The purpose of this study is to examine the acute effect of being choked during partnered sex on neurological measures. The study is designed to identify the effects being choked during partnered sex on the brain through the use of neural-injury blood biomarkers, functional, diffusion, and perfusion MRI, and ocular-motor function across 3 time points (baseline, post-choking, post-non-choking). The central hypothesis is that acute neuronal structural, physiological, and functional alterations will be amplified after an incidence of choking-involved sex. The neural-injury blood biomarkers neurofilament light (NfL), glial fibrillary acidic protein (GFAP), Ubiquitin C-Terminal Hydrolase L1 (UCH-L1), and Tau will be measured in plasma, with the hypothesis that having choking involved sex will result in a increased heightened response compared to baseline and post non-choking involved sex timepoints. An additional panel of inflammatory cytokines may be considered if/when brain injury biomarkers show changes. It is also hypothesized that engaging in choking-involved sex will be associated with changes in fMRI activation patterns. White matter microstructure will be measured by diffusion imaging metrics, with the hypothesis that engaging in choking-involved sex will significantly disrupt microstructure at a post-choking involved sex time point, compared to baseline, but not at the post non-choking involved sex timepoint. The study will also assess oculomotor function as measured by near-point-of-convergence (NPC) in response to engaging in choking involved sex. The hypothesis is that NPC performance will be significantly impaired at the post choking-involved sex timepoint in comparison to both baseline and non-choking involved sex timepoints.

The researchers will use a randomized controlled trial design and recruit participants on a first-come, first-serve basis for the study. This will be a crossover study where subjects will experience the same research interactions and data collection methods. Path 1 will involve 3 data collection time points including baseline data collection, post choking involved sex data collection time point, and post non-choking involved sex time point, in that order. Path 2 will involve 3 data collection time points including baseline data collection, post non-choking involved sex time point, and post choking involved sex time point, in that order. Each data collection timepoint will take approximately 2 hours. After enrollment, subjects will be sent a brief Qualtrics survey link once a day to determine when they are eligible for data collection based on their sexual activity within the last 24 hours. If a subject is eligible for data collection, they will come in on the following day.

When written informed consent is obtained, the researchers will use a self-reported health questionnaire to obtain demographic information. The information includes age, sex, romantic relationship status, sexual behavior habits, number and age of previous concussions, as well as assessment of other neurological conditions, psychosis screening, and MRI contradictions to screen participants' eligibility. Participants who meet the inclusion criteria and are free of exclusionary factors will advance to the testing procedures.

Enrollment Questionnaire:

The researchers will asses (1) impulsive behavior using SUPPS-P; (2) Childhood trauma load using CTQ; (3) lifetime trauma load using LEC5; (4) ADHD symptoms using WHO ASRS for DSM-5; (5) aggression in relationships using CTS2S; (6) insomnia symptoms using ISI, (7) migraine disability in the last 3 months using MIDAS (8) sex & sex behavior habits; (9) lifetime choking history; (10) lifetime sexual smothering/slapping history; (11) demographics; (12) alcohol use disorder using AUDIT; (13) cannabis use disorder using CUDIT; (14) MRI contradictions using MRI safety screening form

Data Collection Questionnaires:

The researchers will assess (1) depression, anxiety, perceived stress symptoms using the PHQ-9, GAD-7, and the Perceived Stress Scale; (2) neurobehavioral symptoms using the Neurobehavioral Symptom Inventory; (3) menstrual cycle; (4) health and behaviors in the last 24 hours related to sleep, head impacts, caffeine intake exercise, medication; (5) recent masturbation; (6) event level choking/slapping history

NPC:

During each test session, NPC assessment will be conducted on each participant. Near point of convergence (NPC) will be used to assessed ocular-motor function. The NPC measures the closest point to which one can maintain convergence while focusing on an object before double vision occurs. Assessment will be repeated twice, and mean NPC scores will be used for statistical analyses.

