Frontal lobe role in simple arithmetic calculations: An fNIR study

► Frontal lobe is involved in automatic and method-based arithmetic processing. ► We measured frontal deoxygenated hemoglobin during math calculations with fNIR. ► Levels of frontal lobe hemoglobin differed between adults with and without MD. ► Within-group differences exist in frontal lobe function for different operands. This study aimed to affirm the use of functional near-infrared spectroscopy (fNIR) in examining frontal lobe role during automatic (i.e., requires retrieval from long-term memory) and method-based (i.e., requires calculation) arithmetic processing. Adult university students (math difficulties [MD] and control) performed simple arithmetic calculations while monitored using an fNIR system designed to image regions within the frontal cortices. Addition and subtraction problems presented on a computer screen belonged to one of three categories: triples “under 10” (e.g., 2+3=?, 5−3=?), triples that “break 10” (e.g., 5+8=?, 13−5=?), or triples “including 10” (e.g., 10+7=?, 17−10=?). fNIR recordings indicated significant interactions between type of triple, operation, and group over left frontal lobe, and between type of triple and group over right frontal lobe. Within-group differences among controls were found in the “break 10” triples with higher DeOxyHb level recorded during subtraction processing. Between-group differences were found in the “break 10” and “including 10” triples for subtraction with higher levels of DeOxyHb recorded among controls. Results imply that among adults frontal lobe is still involved during simple mathematical processing and fNIR recordings can differentiate its role in adults of varying mathematical ability.