Abstract
Encoding, storage and retrieval constitute three fundamental stages in information processing and memory. They allow for the creation of new memory traces, the maintenance and the consolidation of these traces over time, and the access and recover of the stored information from short or long-term memory. Functional near-infrared spectroscopy (fNIRS) is a non-invasive neuroimaging technique that measures concentration changes of oxygenated-hemoglobin (O2Hb) and deoxygenated-hemoglobin (HHb) in cortical microcirculation blood vessels by means of the characteristic absorption spectra of hemoglobin in the near-infrared range. In the present study, we monitored, using a 16-channel fNIRS system, the hemodynamic response during the encoding and retrieval processes (EP and RP, respectively) over the prefrontal cortex (PFC) of 13 healthy subjects (27.2 ± 2.6 years) while were performing the “Logical Memory Test” (LMT) of the Wechsler Memory Scale. A LMT-related PFC activation was expected; specifically, it was hypothesized a neural dissociation between EP and RP. The results showed a heterogeneous O2Hb/HHb response over the mapped area during the EP and the RP, with a O2Hb progressive and prominent increment in ventrolateral PFC (VLPFC) since the beginning of the EP. During the RP a broader activation, including the VLPFC, the dorsolateral PFC and the frontopolar cortex, was observed. This could be explained by the different contributions of the PFC regions in the EP and the RP. Considering the fNIRS applicability for the hemodynamic monitoring during the LMT performance, this study has demonstrated that fNIRS could be utilized as a valuable clinical diagnostic tool, and that it has the potential to be adopted in patients with cognitive disorders or slight working memory deficits.
Highlights
Encoding, storage and retrieval constitute three fundamental stages in information processing and memory
Encoding is the initial elaboration of input data, that allows the creation of new memory traces; storage refers to the maintenance and the consolidation of new memory traces over time, while retrieval refers to the process of accessing and recovering stored information from short or long-term memory (Buckner and Koutstaal, 1998; for a review see Cabeza and Nyberg, 2000)
The prominent activation found in channels 7 and 15, corresponding to the right and left ventrolateral PFC (VLPFC), is in line with its role in the selection, comparison, or decision about the information held in memory (Petrides, 1989), and in the specification and/or maintenance of cues for long-term encoding (Mar, 2004)
Summary
Storage and retrieval constitute three fundamental stages in information processing and memory. A wide range of complex cognitive activities as reasoning, language comprehension, planning, and spatial elaboration, requires the combination of the short-term storage and the manipulation of the information, processes that, taken together, are defined as working memory (WM; Baddeley, 2012). Among the several theories regarding the cognitive structure and functioning of WM, the Baddeley’s model (Baddeley and Hitch, 1974) is likely to be the most influential one. Such model holds that WM is based on a supervisory system, the central executive, and three subsystems, each one specialized in the maintenance and manipulation of different types of information. Other major theories of WM (e.g., Kane et al, 2001; Cowan, 2005; Oberauer, 2009) underline the importance of the attentional role in controlling the activation, maintenance, and manipulation of Frontiers in Human Neuroscience www.frontiersin.org
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