When we learn, we associate a sensory¹ experience either with other stimuli³ or with a certain type of behaviour. The neurons in the cerebral⁴ cortex that transmit the information modify the synaptic connections that they have with the other neurons. According to a generally-accepted model of synaptic plasticity（突触可塑性）, a neuron that communicates with others of the same kind emits an electrical impulse as well as activating⁵ its synapses⁶ transiently. This electrical pulse, combined with the signal received from other neurons, acts to stimulate⁷ the synapses. How is it that some neurons are caught up in the communication interplay even when they are barely connected? This is the crucial chicken-or-egg puzzle of synaptic plasticity that a team led by Anthony Holtmaat, professor in the Department of Basic Neurosciences in the Faculty⁸ of Medicine at UNIGE, is aiming to solve. The results of their research into memory in silent neurons can be found in the latest edition of Nature. Learning and memory are governed by a mechanism⁹ of sustainable synaptic strengthening. When we embark¹⁰ on a learning experience, our brain associates a sensory experience either with other stimuli or with a certain form of behaviour. The neurons in the cerebral cortex responsible for ensuring the transmission of the relevant information, then modify the synaptic connections that they have with other neurons. This is the very arrangement that subsequently enables the brain to optimize¹¹ the way information is processed when it is met again, as well as predicting its consequences.

 

Neuroscientists typically induce electrical pulses in the neurons artificially in order to perform research on synaptic mechanisms¹².

 

The neuroscientists from UNIGE, however, chose a different approach in their attempt to discover what happens naturally in the neurons when they receive sensory stimuli. They observed the cerebral cortices of mice whose whiskers were repeatedly stimulated¹³ mechanically without an artificially-induced electrical pulse. The rodents¹⁴ use their whiskers as a sensor² for navigating¹⁵ and interacting; they are, therefore, a key element for perception in mice.

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