Visual Working Memory in Adolescents with Autism Spectrum Disorder

Background: Impairment in working memory (WM) performance has been reported in individuals with Autism Spectrum Disorder (ASD; Geurts et al., 2014) though questions remain regarding which core processes of WM are impaired (e.g., capacity, attention, and/or filtering ability). A recent investigation (Bodner et al., in prep) found that visual WM performance was relatively spared in adults with ASD when memory load was low; however, at higher memory loads, ASD participants exhibited difficulty in optimally allocating WM capacity.

Objectives: The current research investigated whether this selective WM impairment extended to youth with ASD (ages 11 to 15) and whether differences existed in the neurocognitive profile of girls and boys with ASD.

Methods: Sixty participants [29 with ASD (12 females); 31 without ASD (17 females)] completed a computerized visual WM task assessing WM capacity and attentional control. Full-scale IQ for all participants fell at or above 75 (ASD mean = 100.6; non-ASD mean = 106.4). For each trial, participants were shown a visual array consisting of four or six colored circles and squares. After a short delay, memory for one of the stimuli was probed, and participants responded whether the shape was the same or different color from when first presented. Note that participants were informed beforehand that one of the shapes (e.g., circles; high-frequency probes) was more likely to be probed than the other shape (e.g., squares; low-frequency probes) – thus prompting participants to allocate their attention and memory capacity accordingly. Trial blocks were presented with 80% high-frequency and 20% low-frequency probes. Further, for half of the blocks, shapes in the visual array were presented simultaneously (all at once). For the other half, visual array shapes were presented serially (one at a time).

Results: Primary dependent variables were WM capacity (Cowan’s k; Cowan, 2010) and attentional control. Preliminary analyses of WM capacity data revealed a significant three-way interaction between group (ASD, non-ASD), presentation type (simultaneous, serial), and memory probe (high frequency, low frequency) [F(1,45)=4.94, p=.03, η_p²=.10]. In the simultaneous presentation condition, participants in the ASD group devoted relatively less capacity to high frequency probes as compared to participants in the non-ASD group. A main effect of group and group-by-sex interaction also trended towards significance (p<.10 in both instances). The non-ASD group had a higher capacity than the ASD group which was primarily driven by poorer WM performance in males as compared to females with ASD. No group differences or interactions were observed for attentional control (p>.05 in all instances).

Conclusions: Youth with ASD demonstrated selective impairment in WM capacity: when visual information was presented all at once, the ASD group was impaired on the high-frequency probes compared to the non-ASD group. Although preliminary, our data suggest that boys with ASD may display a different profile of WM capacity than girls. Future research should evaluate WM capacity and attention control across the lifespan as well as investigate the relationship between WM performance and everyday functioning.