Effects of Prenatal Methamphetamine Exposure on Verbal Memory Revealed with Functional Magnetic Resonance Imaging

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Abstract

Objective:

Efforts to understand specific effects of prenatal methamphetamine (MA) exposure on cognitive processing are hampered by high rates of concomitant alcohol use during pregnancy. We examined whether neurocognitive systems differed among children with differing prenatal teratogenic exposures when they engaged in a verbal memory task.

Patients and Methods:

Participants (7–15 years) engaged in a verbal paired associate learning task while undergoing functional magnetic resonance imaging. The MA group included 14 children with prenatal MA exposure, 12 of whom had concomitant alcohol exposure. They were compared with 9 children with prenatal alcohol but not MA exposure (alcohol-exposed only) and 20 unexposed controls. Groups did not differ in age, gender, or socioeconomic status. Participants’ IQ and verbal learning performance were measured using standardized instruments.

Results:

The MA group activated more diffuse brain regions, including bilateral medial temporal structures known to be important for memory, than both the alcohol-exposed only and the CON groups. These group differences remained after IQ was covaried. More activation in medial temporal structures by the MA group compared with the alcohol-exposed only group cannot be explained by performance differences because both groups performed at similar levels on the verbal memory task.

Conclusions:

More diffuse activation in the MA group during verbal memory may reflect recruitment of compensatory systems to support a weak verbal memory network. Differences in activation patterns between the MA and alcohol-exposed only groups suggest that prenatal MA exposure influences the development of the verbal memory system above and beyond effects of prenatal alcohol exposure.

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