Aging Potentiates Lateral but Not Local Inhibition of Orientation Processing in Primary Visual Cortex.

Zhengchun Wang,Shan Yu,Yifeng Zhou,Tzvetomir Tzvetanov,Yu Fu

doi:10.3389/fnagi.2018.00014

Abstract

Aging-related declines in vision can decrease well-being of the elderly. 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 older adults, or proposed stronger surround suppression. Through psychophysical experiments and computational modeling, we resolved these discrepancies by suggesting that lateral inhibition increased in older adults while neuronal orientation tuning widths, related to local inhibition, stayed globally intact across age. We confirmed this later result by re-analyzing published neurophysiological data, which showed no systematic tuning width changes, but instead displayed 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 people previously thought.

Highlights

Aging has a profound impact on human visual function, where early neuronal processing and perceptual abilities modifications with age have been intensively studied in the last 25 years (Owsley, 2011; Andersen, 2012)
In Supplementary Material-4, we show that there are no essential differences in fit quality between old and young cell types once variability is properly accounted for
Our psychophysical modeling and re-analysis of neurophysiological results consistently revealed a detail picture of age-related changes in orientation processing, which we think solved some contradictions between neurophysiological and behavioral reports, and uncovered a differential age-related effects on local inhibition

Summary

Introduction

Aging has a profound impact on human visual function, where early neuronal processing and perceptual abilities modifications with age have been intensively studied in the last 25 years (Owsley, 2011; Andersen, 2012). Neurophysiological studies suggested that a reduction in inhibitory function might be related to age-related perceptual dysfunctions in spatial vision (Schmolesky et al, 2000; Leventhal et al, 2003). Some behavioral studies have shown that there are low-level processes of visual functions which are inconsistent with the physiological interpretation of decreased inhibition: (1) psychophysical sensitivities to orientation processing in older populations are not systematically and substantially changed when compared to younger adults (Betts et al, 2007; Delahunt et al, 2008; Govenlock et al, 2009), while the neurophysiological counterpart strongly suggests such a deficit; (2) contrast surround suppression in older adults was found increased, which was Lateral Inhibition Increases in Aging interpreted with stronger inhibitory interactions (Karas and McKendrick, 2015). Since the changed cellular properties are commonly attributed to intracortical inhibition (Somers et al, 1995; Shapley et al, 2003), it appears that intracortical local inhibition and lateral inhibition could have underwent heterogeneous modifications with old age

Methods

Results

Conclusion