Biology subjects

Friedmann, N.

Publications and source records attributed to Friedmann, N..

3 recordsLinked to original sources

bioRxiv2026

Distinct cortical patches for syntactic and semantic composition in the human brain

Although the brain areas for language processing are well delimited, whether lexical-semantic and syntactic processes are spatially segregated remains debated. To clarify this issue, we conducted two experiments using 7-Tesla functional MRI in 20 participants performing: a functional localizer involving reading sequences of words of increasing linguistic complexity; and a presentation of short, semantically impoverished three-word mini-sentences, flashed in a single glance (e.g., "he does it"), whose grammaticality and syntactic complexity was manipulated through syntactic movement. Our results reveal two functionally dissociable sets of cortical patches within the language system: one sensitive to syntactic structure even in the absence of meaning, and the other involved in semantic composition. This dual-network architecture was consistently observed in the majority of participants, although its precise anatomical localization varied. The two types of voxels coexisted even within a given brain region of the Glasser atlas. Results were confirmed using subject-specific analyses and region-by-condition interactions, as voxels in those two systems displayed markedly different responses to mini-sentences. Thus, high-resolution functional imaging reveals a division of labor between syntactic and semantic composition within the classical language network.

neuroscience↗

bioRxiv2024

Modality-Specific and Amodal Language Processing by Single Neurons

According to psycholinguistic theories, during language processing, spoken and written words are first encoded along independent phonological and orthographic dimensions, then enter into modality-independent syntactic and semantic codes. Non-invasive brain imaging has isolated several cortical regions putatively associated with those processing stages, but lacks the resolution to identify the corresponding neural codes. Here, we describe the firing responses of over 1000 neurons, and mesoscale field potentials from over 1400 microwires and 1500 iEEG contacts in 21 awake neurosurgical patients with implanted electrodes during written and spoken sentence comprehension. Using forward modeling of temporal receptive fields, we determined which sensory or abstract dimensions are encoded. We observed a double dissociation between superior temporal neurons sensitive to phonemes and phonological features and previously unreported ventral occipito-temporal neurons sensitive to letters and orthographic features. We also discovered novel neurons, primarily located in middle temporal and inferior frontal areas, which are modality-independent and show responsiveness to higher linguistic features. Overall, these findings show how language processing can be linked to neural dynamics, across multiple brain regions at various resolutions and down to the level of single neurons.

neuroscience↗

bioRxiv2019

Single-cell activity in human STG during perception of phonemes is organized according to manner of articulation

A long-standing controversy persists in psycholinguistic research regarding the way phonemes are coded in human auditory cortex during speech perception. Whereas the motor theory of speech perception suggests that phonemes are organized in terms of common articulatory gestures that generate them, auditory theories argue that phonetic processing is organized based on common spectro-temporal patterns in phoneme waveforms. Here, we recorded spiking activity in the superior temporal gyrus (STG) from six neurosurgical patients who performed a listening task with phoneme stimuli. Using a Naive-Bayes model, we show that single-cell responses to phonemes are governed by articulatory features that have acoustic correlates (manner-of-articulation) and organized according to sonority, with two main clusters for sonorants and obstruents. We further find that neural similarity (i.e. the similarity of evoked spiking activity between pairs of phonemes), is comparable to the perceptual similarity (i.e. how much the pair of phonemes sound similar) based on perceptual confusion assessed behaviorally in healthy subjects. Thus phonemes that were perceptually similar, also had similar neural responses. Our findings establish that phonemes are encoded according to manner-of-articulation, supporting the auditory theories of perception, and that the perceptual representation of phonemes can be reflected by the activity of single neurons in STG.

neuroscience↗