Mental rotation of sequentially presented 3D figures: sex and sex hormones related differences in behavioural and ERP measures

[Effects of transcranial direct current stimulation on event-related potentials of mental rotation]

There are few researches on the modulation effect of transcranial direct current stimulation(tDCS) on complex spatial cognition. Especially, the influence of tDCS on the neural electrophysiological response in spatial cognition is not yet clear. This study selected the classic spatial cognition task paradigm (three-dimensional mental rotation task) as the research object. By comparing the changes in behavior and event-related potentials in different modes of tDCS before, during and after the application of tDCS, this study analyzed the behavioral and neurophysiological effects of tDCS on mental rotation. The comparison between active-tDCS and sham-tDCS showed no statistically significant difference in behavior between different stimulation modes. Still, the changes in the amplitudes of P2 and P3 during the stimulation were statistically significant. Compared with sham-tDCS, the amplitudes of P2 and P3 in active-tDCS mode showed a greater decrease during the stimulation. This study clarifies the influence of tDCS on the event-related potentials of the mental rotation task. It shows that tDCS may improve the brain information processing efficiency during the mental rotation task. Also, this study provides a reference for an in-depth understanding and exploration of the modulation effect of tDCS on complex spatial cognition.

Eye movement characteristics in a mental rotation task presented in virtual reality

Introduction

Eye-tracking technology provides a reliable and cost-effective approach to characterize mental representation according to specific patterns. Mental rotation tasks, referring to the mental representation and transformation of visual information, have been widely used to examine visuospatial ability. In these tasks, participants visually perceive three-dimensional (3D) objects and mentally rotate them until they identify whether the paired objects are identical or mirrored. In most studies, 3D objects are presented using two-dimensional (2D) images on a computer screen. Currently, visual neuroscience tends to investigate visual behavior responding to naturalistic stimuli rather than image stimuli. Virtual reality (VR) is an emerging technology used to provide naturalistic stimuli, allowing the investigation of behavioral features in an immersive environment similar to the real world. However, mental rotation tasks using 3D objects in immersive VR have been rarely reported.

Methods

Here, we designed a VR mental rotation task using 3D stimuli presented in a head-mounted display (HMD). An eye tracker incorporated into the HMD was used to examine eye movement characteristics during the task synchronically. The stimuli were virtual paired objects oriented at specific angular disparities (0, 60, 120, and 180°). We recruited thirty-three participants who were required to determine whether the paired 3D objects were identical or mirrored.

Results

Behavioral results demonstrated that the response times when comparing mirrored objects were longer than identical objects. Eye-movement results showed that the percent fixation time, the number of within-object fixations, and the number of saccades for the mirrored objects were significantly lower than that for the identical objects, providing further explanations for the behavioral results.

Discussion

In the present work, we examined behavioral and eye movement characteristics during a VR mental rotation task using 3D stimuli. Significant differences were observed in response times and eye movement metrics between identical and mirrored objects. The eye movement data provided further explanation for the behavioral results in the VR mental rotation task.

Does mental rotation emulate motor processes? An electrophysiological study of objects and body parts

Several arguments suggest that motor planning may share embodied neural mechanisms with mental rotation (MR). However, it is not well established whether this overlap occurs regardless of the type of stimulus that is manipulated, in particular manipulable or non-manipulable objects and body parts. We here used high-density electroencephalography (EEG) to examine the cognitive similarity between MR of objects that do not afford specific hand actions (chairs) and bodily stimuli (hands). Participants had identical response options for both types of stimuli, and they gave responses orally in order to prevent possible interference with motor imagery. MR of hands and chairs generated very similar behavioral responses, time-courses and neural sources of evoked-response potentials (ERPs). ERP segmentation analysis revealed distinct time windows during which differential effects of stimulus type and angular disparity were observed. An early period (90-160 ms) differentiated only between stimulus types, and was associated with occipito-temporal activity. A later period (290-330 ms) revealed strong effects of angular disparity, associated with electrical sources in the right angular gyrus and primary motor/somatosensory cortex. These data suggest that spatial transformation processes and motor planning are recruited simultaneously, supporting the involvement of motor emulation processes in MR.

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.

The Link Between Masculinity and Spatial Skills Is Moderated by the Estrogenic and Progestational Activity of Oral Contraceptives

Conversations about gender and spatial skills frequently dissolve into a hackneyed debate over nature and nurture. This is particularly true for conversations concerning three-dimensional (3D) mental rotations skill, which shows the largest gender difference of all aspects of cognition, with men-on average-outperforming women. To advance this empirical area of inquiry, biopsychosocial influences on spatial skills should be considered, and a unique opportunity do to that is provided by combined oral contraceptives (OCs). OCs with relatively low estradiol doses and with highly androgenic progestins have been positively related to spatial skills. Gender self-concepts, including masculine and feminine self-perceptions, have also been positively related to spatial skills. It is wholly unknown, however, whether the exogenous sex hormones contained in OCs moderate the link between self-perceived masculinity and 3D mental rotations. This study filled that knowledge gap by utilizing a sample of 141 naturally cycling (NC) women and 229 OC users who completed a computerized survey and cognitive tests. A series of moderation analyses examined whether the link between masculinity and 3D mental rotations depended on pill use or on the estrogenic, progestational, or androgenic activity in OCs, which were operationalized using a novel coding scheme. Results showed that the positive masculinity-3D mental rotations link was only present for NC women, presumably because it was altered by the exogenous hormones in OCs. Indeed, the link was accentuated in users of OCs with relatively low estrogenic and high progestational activity. Future research on menstrual cycle and pill phase is needed, but these findings importantly delineate ways in which biological and psychosocial factors combine to explain variation in spatial skills among women. They also suggest that focus should be placed on the under-investigated progestational activity of OCs, which is facilitated by the novel quantification of OC action used in this study. Thus, this research increases understanding of the neurocognitive and behavioral correlates of ovarian hormones and has implications for the betterment of women's health.

Relationships between ovarian hormone concentrations and mental rotations performance in naturally-cycling women

Circulating gonadal hormones have been linked to variation in the structure and function of the adult human brain, raising the question of how cognition is affected by sex hormones in adulthood. The impacts of progestogens and estrogens are of special interest due to the widespread use of hormone supplementation. Multiple studies have analyzed relationships between ovarian hormones and mental rotation performance, one of the largest known cognitive sex differences; however, results are conflicting. These discrepancies are likely due in part to modest sample sizes and reliance on self-report measures to assess menstrual cycle phase. The present study aimed to clarify the impact of progestogens and estrogens on visuospatial cognition by relating mental rotation task performance to salivary hormone concentrations. Across two studies totaling 528 naturally-cycling premenopausal women, an internal meta-analysis suggested a small, positive effect of within-subjects changes in progesterone on MRT performance (estimate = 0.44, p = 0.014), though this result should be interpreted with caution given multiple statistical analyses. Between-subjects differences and within-subject changes in estradiol did not significantly predict MRT. These results shed light on the potential cognitive effects of endogenous and exogenous hormone action, and the proximate mechanisms modulating spatial cognition.