The relationship between retrieval success and task performance during the recognition of meaningless shapes: An event-related near-infrared spectroscopy study

Retrieval success of episodic memory has been studied intensively through the investigation of old/new effects. Recognized stimuli used in event-related functional magnetic resonance imaging studies on old/new effects have been words and visual materials which can evoke semantic associations. To elucidate the neural basis of retrieval success uninfluenced by semantic processing, we investigated the correlation between old/new effects and task performance during the recognition of meaningless shapes, by using event-related near-infrared spectroscopy. Forty-two right-handed subjects made recognition judgments about old (studied) or new (unstudied) meaningless shapes. The old/new effects of the shapes were positively correlated with task performance in the bilateral inferior lateral parietal cortex (ILP), but predominantly in the left ILP. This finding indicated that the ILP was directly associated with retrieval success and its lateralization was consistently left-sided irrespective of the type of stimulus.