Spatial vision in strabismic amblyopia

Spatial vision, refers to how the visual system encodes the relationships between simple features in the external world for extraction of meaningful information as to object form and location in space. Amblyopia (from the Greek, meaning "blunt vision") is a developmental monocular deficit arising in an estimated 5% of children and is the most common cause of unilateral blindness in the adult population. The condition is primarily associated with a strabismus (misalignment of an eye) or anisometropia (unequal refractive error in the two eyes) or both (mixed amblyopia) being present at or shortly after birth. The strabismic amblyopic deficit includes a decrease in contrast sensitivity, with an accompanying loss in acuity. This population is unique in that unlike the anisometropic group, they experience spatial distortions and non-contrast dependent anomalous spatial localization. This has led to the proposition that tarachopia or "distorted" vision may be a better descriptive term to use as opposed to amblyopia or "blunt" vision.In an effort to characterize the distortions that strabismic amblyopes perceive, we have quantified the deficit in spatial localization across the dimensions of spatial scale, eccentricity and exposure duration. The results show that: (1) the deficits of spatial localization, spatial uncertainty (increased alignment threshold) and bias (perceived point of subjective alignment) are uncorrelated; (2) both deficits are scale invariant for well separated elements; (3) the form of the regional distribution depends on the spatial measure used and the scale at which it is measured; (4) there is a poor correlation between the deficit for either spatial measure and the contrast sensitivity loss; and (5) spatial uncertainty is invariant with exposure duration.In addition we have sought to characterize the neural substrate of the spatial deficits. We psychophysically probe the sampling properties of the neuronal population and analyze the dependence of simple pattern discrimination on stimulus bandwidth properties. Our results show that the detection deficit due to neural pooling is effective in limiting the spatial frequencies where sampling considerations are important. Within this region of visible high frequencies, an irregular arrangement of neurons rather than neural loss is the greater contributor to the strabismic amblyopes' deficit. In addition, the amblyopic eye either has broader orientation and spatial frequency detectors or is deficient only for first-order orientation processing

On the nature, predictors, and outcomes of undergraduate students' psychological distress profiles

Although it is well known that psychological distress is a widespread phenomenon among undergraduate students, especially in the aftermath of the COVID-19 pandemic, research on the heterogeneity of the psychological distress manifestations observed in this population is still lacking. This study sought to investigate the nature of psychological distress profiles among a sample of 1053 undergraduate students (78.2 % female; Mage = 22.60, SDage = 4.72) who completed our measures roughly six months into the COVID-19 pandemic. Levels of depression, generalized anxiety, performance anxiety, and emotional exhaustion were evaluated while also accounting for participants' global levels of distress across all types of manifestations. Moreover, we also considered the role played by contextual (university educational climate) and individual (student trait self-control) factors as predictors of profile membership, while controlling for students' sociodemographic characteristics (age, sex, residence status, parental education level, and immigration status). Finally, students' levels of suicidal ideation and risk behaviors (substance use, sedentary time, and fast-food consumption) were contrasted across profiles. Our analyses revealed five quantitatively and qualitatively distinct profiles of psychological distress (Low Distress, Emotional Exhaustion, Performance Anxiety, General Distress, and Exhausted with Performance Anxiety). Controlling for sociodemographic characteristics, a need supportive educational climate and higher levels of trait self-control predicted a higher likelihood of membership into the most adaptive profiles (e.g., Low Distress). Lastly, membership to the General Distress and Exhausted with Performance Anxiety profiles was associated with the least desirable outcomes. -- Keywords : University students ; Psychological distress ; Educational climate ; Self-control ; Risk behaviors