title: Load-dependent brain activation assessed by time-domain functional near-infrared spectroscopy during a working memory task with graded levels of difficulty.
abstract: We evaluated frontal brain activation during a mixed attentional/working memory task with graded levels of difficulty in a group of 19 healthy subjects, by means of time-domain functional near-infrared spectroscopy (fNIRS). Brain activation was assessed, and load-related oxy- and deoxy-hemoglobin changes were studied. Generalized linear model (GLM) was applied to the data to explore the metabolic processes occurring during the mental effort and, possibly, their involvement in short-term memorization. GLM was applied to the data twice: for modeling the task as a whole and for specifically investigating brain activation at each cognitive load. This twofold employment of GLM allowed (1) the extraction and isolation of different information from the same signals, obtained through the modeling of different cognitive categories (sustained attention and working memory), and (2) the evaluation of model fitness, by inspection and comparison of residuals (i.e., unmodeled part of the signal) obtained in the two different cases. Results attest to the presence of a persistent attentional-related metabolic activity, superimposed to a task-related mnemonic contribution. Some hemispherical differences have also been highlighted frontally: deoxy-hemoglobin changes manifested a strong right lateralization, whereas modifications in oxy- and total hemoglobin showed a medial localization. The present work successfully explored the capability of fNIRS to detect the two neurophysiological categories under investigation and distinguish their activation patterns.
authors.affiliation: Dipartimento di Bioingegneria, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milan, Italy. erika.molteni@polimi.it
authors.forename: Erika
authors.initials: E
authors.lastname: Molteni
authors.forename: Davide
authors.initials: D
authors.lastname: Contini
authors.forename: Matteo
authors.initials: M
authors.lastname: Caffini
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Baselli
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Spinelli
authors.forename: Rinaldo
authors.initials: R
authors.lastname: Cubeddu
authors.forename: Sergio
authors.initials: S
authors.lastname: Cerutti
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Bianchi
authors.forename: Alessandro
authors.initials: A
authors.lastname: Torricelli
mesh_terms: D000328:Adult; D001931:Brain Mapping / Q000379:methods; D058245:Cognitive Reserve / Q000502:physiology*; D005260:Female; D005625:Frontal Lobe / Q000502:physiology*; D059907:Functional Neuroimaging / Q000379:methods*; D006801:Humans; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D010100:Oxygen / Q000378:metabolism*; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D013647:Task Performance and Analysis; D055815:Young Adult
chemical_list: D010100:Oxygen