Clinical Landscape

Transcranial Electrical Stimulation – State of the Art

By applying an electric field, tES alters neuronal excitability and modulates firing frequency. Neuronal subthreshold depolarization by anodal tES increases neural excitability. Hyperpolarization under the cathode inhibits neuronal excitability.
Specific frequency bands are responsible for cognitive functions (e.g. attention = alpha activity & gamma = consciousness).¹

Modulating these frequency bands shows potential in enhancing the linked cognitive functions in various applications.²

¹ Kahana, M. J. (2006). The cognitive correlates of human brain oscillations. J. Neurosci. 26, 1669–1672. doi: 10.1523/JNEUROSCI.3737-05c.2006
² The impact of gamma transcranial alternating current stimulation (tACS) on cognitive and memory processes in patients with mild cognitive impairment or Alzheimer's disease: A literature review. Author links open overlay panelN.R. Nissim a b, D. V.H. Pham a, T. Poddar a, E. Blutt a, R.H. Hamilton
A meta-analysis suggests that tACS improves cognition in healthy, aging, and psychiatric populations. Shrey Grover et al. Sci Transl Med. 2023

Clinical Applications currently investigated

Stroke (Neglect)

tDCS exhibits promising results in clinical trials for neurorehabilitation in post-stroke patients. For e.g. in motor function recovery as well as in enhancing language skill, especially when combined with behavioral training. In neglect patients, tDCS is used to modulate cortical excitability, specifically to inhibit contra-lesional over-activation and following increased inhibition of the damaged hemisphere.

Depression

tDCS has shown to be an effective tool to modulate mood disorders. In Depression, reduced neural activity in the dorsolateral prefrontal cortex can be restored and depressive symptoms alleviated. Additionally, spatial abnormalities in alpha frequencies linked to mood disorders may be restored by frequency specific tACS over the affected brain regions.

Dementia

Recent studies have shown that 40 Hz tACS can restore cognitive functions and improve memory in patients suffering from Alzheimer’s Disease. Further, restoring endogenous oscillations in the gamma frequency has shown the potential to enhancing cerebral blood flow in patients and to reduce the amyloid pathology by modulating the brains own immune cells in animal models.