Theta rhythm as a real-time quantitative marker for non-invasive analysis of adult neurogenesis in the intact brain.

Background: Adult neurogenesis is a regenerative mechanism of the brain that contributes to neuroplasticity and memory consolidation. Aberrant neurogenesis is considered a key pathogenic hallmark of a wide array of neurocognitive disorders. While the functional significance of adult neurogenesis is well established in most experimental and wild animals, its occurrence in the aging human brain remains uncertain. Objective: Most studies on adult neurogenesis in humans rely on post-mortem analysis, as there is currently no method to accurately evaluate the neurogenic process in the intact brain. Theta rhythm, a neural oscillatory pattern, is believed to originate from hippocampal place cells that play a crucial role in creating cognitive maps. Theta rhythm is positively modulated by various factors, such as physical activities and enriched environment, which also promote adult neurogenesis. The strength and stability of theta rhythm are closely linked to mental well-being and cognitive functions, while its disruptions serve as indicators of neuropathogenic events that directly intersect with the regulation of adult neurogenesis. Conclusion: Modulation of the theta rhythm may reciprocally reflect the degree of neurogenesis in the adult brain, as newborn neurons can directly integrate with place cells, especially in the hippocampus. Given their electrophysical properties, newborn neurons may hold an intrinsic potential to generate theta rhythm upon motor sensory inputs and different neural activities. Biomedical tools such as electroencephalography, which measures theta rhythm, could thus be utilized to non-invasively monitor ongoing neurogenic processes in intact brains. Consequently, theta rhythm may function as a potential real-time, quantitative marker of adult neurogenesis.