributor to student satisfaction and examined the degree to which other social factors modified this relationship among a sample of students with disabilities attending public, 4-year universities. A higher sense of belonging was associated with greater student satisfaction in our sample. Through multiple mediation modeling, we found that self-advocacy and perception of the campus climate toward students with disabilities independently modified the relationship between belonging and student satisfaction. These results have important implications for understanding the influence of belonging and student satisfaction, and supporting and retaining students with disabilities.

Dynamic range of frontoparietal functional modulation is associated with working memory capacity limitations in older adults

HIGHLIGHTSOlder adults with greater modulation range exhibited better in‐scanner performance.Frontoparietal functional modulation predicted psychometric working memory capacity.Modulation range decreased with age.Older adults with lower modulation range showed “CRUNCH”‐like pattern of activation. ABSTRACT Older adults tend to over‐activate regions throughout frontoparietal cortices and exhibit a reduced range of functional modulation during WM task performance compared to younger adults. While recent evidence suggests that reduced functional modulation is associated with poorer task performance, it remains unclear whether reduced range of modulation is indicative of general WM capacity‐limitations. In the current study, we examined whether the range of functional modulation observed over multiple levels of WM task difficulty (N‐Back) predicts in‐scanner task performance and out‐of‐scanner psychometric estimates of WM capacity. Within our sample (60–77 years of age), age was negatively associated with frontoparietal modulation range. Individuals with greater modulation range exhibited more accurate N‐Back performance. In addition, despite a lack of significant relationships between N‐Back and complex span task performance, range of frontoparietal modulation during the N‐Back significantly predicted domain‐general estimates of WM capacity. Consistent with previous cross‐sectional findings, older individuals with less modulation range exhibited greater activation at the lowest level of task difficulty but less activation at the highest levels of task difficulty. Our results are largely consistent with existing theories of neurocognitive aging (e.g. CRUNCH) but focus attention on dynamic range of functional modulation as a novel marker of WM capacity‐limitations in older adults.

Neural Mechanisms for the Benefits of Stimulus-Driven Attention

Abstract Stimulus‐driven attention can improve working memory (WM) when drawn to behaviorally relevant information, but the neural mechanisms underlying this effect are unclear. The present study used functional magnetic resonance imaging (fMRI) to test competing hypotheses regarding the nature of the benefits of stimulus‐driven attention to WM: that stimulus‐driven attention benefits WM directly via salience detection, that stimulus‐driven attention benefits WM incidentally via cognitive control mechanisms recruited to reduce interference from salient features, or that both mechanisms are co‐involved in enhancing WM for salient information. To test these hypotheses, we observed activation in brain regions associated with cognitive control and salience detection. We found 2 cognitive control regions that were associated with enhanced memory for salient stimuli: a region in the right superior parietal lobule and a region in the right inferior frontal junction. No regions associated with salience detection were found to show this effect. These fMRI results support the hypothesis that benefits to WM from stimulus‐driven attention occur primarily as a result of cognitive control and top‐down factors rather than pure bottom‐up aspects of stimulus‐driven attention.

Ventral fronto-parietal contributions to the disruption of visual working memory storage.

The ability to maintain information in visual working memory (VWM) in the presence of ongoing visual input allows for flexible goal-directed behavior. Previous evidence suggests that categorical overlap between visual distractors and the contents of VWM is associated with both the degree to which distractors disrupt VWM performance and activation among fronto-parietal regions of cortex. While within-category distractors have been shown to elicit a greater response in ventral fronto-parietal regions, to date, no study has linked distractor-evoked response of these regions to VWM performance costs. Here we examined the contributions of ventral fronto-parietal cortex to the disruption of VWM storage by manipulating memoranda-distractor similarity. Our results revealed that the degree of activation across cortex was graded in a manner suggesting that similarity between the contents of VWM and visual distractors influenced distractor processing. While abrupt visual onsets failed to engage ventral fronto-parietal regions during VWM maintenance, objects sharing categorical- (Related objects) and feature-overlap (Matched objects) with VWM elicited a significant response in the right TPJ and right AI. Of central relevance, the magnitude of activation in the right AI elicited by both types of distractor objects subsequently predicted costs to binding change detection accuracy. In addition, Related and Matched distractors differentially affected ventral-dorsal connectivity between the right AI and dorsal parietal regions, uniquely contributing to disruption of VWM storage. Together, our current results implicate activation of ventral fronto-parietal cortex in disruption of VWM storage, and disconnection between ventral frontal and dorsal parietal cortices as a mechanism to protect the contents of VWM.

Validating a Model of Psychological Capital in Vocational Rehabilitation Consumers

Background: Psychological Capital (PsyCap) is a prominent, well-established model of psychosocial strengths in the organizational positive psychology literature. PsyCap is a higher order construct consisting of hope, optimism, resilience, and self-efficacy that has been identified as a powerful predictor of work-related outcomes, with strong potential for application in vocational rehabilitation (VR). However, PysCap has not yet been validated for individuals with disabilities in rehabilitation settings. Objective: The purpose of this study was to explore the relevance of PsyCap for individuals with disabilities in VR. Methods: Confirmatory Factor Analysis was used to validate the structural model of PsyCap in a sample of adults with disabilities who have received public VR services (N= 229). Findings: VR client data supported the hypothesized factor structure of PsyCap. In an initial exploration of the relationship between PsyCap and employment status, individuals who reported employment had a higher mean PsyCap score than those reporting unemployment. Conclusions: These results highlight the potential utility of PsyCap for VR consumers. Additional research is needed to explore this construct as it pertains to VR services.