• Neurons (excitatory and inhibitory): Stimulation triggered rapid upregulation of immediate early genes (e.g., FOS, EGR1, ARC) and activity-dependent plasticity genes, with stronger responses in pyramidal neurons than interneurons .
• Glial cells: Transcriptomic shifts were detected in astrocytes and microglia, showing that electrical stimulation engages non-neuronal cells as well .
• Epigenomic remodeling: Chromatin accessibility changed at activity-regulated enhancers, indicating that stimulation alters the epigenomic landscape in a cell-type-specific manner .

A 2025 ex vivo study of human temporal cortex reported that DBS preferentially increases firing rates in pyramidal cells over interneurons and strengthens cell assemblies, linking these physiological effects to underlying gene networks involved in learning and memory .

In a mouse model of stroke, hippocampal DBS — analyzed with single-cell transcriptomics — was shown to remodel microglial subpopulations and promote neurorepair, including upregulation of neurotrophic factors and downregulation of inflammatory gene signatures . While rodent data, this aligns with the neuroprotective transcriptional themes seen in human tissue.

Cell-Type-Specific Transcriptional Effects of DBS

The table below summarizes the observed molecular responses across different brain cell types from human and animal studies:

Implications for Treating Cognitive Decline

Fornix DBS in Alzheimer's Disease — The Most Advanced Application

Fornix DBS is the leading DBS target for cognitive decline, with active clinical trials in Alzheimer's disease . The mechanistic rationale is directly tied to the gene-expression findings:

1. Neurogenesis and plasticity. In a Rett syndrome mouse model, forniceal DBS induced gene-expression and splicing changes that promote adult neurogenesis and synaptic plasticity in the hippocampus . These same pathways (e.g., BDNF, CREB signaling) are being targeted in Alzheimer's trials.

2. Circuit-level rescue. DBS of the fornix activates the memory circuit (hippocampus–mammillary bodies–anterior thalamus), and the transcriptional changes described above are thought to enhance long-term potentiation and synaptic maintenance .

3. Clinical outcomes. A 2025 systematic review and meta-analysis of forniceal DBS for Alzheimer's found that patients showed slowed cognitive decline and, in some subgroups, modest improvement on the ADAS-Cog and MMSE . A 2025 biomarker study from the ADvance trial reported that 12 months of fornix DBS was associated with reduced hippocampal atrophy compared to matched untreated AD patients .

4. Cholinergic and amyloid-related effects. A 2025 comprehensive review on DBS for Alzheimer's concluded that therapeutic mechanisms include reducing amyloid-β deposition, activating the cholinergic system, increasing neurotrophic factors, and enhancing synaptic activity — all consistent with the gene-expression changes observed in human and animal models .

Key Caveats and Evidence Gaps

• The most definitive human cortical gene-expression data (Caglayan et al.) is still a preprint and used acute electrical stimulation during neurosurgery, not chronic implanted DBS .
• Direct single-cell transcriptomic data from chronically implanted DBS patients (before vs. after months of stimulation) does not yet exist — living human brain biopsies are not feasible for this purpose.
• Clinical trials for cognitive decline remain small, and the magnitude of cognitive benefit is modest; no DBS approach has received regulatory approval for Alzheimer's .
• Whether the cell-type-specific transcriptional changes translate into durable cognitive improvement depends on many factors including target selection, stimulation parameters, disease stage, and individual genetics.

In summary, DBS produces rapid, cell-type-specific transcriptional and epigenomic changes in human cortex — most prominently in excitatory neurons but also in glia — that align with pro-plasticity, neuroprotective, and anti-inflammatory mechanisms. These findings provide a molecular framework for why forniceal DBS may slow hippocampal degeneration and cognitive decline in Alzheimer's disease, though the evidence base remains preliminary and larger confirmatory trials are needed.

• Neurons (excitatory and inhibitory): Stimulation triggered rapid upregulation of immediate early genes (e.g., FOS, EGR1, ARC) and activity-dependent plasticity genes, with stronger responses in pyramidal neurons than interneurons .
• Glial cells: Transcriptomic shifts were detected in astrocytes and microglia, showing that electrical stimulation engages non-neuronal cells as well .
• Epigenomic remodeling: Chromatin accessibility changed at activity-regulated enhancers, indicating that stimulation alters the epigenomic landscape in a cell-type-specific manner .

A 2025 ex vivo study of human temporal cortex reported that DBS preferentially increases firing rates in pyramidal cells over interneurons and strengthens cell assemblies, linking these physiological effects to underlying gene networks involved in learning and memory .

In a mouse model of stroke, hippocampal DBS — analyzed with single-cell transcriptomics — was shown to remodel microglial subpopulations and promote neurorepair, including upregulation of neurotrophic factors and downregulation of inflammatory gene signatures . While rodent data, this aligns with the neuroprotective transcriptional themes seen in human tissue.

Cell-Type-Specific Transcriptional Effects of DBS

The table below summarizes the observed molecular responses across different brain cell types from human and animal studies:

Implications for Treating Cognitive Decline

Fornix DBS in Alzheimer's Disease — The Most Advanced Application

Fornix DBS is the leading DBS target for cognitive decline, with active clinical trials in Alzheimer's disease . The mechanistic rationale is directly tied to the gene-expression findings:

1. Neurogenesis and plasticity. In a Rett syndrome mouse model, forniceal DBS induced gene-expression and splicing changes that promote adult neurogenesis and synaptic plasticity in the hippocampus . These same pathways (e.g., BDNF, CREB signaling) are being targeted in Alzheimer's trials.

2. Circuit-level rescue. DBS of the fornix activates the memory circuit (hippocampus–mammillary bodies–anterior thalamus), and the transcriptional changes described above are thought to enhance long-term potentiation and synaptic maintenance .

3. Clinical outcomes. A 2025 systematic review and meta-analysis of forniceal DBS for Alzheimer's found that patients showed slowed cognitive decline and, in some subgroups, modest improvement on the ADAS-Cog and MMSE . A 2025 biomarker study from the ADvance trial reported that 12 months of fornix DBS was associated with reduced hippocampal atrophy compared to matched untreated AD patients .

4. Cholinergic and amyloid-related effects. A 2025 comprehensive review on DBS for Alzheimer's concluded that therapeutic mechanisms include reducing amyloid-β deposition, activating the cholinergic system, increasing neurotrophic factors, and enhancing synaptic activity — all consistent with the gene-expression changes observed in human and animal models .

Key Caveats and Evidence Gaps

• The most definitive human cortical gene-expression data (Caglayan et al.) is still a preprint and used acute electrical stimulation during neurosurgery, not chronic implanted DBS .
• Direct single-cell transcriptomic data from chronically implanted DBS patients (before vs. after months of stimulation) does not yet exist — living human brain biopsies are not feasible for this purpose.
• Clinical trials for cognitive decline remain small, and the magnitude of cognitive benefit is modest; no DBS approach has received regulatory approval for Alzheimer's .
• Whether the cell-type-specific transcriptional changes translate into durable cognitive improvement depends on many factors including target selection, stimulation parameters, disease stage, and individual genetics.

In summary, DBS produces rapid, cell-type-specific transcriptional and epigenomic changes in human cortex — most prominently in excitatory neurons but also in glia — that align with pro-plasticity, neuroprotective, and anti-inflammatory mechanisms. These findings provide a molecular framework for why forniceal DBS may slow hippocampal degeneration and cognitive decline in Alzheimer's disease, though the evidence base remains preliminary and larger confirmatory trials are needed.