In a new study published in the Journal of Neuroscience, French and Dutch researchers say human brains “independently measure episodic movement.”
What does this mean?
Our brains have “an internal or inherent flow of time, that was not driven by something going on in the external world,” neuroscientist and lead study author Leila Reddy said. She says this is evidence of the human mind’s “mental time travel” ability.
In order to obtain evidence of this hard-to-grasp concept, Reddy and her team studied the brains of people with epilepsy who already needed invasive electrode implants in their brains, regardless of the research.
“These patients have severe, drug-resistant epilepsy and are awaiting surgery,” Reddy said. “Part of the pre-surgical procedure involves implanting electrodes in the brain to monitor seizure activity. Once the electrodes are inserted in the brain, we ask the patients if they are willing to participate in short experiments for us, and we can record from single neurons to test different hypotheses.”
Researchers found the participants’ brains’ “time cells” fired at specific moments, including moments when there was not any external stimuli present. This suggests that their brains were responding to some internal sense of sequencing.
“I think a big question here is to ultimately understand how memories are encoded,” Reddy said. “Episodic memory, in particular, is the memory of what happened, when, and where. Time cells could provide the scaffolding for representing the ‘when.’ Emerging evidence suggests that the same hippocampal neurons might also encode the ‘where’ and the ‘what,’ providing a broader framework for encoding memories.”
In the future, to better understand how human brains process time, Reddy believes researchers will need to look even closer at the mechanisms by which the brain encodes both time’s passage and memories.