FMRI to probe sex-related differences in brain function with multitasking

Acute exercise has specific effects on the formation process and pathway of visual perception in healthy young men

Visual perception is formed over time through the formation process and visual pathway. Exercise improves visual perception, but it is unclear whether exercise modulates nonspecifically or specifically the formation process and pathway of visual perception. Healthy young men performed the visual detection task in a backward masking paradigm before and during cycling exercise at a mild intensity or rest (control). The task presented gratings of a circular patch (target) and annulus (mask) arranged concentrically as a visual stimulus and asked if the presence and striped pattern (feature) of the target were detected. The relationship between the orientations of the gratings of the target and the mask included iso-orientation and orthogonal orientation to investigate the orientation selectivity of the masking effect. The masking effect was evaluated by perceptual suppressive index (PSI). Exercise improved feature detection (∆PSI; Exercise: -20.6%, Control: 1.7%) but not presence detection (∆PSI; Exercise: 8.9%, Control: 29.6%) compared to the control condition, and the improving effect resulted from the attenuation of the non-orientation-selective (∆PSI; Exercise: -29.0%, Control: 16.8%) but not orientation-selective masking effect (∆PSI; Exercise: -3.1%, Control: 11.7%). These results suggest that exercise affects the formation process of the perceptual feature of the target stimulus by suppressively modulating the neural networks responsible for the non-orientation-selective surround interaction in the subcortical visual pathways, whose effects are inherited by the cortical visual pathways necessary for perceptual image formation. In conclusion, our findings suggest that acute exercise improves visual perception transiently through the modulation of a specific formation process of visual processing.

Delay eyeblink conditioning performance and brain-wide c-Fos expression in male and female mice

Delay eyeblink conditioning has been extensively used to study associative learning and the cerebellar circuits underlying this task have been largely identified. However, there is a little knowledge on how factors such as strain, sex and innate behaviour influence performance during this type of learning. In this study, we used male and female mice of C57BL/6J (B6) and B6CBAF1 strains to investigate the effect of sex, strain and locomotion in delay eyeblink conditioning. We performed a short and a long delay eyeblink conditioning paradigm and used a c-Fos immunostaining approach to explore the involvement of different brain areas in this task. We found that both B6 and B6CBAF1 females reach higher learning scores compared to males in the initial stages of learning. This sex-dependent difference was no longer present as the learning progressed. Moreover, we found a strong positive correlation between learning scores and voluntary locomotion irrespective of the training duration. c-Fos immunostainings after the short paradigm showed positive correlations between c-Fos expression and learning scores in the cerebellar cortex and brainstem, as well as previously unreported areas. By contrast, after the long paradigm, c-Fos expression was only significantly elevated in the brainstem. Taken together, we show that differences in voluntary locomotion and activity across brain areas correlate with performance in delay eyeblink conditioning across strains and sexes.

Sex Differences in Cognition Across Aging

Sex and gender differences are seen in cognitive disturbances in a variety of neurological and psychiatry diseases. Men are more likely to have cognitive symptoms in schizophrenia whereas women are more likely to have more severe cognitive symptoms with major depressive disorder and Alzheimer's disease. Thus, it is important to understand sex and gender differences in underlying cognitive abilities with and without disease. Sex differences are noted in performance across various cognitive domains - with males typically outperforming females in spatial tasks and females typically outperforming males in verbal tasks. Furthermore, there are striking sex differences in brain networks that are activated during cognitive tasks and in learning strategies. Although rarely studied, there are also sex differences in the trajectory of cognitive aging. It is important to pay attention to these sex differences as they inform researchers of potential differences in resilience to age-related cognitive decline and underlying mechanisms for both healthy and pathological cognitive aging, depending on sex. We review literature on the progressive neurodegenerative disorder, Alzheimer's disease, as an example of pathological cognitive aging in which human females show greater lifetime risk, neuropathology, and cognitive impairment, compared to human males. Not surprisingly, the relationships between sex and cognition, cognitive aging, and Alzheimer's disease are nuanced and multifaceted. As such, this chapter will end with a discussion of lifestyle factors, like education and diet, as modifiable factors that can alter cognitive aging by sex. Understanding how cognition changes across age and contributing factors, like sex differences, will be essential to improving care for older adults.

Dump the "dimorphism": Comprehensive synthesis of human brain studies reveals few male-female differences beyond size

With the explosion of neuroimaging, differences between male and female brains have been exhaustively analyzed. Here we synthesize three decades of human MRI and postmortem data, emphasizing meta-analyses and other large studies, which collectively reveal few reliable sex/gender differences and a history of unreplicated claims. Males' brains are larger than females' from birth, stabilizing around 11 % in adults. This size difference accounts for other reproducible findings: higher white/gray matter ratio, intra- versus interhemispheric connectivity, and regional cortical and subcortical volumes in males. But when structural and lateralization differences are present independent of size, sex/gender explains only about 1% of total variance. Connectome differences and multivariate sex/gender prediction are largely based on brain size, and perform poorly across diverse populations. Task-based fMRI has especially failed to find reproducible activation differences between men and women in verbal, spatial or emotion processing due to high rates of false discovery. Overall, male/female brain differences appear trivial and population-specific. The human brain is not "sexually dimorphic."

