Effect And Mechanism Of Green Light Treatment In The Regulation Of Learning And Memory

Phototherapy has been shown to be effective for a variety of mental diseases.For example,blue light treatment can effectively improve learning and memory functions in Alzheimer's patients.However,the known retinal damage effect of blue light stimulation limits its application.Compared with the blue light,green light has a similar wavelength,and the study found that green light will not cause phototoxic damage to the retina.If green light therapy is beneficial in improving cognitive function,it will be an important strategy for optimizing and upgrading the existing phototherapy.In this study,we thus investigated the effect of green light(530nm)illumination on learning and memory functions in mice.The results showed that green-light treatment significantly improved whisker-dependent novel texture discrimination ability in mice compared to that in room light treatment animals,which indicated that the learning and memory ability were significantly enhanced.Two-photon microscopy imaging revealed that the synaptic plasticity of barrel cortex increased after green light illumination in mice compared to room light animals,focusing on the number of mature dendritic spines which tends to be more stable.We further investigated the neural mechanisms under the enhanced learning and memory functions and the effect of synaptic plasticity in cortical induced by green light therapy.Compared to room light group,western blot showed BDNF protein levels significantly increased in mice barrel cortex after green light treatment.Blocking the BDNF-TrkB signaling pathway can significantly weaken the effect of green light on synaptic plasticity in the cortex and learning and memory functions.Above-memtioned results suggest that green light illumination could promot the spines pruning and maturation thus improve learning and memory abilities of novel texture in mice,possibly via the BDNF-Trk B pathway.