Neuroanatomical correlates of encoding in episodic memory: levels of processing effect.

TLDR

Memory for stimuli depends on encoding depth, with semantic processing yielding better recall than shallow perceptual processing. The study investigates the neural correlates of the levels‑of‑processing effect and proposes that encoding preferentially activates the left inferior prefrontal cortex. Twelve participants performed a letter‑a detection task and a living/non‑living categorization task on nouns while PET scans with 15O‑water were acquired. Recognition memory was markedly higher for nouns in the semantic task, and PET revealed greater activation of the left inferior prefrontal cortex during that task.

Abstract

Cognitive studies of memory processes demonstrate that memory for stimuli is a function of how they are encoded; stimuli processed semantically are better remembered than those processed in a perceptual or shallow fashion. This study investigates the neural correlates of this cognitive phenomenon. Twelve subjects performed two different cognitive tasks on a series of visually presented nouns. In one task, subjects detected the presence or absence of the letter a; in the other, subjects categorized each noun as living or nonliving. Positron emission tomography (PET) scans using 15O-labeled water were obtained during both tasks. Subjects showed substantially better recognition memory for nouns seen in the living/nonliving task, compared to nouns seen in the a-checking task. Comparison of the PET images between the two cognitive tasks revealed a significant activation in the left inferior prefrontal cortex (Brodmann's areas 45, 46, 47, and 10) in the semantic task as compared to the perceptual task. We propose that memory processes are subserved by a wide neurocognitive network and that encoding processes involve preferential activation of the structures in the left inferior prefrontal cortex.