Dual-Task Effect on Gait in Healthy Adolescents: Association between Health-Related Indicators and DT Performance

The purpose of this study was to determine how dual-task (DT) effect on gait differs among adolescents with different fitness and health profiles. The gait performances of 365 adolescents aged 13-14 years were assessed at single and DT walking. The proportional changes in gait parameters from single to dual were regressed against gender, body mass index (BMIz), three components of MABC-2 (balance, aiming &catching and manual dexterity), group (high vs low motor competence), body strength, physical fitness level using multiple regression analyses; and gender and four items of balance subtest of MABC-2 in the secondary analysis. The analyses showed that being female was associated with greater reduction in gait speed and stride length and an increase in double support time and step time; and having lower score in balance was related to greater reduction in gait speed, and cadence, and an increase in step time. Only zig-zag hopping item of the balance subtest was associated with DT effect on gait speed and stride length. No significant relationships were found between DT effect on gait and the rest of the predictors. Females and adolescents with lower level of balance function may be at higher risk of having DT deficit during walking.

A systematic review and meta-analysis of behavioural sex differences in executive control

Literature investigating whether an individuals' sex affects their executive control abilities and performance on cognitive tasks in a normative population has been contradictory and inconclusive. Using meta-analytic procedures (abiding by PRISMA guidelines), this study attempts to identify the magnitude of behavioural sex differences in three prominent executive control domains of cognitive set-shifting, performance monitoring, and response inhibition. PubMed, Web of Science, and Scopus were systematically searched. Across 46 included studies, a total of 1988 females and 1884 males were included in the analysis. Overall, males and females did not differ on performance in any of the three domains of performance monitoring, response inhibition, or cognitive set-shifting. Task-specific sex differences were observed in the domains of performance monitoring, in the CANTAB Spatial Working Memory task-males scored statistically higher than females (Hedges' g = -0.60), and response inhibition, in the Delay Discounting task-females scored statistically higher than males (Hedges' g = 0.64). While the meta-analysis did not detect overall behavioural sex differences in executive control, significant heterogeneity and task-specific sex differences were found. To further understand sex differences within these specific tasks and domains, future research must better control for age and sex hormone levels.

Putting a stereotype to the test: The case of gender differences in multitasking costs in task-switching and dual-task situations

According to a popular stereotype, women are better at multitasking than men, but empirical evidence for gender differences in multitasking performance is mixed. Previous work has focused on specific aspects of multitasking or has not considered gender differences in abilities contributing to multitasking performance. We therefore tested gender differences (N = 96, 50% female) in sequential (i.e., task switching) and concurrent (i.e., dual tasking) multitasking, while controlling for possible gender differences in working memory, processing speed, spatial abilities, and fluid intelligence. Applying two standard experimental paradigms allowed us to test multitasking abilities across five different empirical indices (i.e., performance costs) for both reaction time (RT) and accuracy measures, respectively. Multitasking resulted in substantial performance costs across all experimental conditions without a single significant gender difference in any of these ten measures, even when controlling for gender differences in underlying cognitive abilities. Thus, our results do not confirm the widespread stereotype that women are better at multitasking than men at least in the popular sequential and concurrent multitasking settings used in the present study.

Monitoring Multiple Deadlines Relies on Spatial Processing in Posterior Parietal Cortex

Proactively coordinating one's actions is an important aspect of multitasking performance due to overlapping task sequences. In this study, we used fMRI to investigate neural mechanisms underlying monitoring of multiple overlapping task sequences. We tested the hypothesis that temporal control demands in multiple-task monitoring are offloaded onto spatial processes by representing patterns of temporal deadlines in spatial terms. Results showed that increased demands on time monitoring (i.e., responding to concurrent deadlines of one to four component tasks) increasingly activated regions in the left inferior parietal lobe and the precuneus. Moreover, independent measures of spatial abilities correlated with multiple-task performance beyond the contribution of working memory. Together, these findings suggest that monitoring and coordination of temporally overlapping task timelines rely on cortical processes involved in spatial information processing. We suggest that the precuneus is involved in tracking of multiple task timelines, whereas the inferior parietal lobe constructs spatial representations of the temporal relations of these overlapping timelines. These findings are consistent with the spatial offloading hypothesis and add new insights into the neurocognitive mechanisms underlying the coordination of multiple tasks.

No sex difference in an everyday multitasking paradigm

According to popular beliefs and anecdotes, females best males when handling multiple tasks at the same time. However, there is relatively little empirical evidence as to whether there truly is a sex difference in multitasking and the few available studies yield inconsistent findings. We present data from a paradigm that was specifically designed to test multitasking abilities in an everyday scenario, the computerized meeting preparation task (CMPT), which requires participants to prepare a room for a meeting and handling various tasks and distractors in the process. Eighty-two males and 66 females with a wide age range (18–60 years) and a wide educational background completed the CMPT. Results revealed that none of the multitasking measures (accuracy, total time, total distance covered by the avatar, a prospective memory score, and a distractor management score) showed any sex differences. All effect sizes were d ≤ 0.18 and thus not even considered “small” by conventional standards. The findings are in line with other studies that found no or only small gender differences in everyday multitasking abilities. However, there is still too little data available to conclude if, and in which multitasking paradigms, gender differences arise.