. 2015 May 12;2(2):025001. doi: 10.1117/1.NPh.2.2.025001

Table 1.

Eleven mental tasks used in sessions 1 to 3.

Task	Description
Mental math (Math)	Participants were prompted with a math problem that appeared in the top right corner of the screen, and they were asked to repeatedly subtract a two digit number from a three digit number. For example, given 986-12; the participant would mentally evaluate 986-12=974; 974-12=962; 962-12=950; and so on. Numbers were randomly generated. This task has been used in several previous NIRS-BCI studies.²^,⁹^,¹⁴^,²²^–²⁹^,⁵⁶^,⁵⁷
Mental singing (Music)	Participants were asked to sing a song in their head. They were informed they could choose to sing any song they wanted, but they were asked to pick a song that they liked. This task has been used in previous NIRS-BCI studies.⁹^,²²^–²⁴
Word generation (Words)	Participants were asked to think of as many words as possible that start with a specific letter. For example, if the letter “D” appeared on the screen, the user may think of the words: dog, draft, door, deli, and so on. Letters (excluding x and z) were randomly generated. This task has been used in previous NIRS-BCI studies.²²^,²⁶^,²⁸^,⁵⁸
Tangram puzzle (Rotation)	Participants were prompted with a tangram puzzle in the top right corner of the screen, and were asked to imagine rotating the pieces to make a final picture. This task was chosen because it has been shown to alter PFC activity, measured using NIRS in a non-BCI study.⁵⁹ A similar task was also used in a previous NIRS-BCI study.²²^,⁵⁹
Relaxing with counting (Counting)	Participants were asked to slowly count in their heads while relaxing. A similar task has been used in a previous NIRS-BCI study.³⁰^,⁵⁷
Happy thoughts (Happy)	Participants were asked to think about the details of a past event in their life that made them very happy. This task has been used in a previous NIRS-BCI study.⁶⁰ This task also uses episodic memory, which has been shown to alter activity in the PFC.¹⁹
Word color (Stroop)	Participants were prompted with a series of color names. The words were also colored, but the color of the words did not always match the written word. For example, the word blue may have been written in red ink. The participants were asked to say the real color of the word in their head. This task is commonly referred to as the stroop task. This task has been used in a previous NIRS non-BCI study.⁶¹^,⁶²
Visualizing the future (Future)	Participants were asked to imagine their life in five years, specifically focusing on their future day-to-day activities. This task was chosen for its potential to alter activity in the PFC. The PFC is part of the default mode network and has been shown to be activated when envisioning the future and during self-relevant mentalization.²⁰
Relaxing with focus on the feedback (Focus)	Participants were asked to relax and focus on the feedback. A similar task has been used in a previous NIRS-BCI study.³¹
Motor imagery (Motor)	Participants were asked to imagine moving their arms or legs. Motor imagery has been investigated in previous NIRS-BCI studies, but strictly over the motor cortex.³^,⁸^,³³ This task was included since it has been shown that the PFC is also affected by motor imagery.⁶³^,⁶⁴
Rest (Rest)	Participants were asked to relax and let their minds rest. This task has been used in previous NIRS-BCI studies.²^,⁶^,⁹^,²²^,²⁴^,²⁵^,²⁷^,²⁹^,³⁰^,⁵⁶