Sex differences in lateralization of attention functions

Performance on two lateralized attention tasks, a unique, modified version of the Stroop task, and the Lateralized Attention Network Task, was investigated to add evidence to the topic of lateralized hemispheric strengths and weaknesses between the sexes. Sixty total participants at a mid-sized public university completed both tasks to obtain research credit for their classes. Results concluded that there were no significant differences between the sex of the participant and visual field in their efficiency in responding to the three metrics of the Lateralized Attention Network Task. Individual analysis of the six cue types showed some interactions between sex and visual field on response accuracy however, generally the results were not significant. Stroop task data analysis yielded no significant differences between sex and visual field in either Stroop effect or response accuracy. Overall, results were not consistent with our hypotheses. There was, however, a noticeable trend that males were likely to be more efficient at responding to the tasks when the stimuli were presented in the left visual field, as well as that women tended to perform more efficiently when the stimuli was presented in the right visual field. Although not a significant finding, the trend does add further evidence to the current belief that men respond better to items lateralized to the right hemisphere and that women respond better to items lateralized to the left hemisphere

Testing the Darwinian function of lateralization:Does separation of workload between brain hemispheres increase cognitive performance?

Brain lateralization is a fundamental aspect of the organization of brain and behavior in the animal kingdom, begging the question about its Darwinian function. We tested the possibility that lateralization enhances cognitive performance in single- and dual-tasks. Previous studies reported mixed results on this topic and only a handful of studies have measured functional brain lateralization and performance independently and simultaneously. We therefore examined a possible positive effect of the strength and direction of lateralization on two demanding cognitive tasks: A visuospatial task (mental rotation MR), and a language task (word generation WG), executed either as a singletask or as dual-task. Participants (n = 72) performed these tasks while their single-task brain lateralization was assessed with functional Transcranial Doppler for both tasks. From these measurements we determined strength and direction of lateralization for both tasks and the individual pattern of lateralization (contralateral or ipsilateral) was derived. These factors, along with sex, were used in a GLM analysis to determine if they predicted the respective performance measure of the tasks. We found that for MR there was a significant medium effect of direction of lateralization on performance with better performance in left-lateralized (atypical) participants (partial eta squared 0.061; p = .039). After correction for outliers, there was a significant effect for strength (p = .049). For the dual-task, there was a significant positive medium effect of strength of lateralization on performance (partial eta squared 0.062; p = .038, respectively) No other association between direction or strength in either tests were found. We conclude that there is no evidence for hemispheric crowding, and that strength of lateralization may be a factor that contributes to the evolutionary selection of functional brain lateralization. Pattern of lateralization does not, explaining the large inter-individual variation in these traits

Baked and Buzzed: Investigating the Influence of Co-Use of Cannabis and Alcohol on White Matter Integrity in Emerging Adults

Objective: Growing evidence suggests alcohol and cannabis use independently alter neural structure and functioning, particularly during sensitive developmental time periods such as adolescence and emerging adulthood. However, there has been minimal investigation into the effects co-occurring use of these two substances, despite preliminary evidence of unique acute and psychopharmacological changes due to using alcohol and cannabis together. Method: Data drawn from the IDEAA Consortium was utilized to assess white matter integrity as measured by FreeSurfer’s TRACULA in emerging adults (n=192; 16-27 years old). Timeline Follow-Back was used to calculate past month cannabis use, alcohol use, co-use days, binge alcohol episode, and co-use-binge days. The Stroop task was administered and normed scores were used. Multiple regressions investigated white matter integrity by past month cannabis, alcohol, and co-use days, controlling for appropriate covariates (e.g., site, gender, education, length of abstinence). Analyses were run twice, once with alcohol as measured in standard units and once with binge episodes. Follow-up brain-behavior analyses assessed whether substance use or tracts that differed significantly by substance use then related to Stroop performance. Correction for multiple comparisons was conducted using Benjamini and Hochberg’s (1995) False Discovery Rate correction method. Results: Corrected for multiple comparisons, cannabis use was significantly related to increased mean diffusivity in 12 fronto-limbic and fronto-parietal tracts. Cannabis use also associated with poorer performance on Stroop word reading. Within the MJ+ALC group, increased mean diffusivity associated with better Stroop interference performance. Discussion: The present study found cannabis use was associated with decreased white matter integrity, as measured by mean diffusivity, across fronto-parietal and fronto-limbic tracts. These results suggest a robust relationship between cannabis use and white matter integrity in this neurodevelopmentally sensitive time period. Despite our hypotheses, co-use, alcohol use, and binge drinking did not significantly predict any measures. Future research should further investigate the potential independent and interactive affects of these substances on preclinical and clinical levels. Efforts should be made to inform the public of the likely negative impact of cannabis on white matter quality

Neurophysiological Investigation of the Functional Interactions between Manual Action Control and Working Memory

Gündüz Can R. Neurophysiological Investigation of the Functional Interactions between Manual Action Control and Working Memory. Bielefeld: Universität Bielefeld; 2020

Causal role of the posterior parietal cortex for two-digit mental subtraction and addition: A repetitive TMS study

