Literacy, but not memory, is associated with hippocampal connectivity in illiterate adults

Abstract

AbstractBackgroundThe role of hippocampal connectivity for good memory performance is well known in persons with high educational level. However, it is understudied the role of hippocampal connectivity in illiterate populations.MethodsThirty‐nine illiterate adults from Brazil underwent a literacy assessment, structural and resting state functional MRI and an episodic memory test (Free and Cued Selective Reminding Test). We correlated the hippocampal connectivity at rest with the free recall scores and the literacy scores. Analyzes were done in SPM 12, corrected for head motion and physiological BOLD signal.ResultsParticipants were most female (66%) and black (79%) and the mean age was 49 years‐old (±13.9). The mean score on free recall was 27.2 (±10.7) out of 48 points and the mean literacy score was 34.9 (±21.1) out of 100 points. The median hippocampal gray matter volume was 2.4 [0.9, 2.3]cm3 in the left and 2.1 [2.1, 2.4] cm3 in the right side. There was a significant connectivity between both hippocampi and the precuneus and the ventral medial prefrontal cortex. However, this connectivity did not correlate with episodic memory scores, but the right hippocampal connectivity correlated with the literacy scores (R2 = 0.13, p = 0.014, CI 1.0‐1.0). Furthermore, the hippocampal gray matter volume did not correlate with memory scores.ConclusionsAlthough we did not find a significant correlation between memory and the connectivity between both hippocampi and the precuneus and ventral medial prefrontal cortex, we found that this connectivity correlated with literacy scores on the right side. The lack of association with memory scores might be associated with low brain reserve in illiterate adults. The association between hippocampal connectivity and low literacy scores suggest a room for improvement if those adults learn how to read later in life.