Eye gaze position before, during and after percept switching of bistable visual stimului

A bistable visual stimulus, such as the Necker Cube or Rubin’s Vase, can be perceived in two different ways which compete against each other and alternate spontaneously. Percept switch rates have been recorded in past psychophysical experiments, but few experiments have measured percept switches while tracking eye movements in human participants. In our study, we use the Eyelink II system to track eye gaze position during spontaneous percept switches of a bistable, structure-from-motion (SFM) cylinder that can be perceived to be rotating clockwise (CW) or counterclockwise (CCW). Participants reported the perceived direction of rotation of the SFM cylinder using key presses. Reliability of participants’ reports was ensured by including unambiguous rotations. Unambiguous rotation was generated by assigning depth using binocular disparity. Gaze positions were measured 50 – 2000 ms before and after key presses. Our pilot data show that during ambiguous cylinder presentation, gaze positions for CW reports clustered to the left half of the cylinder and gaze positions for CCW reports clustered to the right half of the cylinder between 1000ms before and 1500ms after key presses, but no such correlation was found beyond that timeframe. These results suggest that percept switches can be correlated with prior gaze positions for ambiguous stimuli. Our results further suggest that the mechanism underlying percept initiation may be influenced by the visual hemifield where the ambiguous stimulus is located.Published versio

Investigating human memory of self-position using a virtual 3-dimensional visual environment

Knowing one's location in space is crucial for navigation, especially in unknown environments. Recently, systems involved in self-localization for spatial navigation have been found in rodent brains, but the mechanisms for self-localization are not completely understood. Human behavioral experiments can enhance understanding of self-localization systems in human brains. In this study, human observers are placed in a visual virtual reality (VR) to perform a self-positioning task. The VR is created using a 120 Hz projector and a polarizing filter which separates left and right eye images when passed through 3D glasses. Disparity and size cues generate the perception of depth. Participants are placed in a virtual position on the ground for five seconds and then moved by changing their virtual environment around a stable object. Their task is to return to their initial position on the ground with button controls. Principal component analyses show that errors in self-repositioning are not along any particular axes and each participant has a unique pattern of repositioning. Trial durations do not affect accuracy of repositioning and lack of disparity cues increases the standard error of repositioning in all directions. Some participants have lower errors when initial self-positions appear to be on one or the other side of the stable object, suggesting a link between memory of self-position and a preferred point of reference. Future directions of this project are to explore between-subject differences and the effect of stimulus presentation at different frequencies on memory of self-position.Published versionSupporting documentatio

Human egocentric position estimation

The study of egocentric position estimation may shed light on visuospatial memory processes, such as physical space representation in our visual system. However, little has been done to test egocentric position estimation in humans and the few studies to date have investigated egocentric position estimation with context to ground or other stable visual cues. In this study, human participants are introduced to a three-dimensional virtual reality (VR) generated by a 120 Hz projector with a polarization filter and polarizing glasses that separated left and right eye images in a frame sequential stereoscopic configuration. Participants were placed in the center of a VR cylinder where 5,000 sesame dots were distributed at random distances (112cm to 168cm) from the participant, azimuth (+/- 29.12°), and height (120cm to 188cm from the floor). Nine possible targets were located on a horizontal plane 50cm from the participant’s eye level on a three by three matrix at right, left, center azimuths (+/- 18.64°, 0°), and near, middle, and far distances (126cm, 137cm, 147cm from the participant). Participants were presented with one randomly selected target for 3 to 5 seconds before the target was relocated to a random location within the sesame dot field. The task was to reposition the target back to the original position. Depth was induced using disparity and size cues, except for sesame dots that had only disparity cues. Errors in distance repositioning occurred along the line of sight and repositioning showed an attraction bias toward the relocated target. Elevation repositioning was higher for farther targets (P < 0.05, F = 3.19). Azimuth repositioning for left targets were significantly shifted to the right (P< 0.01, F= 18.42). Standard deviations for distance repositioning were invariant against target distance, suggesting that egocentric visuospatial representation is based on Cartesian metrics rather than polar coordinates.Published versio

Involuntary saccades and binocular coordination during visual pursuit in Parkinson's disease

