Differential neural plasticity of individual fingers revealed by fMRI neurofeedback

Abstract

Previous work has shown that fMRI activity patterns associated with individual fingers can be 1 shifted by temporary impairment of the hand (e.g. by gluing two fingers together for 24 hours). 2 Here, we investigated whether these neural activity patterns could be modulated endogenously 3 and whether any behavioral changes result from modulation of these patterns. We used decoded 4 neurofeedback in healthy individuals to encourage participants to shift the neural activity pattern in 5 sensorimotor cortex of the middle finger towards the index finger, and the ring finger towards the 6 little finger. We first mapped out the neural activity patterns for all fingers of the right hand in an 7 fMRI pattern localizer session. Then, in three subsequent neurofeedback sessions, participants 8 were rewarded after middle/ring finger presses according to their activity pattern overlap during 9 each trial. A force-sensitive keyboard was used to ensure that participants were not altering their 10 physical finger coordination patterns. We found evidence that participants could learn to shift 11 the activity pattern of the 4th digit (ring finger) but not of the 3rd digit (middle finger). Increased 12 variability of these activity patterns during the localizer session was associated with the ability 13 of participants to modulate them using neurofeedback. Participants also showed an increased 14 preference for the ring finger but not for the middle finger in a post-neurofeedback motor task. Our 15 results show that neural activity and behaviors associated with the ring finger are more readily 16 modulated than those associated with the middle finger. These results have broader implications 17 for rehabilitation of individual finger movements, which may be limited or enhanced by individual 18 finger plasticity after neurological injury. 19 1

Graded fMRI Neurofeedback Training of Motor Imagery in Middle Cerebral Artery Stroke Patients: A Preregistered Proof-of-Concept Study

“…Multivariate approach yield higher sensitivity compared to mass univariate models. These allow detecting neural correlates of imagined (Zabicki et al, 2016 ) and executed movements (Ejaz et al, 2015 ; Kolasinski et al, 2020 ) down to the level of individual fingers (Oblak et al, 2020 ). Albeit promising, both approaches are highly susceptible to spurious correlations resulting from excessive head motion.…”

Towards a common template for neural reinforcement of finger individuation

“…To better understand how this classifier was influenced by the uninstructed fingers, we analyzed the degree of physical overlap, measured by mean devia- www.nature.com/scientificreports/ tion from baseline force 49 , and representational overlap, measured by representational similarity between neural patterns 50 . Only information from the 11 participants from Oblak et al 35 whose responses were collected with the force keyboard were included in these analyses. The force data presented in Fig.…”

“…. Data is only shown from the 11 participants from Oblak et al 35 whose force data was collected. 6; t(16) = 0.433, p = 0.67).…”

“…Strengthening these unique activity patterns has also been linked to improved motor control, such as improved reaction time and movement accuracy, in healthy individuals [32][33][34] . In a recent study from our group, finger preference during a motor task was altered after healthy participants were trained to endogenously shift their finger representations during fMRI neurofeedback training 35 . In a typical neurofeedback experiment, the neural target would be derived anatomically or functionally from the participant 36 .…”

“…Such a template could be used in an fMRI neurofeedback intervention for patients with fine motor deficiencies and who are unable to provide a personalized training target. We conducted an offline analysis to validate this method on previously gathered data from N = 17 healthy participants in a single session to identify unique fMRI activity patterns in sensorimotor cortex for each of the four fingers (index, middle, ring, and little) of the right hand 35,44 . During this session, participants were asked to press one cued finger while maintaining a constant force with the non-cued fingers (Fig.…”