Parameter-Efficient Token Embedding Editing for Clinical Class-Level Unlearning

Fuente: arXiv
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Main Authors: Hou, Iyad Ait, Borad, Shrenik, Sharma, Harsh, Srinivasan, Pooja, Hwa, Rebecca, Zirikly, Aya
Format: Preprint
Published: 2026
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author Hou, Iyad Ait
Borad, Shrenik
Sharma, Harsh
Srinivasan, Pooja
Hwa, Rebecca
Zirikly, Aya
author_facet Hou, Iyad Ait
Borad, Shrenik
Sharma, Harsh
Srinivasan, Pooja
Hwa, Rebecca
Zirikly, Aya
contents Machine unlearning is increasingly important for clinical language models, where privacy regulations and institutional policies may require removing sensitive information from deployed systems without retraining from scratch. In practice, deletion requests must balance effective forgetting of targeted information with preservation of model utility and minimal parameter modification. We introduce Sparse Token Embedding Unlearning (STEU), a parameter-efficient method for behavioral class-level unlearning that updates only PMI-selected token embeddings together with a small classifier head while keeping all encoder layers frozen. Across experiments on MIMIC-IV, MIMIC-III, and eICU using BioClinicalBERT, BERT-base, and DistilBERT, STEU consistently suppresses the target class while largely preserving retained task performance. In the primary MIMIC-IV setting, STEU achieves near-complete forgetting (forget F1 = 0.0004) while maintaining competitive retained utility (retain avg F1 = 0.4766) after modifying only 0.19\% of model parameters. These results suggest that targeted behavioral unlearning can be achieved through sparse embedding edits without modifying deeper encoder representations.
format Preprint
id arxiv_https___arxiv_org_abs_2603_19302
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Parameter-Efficient Token Embedding Editing for Clinical Class-Level Unlearning
Hou, Iyad Ait
Borad, Shrenik
Sharma, Harsh
Srinivasan, Pooja
Hwa, Rebecca
Zirikly, Aya
Machine Learning
Artificial Intelligence
Machine unlearning is increasingly important for clinical language models, where privacy regulations and institutional policies may require removing sensitive information from deployed systems without retraining from scratch. In practice, deletion requests must balance effective forgetting of targeted information with preservation of model utility and minimal parameter modification. We introduce Sparse Token Embedding Unlearning (STEU), a parameter-efficient method for behavioral class-level unlearning that updates only PMI-selected token embeddings together with a small classifier head while keeping all encoder layers frozen. Across experiments on MIMIC-IV, MIMIC-III, and eICU using BioClinicalBERT, BERT-base, and DistilBERT, STEU consistently suppresses the target class while largely preserving retained task performance. In the primary MIMIC-IV setting, STEU achieves near-complete forgetting (forget F1 = 0.0004) while maintaining competitive retained utility (retain avg F1 = 0.4766) after modifying only 0.19\% of model parameters. These results suggest that targeted behavioral unlearning can be achieved through sparse embedding edits without modifying deeper encoder representations.
title Parameter-Efficient Token Embedding Editing for Clinical Class-Level Unlearning
topic Machine Learning
Artificial Intelligence
url https://arxiv.org/abs/2603.19302