What Does Sadness Look Like In The Brain?

January 26, 2021

A new study suggests that feelings of sadness or anxiety may be linked to an increase in “chat” between two regions of the brain.

In the study, published today (Nov. 8) in the journal Cell, a team of researchers listened in on electrical conversations in the brain – in other words, signals that brain regions send to each other. When a person felt depressed, they found increased communication between brain cells in two specific regions of the brain involved in memory and emotion.

The researchers noted that it’s unclear whether this increase in brain communication is the cause or effect of a bad mood. However, the finding allowed them to identify the part of the brain where the action takes place.

What is clear, however, is that anxiety, depression, and mood have physical manifestations in the brain.” For many patients, knowing that when they feel depressed, it’s because of something specific and measurable in their brains,” said co-senior study author Dr. Vikaas Sohal, a psychiatrist at the University of California, San Francisco.” For some patients, this can provide important validation and remove stigma, empowering them to seek appropriate treatment.”

The researchers used a technique called intracranial electroencephalography (EEG) to conduct the study. As the term “intracranial” implies, the method involves implanting electrodes or wires inside the skull – in and on the brain. These implanted electrodes record the electrical activity of brain cells (in other words, record their communications).

Most previous studies of brain activity and mood and emotion have been done using functional magnetic resonance imaging (fMRI), an imaging modality that measures changes in blood flow to different parts of the brain. But these “are indirect measures of brain activity” and they “cannot measure changes in brain activity that occur on very fast time scales” like the ones measured in this study, Sohal said.

However, implanting electrodes in a person’s brain is an invasive procedure. Therefore, the researchers recruited patients who were awaiting surgery and already had electrodes implanted in their brains – in this case, 21 epilepsy patients whose brain electrodes were used primarily to determine which areas of the brain were causing their seizures.

The researchers recorded the brain activity of these patients over a period of seven to 10 days. During the same time period, these patients used mood diaries to track their emotions.

The study found that in 13 of the 21 patients, negative emotions were associated with increased communication between the amygdala (the area of the brain involved in processing emotions) and the hippocampus (involved in memory).

“The idea that memories of negative experiences and negative emotions are closely related is an old idea in psychiatry and is central to cognitive behavioral therapy,” Sohal told Live Science. “Our findings may represent the biological basis for this relationship.” (Cognitive behavioral therapy is an approach used by mental health professionals to treat conditions such as depression and anxiety, and involves changing the way a person thinks and behaves).

Sad tunes on the radio.
Both the amygdala and the hippocampus have long been known to be associated with mood, depression and anxiety, Sohal said. However, he likens that previous knowledge to knowing that a radio station is playing a song, but not knowing which station to tune into.

Now, we know the radio frequencies – the activity patterns or communications of neurons – so we can set our devices correctly, Sohal says. In other words, these findings could be useful in developing new treatments that target this activity in the brain, Sohal said. For example, such treatments could aim to manage or reduce excessive communication between the amygdala and hippocampus.

However, it’s unclear exactly how emotions and memories are intertwined, and Sohal speculates that perhaps negative emotions in the amygdala trigger the recollection of sad memories when a person is depressed, or vice versa.

It’s also unclear whether bad moods lead to increased chatter in these areas or whether increased chatter leads to bad moods.Even if it’s the latter, Sohal says, it turns out that another part of the brain is the ultimate cause of a person’s bad mood, and it’s likely that increased signaling still helps amplify the mood. But if brain activity is a result of bad mood, researchers might be able to tap into that and measure it – much like a pacemaker measures heart rhythm – to monitor the level of sadness in people with severe depression, for example.

Now, the team wants to understand how this signal is generated and whether it affects other parts of the brain.