A Cedars-Sinai study illuminates how the human brain forms new recollections—providing insights into potential treatments for neurodegenerative diseases.

Investigators examined neurons that produce dopamine, a chemical that carries messages between brain cells. They found that these neurons are critical to the creation of episodic memory—the type that, for instance, enables you to recall where you parked your car or what you ate last night.

The team observed neuron responses in patients undergoing deep brain stimulation surgery to reduce the symptoms of Parkinson’s disease. The procedure, during which patients remain awake, includes lowering an electrode into the brain to localize treatment where dopamine neurons reside.

“This procedure is a rare opportunity for researchers to observe the activity of dopamine neurons in an awake human being,” says Adam Mamelak, MD, professor of Neurosurgery at Cedars-Sinai. “It provides extremely valuable insights into how humans form memories.”

Patients were shown a sequence of images—some they had never seen before and others that were familiar. The dopamine neurons responded only when an image was novel, implying that a new memory was forming.

“Dopamine neurons degrade in neurodegenerative diseases such as Parkinson’s, which, in addition to motor symptoms, is often also accompanied by cognitive issues such as memory problems,” according to Ueli Rutishauser, PhD, the study’s senior author and the Board of Governors Chair in Neurosciences.

“This study suggests that short bursts of dopamine—activated by novel stimuli—are what trigger learning or new memories,” he says.