Researchers at the University Hospital Gasthuisberg of the Katholieke Universiteit Leuven in Belgium published a new report this week in the Journal of Clinical Oncology that describes what they found when they examined whether cognitive complaints after breast cancer treatment involving chemotherapy are associated with observable brain activity changes. The complaints are well-documented and collectively referred to as “chemo brain,” a perception of greater effort needed to complete cognitive tasks after treatment of cancer with chemotherapy.

“Cognitive complaints of people increase with chemotherapy and we are trying to find out why,” said Sabine Deprez, lead author on the paper. “Difficulty multitasking is one of the biggest complaints.”

Cognitive performance decreases have been reported in cancer patients following chemotherapy and also after no chemotherapy. The distinction between mental performance decreases related to chemotherapy and those possibly caused by the advance of the disease itself has been difficult to make. To date, brain imaging studies focused on comparing cancer patients treated with chemotherapy and healthy individuals. Deprez and colleagues compared mental function before and several months after chemotherapy in the same 18 women treated with chemotherapy for breast cancer. These women were also compared to other women with breast cancer but not receiving chemotherapy as well as with women with no cancer or treatment.

“The special thing about how we did the design was that before we did it we adjusted the difficulty for each patient, and the performance of everyone was between 70 and 80 percent,” Deprez said.

The measurements of the study were made by imaging the brains of the women with functional magnetic resonance imaging, or fMRI, while they were in the fMRI machine and engaging in multitasking behavior routines. The routines involved indicating whether two sounds were of the same frequency and if two moving objects were oriented in the same way, both while remembering two symbols presented earlier.

The researchers found that while the healthy and cancer with no chemotherapy groups exhibited no change in brain activation magnitude and location, the cancer with chemotherapy group experienced significantly decreased brain activity in regions that were more active at the beginning of the study, before chemotherapy was administered. This group complained of “foggy thinking” after their chemotherapy regimens.

“The important thing that we found was a relation with subjective cognitive complaint,” Deprez said in an interview. “It feels like they have to do more effort to get the same result after chemo.”