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As one of major types of microplastics (MPs), microfibers (MFs) are widely found in the marine ecosystem and can induce diverse impacts on various marine organisms. Sedentary species, such as mussels, can act as bioindicators for monitoring marine contamination. Hence, in this study, we used mussels (Mytilus galloprovincialis) to examine the toxicity of polyethylene terephthalate (PET) MFs of 100 μm size at concentrations of 0.0005, 0.1, 1, 10, and 100 mg/L for 32 days. PET MFs accumulated only in the stomachs and intestines of the mussels and caused digestive tubule atrophy. After exposure to PET MFs, no alteration in the mortality rate, shell height, length, and weight of the mussels was observed. However, the gonadal index decreased with increasing concentrations of PET MFs. This is because PET MFs decrease the sex hormones estradiol and testosterone in mussels, even at environmentally relevant concentrations. Furthermore, chronic exposure to PET MFs increased the activities of antioxidant-related (catalase and superoxide dismutase) and neurotoxicity-related (acetylcholine esterase) enzymes in the digestive gland and gill tissues of mussels. In addition, cellular immune parameters of apoptosis and DNA damage were observed in mussel hemocytes. Thus, this study demonstrates the risks of MPs in real marine environments by assessing how long-term exposure to low concentrations of PET MFs can cause potential sublethal impacts and reproductive failure in mussels.

BACKGROUND Spatial navigation impairment is recognized as a potential marker of preclinical dementia. Virtual reality (VR) technology has been introduced as a promising framework for dementia research. Recent work has demonstrated further possibilities that integrating electroencephalography (EEG) sensors into VR headsets can provide invaluable information relevant to cognitive impairment. OBJECTIVE The aim of this study is to explore the feasibility of spatial navigation assessment in EEG-integrated VR devices for assessing cognitive impairment. This study will further investigate the neurophysiological characteristics of wearable EEG sensors during a VR spatial navigation game. METHODS Participants recruited for the study will be grouped into three based on their cognitive status (mild Alzheimer’s disease group, mild cognitive impairment group, and healthy controls). The spatial navigation game is designed based on the hidden goal task to assess egocentric and allocentric spatial information processing. As outcome measures, spatial navigation errors, spectral density characteristics of EEG signals, and behavioral responses in VR will be analyzed. RESULTS A spatial navigation game for VR was developed in March 2021. Recruitment commenced in June 2021. CONCLUSIONS The results of this study will provide a comprehensive understanding of VR-based spatial navigation assessment, in terms of cognitive measurement including early screening. If positive, our approach based on EEG-integrated VR devices could constitute an effective cognitive impairment screening test tool that can provide brain dynamic characteristics as well as information on spatial navigation deficits.