Yifeng Zhou | bioRxiv Science

bioRxiv2016

Bayesian Inference of Two-Dimensional Contrast Sensitivity Functions

The contrast sensitivity function (CSF) is crucial in predicting functional vision both in research and clinical areas. Recently, a group of novel strategies, multi-dimensional adaptive methods, were proposed and allowed more rapid measurements when compared to usual methods such as {Psi} or staircase. Our study further presents a multi-dimensional Bayesian framework to estimate parameters of the CSF from experimental data obtained by classical sampling. We extensively simulated the frameworks performance as well as validated the results in a psychophysical experiment. The results showed that the Bayesian framework significantly improves the accuracy and precision of parameter estimates from usual strategies, and requires about the same number of observations as the novel methods to obtain reliable inferences. Additionally, the improvement with the Bayesian framework was maintained when the prior poorly matched the observers CSFs. The results indicated that the Bayesian framework is flexible and sufficiently precise for estimating CSFs.

Neuroscience↗

bioRxiv2016

Aging increases lateral but not local inhibition of orientation processing in primary visual cortex

Aging-related declines in vision can decrease well-being of the elder. Concerning early sensory changes as in the primary visual cortex, physiological and behavioral reports seem contradictory. Neurophysiological studies on orientation tuning properties suggested that neuronal changes might come from decreased cortical local inhibition. However, behavioral results either showed no clear deficits in orientation processing in the elder, or proposed stronger surround suppression. Through psychophysical experiments conducted on old and young human subjects combined with computational modeling, we resolved these discrepancies by demonstrating stronger lateral inhibition in the elder while neuronal orientation tuning widths, related to local inhibition, stayed globally intact across age. We confirmed this later finding by re-analyzing published neurophysiological data from rhesus monkeys, which showed no systematic tuning width changes, but instead a higher neuronal noise with aging. These results suggest a stronger lateral inhibition and mixed effects on local inhibition during aging, revealing a more complex picture of age-related effects in the central visual system than previously thought.\n\nSignificance StatementVisual functions decline during aging, adversely affecting quality of life. Much of this dysfunction is probably mediated by disturbances in the balance between inhibition and excitation in the central visual system. It was proposed that the inhibitory function within the aging visual cortex might be modified, but huge discrepancies exist among different reports. Here we identify the specific inhibitory circuit change, which has not been clearly evaluated, by using behavioral measures, neural modeling and re-analysis of non-human primate electrophysiological data. We provide evidence that a stronger lateral inhibition and mixed effects on local inhibition during aging, revealing a more complex picture of age-related effects in the central visual system than previously thought.\n\nAuthor contributionsZCW and TT designed and analyzed behavioral experiments; ZCW performed experiments; ZCW and TT performed data analysis and neurophysiological re-analysis; YS and FY provided physiological data and discussed its re-analysis; TT performed modeling; ZCW, YFZ and TT provided project supervision and funds; ZCW and TT wrote the paper; all authors discussed and commented on the manuscript.

Neuroscience↗