UTSA biology research could lead to treatments for PTSD and Alzheimer's

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(Dec. 15, 2009)--Led by Joe L. Martinez Jr., UTSA Ewing Halsell Distinguished Chair in Biology, a team of UTSA researchers found that radiation therapy can prevent the brain from forming some types of fearful memories. Further research may lead to treatments for post-traumatic stress disorder and Alzheimer's disease.

Radiation therapy reduces the number of new granule cells in the hippocampus, the part of the brain responsible for autobiographical memory. Cranial irradiation, or radiation of the skull, is commonly used as a treatment to prevent cancer from spreading to the brain. However, long-term cognitive impairments, such as the inability to learn or remember new tasks, often occur as a result of the procedure.

The researchers tested the ability of rats to form three types of fear memories: delay fear memories, context fear memories and trace fear memories. Delay fear memories form when a fearful situation occurs simultaneously with another event. Context fear memories form when a fearful situation follows another event and both take place in the same physical space. Trace fear memories form when an event and a fearful situation are separated by a pause.

Combining biological and psychological approaches in the laboratory, the researchers observed the behavior of rats not producing new granule cells in their brains. The researchers observed that the rats were able to form delay and fear memories but were unable to form trace fear memories. The findings led them to believe that new granule cells are not required in the hippocampus of the brain to form delay and context fear memories but are required for the formation of trace fear memories.

"This research has broad applications including treatments for post-traumatic stress disorder and Alzheimer's disease," said Martinez. "If we can pinpoint the neurons in the hippocampus that are responsible for storing trace fear memories, we may be able to selectively erase negative memories by decreasing the number of new granule cells in the brain. Or, we may be able to prevent memory loss by preventing the death of new granule cells. Such therapies could definitely enhance an individual's life, but we have a long way to go before we put the theory into practice."