“We wanted to compare the two most common tPBM paradigms head\u2011to\u2011head in a well\u2011established AD mouse model,” explains Professor Li. “CW light is traditionally used for mitochondrial enhancement, while 40\u2011Hz light is known to entrain gamma oscillations. But no one had systematically compared their effects on neurovascular pathology and glial cells.”<\/p>\n
The researchers treated 5\u2011month\u2011old 5xFAD mice \u2013 a model with aggressive amyloid deposition \u2013 with 810\u2011nm light (25\u202fmW\/cm\u00b2 at the scalp, ~6.25\u202fmW\/cm\u00b2 brain dose for CW, and half that for 40\u2011Hz due to 50% duty cycle) for 10 minutes daily over 37 days. Monte Carlo simulations confirmed that the light effectively reached the hippocampus and cortex, with ~30% of incident energy penetrating the brain parenchyma.<\/p>\n
Both CW and 40\u2011Hz light significantly improved spatial learning and memory in the Morris water maze, with the 40\u2011Hz group showing slightly faster acquisition. However, the novel object recognition test showed no significant difference, suggesting that the effect may be hippocampus\u2011dependent\u2013a clue that pointed towards vascular and structural changes rather than purely cognitive enhancement.<\/p>\n
When the team measured A\u03b2\u2081\u208b\u2084\u2082 levels, a clear difference emerged. In the hippocampus, 40\u2011Hz light reduced A\u03b2 by 87.7%, while CW light achieved a more modest 60.1% reduction. Immunofluorescence confirmed that 40\u2011Hz light significantly reduced plaque numbers and area in both the dentate gyrus and CA1 subregions, while CW showed stronger effects in the dentate gyrus but less in CA1.<\/p>\n
“The key wasn’t just the reduction in plaques,” says Professor Yan. “We found that 40\u2011Hz light didn’t simply increase the total number of microglia. Instead, it drove their spatial redistribution \u2013 microglia clustered tightly around A\u03b2 plaques, forming a dense barrier that effectively cleared the amyloid without triggering the widespread neuroinflammation that often follows global microglial activation.” In CA1, 40\u2011Hz stimulation doubled the number of peri-plaque microglia, while CW light increased microglial clustering in CA23 by 2.5\u2011fold.<\/p>\n
In contrast, CW light primarily targeted astrocytes. Whole\u2011brain vascular reconstruction using fluorescence micro\u2011optical sectioning tomography (fMOST)\u2013a technique that provides 3\u2011D visualization of the entire cerebrovascular network\u2013revealed that both CW and 40\u2011Hz light increased vessel density and diameter in the hippocampus and cortex. However, the underlying cellular mechanism differed significantly.<\/p>\n
CW light dramatically increased the number of GFAP\u207a astrocytes (by 84.6% in the cortex and 78.7% in the dentate gyrus) and enhanced their coupling with CD31\u207a blood vessels. Pearson colocalization analysis showed a significant increase in astrocyte\u2011vascular association in CA1 and the cortex. “This is the structural foundation of the neurovascular unit,” explains Professor Wei. “Astrocytes physically connect neurons to capillaries and regulate blood flow. By strengthening this link, CW light restores the metabolic support that neurons need to survive and function.”<\/p>\n
Critically, synaptic density\u2013measured by synaptophysin staining \u2013 was strongly correlated with both vessel density and astrocyte\u2011vascular coupling. “This tells us that CW light doesn’t act directly on synapses,” notes Professor Li. “It works indirectly by repairing the vascular and astrocytic infrastructure, which in turn sustains synaptic integrity. In contrast, 40\u2011Hz light’s synaptic protection likely stems from reducing A\u03b2 toxicity, which is a different route entirely.”<\/p>\n
A striking observation was that 40\u2011Hz light delivered only half the total energy (50% duty cycle) but achieved comparable or even superior cognitive and amyloid\u2011clearing effects. “This suggests that 40\u2011Hz light engages alternative pathways beyond mitochondrial ATP production \u2013 likely through gamma\u2011frequency neuronal entrainment, calcium oscillations, or direct microglial modulation,” says Professor Yan.<\/p>\n
The authors propose a precision medicine framework: CW light may be preferentially indicated for patients with vascular dementia or significant hypoperfusion, while 40\u2011Hz light could be more suitable for early\u2011stage AD where amyloid burden is the dominant pathology. Future combinatorial protocols \u2013 alternating or superimposing both modes\u2013might theoretically address both vascular and amyloid components simultaneously.<\/p>\n
While the study provides compelling mechanistic insights, the authors acknowledge that the findings are phenotype\u2011based; molecular signaling pathways and transcriptomic validation are still needed. The sex\u2011balanced design (male and female mice were included evenly) is a strength, but sex\u2011specific effects on microglial metabolism and phagocytosis should be explored in future translational studies. Electrophysiological recordings and in vitro assays are also required to confirm the frequency\u2011dependent cellular responses.<\/p>\n
Nevertheless, this work establishes a fundamental framework for optimizing tPBM protocols in AD. “We now have a clear biological rationale for choosing CW or 40\u2011Hz light\u2013or combining them\u2013based on the dominant pathology in each patient,” concludes Professor Li. “This moves tPBM from a one\u2011size\u2011fits\u2011all approach towards a truly personalized, mechanistic\u2011guided therapy.”<\/p>\n
Source:<\/p>\n
Beijing Institute of Technology<\/a><\/p>\n Journal reference:<\/p>\n Zhang, B., et al. (2026) Frequency-Specific Transcranial Photobiomodulation Elicits Complementary Glial Mechanisms for Neurovascular Protection and Amyloid Clearance in Alzheimer Disease. Cyborg and Bionic Systems. DOI: 10.34133\/cbsystems.0551.\u00a0https:\/\/spj.science.org\/doi\/10.34133\/cbsystems.0551<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"“We wanted to compare the two most common tPBM paradigms head\u2011to\u2011head in a well\u2011established AD mouse model,” explains…\n","protected":false},"author":2,"featured_media":302694,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[10],"tags":[38759,4250,1596,6916,26211,134,17560,25431,37481,6918,111,139,69,6842,21651],"class_list":["post-512923","post","type-post","status-publish","format-standard","has-post-thumbnail","category-health","tag-astrocyte","tag-blood","tag-brain","tag-cortex","tag-frequency","tag-health","tag-hippocampus","tag-microglia","tag-mouse-model","tag-neurons","tag-new-zealand","tag-newzealand","tag-nz","tag-pathology","tag-vascular"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/512923","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/comments?post=512923"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/512923\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media\/302694"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media?parent=512923"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/categories?post=512923"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/tags?post=512923"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}