“Key brain regions that we know are typically involved in autobiographical memory formation and retrieval, especially the hippocampus, are located quite far from the primary tumor bed, and thus far from the site of focal radiation,” Sekeres, who is director of the Sekeres Memory Laboratory at Baylor University, said in an interview with CURE.
BY Kristie L. Kahl
Children with pediatric posterior fossa tumors, such as medulloblastoma, who are treated with radiotherapy may be less likely to recall specific details of events that occurred after treatment compared with events that happened before, according to study results published in the Journal of Neuroscience
Lead study author Melanie Sekeres, Ph.D., noted that this finding is significant because after treatment, children had less volume in the hippocampus — a part of the brain that plays an important role in memory
Medulloblastomas – the most common malignant brain tumor in children
– are typically treated with radiotherapy, which has been found to improve survival rates among these patients; however, radiotherapy significantly affects a developing brain. As a result, this treatment option is known to suppress the growth of new neurons in the nervous system, including the hippocampus, which is a process known as neurogenesis and is critical for the formation of new memories.
“Key brain regions that we know are typically involved in autobiographical memory formation and retrieval, especially the hippocampus, are located quite far from the primary tumor bed, and thus far from the site of focal radiation,” Sekeres, who is director of the Sekeres Memory Laboratory at Baylor University, said in an interview with CURE
“But, given that whole-head radiation and systemic chemotherapy are typically used as part of the treatment protocol, it should not be that surprising that we see brain-wide effects of these treatments,” she added.
As a result, radiotherapy and chemotherapy appeared to be impairing pediatric patients’ long-term ability to form new, post-treatment memories, while leaving the older, pre-treatment memories unaffected.
Although several aspects of memory have been examined in this population before, the impact of radiotherapy on autobiographical memory – the link to unique personal events and involves the recollection of emotional and perceptual details that allow a person to mentally re-experience the event – had not been evaluated.
So, Sekeres and colleagues retrospectively assessed episodic and nonepisodic details for events that either preceded or followed treatment in 13 children who received radiotherapy for posterior fossa tumors at least one year before the study. These children were then compared to 28 healthy youths of the same age.
All children completed the Children’s Autobiographical Interview, a standardized memory test, and underwent an MRI of the brain. In addition, during individual interviews, children were asked to recall memories from personal events that occurred at a specific time and place and a very old memory from an event before their radiation treatment, as well as a recent memory from within the past month.
Children could choose from a list of events such as a birthday party, family trip, graduation or getting a pet, but were also told that they could pick another event. The interview also allowed children to freely recall without prompting before being asked general and specific questions about the event.
Children treated with radiotherapy reported fewer episodic details of post-treatment events compared with the healthy control group. However, these children reported equivalent episodic details about pretreatment events.
The researchers concluded this finding of lost episodic details was associated with hippocampal volume loss – which is associated with things like Alzheimer’s disease, dementia, brain injury, epileptic amnesia, encephalitis and aging.
“These findings have significant implications for the patient’s quality of life. The ability to form and to retain detailed personal memories for important events in one’s life is a big part of what gives our lives rich meaning,” said Sekeres, who is also an assistant professor of psychology and neuroscience in Baylor University’s College of Arts & Sciences.
She noted that clinicians should take this in to consideration when deciding on treatment options, and that further research is warranted.
“Given the decreased volume we observed in the hippocampus, and other cortical regions of the recollection network it will be important for follow-up studies to assess differences in neural network activity, and in functional connectivity within these regions using MRI in patients and healthy controls in order to gain a better understanding of potential functional disruptions that may be underlying the observed deficits in memory performance,” Sekeres said.