Fig 1.
Configuration of channels in the fNIRS cap covering four regions of interest (ROI): right dorsolateral prefrontal cortex (S02-D02, S03-D03, S03-D02, S04-D03); left dorsolateral prefrontal cortex (S05-D05, S05-D07, S06-D05, S07-D07); right frontopolar area (S01-D01, S04-D01, S04-D04); left frontopolar area (S01-D06, S07-D04, S07-D06). Each line represents a channel with a source and a detector; seven in each hemisphere. Red labels represent sources (S) and blue labels represent detectors (D).
Fig 2.
Task sequence arranged in a block design.
Participants executed the task for 20s, followed by 20s of rest. Task order was randomized for each participant.
Table 1.
Participant characteristics.
Fig 3.
Differences in trait and state fatigue between MS and controls.
(A) Trait fatigue was significantly higher in MS compared to controls. (B) MS participants showed a significantly higher state fatigue after the experiment compared to baseline. Although non-significant, levels of fatigue in controls increased slightly after the procedure. VAS: Visual Analogue Scale, FSMC: Fatigue Scale for Motor and Cognitive Functions.
Fig 4.
Oxyhemoglobin (HbO) levels detected in channels in four prefrontal cortex subregions.
Plots of left dorsolateral prefrontal cortex (dlPFC, blue), left frontopolar cortex (FPC, green), right frontopolar cortex (FPC, orange) and right dorsolateral prefrontal cortex (dlPFC, red) in controls (AB) and multiple sclerosis (MS) (CD) during single (AC) and dual (BD) tasks. Correlograms of channels in prefrontal cortex in controls (EF) and MS (GH) during single (EG) and dual (FH) tasks. Each block shows the relationship between two channels (R-values); red represents positive correlations and blue represents negative correlations. Bottom panels are heat maps representing correlation p-values in controls (IJ) and MS (KL) during single (IK) and dual (JL) tasks. Lower p-values are brighter green. R, right; L, left; dlPFC, dorsolateral prefrontal cortex; FPA, frontopolar area.
Table 2.
Group and task differences in peak oxy-hemoglobin concentration, time-to-peak concentration, and functional connectivity (z-score) by region of interest.
Fig 5.
Oxyhemoglobin (HbO) levels detected in channels in right and left dorsolateral prefrontal cortices in the multiple sclerosis (MS) group.
A. Right and B. Left dorsolateral prefrontal cortex correlograms showing coherence between channels during single and dual tasks (CEGI). Each block shows the relationship between two channels (R-values); red represents positive correlations and blue represents negative correlations. Panels to the right of correlograms are heat maps representing correlation p-values during single and dual tasks (DFHJ). Lower p-values are brighter green. R, right; L, left; dlPFC, dorsolateral prefrontal cortex; FPA, frontopolar area.
Fig 6.
Relationship between feelings of cognitive fatigue, in multiple sclerosis and controls, and functional connectivity (z-score).
Z-score is average of all channels for both groups (R = -0.386, p = 0.047). MS, multiple sclerosis; FSMC, Fatigue Scale for Motor and Cognitive functions.