Weak correlations between visual abilities in healthy older adults, despite long-term performance stability.

Using batteries of visual tests, most studies have found that there are only weak correlations between the performance levels of the tests. Factor analysis has confirmed these results. This means that a participant excelling in one test may rank low in another test. Hence, there is very little evidence for a common factor in vision. In visual aging research, cross-sectional studies have repeatedly found that healthy older adults' performance is strongly deteriorated in most visual tests compared to young adults. However, also within the healthy older population, there is no evidence for a visual common factor. To investigate whether the weak between-tests correlations are due to fluctuations in individual performance throughout time, we conducted a longitudinal study. Healthy older adults performed a battery of eight visual tests, with two re-tests after approximately four and seven years. Pearson's, Spearman's and intraclass correlations of most visual tests were significant across the three testing, indicating that the tests are reliable and individual differences are stable across years. Yet, we found low between-tests correlations at each visit, which is consistent with previous studies finding no evidence for a visual common factor. Our results exclude the possibility that the weak correlations between tests are due to high within-individual variance across time.

Evaluating Contrast Sensitivity in Early and Intermediate Age-Related Macular Degeneration With the Quick Contrast Sensitivity Function.

Purpose: The purpose of this study was to describe, validate, and compare the contrast sensitivity functions (CSFs) acquired with the novel quick CSF (qCSF) method from patients with early and intermediate age-related macular degeneration (eAMD and iAMD) and healthy controls. Methods: This is a cross-sectional analysis of contrast sensitivity (CS) and visual acuity (VA) baseline data from the prospective Multimodal Functional and Structural Visual System Characterization (MUMOVI) study. The qCSF testing was conducted with the manifold contrast vision meter (Adaptive Sensory Technology, San Diego, CA, USA). CS levels at spatial frequencies from 1 cycle per degree (CPD) to 18 CPD, the area underneath the logarithmic contrast sensitivity function (AULCSF), and contrast acuity (CA) were analyzed. The association of functional metrics with variables of interest was tested with linear models. Results: Ninety-four study eyes from 94 study patients were included in the analysis (13 patients with eAMD, 33 patients with iAMD, and 48 healthy controls). Significant differences between the eAMD and the iAMD model estimates were only found for CS at 1 CPD (t value = -2.9, P value = 0.006) and CS at 1.5 CPD (-2.7, 0.01). A specific association between smoking years and CS at 1 CPD (P = 0.02) and CS at 1.5 CPD (P = 0.03) could be described in patients with AMD. Conclusions: The qCSF testing allows the fast measurement of the whole CSF, enabling the integration into clinical routine. We showed that novel qCSF-derived metrics detect slight functional differences between AMD stages, which testing by Pelli-Robson charts or VA testing would miss. This study, therefore, yields novel qCSF-derived candidate metrics for therapeutic trials in AMD.

Do we really measure what we think we are measuring?

Tests used in the empirical sciences are often (implicitly) assumed to be representative of a given research question in the sense that similar tests should lead to similar results. Here, we show that this assumption is not always valid. We illustrate our argument with the example of resting-state electroencephalogram (EEG). We used multiple analysis methods, contrary to typical EEG studies where one analysis method is used. We found, first, that many EEG features correlated significantly with cognitive tasks. However, these EEG features correlated weakly with each other. Similarly, in a second analysis, we found that many EEG features were significantly different in older compared to younger participants. When we compared these EEG features pairwise, we did not find strong correlations. In addition, EEG features predicted cognitive tasks poorly as shown by cross-validated regression analysis. We discuss several explanations of these results.

No Common Factor Underlying Decline of Visual Abilities in Mild Cognitive Impairment.

INTRODUCTION: Recent work has shown an association between cognitive and visual impairments and two main theories were advanced, namely the sensory deprivation and the common cause theories. Most studies considered only basic visual functions such as visual acuity or visual field size and evaluated the association with dementia. OBJECTIVES: To reconcile between these theories and to test the link between visual and cognitive decline in mildly cognitive impaired people. METHODS: We employed a battery of 19 visual tasks on 39 older adults with mild cognitive impairment and 91 without any evidence of cognitive decline, as measured by the Montreal Cognitive Assessment. RESULTS: Our results show a strong association between visual impairment and mild cognitive impairment. In agreement with previous results with younger and healthy older adults, we found also only weak correlations between most tests in older adults with mild cognitive impairment. CONCLUSION: Our results suggest that visual and cognitive abilities decline simultaneously, but they do so independently across visual and cognitive functions and across participants.

Electrophysiological correlates of visual backward masking in patients with bipolar disorder.

In visual backward masking (VBM), a target is followed by a mask that decreases target discriminability. Schizophrenia patients (SZ) show strong and reproducible masking impairments, which are associated with reduced EEG amplitudes. Patients with bipolar disorder (BP) show masking deficits, too. Here, we investigated the neural EEG correlates of VBM in BP. 122 SZ, 94 unaffected controls, and 38 BP joined a standard VBM experiment. 123 SZ, 94 unaffected controls and 16 BP joined a corresponding EEG experiment, analyzed in terms of global field power. As in previous studies, SZ and BP show strong masking deficits. Importantly and similarly to SZ, BP show decreased global field power amplitudes at approximately 200 ms after the target onset, compared to controls. These results suggest that VBM deficits are not specific for schizophrenia but for a broader range of functional psychoses. Potentially, both SZ and BP show deficient target enhancement.