Biology subjects

Vlachou, M. E.

Publications and source records attributed to Vlachou, M. E..

3 recordsLinked to original sources

bioRxiv2026

A hybrid geometric-feature algorithm for 2D shape similarity

In this paper, we address the problem of quantifying similarity between planar 2D shapes, which is relevant to studies of internal representations in cognitive, developmental, and neurological research. We designed a set of test shapes arranged along a visually defined perceptual similarity gradient and used them to evaluate classical geometric methods for shape comparison, including Procrustes and Chamfer distance, as well as a convolutional neural network (CNN)-inspired feature-based method. Based on the limitations identified for these individual methods, we developed a hybrid Geometric-Feature Similarity (GFS) algorithm that combines geometric alignment, global contour properties, and convolutional feature-based descriptors into a unified weighted similarity score. By combining global geometric information with local structural features, the GFS algorithm more accurately reproduces human perceptual judgments of shape similarity than either geometric or feature-based methods alone. Requiring neither network training nor large labelled datasets, the proposed algorithm provides an efficient and interpretable tool for a broad range of studies involving quantitative shape comparison.

neuroscience↗

bioRxiv2026

Making sense of touch: spatial tactile cues promote efficient visuosomatosensory integration and restore motor accuracy under sensory conflict

Effective interaction with complex environments relies on integrating somatosensory and visual signals into coherent spatial representations of the body in external space. When these signals conflict, as during movement under mirror-reversed visual feedback, motor performance deteriorates. Under such conflict, visual information typically facilitates motor performance, whereas tactile feedback impairs it. Here, we tested whether providing tactile input with explicit spatial structure renders visuo-somatosensory integration functionally relevant and stabilizes motor behaviour under sensory conflict. Healthy adults performed a mirror-tracing task, tracing a shapes contour with the index finger while tactile feedback conveyed either motion-related cues alone or additional discrete spatial landmarks aligned with the outline. Spatially structured tactile cues preserved accuracy and smoothness relative to motion-related tactile input, indicating more effective online motor control. EEG source analyses further revealed that, when spatial tactile cues were present, somatosensory activity increased and functional connectivity became more focal within sensorimotor networks. In contrast, when absent, sensory conflict was associated with widespread reductions in cortical activity, including in somatosensory areas, and with a diffuse functional connectivity pattern consistent with elevated sensorimotor uncertainty. Together, these findings demonstrate that spatial tactile cues bias hand-displacement encoding toward an external reference frame, promote efficient visuo- somatosensory integration and mitigate the detrimental impact of sensory conflict on motor action.

neuroscience↗

bioRxiv2024

Guided by touch: Tactile Cues in Hand Movement Control

Traditionally, touch is associated with exteroception and is rarely considered a relevant sensory cue for controlling movements in space, unlike vision. We developed a technique to isolate and evaluate tactile involvement in controlling sliding finger movements over a surface. Young adults traced a 2D shape with their index finger under direct or mirror-reversed visual feedback to create a conflict between visual and somatosensory inputs. In this context, increased reliance on somatosensory input compromises movement accuracy. Based on the hypothesis that tactile cues contribute to guiding hand movements, we predicted poorer performance when the participants traced with their bare finger compared to when their tactile sensation was dampened using a smooth finger splint. The results supported this prediction. EEG source analyses revealed smaller current in the presumed somatosensory cortex during sensory conflict, but only when the finger directly touched the surface. This finding suggests the gating of task-irrelevant somatosensory inputs. Together, our results emphasize touchs involvement in movement control, challenging the notion that vision predominantly governs goal-directed hand or finger movements.

neuroscience↗