Patterns of electrical brain activity have been used for the first time to tell when people are sad, happy or depressed. It’s a first step towards treating people with depression or anxiety with devices which would constantly monitor their mood using brain signals.
Ultimately, the aim is to programme the devices so they actually help people overcome potentially dangerous negative emotions in real time by activating other, more uplifting networks in the brain.
Already, brain implants are helping people who are “locked-in” or paralysed communicate with caregivers and friends through computer interfaces. And by implanting and activating electrodes in specific regions of people’s brains – a process called deep brain stimulation, or DBS – researchers have helped to ease a range of conditions including depression, bipolar disorder, Tourette’s syndrome and obsessive compulsive disorder. There are even advances towards “mind-reading” – deciphering memories and internal thoughts by monitoring the brain’s electrical activity.
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Mood decoded
Now it’s possible to capture mood too. “We’ve discovered how mood variations can be decoded from neural signals in the human brain,” says lead researcher on the project, Maryam Shanechi of the University of Southern California in Los Angeles. “It’s a significant step towards creating new therapies that use brain stimulation to treat debilitating mood and anxiety disorders in millions of patients who don’t respond to current treatments.”
In the US alone, the 2016 revealed that 16.2 million adults experienced depressive episodes the previous year – almost 7 per cent of the US population – but a third didn’t respond to treatment.
Shanechi and her colleagues captured a chance to study brain patterns correlating with mood by recruiting seven people with epilepsy. Each had been temporarily fitted with implanted electrodes to identify major sources of their seizures. By monitoring continuously the electrical output from the electrodes, the team homed in on “fingerprint” patterns of activity across the brain that corresponded very closely with specific moods in each person.
To make this possible, each of the seven participants had periodically filled out questionnaires on their mood. For each answer, they rated how they felt on a seven-point scale. “We were able to uncover the patterns of brain signals that matched the self-reported moods,” says Shanechi. “We then used this knowledge to build a decoder that would independently recognise the patterns of signals corresponding to a certain mood.”
The patterns were different for each participant, because the tell-tale signatures of mood came from all over the brain rather than specific locations. But almost all the patterns were confined to the limbic system, the network of brain regions crucial for triggering emotion and mood swings.
Shanechi stresses that decoding is only a first step. For a device to treat as well as monitor, for example, the team needs to establish which parts of the brain to stimulate to head-off impending depression or anxiety. The safety and inconvenience of implanting electrodes is also a major hurdle, but non-invasive systems that stimulate brain regions from electrodes on the skull are under development.
“Mood is very hard to measure,” says Thomas Schlaepfer, who treats depression with DBS at University Hospital Freiburg in Germany. “The fact they find mood correlates with predictive electrical signals is stunning, and a lovely concept,” he says.
Nature Biotechnology
