MODULATION OF EXECUTIVE FUNCTIONS IN HEALTHY HUMANS THROUGH <EM>OPUNTIA FICUS-INDICA</EM> FRUIT CONSUMPTION AND NON-INVASIVE BRAIN STIMULATION

The dorsolateral prefrontal cortex (dlPFC) is a key hub for executive functions, particularly working memory (WM). While non-invasive brain stimulation (NIBS) is a well-established tool for modulating executive functions, recent evidence suggests that these functions may also be influenced by functional foods containing blood–brain barrier–permeable molecules. Among these, Indicaxanthin (IX), a pigment found in yellow–orange Opuntia ficus-indica fruits (OFIF), has attracted interest for its effects on cortical excitability. This study investigates the impact of IX-rich OFIF consumption on visuospatial WM and its interaction with offline anodal transcranial direct current stimulation (a-tDCS) applied to the right dlPFC.

Eighteen healthy participants took part in a single-blind, placebo-controlled study: twelve received 400g of yellow-orange IX-rich fruits, while six received 400g of white IX-devoid fruits, serving as the placebo group. Participants completed a visuospatial N-back task (1-back and 2-back) under three conditions: OFIF intake alone, a-tDCS over right dlPFC alone and their combination. Results showed that a-tDCS selectively improved 2-back accuracy, whereas OFIF intake improved accuracy in both 1-back and 2-back tasks, with stronger effects for the yellow-orange variety. Interestingly, the combination of yellow-orange OFIF and a-tDCS did not produce additive effects, suggesting a potential homeostatic plasticity that prevents excessive cortical excitability.

These results suggest that Opuntia ficus-indica fruits, especially the yellow-orange variety rich in Indicaxanthin, could act as a potent neuromodulator of prefrontal WM function and interact with a-tDCS-induced plasticity, providing a new perspective on how functional food may support cognitive performance and overall brain health.