Washington D.C. [USA], Feb 16 : A recent study has demonstrated that the brains of individuals whose parents suffered from alcohol use issues are unable to switch between active and resting states. This abnormality manifests itself in the affected people regardless of their own drinking habits.
The study, conducted by researchers at Purdue University and the Indiana University School of Medicine, discovered that the brain reconfigures itself between completing a mentally demanding task and resting.
But for the brain of someone with a family history of an alcohol use disorder, this reconfiguration doesn't happen.
While the missing transition doesn't seem to affect how well a person performs the mentally demanding task itself, it might be related to larger-scale brain functions that give rise to behaviours associated with addiction. In particular, study subjects without this brain process demonstrated greater impatience in waiting for rewards, a behaviour associated with addiction.
Findings are published in the journal NeuroImage.
The work was led by Enrico Amico, a former Purdue postdoctoral researcher who is now a researcher at EPFL in Lausanne, Switzerland.
"The moment you close a program, a computer has to remove it from memory, reorganize the cache and maybe clear out some temporary files. This helps the computer to prepare for the next task," said Joaquin Goni.
"In a similar way, we've found that this reconfiguration process in the human brain is associated with finishing a task and getting ready for what's next."
Past research has shown that a family history of alcoholism affects a person's brain anatomy and physiology, but most studies have looked at this effect only in separate active and quiet resting states rather than the transition between them.
"A lot of what brains do is switch between different tasks and states. We suspected that this task-switching might be somewhat lower in people with a family history of alcoholism," said David Kareken, a professor of neurology.
The study defined a "family history of alcoholism" as someone with a parent who had enough symptoms to constitute an alcohol use disorder. About half of the 54 study participants had this history.
Researchers at Indiana University measured the brain activity of subjects with an MRI scanner as they completed a mentally demanding task on a computer. The task required them to unpredictably hold back from pressing a left or right key. After completing the task, the subjects rested while watching a fixed point on the screen.
A separate task outside of the MRI scanner gauged how participants responded to rewards, asking questions such as if they would like $20 now or $200 in one year.
Amico and Goni processed the data and developed a computational framework for extracting different patterns of brain connectivity between completing the mentally demanding task and entering the resting state, such as when brain areas rose and fell together inactivity, or one brain area rose while another fell at the same time.
The data revealed that these brain connectivity patterns reconfigured within the first three minutes after finishing the task. By the fourth minute of rest, the effect had completely disappeared.
"These brain regions talk to each other and are very strongly implicated in the task even though by this point, the task is already completed. It almost seems like an echo in time of what had been going on," Kareken said.
Subjects lacking the transition also had the risk factors that researchers have seen to be consistent with developing alcoholism. These include being male, a greater number of symptoms of depression, and reward-impatience.
A family history of alcoholism, however, stood out as the most statistically significant difference in this brain reconfiguration.
The finding affects research going forward.
"In the past, we've assumed that a person who doesn't drink excessively is a 'healthy' control for a study. But this work shows that a person with just a family history of alcoholism may also have some subtle differences in how their brains operate," Goni said.