Altered Visual Plasticity in Morbidly Obese Subjects

Abstract

Growing evidence indicates a close link between energy metabolism and neural plasticity as obesity is associated with alterations of cognitive functions, memory, and hippocampal neurogenesis. However, it is still unknown whether obesity can affect low-level sensory plasticity. Here we investigated this issue by probing early visual plasticity induced by short-term (2 h) monocular deprivation in a group of adult volunteers with a wide range of Body Mass Index (BMI), from normal weight to morbid obesity. We found that the effect of monocular deprivation decreased with increasing BMI, and morbidly obese subjects (BMI>40) failed to show the homeostatic plasticity effect seen in normal-weight participants. In addition, morbidly obese subjects exhibited altered binocular rivalry dynamics compared with normal-weight observers. These results show for the first time that the impact of obesity observed at the neural and cognitive level extends to basic sensory processing and plasticity.

Keywords: Biological Sciences; Neuroscience; Physiological State; Sensory Neuroscience.

Graphical abstract

Figure 1

Short-term Monocular Deprivation Effect and Binocular Rivalry Dynamics as a Function of BMI (A) Diagram of the experimental paradigm. (B) The effect of monocular deprivation (difference between ocular dominance measured after and before 2 h of monocular deprivation) plotted as a function of subjects' Body Mass Index (BMI). The bars represent the average effect for three different BMI categories (gray, normal to overweight; red, obese class I and II; blue, obese class III), error bars represent 1 ± SEM. Black symbols represent single subjects' data. (C) Same as (B) but for the proportion of the total time of mixed percepts measured during binocular rivalry before monocular deprivation.

Figure 2

Decay of the Effect of Monocular Deprivation across Different BMI Groups The effect of monocular deprivation is plotted for each of the four experimental blocks acquired after eye-patch removal and for the three different BMI groups (black symbols, normal weight to overweight subjects; red symbols, class I and class II obese subjects; blue symbols, class III obese subjects). Error bars represent 1 ± SEM.

Figure 3

Ocular Dominance as a Function of BMI The ocular dominance index measured before deprivation is plotted as a function of subjects' BMI. Individual subjects are represented by black symbols. Average ocular dominance values for each BMI group are represented by the bars (same color code as in Figure 2). Error bars represent 1 ± SEM.