Dissociable effects of mild COVID-19 on short- and long-term memories

TL;DR

People recovering from mild COVID-19 show specific long-term memory issues, but not short-term memory issues, which improve over time.

Contribution

The study introduces a controlled task to compare memory timescales in mild COVID-19 patients, revealing selective long-term memory impairments.

Findings

Long-term memory precision is selectively impaired in mild COVID-19 patients.

Impairment in long-term memory improves with days since diagnosis.

Short-term memory performance remains unaffected and comparable to healthy controls.

Abstract

Recent studies have highlighted the presence of cognitive deficits following COVID-19 that persist beyond acute infection, regardless of the initial disease severity. Impairments in short- and long-term memory are among the core deficits reported by patients and observed in objective tests of memory performance. We aimed to extend previous studies by examining performance in a task that allows us to directly compare and contrast memories at different timescales. More specifically, we assessed both short- and long-term memories for contextual–spatial associations encoded during a common session and probed at different durations using an equivalent task in non-hospitalized individuals recovering from mild COVID-19 compared to healthy controls. The approach equated all aspects of memory materials and response demands, isolating performance changes resulting only from memory timescales and thus allowing us to quantify the impact of COVID-19 on cognition. In addition to providing measures of accuracy and response times, the task also provided a sensitive continuous readout of the precision of memory representations, specifically by examining the resolution with which spatial locations were retained in memory. The results demonstrated selective impairment of long-term memory performance in individuals recovering from mild COVID-19 infection. Short-term memory performance remained comparable to healthy controls. Specifically, poor precision of long-term memory representations was demonstrated, which improved with days since diagnosis. No such relationship was observed for short-term memory performance. Our findings reveal a specific impairment to the precision of spatial–contextual long-term memory representations in individuals recovering from mild COVID-19 and demonstrate evidence of recovery in long-term memory over time. Further, the experimental design provides a carefully controlled and sensitive framework to assess memory across different durations with the potential to provide more detailed phenotyping of memory deficits associated with COVID-19 in general.

Atkinson et al. report a selective impairment in long-term but not short-term memory performance in individuals recovering from mild COVID-19 infection, which improved with days since diagnosis. Memory was examined in a well-controlled task for contextual–spatial associations utilizing equivalent stimulus materials and response demands for different memory durations.

Graphical Abstract

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