A simple spatial working memory and attention test on paired symbols shows developmental deficits in schizophrenia patients

Abstract

People with neuropsychiatric disorders such as schizophrenia often display deficits in spatial working memory and attention. Evaluating working memory and attention in schizophrenia patients is usually based on traditional tasks and the interviewer's judgment. We developed a simple Spatial Working Memory and Attention Test on Paired Symbols (SWAPS). It takes only several minutes to complete, comprising 101 trials for each subject. In this study, we tested 72 schizophrenia patients and 188 healthy volunteers in China. In a healthy control group with ages ranging from 12 to 60, the efficiency score (accuracy divided by reaction time) reached a peak in the 20-27 age range and then declined with increasing age. Importantly, schizophrenia patients failed to display this developmental trend in the same age range and adults had significant deficits compared to the control group. Our data suggests that this simple Spatial Working Memory and Attention Test on Paired Symbols can be a useful tool for studies of spatial working memory and attention in neuropsychiatric disorders.

Figure 1

Example of a single trial and examples of 4 loads of difficulty. An example of a single trial ((a), (b), and (c)). The stimulus phase with learning time (Lt) of either 2 seconds or 0.5 seconds (a), the symbols then disappear during delay span (D) for either 2 seconds or 0.5 seconds (b). After the delay span, the participant is prompted to select the location of the missing part of the symbol pair with the pointing device (c). (d) shows a participant taking the test. (e)–(h) show examples of the 4 loads of difficulty. Difficulty load 1 is not used in results and exists only to provide a short practice exercise for the subject prior to the administration of the real test. Loads 2 to 4 are used to produce test results, and illustrate the number of paired symbols in each load.

Figure 2

Comparison of schizophrenic and healthy groups. SWAPS showed the highest score in the age 20–27 healthy control group (group 20s) but not in schizophrenia patients ages 20–29 (group SZ20s). (a–d) show the accuracy per second in 5 healthy control age groups (10s, 20s, 30s, 40s, and 50s), at different difficulty loads and with different combinations of learning time and delay span. (e–h) show the accuracy per second for 3 age groups in schizophrenia patients (SZ10s, SZ20s, SZ30s), under the same learning time and delay span conditions as the healthy control groups. Lt: learning time (0.5 seconds or 2 seconds); D: delay span (0.5 seconds or 2 seconds).

Figure 3

Comparative results of SZ20s and 20 s age groups. a–d show the accuracy per second of SZ20s and 20s age groups, at the different loads of difficulty with combinations of different learning time and delay span. *P < 0.05; **P < 0.01;^∗∗∗ P < 0.0001.