Once a person memorizes a sequence of numbers, they can recall the numbers either in the same order or in reverse. This raises the question of how the brain organizes a sequence of items in a specific order within short-term or working memory.
To investigate the neural mechanisms involved in sorting sequences within working memory, Chinese scientists trained two macaque monkeys to complete a visuospatial delayed sequence-sorting task. They also conducted extensive electrophysiological recordings in the monkeys’ frontal cortex.
The research was conducted by a team led by Wang Liping, a researcher at the Center for Excellence in Brain Science and Intelligence Technology under the Chinese Academy of Sciences (CAS). Their findings were published in the journal Science on Friday.
Memory is generally categorized into short-term and long-term memory. Daily experiences, such as images seen and words heard, are initially stored as short-term memory before undergoing processes like sorting, compression, and forgetting based on necessity, according to Wang.
The study found that spatial locations for each rank were encoded in distinct subspaces according to rule cues. Information was exchanged between these subspaces through two additional temporary subspaces in two parallel operational steps.
Tian Zhenghe, a doctoral student at the center, explained that this process involves more than a straightforward exchange. Instead, each subspace utilizes a temporary subspace to store information; once its information is cleared, it then receives information from the other subspace through another temporary subspace.
Sequence sorting, which involves the mental handling of multiple items with different ranks in working memory, is crucial for various daily tasks such as planning, navigation, and speech. Peter Stern, a senior editor at Science focusing on neuroscience and brain research, remarked that these findings represent a significant advancement in understanding the neural mechanisms behind reasoning and planning.
The Friday issue of the journal also included research from another team at the center, led by CAS academician Pu Muming, which produced single-cell spatial transcriptomic atlases of the cerebella of macaques, marmosets, and mice.
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