Cancer and chemotherapy cause separate but related brain changes
The first change to the brain involved the cytokines. Cytokines are proteins that your body uses as signaling agents and are an important part of the autoimmune response.
However, their role is often to cause inflammation, which is detrimental when it goes out of control. Such as the dysregulation that occurs when your body’s immune system is trying to respond to a cancerous tumor.
In fact, the cytokines released in response to the breast cancer even caused inflammation of the nervous system. An inflamed nervous system makes it harder for your brain to function properly.
Secondly, the cancer somehow impaired neural regeneration in the hippocampus. Since the hippocampus is the part of the brain mostly responsible for storing and recalling memories, this impairment lead to memory loss.
Thirdly, the cancer tumors also had an effect on the volume of the brain, especially the hippocampus and frontal lobes. This change in volume had a detrimental effect on the mice’s ability to think and learn.
That was all before the chemo drugs were injected. The methotrexate and 5-fluorouracil combination made all of the problems worse.