Blood Biomarkers:

Antecubital vein blood draws will be performed each test session to help determine serum biomarker concentrations. A trained phlebotomist will thoroughly clean the inner elbow surface with an alcohol swab and draw 7 ml of whole blood into sterile Vacutainer tubes with 21G butterfly needle. After the blood draw, the participant will use gauze to maintain direct pressure and a bandage will be provided. Plasma will be assessed by the 4-plex Simoa assay platform (Quanterix), which is a magnetic bead-based ELISA that allows detection of biomarkers in femtomolar concentrations. Additional panels of inflammatory cytokines/chemokines will be assessed by the Luminex system.

MRI Techniques:

Once completing the MRI screening procedure, participants will undergo the following standardized MRI protocols.

Diffusion tensor imaging (DTI): DTI is the most widely used technique to study the microstructural integrity of white matter in vivo. DTI provides simple markers, such as mean diffusivity (MD) and fractional anisotropy (FA), that have been used to reflect microstructural tissue change during aging, neurological disorders, and traumatic brain injury (i.e., concussion). However, despite their sensitivity, MD and FA represent cellular diffusivity estimated by basic statistical descriptions that do not directly correspond to biophysiological parameters of the neural cellular integrity. DTI assumes Gaussian diffusion within a single microstructural compartment and thus has proven non-specific to axonal structural damage. To address this limitation, neurite orientation dispersion and density imaging (NODDI) has been characterized to assess microstructural integrity of axons using a non-Gaussian model with multiple compartments. NODDI allows researchers to measure axonal density within white matter, orientation of axonal dispersion, and free water diffusion. The combined approach using NODDI and DTI will uncover greater depth of progressive axonal degeneration in response to sexual choking.

Perfusion: ASL (arterial spin labeling) MRI is an emerging non-invasive technique used to measure cerebral blood flow. ASL creates an image of blood flow throughout the brain by magnetically labeling blood water molecules as an intrinsic tracer while they travel to the brain. ASL offers an advantage over contrast bolus techniques as it is non-invasive and does not require the use of a contrast agent. Additionally ASL allows for the quantification of cerebral blood flow which offers an advantage over traditional contrast MR perfusion. The use of ASL MRI will uncover potential alteration in cerebral blood flow in response to sexual choking.

Resting-state fMRI: Measures of functional connectivity will be computed using a seed-based, correlational approach adapted for cortical surface-based analysis. The dorsolateral prefrontal cortex is set as our primary seed region, but all other regions (e.g., corpus callosum, angular gyrus, cingulate gyrus) will also be tested. Pre-analysis processing, surface sampling, ROI averaging, and motion censoring are adapted from the ABCD protocol. For network analysis, the investigators will calculate correlation values for each pair of ROIs, which are Fisher-transformed to z-statistics and averaged within or between networks to provide summary measures of network strength. The investigators will compute network metrics using the brain connectivity toolbox and compare connectivity measures within and between groups at each time point.

Inclusion Criteria:

• Female
• Between the age of 18-30
• Proficient in English
• Reports engaging in sex involving being choked at least 2 times in the past month

Exclusion Criteria:

• Pregnant
• History of moderate to severe TBI
• Has had a concussion in the last 6 months
• Any MRI contraindication (metal inside body near neck, face, head; metal IUD; severe claustrophobia; etc)
• Neurological condition (epilepsy, neurodegenerative disease, aneurysm, tumor, SCI, etc)
• Reports experiencing psychotic symptoms as measured by the Revised Behavior and Symptom Identification Scale
• Reports currently taking antipsychotic medication
• Reports less than 2 instances of being choked during partnered sexual events during the past month
• Reports engaging in sex without choking no times in the past month (i.e. reports strictly engaging in sex involving choking in the past month)

All study data will be included in publications.

The primary investigator will be blinded to the study participants' study group status, and the statistician will be blinded from group assignment. Additionally, participants will be blinded to their own group status.