79. Relational reasoning and semantic inhibition in human prefrontal cortex

Reasoning relies on the ability to detect and manipulate relations among objects or events, while inhibiting semantically related, but irrelevant information. It has been suggested that the prefrontal cortex plays a central role in these abilities. We present preliminary findings from two experiments comparing the reasoning performance of patients with frontal-variant frontotemporal dementia (FTD) with that of normal controls. A verbal analogy task revealed that patients' analogy performance was lower than that of controls. Additionally, the results suggested that patients have difficulty inhibiting highly related semantic information. A picture analogy task revealed that patients tend to make fewer relational responses than controls and instead tend to respond based on perceptual or semantic similarity. These results support the hypothesis that prefrontal cortex is important in relational reasoning.