Electrically stimulating a nerve in the face has shown promise for boosting memory. Bursts of stimulation, delivered via skin electrodes, appear to improve signalling between cells in the hippocampus, a brain region crucial for memory. In a small study, this then enabled people to better remember what a group of strangers did for a living.
“If the benefits hold up, that could make [this stimulation] suitable for a wearable device and potentially accessible to many more people,” says Siyar Bahadir at The Feinstein Institutes in New York, who wasn’t involved in the study.
Electrical stimulation has been linked to improved memory before, but this is usually highly invasive or requires people to lie in a scanner. In 2024, Myles McLaughlin at the Leuven Brain Institute in Belgium and his colleagues showed that a non-invasive technique, called transcranial direct current stimulation, sparks the trigeminal nerve – a three-part nerve in the head that carries sensory information between parts of the face and the brain. This then activated a pathway leading to the hippocampus.
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Now, the researchers have set out to understand whether this affects memory. They first established the best type of stimulation to apply, by delivering electrical stimulation to the trigeminal nerve of anaesthetised rats, via small electrodes under the skin.
They found that 1-second bursts of 200-hertz electrical stimulation, separated by 29 seconds of rest, increased signalling between hippocampal neurons by about 20 per cent. This continued for at least 90 minutes after the stimulation ended. In contrast, continuous stimulation at 100 hertz had no effect.
The researchers think intermittent stimulation specifically activates the locus coeruleus, a blue blob of neurons measuring just a few millimetres. This is the brain’s primary producer of noradrenaline, or norepinephrine – a chemical messenger that helps transmit nerve signals between neurons, and may also enhance memory.
When the researchers repeated the intermittent stimulation, but this time with the locus coeruleus chemically suppressed, they found there was no lasting increase in hippocampal activity.
Next, the researchers studied nine people with drug-resistant epilepsy who had electrodes implanted in their brains for routine monitoring. Skin electrodes around their jaw delivered the same pattern of 200-hertz stimulation to the trigeminal nerve for 20 minutes. This produced a similar electrical response in the hippocampus as that observed in the rats.
Finally, the researchers tested the effects of this on memory. Thirty-six adults with no known health conditions completed one session of bursts of stimulation, delivered via skin electrodes, and one sham session, at least two days apart. During these sessions, they were tasked with remembering the names and occupations that went with 12 faces, which they were tested on 2 minutes later. They then received bursts of stimulation for 20 minutes while they rested, before being tested on their memory again.
The stimulation improved occupation recall, but only at the 20-minute mark, which may be due to this resting period giving people time to consolidate what they had learned. The degree of improvement corresponds to “roughly one extra association being retained”, says McLaughlin.
“What impressed me was how the authors followed the question from synaptic changes in rats to direct recordings from the human hippocampus, then to memory testing in healthy volunteers,” says Bahadir. “That is a substantial amount of work, and it makes the findings more convincing.”
It’s unclear why there was an improvement only in occupation recall, and not names. McLaughlin suggests jobs like being a teacher bring to mind images of schools and classrooms, whereas someone’s name may be harder to remember if it has no personal connection to us.
The team is now comparing the effects of external electrical stimulation to the trigeminal nerve with that to the median nerve in the arm in up to 40 volunteers, which should reveal whether peripheral nerve stimulation may also be helpful.
Facts Only
* Electrical stimulation of a nerve in the face has shown promise for boosting memory.
* Stimulation appears to improve signaling between cells in the hippocampus.
* A study showed that 1-second bursts of 200-hertz electrical stimulation, separated by 29 seconds of rest, increased signaling between hippocampal neurons by about twenty percent.
* Continuous stimulation at 100 hertz had no effect.
* Intermittent stimulation appears to activate the locus coeruleus.
* The locus coeruleus produces noradrenaline (norepinephrine), a chemical messenger that may enhance memory.
* Replicating the intermittent stimulation with the locus coeruleus chemically suppressed resulted in no lasting increase in hippocampal activity.
* Skin electrodes around the jaw delivered 200-hertz stimulation to the trigeminal nerve for 20 minutes in people with drug-resistant epilepsy, producing a similar electrical response in the hippocampus as observed in rats.
* Thirty-six adults tested on remembering names and occupations showed improved occupation recall at the twenty-minute mark post-stimulation.
* The degree of improvement corresponded to retaining roughly one extra association.
Executive Summary
Full Take
The study follows a layered approach, moving from cellular mechanisms in animals to human responses, which lends significant weight to the findings despite the observed limitation in memory recall type. The pattern involving intermittent stimulation targeting the trigeminal nerve and linking it to noradrenaline systems suggests a potential pathway for non-invasive neuromodulation affecting higher-order functions like memory consolidation. The shift from robust synaptic changes in rats to correlating electrical responses in human hippocampal tissue creates a powerful bridge, suggesting that peripheral nerve input can modulate central memory structures.
The observation that the memory improvement was specific to occupation recall rather than names invites deeper scrutiny regarding the nature of memory encoding. If occupations trigger associative visual memories (schools, classrooms), it suggests the stimulation may be impacting the formation or retrieval of context-rich episodic memory rather than mere rote factual storage. The subsequent comparison with median nerve stimulation opens a critical avenue for assessing whether this effect is dependent on specific facial pathways or is a general property of peripheral nervous system engagement. Further investigation must focus on understanding why rest was necessary for consolidation and whether manipulating the locus coeruleus directly modulates this associative learning process in humans.
Bridge Questions: What specific neurological correlates distinguish name memory from occupation memory, and how might that difference inform future stimulation protocols? Does stimulating the median nerve yield equivalent benefits to facial nerve stimulation for hippocampal engagement, and if so, what is the functional basis of these differences? What are the long-term consequences of this temporary enhancement on memory consolidation?
Sentinel — Human
The text appears to be a synthesis of specific scientific findings presented in a narrative structure, likely written by an informed journalist or scientist relaying primary research.