Biology subjects

Van Audenhaege, A.

Publications and source records attributed to Van Audenhaege, A..

3 recordsLinked to original sources

bioRxiv2025

Aligned representation of visual and tactile motion directions in hMT+/V5 and fronto- parietal regions

Moving events on the skin can be perceived through vision and touch. How does the brain create a unified multisensory representation of motion directions initially acquired in different coordinate systems? We show that the middle occipito-temporal region (hMT+/V5), along with a fronto-parietal network, encodes visual and tactile directions using a common external frame of reference independent of body posture. We characterized brain activity using fMRI in participants exposed to directional visual and tactile motion stimuli across different hand postures. We demonstrate that individually and functionally defined hMT+/V5 shows univariate preference for both visual and tactile motion and encodes motion directions across hand postures. Unlike somatosensory regions, information about tactile directions was enhanced in right hMT+/V5 when mapped using an external as compared to a somatotopic frame of reference. Crossmodal decoding showed that tactile directions defined in an external frame of reference, but not a somatotopic one, align with the representation of visual directions in the right hMT+/V5 (both in MT and MST). A whole brain searchlight group analysis confirmed these individually defined regions-of-interest results and extended the presence of an aligned visual-tactile code for directional motion in external space to the parietal and frontal cortex. Our findings reveal a brain network involving hMT+/V5 that encodes motion directions in vision and touch using a common external frame of reference.

neuroscience↗

bioRxiv2024

Phonological representations of auditory and visual speech in the occipito-temporal cortex and beyond

Speech is a multisensory signal that can be extracted from the voice and the lips. Previous studies suggested that occipital and temporal regions encode both auditory and visual speech features but their precise location and nature remain unclear. We characterized brain activity using fMRI (in male and female) to functionally and individually define bilateral Fusiform Face Areas (FFA), the left Visual Word Form Area (VWFA), an audio-visual speech region in the left Superior Temporal Sulcus (lSTS) and control regions in bilateral Para-hippocampal Place Areas (PPA). In these regions, we performed multivariate patterns classification of corresponding phonemes (speech sounds) and visemes (lip movements). We observed that the VWFA and lSTS represent phonological information from both vision and sounds. The multisensory nature of phonological representations appeared selective to the anterior portion of VWFA, as we found viseme but not phoneme representation in adjacent FFA or even posterior VWFA, while PPA did not encode phonology in any modality. Interestingly, cross-modal decoding revealed aligned phonological representations across the senses in lSTS, but not in VWFA. A whole-brain cross-modal searchlight analysis additionally revealed aligned audio-visual phonological representations in bilateral pSTS and left somato-motor cortex overlapping with oro-facial articulators. Altogether, our results demonstrate that auditory and visual phonology are represented in the anterior VWFA, extending its functional coding beyond orthography. The geometries of auditory and visual representations do not align in the VWFA as they do in the STS and left somato-motor cortex, suggesting distinct multisensory representations across a distributed phonological network. Significance statementSpeech is a multisensory signal that can be extracted from the voice and the lips. Which brain regions encode both visual and auditory speech representations? We show that the Visual Word Form Area (VWFA) and the left Superior Temporal Sulcus (lSTS) both process phonological information from speech sounds and lip movements. However, while the lSTS aligns these representations across the senses, the VWFA does not, indicating different encoding mechanisms. These findings extend the functional role of the VWFA beyond reading. An additional whole-brain approach reveals shared representations in bilateral superior temporal cortex and left somato-motor cortex, indicating a distributed network for multisensory phonology.

neuroscience↗

bioRxiv2024

Widespread neural reorganization related to expertise in reading visual Braille

Learning to read assigns linguistic value to an abstract visual code. Whether regions of the reading network tune to visual properties common to most scripts or code for more abstracted units of language remains debated. Here we investigate this question using visual Braille, a script developed for touch that does not share the typical explicit shape information of other alphabets, yet maps onto the same phonology and lexicon as other more regular scripts. First, we compared univariate responses in visual Braille readers and a naive control group and found that individually localized Visual Word Form Area (VWFA) was selectively activated for visual Braille when compared to scrambled Braille only in expert Braille readers. Multivariate analyses showed that linguistic properties can be decoded from Latin script in both groups and from Braille script in expert readers in an extended network of brain regions including the early visual cortex (V1), the lateral occipital region (LO), the VWFA and the left Posterior Temporal area (l-PosTemp). These results suggest that the tuning of an extended reading network to orthography relies more on the linguistic content of the script rather than their specific visual features (e.g. line junctions). Nevertheless, cross-scripts generalization was significantly lower than within-script decoding and failed to reveal common representations across Latin and Braille in experts in all regions except the l-PosTemp. These results suggest that V1, LO and VWFA encode orthographic representations in a script-specific manner, whereas l-PosTemp encodes abstracted linguistic information.

neuroscience↗