Memory in Autism: A Case of Remembering Versus Knowing
Tulving (1983) divides human memory into two distinct systems that are open to conscious awareness: The semantic system stores timeless facts available mostly upon cued recall recognition, while the episodic system relies on an individual’s ability to put stored memories into a spatio-temporal and self-referential context upon free recall (Tulving, 2002). The Remember/Know (R/K) procedure (Tulving, 1985) is used in recognition tasks to study both memory systems. Zelazo and Frye (2001) have shown that children with ASD have problems with episodic remembering. Episodic recognition involving the recollection of contextual information (R) is mediated by hippocampal processes while familiarity based recognition (K), which is intact in ASD, is mediated by perirhinal processes (Brown & Aggleton, 2001). Morphological abnormalities of the hippocampus are well documented in ASD (Groen et al., 2010; see Nicolson et al., 2006).
Our study was interested in finding out how adolescents with ASD process their own first name as opposed to other names. We planned to compare their results to those of neurotypical peers. We predicted that control subjects would activate areas of self-reference and episodic memory, such as the left tempo-parietal cortex, the superior temporal gyrus, and the hippocampus when hearing their own name. Subjects with ASD, on the other hand, were expected to employ compensatory processes including the perirhinal regions when hearing their own name.
In this preliminary functional magnetic resonance imaging (fMRI) investigation, we compared brain activity of 9 adolescents with ASD with those of 9 neurotypical adolescents to four categories of auditory language stimuli: their own first name (SFN), familiar people’s names (OFN), names of objects of high interest (OBJ), and numbers (NUM). Each participant listened passively to the randomly sequenced names during three sessions. Each session contained the subject’s name five times and five different names from each of the other categories. We also administered a test of verbal receptive ability to test whether our results may align with scores on the test.
When hearing their own names, controls and subjects with ASD who scored high on the verbal ability test activated regions in the insula, superior temporal gyrus as well as the hippocampus, brain regions associated with self-referential processing and long term memory, or, R (remembering). In contrast, subject with ASD who scored low on our test of receptive verbal ability lower-scoring subjects showed activity in the prefrontal cortex and the thalamus, regions associated with new learning and K (knowing).
Our findings support prior research on episodic memory processing differences in ASD. They also suggest that ASD subjects with lower verbal ability recognize, or, “know” their own name like a newly acquired fact rather than “remember” their name in a self-referential and spatio-temporal context. We also found that the results of controls and ASD subjects with higher verbal ability were more like each other than the results of the higher and the lower scoring ASD groups, which indicates that memory function in ASD aligns with verbal ability. Future studies have to explore these findings with larger samples.