Memory can be strengthened in human patients by stimulating a crucial junction in the brain, say UCLA neuroscientists who discovered the possibility.
The finding could lead to a new method for boosting memory in patients with early Alzheimer's disease.
The UCLA team focused on a brain site called the entorhinal cortex. Considered the doorway to the hippocampus, which helps form and store memories, the entorhinal cortex plays a crucial role in transforming daily experience into lasting memories.
"The entorhinal cortex is the golden gate to the brain's memory mainframe," explained senior author Dr. Itzhak Fried, professor of neurosurgery at the David Geffen School of Medicine at UCLA.
"Every visual and sensory experience that we eventually commit to memory funnels through that doorway to the hippocampus. Our brain cells must send signals through this hub in order to form memories that we can later consciously recall," Dr. Fried explained.
Fried and his colleagues followed seven epilepsy patients who already had electrodes implanted in their brains to pinpoint the origin of their seizures. The researchers monitored the electrodes to record neuron activity as memories were being formed.
Using a video game featuring a taxi cab, virtual passengers and a cyber city, the researchers tested whether deep-brain stimulation of the entorhinal cortex or the hippocampus altered recall. Patients played the role of cab drivers who picked up passengers and travelled across town to deliver them to one of six requested shops.
"When we stimulated the nerve fibers in the patients' entorhinal cortex during learning, they later recognized landmarks and navigated the routes more quickly," said Fried.
"They even learned to take shortcuts, reflecting improved spatial memory.
"Critically, it was the stimulation at the gateway into the hippocampus - and not the hippocampus itself - that proved effective," he added.
The use of stimulation only during the learning phase suggests that patients need not undergo continuous stimulation to boost their memory, but only when they are trying to learn important information, Fried noted. This may lead the way to neuro-prosthetic devices that can switch on during specific stages of information processing or daily tasks.
"Losing our ability to remember recent events and form new memories is one of the most dreaded afflictions of the human condition," said Fried.
"Our preliminary results provide evidence supporting a possible mechanism for enhancing memory, particularly as people age or suffer from early dementia. At the same time, we studied a small sample of patients, so our results should be interpreted with caution," he added.
The result of the study has been published in the Feb. 9 edition of the New England Journal of Medicine.