Why do we daydream? We tend to think of this as why we have lapses in concentration that often lead us to thoughts we have no control over, but rarely do we consider the processes by which our brains often default to a somewhat vivid place we have little control over. A newly published study by a team of scientists at Osaka University has recognized specific activity patterns of the brain, associated with the phenomenon of daydreaming and mind-wandering. Their work was published in the journal Nature Communications.
We might not think of it as much besides a distraction from our own productivity, but the ability to imagine things or places that are not not immediately present is one of the chief tenets of human cognition, one that enables us to make plans for the future, and create with solutions based on our knowledge of the past, while also coming up with hypothetical worst-case scenarios.
Finally shedding light on these processes would have massive implications – possible breakthroughs in treating conditions like autism, or attention deficit disorder. It could also lead to technological developments that allow people with paralysis or an inability to speak to communicate effectively.
“We are developing a brain-computer interface that decodes a person’s thoughts from brain activities and enables them to communicate without physical movement. This technology can be applied to aid communication in severely paralyzed patients such as amyotrophic lateral sclerosis (ALS),” explains the study’s chief author Takufumi Yanagisawa, who is a professor at the Institute for Advanced Co-Creation Studies at Osaka University in Japan.
“For this purpose, it is necessary to clarify what kind of brain activity occurs when a person thinks. Therefore, in this study, we investigated people’s spontaneous thoughts over a period of 10 days and examined the brain activity during these thoughts. In particular, we focused on activity in the hippocampus, which is thought to be important when people imagine something.”
In order to further probe this connection between the brain’s activity and the nature of our self-generated thoughts, the research team gathered data from a group of patients suffering from categories of drug-resistant epilepsy. The test subjects were undergoing a surgical procedure to isolate the origin of their brain’s seizure activity, a process that required surgically implanted electrodes on the hippocampus of the brain in order to screen neural activity continuously.
Throughout a span of ten successive days, the patients’ brain activity was constantly monitored and recorded as they carried out their usual day to day activities within the confines of a hospital setting. In addition to recordings of their brain waves, the test subjects were all asked to fill out an electronic survey every hour on an electronic tablet device that asked them to update their own thoughts and emotions. The researchers’ questionnaire asked a list of 17 different questions that they used to assess both their mood and how it changed, as well as the nature of their own thoughts, and had them routinely rate their daily experiences using a simple numerical scale from 1 to 7.
The research team also collected physiological data with the aid of a wristband device worn by the study participants. Like a FitBit, this device measures the heart rate, the degree of physical activity they carry out during the day, as well as other physiological signals, offering an additional degree of context to understanding the brain’s activity. By connecting these detailed measurements with the patients’ own self-documented thoughts and feelings, the researchers sought to recognize any patterns that could link the brain’s activity to specific thoughts when they occurred.
The study research team found that sharp-wave ripples appeared in the brain’s hippocampus more frequently at intervals when the patients described vivid, imaginative, and less task-related thoughts — basically, what happens when we daydream, and high activity occurs in the temporal lobe associated with learning and memory. These brain waves are defined by the pattern they produce: a sharp wave or crest, shortly succeeded by a quick blast of synchronized neuronal activity, which appear on the chart as ripples. These waves typically peak at frequencies between 100 and 200 Hertz and they last anywhere between 50 to 200 milliseconds.
The ripples occurred predominantly at night as the patients slept but also surfaced at either wakeful periods when they were at rest or engaged in low levels of activity. This pattern indicates that there exists a strong link between the hippocampal activity and the production of spontaneous thoughts.
“The thought state that induces spontaneous thought correspond to a specific brain activity, hippocampal sharp-wave ripple, which is the same activity involved in memory fixation during sleep,” Yanagisawa said in a statement to PsyPost. “The thoughts that spontaneously come to mind may also have a memory-related function. It has also been suggested that it is possible to estimate from brain activity whether a person is in a state of mind wandering.”
Although their study was conducted on patients who have epileptic conditions, the research team was careful to filter out any data they deemed directly related to epileptic activity. After they accounted for this control, they found their observation data was congruent with prior research carried out on healthy individuals and also animal models, a reinforcement of how broadly they can apply their findings.
The study’s authors emphasized that these sharp-wave ripples happened consistently in the same manner in each of their patients and the trials demonstrated that the sharp waves were inextricably associated with a type of thought patterns less related to completing immediate tasks or future planning. Instead, when thoughts surfaced during the sharp-waves, they were more likely to be very vivid and dream-like, with clear visuals, and sometimes they were intrusive to the patient, or conflicted with their own desires.
“We found that there is a common relationship between hippocampal activity and thought in different people,” says Yanagisawa. “Although the detailed content of thoughts are different among people, we found that it is possible to estimate whether people are mind-wandering or thinking about things they don’t want to think about, regardless of the person.”
Although their new study offers some invaluable insights, there are also a number of caveats to bear in mind. For example, the correlation between the sharp-wave ripples and content of thought cannot be established as a causative relationship. It is also, consequently, not yet imminent whether these brain waves directly impact certain types of thoughts or that they merely coincide with them. Future research endeavors will likely use controlled manipulation of the brain ripples could help further distinguish the role they play in generating our thoughts.
“In the future, more data will be collected and technology will be developed that can decode the content of thoughts in detail,” Yanagisawa explains. “This will enable us to understand how people’s natural thoughts arise and the technology to decode them, which will then be applied clinically as a communication technology for patients with severe paralysis.”
“In this study, patients who had electrodes implanted intracranially for the purpose of epilepsy treatment cooperated with us, allowing us to record their thoughts while directly measuring the hippocampal EEG. With current technology, accurate measurement of hippocampal EEG requires techniques such as this one that require surgery.
“However, it may be possible to estimate hippocampal EEG using technology that does not require surgery, such as scalp EEG,” said Yanagisawa. “In the future, anyone will be able to know the state of their hippocampus in real time, which may enable them to look at their thought state objectively.”
The new paper, titled: “Hippocampal sharp-wave ripples correlate with periods of naturally occurring self-generated thoughts in humans,” was written by Takamitsu Iwata, in collaboration with researchers Takufumi Yanagisawa, Yuji Ikegaya, Jonathan Smallwood, Ryohei Fukuma, Satoru Oshino, Naoki Tani, Hui Ming Khoo, and Haruhiko Kishima.
