1000 Section - Replaying the Neural Symphony: Temporal Interference Stimulation Repairs Hippocampal-Cognitive Rhythms after Traumatic Brain Injury

Traumatic brain injury (TBI) often results in persistent hippocampal dysfunction, manifesting as severe cognitive impairment and sleep-wake disturbances. Current therapeutic options are limited. Temporal interference stimulation (TIS) represents an emerging non-invasive technique capable of precisely modulating deep brain structures like the hippocampus, offering a novel potential avenue for circuit-based repair and recovery.

Design:

Adult C57BL/6 mice received controlled cortical impact to model moderate TBI. Starting 3 days post-injury, animals underwent 14 days of daily hippocampal-targeted TIS (2 kHz/2.01 kHz carriers, 10 Hz envelope, 30 min/day). In vivo calcium dynamics in hippocampal neurons were longitudinally monitored via GCaMP fiber photometry. Cognitive function was evaluated using the Morris water maze and novel object recognition tests. Histopathological and molecular analyses included neuronal integrity (H&E, Nissl), neuroinflammation (GFAP, Iba1, IL-1β, TNF-α), cellular senescence (p16, p21), adult hippocampal neurogenesis (DCX, BrdU/NeuN), and expression of the redox-sensitive ion channel TRPM2.

Results:

TIS significantly enhanced and stabilized hippocampal neuronal excitability, evidenced by elevated and more synchronous calcium transients. This was accompanied by robust restoration of adult hippocampal neurogenesis (increased DCX⁺ and BrdU⁺/NeuN⁺ cells), reduced neuronal loss, attenuated glial activation and pro-inflammatory cytokine expression, and decreased markers of cellular senescence. Notably, TIS modulated the expression of TRPM2—a key mediator of oxidative stress–induced calcium dysregulation—suggesting a potential role in rebalancing activity-dependent signaling. These multi-level restorative effects correlated with significant improvements in spatial learning, memory, and arousal regulation.

Conclusion: Repeated hippocampal-targeted TIS drives coordinated recovery across molecular, cellular, circuit, and behavioral domains after TBI. By enhancing neuronal activity while simultaneously ameliorating neuroinflammation and senescence, TIS creates a permissive microenvironment for neural plasticity and neurogenesis. Our findings position TIS as a highly promising, non-invasive strategy for circuit-based repair in TBI and related disorders.