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Evaluation of Corneal Subbasal Nerve Plexus Alterations in ARSACS and SPG7 by In Vivo Corneal Confocal Microscopy

Purpose: To investigate corneal subbasal nerve plexus alterations using in vivo corneal confocal microscopy (IVCM) in patients with Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay (ARSACS) and Spastic Paraplegia Type 7 (SPG7). Methods: This cross-sectional pilot study included eight ARSACS patients, five SPG7 patients, and twenty age- and sex-matched healthy controls. All participants underwent neurological and ophthalmological examination followed by central corneal imaging using IVCM. Quantitative corneal nerve parameters were analyzed with automated software, and correlations with clinical severity scales were assessed. Results: The mean age was 34.2 +/- 3.4 years in controls, 34.5 +/- 0.7 years in the ARSACS group, and 38.2 +/- 3.5 years in the SPG7 group. Corneal nerve branch density (CNBD) and corneal nerve total branch density (CTBD) were significantly lower in ARSACS and SPG7 patients compared with healthy controls. CNFD, CNFL, CNFA, CNFW, and CNFrD were lower in ARSACS and SPG7 patients compared with healthy controls; however, these differences did not reach statistical significance. No statistically significant differences in IVCM parameters were detected between ARSACS and SPG7 patients. Spearman correlation analysis did not show significant correlations between corneal nerve parameters and FARS, SARA, ADL scores, or disease duration. Conclusion: IVCM revealed reduced corneal nerve branching parameters in patients with ARSACS and SPG7. These findings indicate involvement of the corneal subbasal nerve plexus and support the potential role of corneal confocal microscopy as a non-invasive ocular imaging modality for evaluating peripheral neural alterations in hereditary spastic ataxias.

It's Complicated: On the Design and Evaluation of AI-Powered AAC Interfaces

arXiv:2606.24854v1 Announce Type: cross Abstract: Artificial intelligence (AI) can enhance what people who use augmentative and alternative communication (AAC) are able to do with their systems. However, evaluating AI-powered AAC interfaces can be difficult. People are intersectional beings and current evaluation metrics can struggle to capture the multifaceted and nuanced desires people may have for their AAC. We explore the complicated nature of six AAC problem spaces, explore how AI might be used in these spaces, and suggest more robust methods of evaluation that take the intersectional nuances of people into account. We also discuss broader issues that arise across these problem spaces and how they could be addressed using our proposed evaluation methods.

Pigeonholing: Bad prompts hurt models to collapse and make mistakes

While in-context learning is generally shown to be effective in Large Language Models (LLMs), bad contexts can cause performance degradation and mode collapse, a phenomenon we call "pigeonholing." **Unintentionally bad** contexts can happen without malicious jailbreaking intents: For example, a user asks the model to justify an incorrect math theorem or fails to correct the model's buggy code. Specifically, we investigate ``pigeonholing" in two scenarios: (1) when the user suggests a solution, and (2) when the conversation context includes the assistant's previous (incorrect) responses. Our experiments across 10 verifiable and open-ended tasks with 10 different models show that pigeonholing manifests in several ways: (1) repeating the incorrect answers from context (leading to 38-40% performance drop), (2) converging on a narrow set of answers in coding and text generation without exploring alternatives, and (3) flipping stance on controversial topics to align with the user or the assistant's previous claims. We find that pigeonholing worsens almost monotonically with the number of conversation turns (performance drops by additional 14+% as repeated mistakes increase from 1 to 5), and pigeonholing-induced mode collapse can happen even when the provided example is correct. As a step toward mitigation, we propose RLVR with synthetic errors which improves models by 43-60% under bad contexts compared to vanilla RLVR baselines.