Arithmetic fact retrieval deficits in chronic stroke - A deficit of relearning?

In acute stroke patients, arithmetic fact retrieval deficits have been observed due to disrupted white matter connections within a left-hemispheric network centered around the angular gyrus and middle temporal gyrus (Smaczny et al., 2023). However, it remains unclear which specific structural disconnections also hinder successful remediation in the chronic stage of stroke. In this study, 92 patients were examined to determine which impairments continue to affect multiplication performance even in the chronic phase after a first-time unilateral left-hemispheric stroke. Our results revealed a strong association between impaired multiplication performance and the disconnection of left long-term memory (para)hippocampal areas from left frontal and right parietal regions. Thus, unlike previous findings in the acute stroke phase, our results in the chronic phase emphasize the importance of (para)hippocampal regions for successful multiplication performance. We suggest that the affected areas and connections in chronic patients with persistent multiplication problems not only indicate areas that are crucial for the relearning of arithmetic facts, but also those crucial for the learning of arithmetic facts in general. More generally, we suggest that the acquisition of arithmetic facts depends on structural integrity of a network centered around the left (para)hippocampus, while the retrieval of consolidated arithmetic facts from memory relies on the integrity of a left-hemispheric network involving angular gyrus and middle temporal gyrus.