Chinese brain study finds monkeys convert time to space to memorise a sequence of events: paper
- Scientists track macaques watching dots on a computer screen to observe how neurons in the lateral prefrontal cortex behave to form memory
- Researchers use AI to track project data but say results may also aid creation of more human-like AI
Monkeys memorise a series of events by converting time to space in their brain, according to a research team in China who reported observing the process.
The discovery sheds light on the fundamental working mechanism of a non-human primate brain, according to the researchers.
In the study, which forms part of the controversial China Brain Project, two macaques were shown a computer screen showing a ring of dots that lit up one at a time in random sequence.
In the monkey brain lateral prefrontal cortex, the part in charge of memory, a cluster of neurons almost identical to the ring started glowing with the brightest spot matching the illuminated dot on the screen.
As the monkey tried to remember the changing dots to earn a reward, the rings of activated neurons were generated one after another in different memory cortex locations. The size of the rings decreased quickly as the number of events increased.
“Our results suggest that the brain transforms time into space,” said the researchers led by Wang Liping with the Institute of Neuroscience, Chinese Academy of Sciences, in Shanghai, in a paper published in Science magazine on Friday.
A wide range of mental activities such as learning a language, finding the way home or telling a life story involve memorising events in the right order. But how our brain handles memory, especially when time is involved, remains poorly understood.
A popular theory is that time information is coded into the activities of some independent neurons.
But Wang and his collaborators from Peking University in Beijing said their study suggested a group of neurons could be working together to hold onto the episodic experience by breaking down the sequence into separate events and storing them in different places, one at a time.
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The monkey brain also compressed the information, so the later an event occurred in the episode, the smaller the impression it produced, a phenomenon similar to that experienced by humans, the researchers said.
The idea that the brain could convert time to space was proposed by American psychologist Karl Lashley more than 70 years ago, but it was largely neglected because of observation difficulties.
The Chinese team injected a virus to stimulate a fluorescent protein in the monkey’s brain. When subjected to quick laser pulses, the infected brain cells emitted light for the researchers to view neuron activity through an opening in the monkey’s skull while it was fixed on a chair.
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The complexity of neuron activity led the Chinese team to use mathematical tools, including an artificial intelligence algorithm, to track and verify the signals.
The researchers said their discovery would in turn aid the development of more human-like AI.
The study is part of the China Brain Project, an unprecedented research programme launched by the Chinese government in 2020 and expected to receive up to 100-billion yuan (US$15.7 billion) in funding over a decade.
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The controversial programme has been accused of spending too much on monkey-related study.
“Regardless of the quality of this paper, it would not suggest that billions of Chinese yuan should be used to study monkeys,” said Rao Yi, president of Capital Medical University, in an email response to a query by the South China Morning Post on Tuesday.
Wang did not respond to a request for comment.
