An fNIRS investigation of associative recognition in the prefrontal cortex with a rapid event-related design

•We used fNIRS with a rapid-presentation event-related design.•We examined prefrontal cortical hemodynamic changes during associative retrieval.•Dorsolateral prefrontal activity was found during successful associative retrieval.•A fast event-related design with fNIRS is useful for studying complex cognition.

BackgroundFunctional near-infrared spectroscopy (fNIRS) measures hemodynamic changes at the cortical level. The use of fNIRS is growing in popularity for studying cognitive neuroscience in which event-related designs are widely used with functional magnetic resonance imaging (fMRI). However, the applicability of event-related designs with fNIRS has not been fully understood. Therefore, the present study employed fNIRS with a rapid-presentation event-related design for investigating prefrontal cortical activity during complex associative recognition.New methodParticipants studied a list of word pairs and were later given an associative recognition test. Throughout the experiment, each event was presented rapidly (∼4 s). Data were sorted based on accuracy of associative memory judgments and analyzed using the general linear model (GLM) with an event-related design.ResultsDuring retrieval, significant increases in oxygenated hemoglobin concentrations were observed in dorsolateral and ventrolateral prefrontal regions for successful associative recognition. When comparing retrieval to encoding, significant increases in oxygenated hemoglobin concentrations were also observed in dorsolateral prefrontal cortex.Comparison with existing methodThe current fNIRS results corroborate previous fMRI findings that have demonstrated the involvement of dorsolateral and ventrolateral prefrontal cortex in associative recognition. Therefore, the present study validates versatile use of fNIRS with a rapid-presentation event-related design in the investigation of neural mechanisms of associative memory.ConclusionThe findings of this study provide evidence that fNIRS can be a viable research method for investigating complex cognitive processes commonly of interest in cognitive neuroscience. Taken together, these results demonstrate that fNIRS can be a cost-effective and accessible experimental tool for cognitive neuroscience.