Role of Prefrontal Cortex during Sudoku task: fNIRS study

Abstract Sudoku is a popular leisure time activity that involves no math, but is based on logic based combinatorial number placement in a matrix. Many studies have been dedicated towards finding an algorithm to solve Sudoku but investigation of the neural substrates involved in Sudoku has been challenging. It is difficult to measure the brain activity during 9×9 Sudoku using traditional fMRI technique due to the procedural constraints. 16 optodes fNIRS (functional near infrared spectroscopy) forms an excellent alternative to study the activity of prefrontal cortex (PFC) during Sudoku task. Sudoku task was divided into two steps to understand the differential function of the PFC while applying heuristic rules. Classical two-way ANOVA as well as General Linear Model based approach was used to analyze the data. 28-noise free recording from right-handed participants revealed increased activity in all 16 optode locations during step 1 (3 × 3 subgrids) and step 2 (easy level 9×9 Sudoku) as compared to rest. Contrasting the step2-step1 revealed that medial regions of PFC were preferentially activated. These findings suggest the role of these regions, while applying multiple heuristic rules to solve 9×9 Sudoku puzzle. Graphical abstract Highlights This is first fNIRS study that tried to unravel the role of PFC during Sudoku task. Uniquely divided the Sudoku task into two steps to understand the differential role of PFC while applying multiple heuristic rules. Both the medial and lateral regions of PFC are activated during Sudoku task. However, the medial regions of PFC play a differential role, especially when we consider the row and the column rule of Sudoku.