Prior studies of oculomotor function in Parkinson's disease (PD) have either focused on saccades while smooth pursuit eye movements were not involved, or tested smooth pursuit without considering the effect of any involuntary saccades. The present study investigated whether these involuntary saccades could serve as a useful biomarker for PD. Ten observers with PD participated in the study along with 10 age-matched normal control (NC) and 10 young control participants (YC). Observers fixated on a central cross while a disk (target) moved toward it from either side of the screen. Once the target reached the fixation cross, observers began to pursue the moving target until the target reached to the other side. To vary the difficulty of fixation and pursuit, the moving target was presented on a blank or a moving background. The moving background consisted of uniformly distributed dots moved in either the same or the opposite direction of the target once the target reached the central fixation cross. To investigate binocular coordination, each background condition was presented under a binocular condition, in which both eyes saw the same stimulus, and under a dichoptic condition, in which one eye saw only the target and the other eye only saw the background. The results showed that in both background conditions, observers with PD made more involuntary saccades than NC and YC during both fixation and pursuit periods while YC and NC showed no difference. Moreover, the difference between left and right eye positions increased over time during the pursuit period for PD group but not for the other two groups. This suggests that individuals with PD may be impaired not only in saccade inhibition, but also in binocular coordination during pursuit. [Meeting abstract presented at VSS 2016.]Accepted manuscrip

Eye movement control during visual pursuit in Parkinson's disease

BACKGROUND: Prior studies of oculomotor function in Parkinson’s disease (PD) have either focused on saccades without considering smooth pursuit, or tested smooth pursuit while excluding saccades. The present study investigated the control of saccadic eye movements during pursuit tasksand assessed the quality of binocular coordinationas potential sensitive markers of PD. METHODS: Observers fixated on a central cross while a target moved toward it. Once the target reached the fixation cross, observers began to pursue the moving target. To further investigate binocular coordination, the moving target was presented on both eyes (binocular condition), or on one eye only (dichoptic condition). RESULTS: The PD group made more saccades than age-matched normal control adults (NC) both during fixation and pursuit. The difference between left and right gaze positions increased over time during the pursuit period for PD but not for NC. The findings were not related to age, as NC and young-adult control group (YC) performed similarly on most of the eye movement measures, and were not correlated with classical measures of PD severity (e.g., Unified Parkinson’s Disease Rating Scale (UPDRS) score). DISCUSSION: Our results suggest that PD may be associated with impairment not only in saccade inhibition, but also in binocular coordination during pursuit, and these aspects of dysfunction may be useful in PD diagnosis or tracking of disease course.This work was supported in part by grants from the National Science Foundation (NSF SBE-0354378 to Arash Yazdanbakhsh and Bo Cao) and Office of Naval Research (ONR N00014-11-1-0535 to Bo Cao, Chia-Chien Wu, and Arash Yazdanbakhsh). There was no additional external funding received for this study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. (SBE-0354378 - National Science Foundation (NSF); ONR N00014-11-1-0535 - Office of Naval Research)Published versio

Correlation between heart rate variability and pulmonary function adjusted by confounding factors in healthy adults

The autonomic nervous system maintains homeostasis, which is the state of balance in the body. That balance can be determined simply and noninvasively by evaluating heart rate variability (HRV). However, independently of autonomic control of the heart, HRV can be influenced by other factors, such as respiratory parameters. Little is known about the relationship between HRV and spirometric indices. In this study, our objective was to determine whether HRV correlates with spirometric indices in adults without cardiopulmonary disease, considering the main confounders (e.g., smoking and physical inactivity). In a sample of 119 asymptomatic adults (age 20-80 years), we evaluated forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1). We evaluated resting HRV indices within a 5-min window in the middle of a 10-min recording period, thereafter analyzing time and frequency domains. To evaluate daily physical activity, we instructed participants to use a triaxial accelerometer for 7 days. Physical inactivity was defined as <150 min/week of moderate to intense physical activity. We found that FVC and FEV1, respectively, correlated significantly with the following aspects of the RR interval: standard deviation of the RR intervals (r= 0.31 and 0.35), low-frequency component (r= 0.38 and 0.40), and Poincare plot SD2 (r= 0.34 and 0.36). Multivariate regression analysis, adjusted for age, sex, smoking, physical inactivity, and cardiovascular risk, identified the SD2 and dyslipidemia as independent predictors of FVC and FEV1 (R-2= 0.125 and 0.180, respectively, for both). We conclude that pulmonary function is influenced by autonomic control of cardiovascular function, independently of the main confounders.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Univ Fed Sao Paulo, Dept Ciencias Movimento Humano, Lab Epidemiol & Movimento Humano, Santos, SP, BrazilUniv Fed Sao Paulo, Dept Biociencias, Santos, SP, BrazilAngioCorpore Inst Med Cardiovasc, Santos, SP, BrazilUniv Fed Sao Paulo, Dept Ciencias Movimento Humano, Lab Epidemiol & Movimento Humano, Santos, SP, BrazilUniv Fed Sao Paulo, Dept Biociencias, Santos, SP, BrazilFAPESP: 2011/07282-6Web of Scienc

