Visual working memory capacity in Korsakoff’s amnesia

Abstract

Introduction: Despite the interest in memory functioning in Korsakoff's syndrome (KS), visual working memory capacity in KS is still poorly understood. Results from the last decades on working memory limitations in KS appear to be mixed, clearly calling for further investigations. Method: We investigated visual working memory storage capacity of patients diagnosed with KS using a change detection paradigm. Nine patients diagnosed with KS and thirty age-and education-matched healthy controls were presented twice with 2, 3, 4, or 6 bars with different orientations and had to detect whether the orientation of the target bar had changed. Results: As a group, KS patients performed significantly worse than controls on all set sizes, with an average capacity of 1.13 items, compared to 1.75 items in the control participants. In case study analysis, 4 out of 9 patients performed significantly worse than control participants, while 5 had relatively intact visual working memory capacity. In patients, deficits in visual working memory could not be explained by other cognitive deficits. Conclusion:Based on these results, we conclude that visual working memory deficits are a prominent characteristic in some, but not all KS patients. Training visual working memory capacity could possibly optimize other cognitive difficulties in this population.

Eye Movements as Proxy for Visual Working Memory Usage: Increased Reliance on the External World in Korsakoff Syndrome

“…The increased reliance on the external world could be explained by deficits in working memory. Indeed, patients with KS performed worse than controls on all (but one) classical tasks that assessed memory subdomains, which confirms their impaired memory ability relative to controls and aligns with earlier findings of compromised (working) memory in patients with KS [19,20,22]. This supports the idea that impaired memory ability causes increased sampling: patients who have difficulty encoding or retrieving information need to sample multiple times (and, importantly, more often than controls) to strengthen the memory trace before being able to make a correct placement.…”

“…Eyes were not tracked; only behavioural responses were recorded. Kmax and d were calculated as outcome measures; Kmax is often used in the VWM literature [1,30] and allowed us to compare our findings with previous findings regarding patients with KS [20]. However, d is stated to yield a more robust outcome for visual working memory performance that is less prone to biases in response tendency than Kmax [31].…”

“…Change detection tasks are often used in experimental research to assess working memory capacity [1]. Here, a simplified version of the paradigm from Luck and Vogel was used [20,29] (see Figure 2). With a varying set size of 2, 3, 4, or 6 items, white bars in different orientations (0 • , 30 • , 60 • , 90 • , 120 • , and 150 • ) were presented on a black screen for 1000 ms, followed by a Gaussian random visual white noise mask for 300 ms. Consecutively, the bars were presented again.…”

“…There is general consensus that these long-term declarative memory deficits are part of the cognitive profile of patients with KS [17]. While it was first assumed that working memory was largely spared (see review [19]), there is converging evidence suggesting that specific aspects of working memory (capacity) might be impaired in patients with KS [19][20][21][22]. As the previously mentioned studies used different outcome measures to estimate memory capacity, and the results show variability in the outcomes of memory capacity [19][20][21][22], straightforward interpretations of capacity scores are difficult.…”

“…While it was first assumed that working memory was largely spared (see review [19]), there is converging evidence suggesting that specific aspects of working memory (capacity) might be impaired in patients with KS [19][20][21][22]. As the previously mentioned studies used different outcome measures to estimate memory capacity, and the results show variability in the outcomes of memory capacity [19][20][21][22], straightforward interpretations of capacity scores are difficult. Furthermore, clinical observations point out that patients oftentimes show normal capacity scores when assessed in a test setting but encounter problems when memory is put to use in daily situations.…”