The concept of cognitive reserve (CR) and resilience originates from clinicopathological observations that amyloid-β deposition, tau pathology and neurodegeneration do not uniformly translate into clinical dementia, highlighting inter-individual differences in the brain’s capacity to tolerate pathology. Although CR and resilience lack a single accepted definition, they broadly describe the ability to maintain cognition in the presence of age-related or pathological brain changes. This review synthesises current molecular, cellular, and brain network mechanisms of cognitive reserve and critically examines key controversies. We also identify convergent biological pathways across multiple levels of organisation. Available evidence implicates that CR is not attributable to a single factor but reflects interactions among environmental exposures, genetic background, epigenetic regulation, cellular homeostasis, glial function, and large-scale brain network organisation. Lifestyle factors are associated with reduced pathology accumulation, preserved brain structure, and maintenance of cognition despite pathology, depending on the mechanism and outcome considered and are understood to exert their effects through epigenetic modulation of neuroplasticity, neurotrophic signalling, metabolic regulation, and inflammatory pathways. At the cellular level, preservation of dendritic spine integrity, synaptic signalling balance, mitochondrial energetic flexibility, and adult hippocampal neurogenesis supports efficient circuit function under pathological stress. Glial cells play central roles in mediating adaptive plasticity, neuroinflammatory control, and metabolic support, with dysregulation accelerating cognitive decline. Collectively, these findings frame CR as an emergent property of coordinated biological processes operating across molecular, cellular, and network scales, with important implications for developing reserve-enhancing therapeutic and lifestyle-based interventions that complement traditional pathology-focused approaches.
Background and objectiveAlzheimer’s disease (AD) is characterized by the accumulation of amyloid-β (Aβ) plaques and tau pathology, with mTORC1 hyperactivation implicated in disease pathogenesis via suppression of autophagy. However, systematic evidence regarding its key upstream repressor, TSC1, in human AD brains remains limited.MethodsUsing an integrated, multi-level bioinformatic approach combining RNA-seq, neuropathological, and clinical data from the ROSMAP cohort, we comprehensively investigated the TSC1-mTORC1 axis in AD. Gene co-expression network analysis and gene set enrichment analysis were applied to contextualize TSC1 within disease-associated molecular networks.ResultsOur analysis revealed significant TSC1 downregulation and concomitant mTOR and RPTOR upregulation in AD brains. Critically, lower TSC1 expression was strongly correlated with higher Aβ plaque density, greater tau tangle burden, worse global cognitive performance, and an exacerbated neuroinflammatory microenvironment characterized by increased microglial and astrocytic activation. Gene co-expression network analysis positioned TSC1 within a disease-associated module showing the strongest association with AD pathology. Gene set enrichment analyses further demonstrated that the TSC1 low-expression phenotype was associated not only with suppression of autophagy-related pathways but also with significant enrichment of broad pro-inflammatory and immune response pathways.Conclusion and discussionThese integrated human data provide compelling evidence that TSC1 deficiency is a hallmark of AD and is associated with mTORC1 hyperactivation, aggravated amyloid-tau pathologies, cognitive impairment, and neuroinflammation. These findings are consistent with a model in which TSC1 deficiency and mTORC1 hyperactivation may contribute to AD pathophysiology, thereby nominating the TSC1-mTORC1 axis and its associated inflammatory networks as promising multi-faceted therapeutic targets. Future replication in independent cohorts is warranted to assess the generalizability of these findings.
Chronic neuroinflammation driven by sustained microglial and astrocyte activation contributes to Alzheimer’s disease progression, yet no therapeutic strategy addresses it with precision or durability in the brain. Interleukin-10 occupies an unresolved position in this problem. Constitutive interleukin-10 overexpression in amyloid precursor protein transgenic mice increased plaque burden by suppressing microglial phagocytic activity, while interleukin-10 deletion has been reported to restrict amyloidosis in one setting and to worsen tau hyperphosphorylation in another. We interpret this pattern as evidence that interleukin-10 carries opposite signs on the two principal pathologies of Alzheimer’s disease, so that any therapy holding it at a fixed concentration is committed in advance to being wrong about one of them. We therefore propose a falsifiable hypothesis: conditional, inflammation-gated interleukin-10 expression may suppress damaging inflammatory signaling while limiting the impairment of microglial phagocytosis associated with continuous exposure. We present a design framework for a synthetic gene circuit combining an adeno-associated viral vector for delivery to the central nervous system, a synthetic Notch receptor that detects membrane-bound tumor necrosis factor alpha on activated microglia through juxtacrine contact, and a PiggyBac transposon intended to integrate the circuit into the astrocyte genome. Receptor engagement is expected to release a transcription factor that drives interleukin-10 from a synthetic promoter, with transcription ceasing as the stimulus is withdrawn. We provide a quantitative packaging analysis showing that the circuit requires a compacted vector design to fit within viral capacity, and we identify three unvalidated assumptions: the recognition domain does not yet exist, ligand surface density on activated microglia is unmeasured, and shed soluble tumor necrosis factor alpha is predicted to act as a competitive inhibitor of receptor activation. A computational analysis of simulated resting-state electroencephalography, in which 45 of 171 electrode pairs differed after false discovery rate correction, is presented as a fully specified analysis workflow for delta-band connectivity as a secondary outcome measure rather than as evidence of effect, and yields effect sizes indicating that a rodent study would need roughly 11 animals per group. A four-arm validation plan is specified that separates the contribution of conditional regulation from that of genomic integration.
Alzheimer’s disease (AD) and mild cognitive impairment (MCI) represent an escalating global public health challenge with major socioeconomic consequences. Although anti-amyloid monoclonal antibodies have introduced disease-modifying treatment options for early symptomatic AD, their benefits remain modest and must be balanced against cost, monitoring burden, and safety risks. Neuromodulatory interventions have therefore emerged as promising investigational strategies that may complement existing therapeutic approaches. This narrative review evaluates current clinical and neurophysiological evidence for seven major neuromodulation approaches: 40 Hz gamma rhythm sensory stimulation, also known as gamma entrainment using sensory stimulation (GENUS), transcranial alternating current stimulation (tACS), transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS), focused ultrasound (FUS), deep brain stimulation (DBS), and transcranial photobiomodulation (tPBM). Integrating clinical findings with mechanistic evidence, we examine synaptic plasticity, neuroinflammation, glymphatic clearance, oscillatory entrainment, and cholinergic signaling as candidate therapeutic mechanisms. A comparative matrix summarizes target specificity, invasiveness, stimulation parameters, and translational status. Finally, we discuss key barriers, including biological heterogeneity, protocol standardization, durability of benefit, caregiver burden, and the uncertain implications of continuous network stimulation for future personalized and closed-loop interventions.
