ORIGINAL RESEARCH article
Front. Behav. Neurosci.
Sec. Learning and Memory
This article is part of the Research TopicPBM and targeted photostimulation in the context of memory mechanisms and spatial cognitionView all 3 articles
Photobiomodulation Mechanisms: Duration of Action in the Human Prefrontal Cortex
Provisionally accepted
- Departments of Psychology, Pharmacology and Toxicology, The University of Texas at Austin, Austin, TX, United States
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Abstract Introduction: Transcranial infrared laser stimulation (TILS) is a form of photobiomodulation (PBM) using a wavelength of 1064 nm shown to enhance metabolic and hemodynamic activity in the human prefrontal cortex (PFC). Prior studies have shown that when applied to the PFC in the right hemisphere, TILS improves PFC-based memory and learning and sustains attention and mood in healthy adults. However, the temporal duration of PBM mechanisms following a single administration remains poorly understood in humans. The objective of this study was to evaluate the duration of functional connectivity effects of a single administration of TILS to the right anterior PFC during both resting-state and memory-activated conditions over a five-day period. Methods: Hemodynamics-derived functional connectivity of the PFC in 12 healthy adults was measured using a 48-channel functional near-infrared spectroscopy (fNIRS) during 5-minute resting-state and 2-back memory task activation phases, collected at six time points over a five-day span. A sham-controlled, within-subject crossover design was employed: all participants received both sham and active TILS in counterbalanced order, with a four-week washout period between sessions. Results: Relative to sham, a single administration of TILS significantly modulated PFC functional connectivity during cognitively demanding memory tasks across the five-day assessment period. No significant effects were observed during resting-state measurements. No adverse effects were reported. Discussion: These findings suggest that a single administration of TILS can induce functional neuroplasticity in the PFC that persists for several days. The results advance understanding of PBM mechanisms and may inform future interventions aimed at promoting longer-lasting neurocognitive benefits.
Keywords: Prefrontal Cortex, photobiomodulation, Transcranial infrared laser stimulation, functional near-infrared spectroscopy, functional connectivity, PBM
Received: 16 Oct 2025; Accepted: 27 Nov 2025.
Copyright: © 2025 O'Connor, Lime, Barrett and Gonzalez-Lima. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: F. Gonzalez-Lima
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