A model of brain circuitry to understand the human language capacity

Friday 12 July 2024, 12:30 pm
PhD candidate
A. Quaresima
prof. dr. P. Hagoort
dr. H. Fitz, dr. K.M. Petersson

When we hear a word utterance, we rapidly recall its meaning. The swift transformation from percepts to language requires we recognise the sequence of speech sounds and retrieve the word associated with it from memory. The thesis investigates how word recognition occurs in the human brain and provides a tentative explanation of a language capacity grounded in the neurobiology of the brain.
In the first half of the thesis, I developed a novel neuron model, the Tripod neuron, which includes properties of human cells, such as the dendritic structure and receptor types. The model shows that dendrites carry a short memory and allow the cell to tell apart simple streams of sequential information, whereas previous soma-only models fail.
In the second part, I integrated the neuron model into a network of a few thousand cells and examined its computational capabilities in a word recognition task. The network succeeded in forming memories with sequential structure and establishing associations between phonemes and words; this was impossible when dendrites were omitted. The dynamics of word memory recall also align with what is observed in experiments with human participants. In conclusion, the model links the brain's physiology and the human capacity to recognize words.

Alessio Quaresima studied Physics at Sapienza University in Rome. He achieved a bachelor's thesis on information theory applied to written text, and a master's thesis on dendritic outgrowth in constrained environments. Aiming to bridge his interest in language and neurobiology, he pursued a PhD at the Max Planck Institute for Psycholinguistics in Nijmegen, working on the neurobiological foundations of word recognition. His main scientific interest is to provide mechanistic, causal explanations for cognitive capacity, such as language comprehension. After the PhD, he will move to the Institut de l'Audition, Paris, to study auditory working memory in a mouse animal model.
Alessio is also active in scientific outreach and popularization. He has edited the science blog Het Talige Brein, organized events for the Nijmegen Science Café, and is part of the scientific staff at The Science Zone in Italy.