Clonal chromosomal mosaicism and loss of chromosome Y in elderly men increase vulnerability for SARS-CoV-2

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, COVID-19) had an estimated overall case fatality ratio of 1.38% (pre-vaccination), being 53% higher in males and increasing exponentially with age. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, we found 133 cases (1.42%) with detectable clonal mosaicism for chromosome alterations (mCA) and 226 males (5.08%) with acquired loss of chromosome Y (LOY). Individuals with clonal mosaic events (mCA and/or LOY) showed a 54% increase in the risk of COVID-19 lethality. LOY is associated with transcriptomic biomarkers of immune dysfunction, pro-coagulation activity and cardiovascular risk. Interferon-induced genes involved in the initial immune response to SARS-CoV-2 are also down-regulated in LOY. Thus, mCA and LOY underlie at least part of the sex-biased severity and mortality of COVID-19 in aging patients. Given its potential therapeutic and prognostic relevance, evaluation of clonal mosaicism should be implemented as biomarker of COVID-19 severity in elderly people. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, individuals with clonal mosaic events (clonal mosaicism for chromosome alterations and/or loss of chromosome Y) showed an increased risk of COVID-19 lethality

Mortality and pulmonary complications in patients undergoing surgery with perioperative SARS-CoV-2 infection: an international cohort study

Background: The impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on postoperative recovery needs to be understood to inform clinical decision making during and after the COVID-19 pandemic. This study reports 30-day mortality and pulmonary complication rates in patients with perioperative SARS-CoV-2 infection. Methods: This international, multicentre, cohort study at 235 hospitals in 24 countries included all patients undergoing surgery who had SARS-CoV-2 infection confirmed within 7 days before or 30 days after surgery. The primary outcome measure was 30-day postoperative mortality and was assessed in all enrolled patients. The main secondary outcome measure was pulmonary complications, defined as pneumonia, acute respiratory distress syndrome, or unexpected postoperative ventilation. Findings: This analysis includes 1128 patients who had surgery between Jan 1 and March 31, 2020, of whom 835 (74·0%) had emergency surgery and 280 (24·8%) had elective surgery. SARS-CoV-2 infection was confirmed preoperatively in 294 (26·1%) patients. 30-day mortality was 23·8% (268 of 1128). Pulmonary complications occurred in 577 (51·2%) of 1128 patients; 30-day mortality in these patients was 38·0% (219 of 577), accounting for 81·7% (219 of 268) of all deaths. In adjusted analyses, 30-day mortality was associated with male sex (odds ratio 1·75 [95% CI 1·28–2·40], p\textless0·0001), age 70 years or older versus younger than 70 years (2·30 [1·65–3·22], p\textless0·0001), American Society of Anesthesiologists grades 3–5 versus grades 1–2 (2·35 [1·57–3·53], p\textless0·0001), malignant versus benign or obstetric diagnosis (1·55 [1·01–2·39], p=0·046), emergency versus elective surgery (1·67 [1·06–2·63], p=0·026), and major versus minor surgery (1·52 [1·01–2·31], p=0·047). Interpretation: Postoperative pulmonary complications occur in half of patients with perioperative SARS-CoV-2 infection and are associated with high mortality. Thresholds for surgery during the COVID-19 pandemic should be higher than during normal practice, particularly in men aged 70 years and older. Consideration should be given for postponing non-urgent procedures and promoting non-operative treatment to delay or avoid the need for surgery. Funding: National Institute for Health Research (NIHR), Association of Coloproctology of Great Britain and Ireland, Bowel and Cancer Research, Bowel Disease Research Foundation, Association of Upper Gastrointestinal Surgeons, British Association of Surgical Oncology, British Gynaecological Cancer Society, European Society of Coloproctology, NIHR Academy, Sarcoma UK, Vascular Society for Great Britain and Ireland, and Yorkshire Cancer Research