FREQUENTLY ASKED
Questions
What is closed-loop tDCS?
Closed-loop tDCS is a neurostimulation architecture in which electrical current delivery is governed by real-time physiological measurement rather than a preset timer. Using continuous HRV monitoring via PPG sensors, the system classifies the user's autonomic state and activates stimulation only when defined readiness criteria are met. It is defined by feedback between the user's biology and the device's stimulation decisions.
How does closed-loop tDCS differ from standard tDCS?
Standard (open-loop) tDCS applies a fixed protocol: fixed current, duration, and timing without any measurement of the user's brain state. Closed-loop tDCS continuously monitors physiological signals and conditions stimulation on whether those signals indicate neural readiness. The core difference is whether the device responds to the individual or applies a uniform protocol regardless of their state at that moment.
Why does brain state matter so much for tDCS outcomes?
tDCS effects are state-dependent because the outcome of any neural input depends on the current excitability of the target neurons — a principle formalised in BCM-model metaplasticity theory. The Bogdanov and Schwabe (2016) study showed the same stimulation protocol prevented stress-induced working memory impairment in stressed individuals while producing no benefit in calm ones. State is a primary moderator of whether stimulation works.
What role does HRV play in closed-loop tDCS?
Heart rate variability is the millisecond variation in intervals between heartbeats. High HRV reflects parasympathetic dominance and correlates with prefrontal engagement and cognitive readiness. Low HRV with elevated sympathetic tone indicates stress-induced prefrontal suppression. In closed-loop systems, HRV provides a non-invasive, continuously measurable proxy for DLPFC functional state, enabling principled inference about stimulation readiness without direct neural recording.
Is closed-loop tDCS proven more effective than open-loop?
The mechanistic and theoretical case for superiority is well-supported. However, large-scale head-to-head controlled trials comparing closed-loop tDCS to well-designed open-loop protocols in real-world conditions have not yet been published. Further pre-registered comparative trials are necessary before superiority claims can be made.
Is closed-loop tDCS safe?
Within established parameters, the tDCS safety record is well-documented. Bikson et al. (2016) found zero Serious Adverse Effects across 33,200+ sessions. Sychedelic operates within these parameters and adds hardware current limits, mandatory impedance verification, CDSCO regulatory approval, and ISO 60601-1-2 certification. Standard contraindications apply: metallic cranial implants, active epilepsy without medical supervision, and pregnancy.
What makes Sychedelic's approach different?
The distinguishing feature is conditional delivery logic: tDCS only activates when HRV-derived metrics indicate physiological readiness. This addresses temporal mismatch, one of the primary documented failure modes in conventional tDCS. The system also uses adaptive alpha binaural beats to prime the user toward readiness rather than simply waiting. Independent, pre-registered comparative trial data are needed to establish whether this approach produces outcomes superior to well-matched open-loop protocols.