Sequences of distinct, ordered elements can be organized hierarchically across multiple levels. Representing such sequences in the brain may require extracting information about transition probabilities and chunks. How these processes are implemented at the neuronal level and the extent to which they are intermingled remain unclear.
To address these questions, we took advantage of the multilevel structure of domesticated canary song, which comprises syllables, phrases, and chunks, as well as the selective auditory responses of neurons in the premotor HVC nucleus to playback of the bird’s own song. Neuronal activity was recorded in response to a selected song bout and to variants of that song bout generated by altering the sequential organization at either the phrase or the chunk level. Reordering chunks could strongly affect responses to one or more phrases.
Moreover, the lower the transition probabilities due to chunk rearrangement, the weaker the responses. In contrast, reordering phrases within a given chunk had little impact on responsiveness, despite a dramatic decrease in transition probabilities. The present study also suggests an encoding of chunk sequencing through the integration of information provided at chunk boundaries and over a preceding period of several seconds.
We would like to thank and acknowledge Mélanie Dumont and Valérie Lavallée for excellent animal caretaking. This work was funded by the Centre national de la Recherche Scientifique, the Paris-Saclay University and the National Research Agency (nIrVAna ANR-23-CE37-0025). X.H. was supported by the Idex Neuro-Saclay Post-doctoral fellowship.
A.C. was supported by the French Minister of Research and Technology. Paris-Saclay Institute of Neurosciences, CNRS UMR 9197, Université Paris-Saclay, Centre CEA Saclay, 91400, Saclay, France Aurore Cazala, Nicolas Giret, Xavier Hinaut & Catherine Del Negro Institut des Maladies Neurodégénératives, CNRS UMR 5293, Université de Bordeaux, Centre Broca Nouvelle-Aquitaine, 33076, Bordeaux, France The authors declare no competing interests. All experimental procedures were approved by the local ethical committee for animal experiment (CEEA59) and the French Ministry of Research and performed under the license number #10913-2020090317198717.
All methods used in this study were carried in accordance with the relevant guidelines and regulations, including the ARRIVE guidelines. Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Below is the link to the electronic supplementary material.
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