"A new unifying account of the roles of neuronal entrainment"
https://www.sciencedirect.com/science/article/pii/S0960982219309558?
Neuronal activity can be aligned to external rhythmic input streams. The phenomenon or process is called entrainment.
"Neuronal entrainment has been demonstrated in all “traditional” frequency ranges (delta, theta, alpha, beta and gamma)." The authors argue here that entrainment is not frequency-specific.
Parallelly, they are inquiring whether frequency-specificity may "be system or brain-state specific" and to what degree.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7099485/
Featuring Figure 1
Neural circuits can adjust their frequency to a given stimulation frequency
Initially, the circuit receives a constant input, P(t)=P, and oscillates at its natural frequency, f. It then receives a sinuisoical wave input which entrains it after a certain time (convergence) to the input frequency.
The entrainment index is then calculated from the power spectrum of the signal E(t) after its convergence.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6601804
Featuring Figure 2
A. Based on the selected parameters, the network shows synchronous alpha activity, with an intrinsic frequency ω0 of ~10 Hz.
B. If the stimulation frequency ω(f) is close to the intrinsic frequency, its harmonics, and/or subharmonics, resonance occurs. While the network response frequency ω′ remains stable, the associated spectral power increases significantly.
C. Whenever the stimulation amplitude increases beyond a certain threshold, the intrinsic activity in entrained by the stimulation drive and the network oscillates at a frequency equal to that of the stimulation, its harmonics, and/or subharmonics. In this example, a strong rhythmic stimulation ω(f) of 17.5 Hz leads to harmonic entrainment at half that frequency (subharmonic) i.e. an ω′ of 8.8 Hz.
D. In high-frequency stimulation, nonlinear interactions account for acceleration of the ongoing synchronous activity, leading to a spectral shift. In this example, a stimulation with an ω(f) of 97 Hz accelerates the baseline activity from an ω(0) of 10 Hz to an ω′ of 15 Hz.
Depatterning and repatterning of the brain — how new patterns may become entrenched in the brain.
How can the brain become an empty canvas?
A review article in Nature Medicine explores how psychedelics affect the brain. The authors describe a two‑stage process:
Stage 1: Neural desynchronization, linked to destabilization of entrenched network patterns.
Stage 2: Neuroplasticity, linked to a window where psychological and behavioral change occurs.
First, psychedelics lead to brain desynchronization thus temporarily loosening deeply established patterns of thought and perception?
Afterwards, the brain enters a period of increased adaptability — the scientific term is neuroplasticity — where it becomes more receptive to forming new connections and interpretations.
The final outcome depends on following interventions. Historically, coercive contexts have been reported. Therapeutic applications are discussed.