Photobiomodulation effects on active brain networks during a spatial memory task

Abstract

Photobiomodulation (PBM) or the use of red to near-infrared irradiation spectrum, is a non-invasive intervention that produces neurostimulatory effects and reaches benefits in several pathologies as well as in healthy subjects. The main objective of this study was to evaluate and compare the effects of PBM in a rat brain network on basal state and functional activity during the execution of a reversal task. Twenty-eight rats were divided into four groups: control group (n = 7), control photobiomodulation group (n = 8), behavioural group (n = 6) and behavioural photobiomodulation group (n = 7). Reversal memory was assessed using a Morris water maze and cytochrome c oxidase (CCO) was used as a brain metabolic activity marker. After five days of PBM, the control photobiomodulation group showed a decrease of CCO levels in the striatum, medial septum, entorhinal, hippocampus, amygdala, thalamus, mammillary nuclei and VTA. Both behavioural groups performed the task correctly, however, the behavioural photobiomodulation group displayed CCO reduction in some regions involved in the execution of the reversal task: septum, entorhinal, CA1, CA3, central amygdala and supramammilar, along with higher levels in accumbens. These results could show the effect of PBM on active brain networks. Further studies will be necessary to elucidate its effects in different brain networks that are involved in the execution of other memory tasks.

Keywords: Brain networks; Cytochrome c oxidase; Near-infrared light; Photobiomodulation; Spatial memory.