biology

Transcranial random noise stimulation

Transcranial random noise stimulation is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Transcranial random noise stimulation rather than just read about it. In short: Transcranial random noise stimulation (tRNS) is a non-invasive brain stimulation technique and a form of transcranial electrical stimulation (tES). Terney et al from Göttingen University was the first group to apply tRNS in humans in 2008.

Key takeaways

Transcranial random noise stimulation belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Transcranial random noise stimulation to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Transcranial random noise stimulation from memory before moving on to harder problems.

Reference excerpt

Transcranial random noise stimulation (tRNS) is a non-invasive brain stimulation technique and a form of transcranial electrical stimulation (tES). Terney et al from Göttingen University was the first group to apply tRNS in humans in 2008. They showed that by using an alternating current along with random amplitude and frequency (between 0.1 and 640 Hz) in healthy subjects, the motor cortex excitability increased (i.e. increased amplitude of motor evoked potentials) for up to 60 minutes after 10 minutes of stimulation. The study included all the frequencies up to half of the sampling rate (1280 samples/s) i.e. 640 Hz, however the positive effect was limited only to higher frequencies. Although tRNS has shown positive effects in various studies the optimal parameters, as well as the potential clinical effects of this technique, remain unclear.

Mechanism of action The physiological mechanisms underlying the effects of tRNS are not well known, however many hypotheses have been suggested. The robust changes in cortical excitability observed after tRNS could be attributed to the repeated opening of sodium channels and changes in their kinetics of activation and inactivation or to the increased sensitivity of neuronal networks to modulation. tRNS may influence cortical oscillations, leading to changes in excitability. These proposed mechanisms are consistent with the observation that reversing electrode polarities in tRNS does not interfere with the augmentation in cortical excitability, suggesting that tRNS-induced cortical excitability is independent of current flow direction. Since tRNS is a repetitive, random, and subthreshold stimulation, it is speculated that tRNS induces direct temporal summation of neural activity because the time constant of a neuron is sufficiently long to permit the summation of two stimuli presented in close succession. The effects of tRNS may also be explained in the context of the stochastic resonance phenomenon. tRNS is, by definition, a stimulation that induces non-finalized random activity in the system (i.e., noise). The presence of neuronal noise might enhance the sensitivity of the neurons to a given range of weak inputs

Comparison with other tES techniques

Transcranial electrical stimulation (tES) generally includes the following techniques:

Transcranial alternating current stimulation (tACS) Transcranial direct current stimulation (tDCS) Transcranial random noise stimulation (tRNS) Transcranial pulsed current stimulation (tPCS) tRNS stimulation differs from tDCS in that instead of constant direct current delivery, current levels are randomly generated, with a normal distribution around a specific mean intensity. Other parameters related to the stimulation electrodes, like position and size, are similar to tDCS. Compared to tDCS, tRNS has also the advantage of being more comfortable, which makes it potentially advantageous for setting and blinding studies. tRNS is easier to blind than tDCS with the 50% perception threshold for tDCS at 400 μA while this threshold was at 1200 μA in the case of tRNS. tACS (transcranial alternating current stimulation) is a frequency-specific stimulation method that is also thought to influence oscillatory neuronal activity. This method differs from tRNS in that a sinusoidal current is applied at a fixed frequency rather than a randomly presented range of frequencies. Often, tACS is applied at frequencies that mirror the predominant frequency bands observed in EEG in different regions of the brain.

See also Neuromodulation Neurotechnology Neurostimulation Transcranial magnetic stimulation (TMS)

References

Worked examples

Example 1 — a first encounter with Transcranial random noise stimulation

Start with the simplest possible case. Write down what Transcranial random noise stimulation claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Transcranial random noise stimulation before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Transcranial random noise stimulation ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Transcranial random noise stimulation

In research: Transcranial random noise stimulation appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Transcranial random noise stimulation in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Transcranial random noise stimulation is common in secondary-school and first-year university syllabi. It links to neighbouring topics Neurophysiology, Neurostimulation, so understanding it makes those chapters shorter.
In everyday life: Look for Transcranial random noise stimulation outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Transcranial random noise stimulation in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Transcranial random noise stimulation means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Transcranial random noise stimulation out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Transcranial random noise stimulation in simple terms?

Why does Transcranial random noise stimulation matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Transcranial random noise stimulation?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Transcranial random noise stimulation.