Discussion
REGRESSION, RECRUITMENT, CORTEX
In the present study, 30 individuals performed a single session of fNIRS-based neurofeedback (NF) targeting the DL-PFC bilaterally that consisted in 15 trials of 30-sec NF periods alternating with 30-sec resting periods. The aims of this study were to investigate different band-pass filters, accounting for confounding extra-physiological noise, and investigate mental strategies related to DL-PFC activity for the methodological improvement of further NF implementations and applications. For the BP 0.01–0.09 Hz filter without SC regression among the 10 best out of 15 trials, 18 out of 30 participants (60%) had at least one channel of interest significantly activated during NF. This result is in line with the literature, where 15 to 30% of participants are categorized as non-responders to NF [We found that the BP 0.01–0.09 Hz filter, as previously suggested [With SC regression and within the 13 individuals for whom we detected at least one activated NF channel, 8 presented an increased activity in other frontal regions and 4 in the motor region. As we provided non-directive instructions and only suggested to engage mental strategies related to cognitive control, some mental strategies used by the participants may have recruited brain areas beyond the DL-PFC. For instance, with SC regression, 4 participants out of 13 showed an activation within the motor cortex. This brain area may have been recruited in relation with the type of mental strategy employed, such as visualization leading to movement picturing. However, the group of participants who declared a subjective feeling of controlling the gauge demonstrated no activated channels in the motor cortex.Interestingly, we detected activation in the 12 channels covering the frontal brain region, independently of a detected activation in the NF channels. In a fMRI-based NF meta-analysis of healthy individuals, it has been shown that NF training involves the recruitment of many other brain regions beyond the targeted brain region or networks [In addition, a general model of biofeedback learning has been proposed, which involves the generalization of skill learning to higher level cognitive functioning and can be applied to NF and defined below [The association between the subjective feeling of control of the visual gauge and its elevation is our objective criterion of success (