Although parietal areas of the left hemisphere are known to be involved in simple mental calculation, the possible role of the homologue areas of the right hemisphere in mental complex calculation remains debated. In the present study, we tested the causal role of the posterior parietal cortex of both hemispheres in two-digit mental addition and subtraction by means of neuronavigated repetitive TMS (rTMS), investigating possible hemispheric asymmetries in specific parietal areas. In particular, we performed two rTMS experiments, which differed only for the target sites stimulated, on independent samples of participants. rTMS was delivered over the horizontal and ventral portions of the intraparietal sulcus (HIPS and VIPS, respectively) of each hemisphere in Experiment 1, and over the angular and supramarginal gyri (ANG and SMG, respectively) of each hemisphere in Experiment 2. First, we found that each cerebral area of the posterior parietal cortex is involved to some degree in the two-digit addition and subtraction. Second, in Experiment 1, we found a stronger pattern of hemispheric asymmetry for the involvement of HIPS in addition compared to subtraction. In particular, results showed a greater involvement of the right HIPS than the left one for addition. Moreover, we found less asymmetry for the VIPS. Taken together, these results suggest that two-digit mental addition is more strongly associated with the use of a spatial mapping compared to subtraction. In support of this view, in Experiment 2, a greater role of left and right ANG was found for addition needed in verbal processing of numbers and in visuospatial attention processes, respectively. We also revealed a greater involvement of the bilateral SMG in two-digit mental subtraction, in response to greater working memory load required to solve this latter operation compared to addition

Functional asymmetries in human working memory

Thesis (Ph.D.)--Boston UniversityWorking memory is the cognitive ability to maintain and manipulate information in mind to guide behavior. This relies on the coordinated activity of a bilateral brain network, which has been modeled as a central executive in control of separate storage systems for verbal and spatial information. Evidence from human and nonhuman primate research demonstrates that the dorsolateral prefrontal cortex (dlPFC) is critical for manipulating information in working memory. However, whether the dlPFC is dissociable by the domain of information remains unsettled. Recent human studies using repetitive transcranial magnetic stimulation (rTMS) suggest the left and right dlPFC may play separable roles in manipulating verbal and spatial information. In the present study, this theory was investigated further with two experiments on healthy right-handed adults. Both experiments utilized the 3-back task of visual working memory with letters and locations serving as verbal and spatial stimuli, respectively. In Experiment 1, tasks were administered during functional neuroimaging in two formats: one using centrally-presented single letters as verbal stimuli, and dots in different locations as spatial stimuli; and another using single letters in different locations for both verbal and spatial tasks. At the whole-brain group-level, letter- and location-specific contrasts did not differ between formats, indicating verbal/spatial differences reflected discrete subsystems in working memory and not simply separate perceptual processing. Nevertheless, in the dlPFC, bilateral activity was observed across versions, suggesting its contributions to working memory are domain-independent. Experiment 2 tested whether this relationship was causal by assessing 3-back performance after applying low-frequency rTMS to the dlPFC. Following rTMS of the right dlPFC, accuracy improved on the letter task, but worsened on the location task, while the opposite was observed after left rTMS. These double-dissociations suggest left and right dlPFC operate as competing subsystems for manipulating verbal and spatial information, respectively. Thus, the observation of equivalent bilateral dlPFC activity during the letter and location tasks might reflect a left-lateralized system for verbally-encoded information and a right-lateralized system for nonverbal representations operating in parallel on all stimuli. Such a functional asymmetry would have implications for therapies aimed at ameliorating working memory impairments in disease and even normal aging

Multi-Level Characterization of Exercise Effects on Depression: Effects on Depressive Symptoms, Cognitive Function, and Brain Health

Exercise has been established an effective treatment for depression, both as an independent treatment and as an augmentation to standard first-line treatments (e.g., medication, psychotherapy). Further, the benefits of exercise for depression have been demonstrated across age groups (i.e., older and younger adults) and in those with clinical and subclinical levels of depressive symptoms. However, the neural mechanisms underlying the antidepressant effects of exercise have only been examined in two studies with significant limitations. To address this critical gap in the literature, this dissertation leveraged data from two randomized pilot intervention studies to characterize the effects of exercise on depression across clinical, cognitive, and brain-based outcomes. To optimally translate exercise treatments to real-world settings, its efficacy in various depressed subgroups was explored, including younger (20-39 years) and older adults (60-79 years) with Major Depression, and older adults with subclinical depressive symptoms and mild cognitive impairment (MCI). Briefly, in study 1, exercise as an augmentation to medication treatment for Major Depression resulted in more rapid and stable decline in depressive symptoms, improvement in cognitive performance in younger but not older adults, and increased hippocampal-default mode network connectivity relative to medication treatment alone. Further, in regions showing reductions in cortical thickness with greater depression severity, intervention-related improvement in aerobic fitness was marginally associated with an increase in regional cortical thickness. In study 2, exercise as an augmentation to psychotherapy for older adults with subclinical depression and MCI was not effective due to suboptimal implementation of the intervention. However, results revealed greater engagement in moderate-to-vigorous physical activity and greater stability of rest-activity patterns prior to the intervention was predictive of greater improvement in cognitive performance and resulted in greater reduction in depressive symptoms over the course of the intervention, respectively. Overarching conclusions from these pilot studies highlight the utility of exercise-based interventions for alleviating clinical and subclinical levels of depression and cognitive decline, possibly via protective effects on neural pathways sensitive to the deleterious effects of depression and cognitive impairment

Enhancing allocentric spatial recall in pre-schoolers through navigational training programme

Unlike for other abilities, children do not receive systematic spatial orientation training at school, even though navigational training during adulthood improves spatial skills. We investigated whether navigational training programme (NTP) improved spatial orientation skills in pre-schoolers. We administered 12-week NTP to seventeen 4- to 5-year-old children (training group, TG). The TG children and 17 age-matched children (control group, CG) who underwent standard didactics were tested twice before (T0) and after (T1) the NTP using tasks that tap into landmark, route and survey representations. We determined that the TG participants significantly improved their performances in the most demanding navigational task, which is the task that taps into survey representation. This improvement was significantly higher than that observed in the CG, suggesting that NTP fostered the acquisition of survey representation. Such representation is typically achieved by age seven. This finding suggests that NTP improves performance on higher-level navigational tasks in pre-schooler