Interpreting Intervention Induced Neuroplasticity with fMRI: The Case for Multimodal Imaging Strategies

Abstract

Direct measurement of recovery from brain injury is an important goal in neurorehabilitation, and requires reliable, objective, and interpretable measures of changes in brain function, referred to generally as “neuroplasticity.” One popular imaging modality for measuring neuroplasticity is task-based functional magnetic resonance imaging (t-fMRI). In the field of neurorehabilitation, however, assessing neuroplasticity using t-fMRI presents a significant challenge. This commentary reviews t-fMRI changes commonly reported in patients with cerebral palsy or acquired brain injuries, with a focus on studies of motor rehabilitation, and discusses complexities surrounding their interpretations. Specifically, we discuss the difficulties in interpreting t-fMRI changes in terms of their underlying causes, that is, differentiating whether they reflect genuine reorganisation, neurological restoration, compensation, use of preexisting redundancies, changes in strategy, or maladaptive processes. Furthermore, we discuss the impact of heterogeneous disease states and essential t-fMRI processing steps on the interpretability of activation patterns. To better understand therapy-induced neuroplastic changes, we suggest that researchers utilising t-fMRI consider concurrently acquiring information from an additional modality, to quantify, for example, haemodynamic differences or microstructural changes. We outline a variety of such supplementary measures for investigating brain reorganisation and discuss situations in which they may prove beneficial to the interpretation of t-fMRI data.

Exercise and Neural Plasticity-A Review Study

“…The researchers used different methods including brain scans, Electroencephalogram (EEG) recordings, functional Magnetic resonance imaging (fMRI), positron emission tomography (PET) scan and blood as well as saliva sampling to investigate the exercise-induced brain activity and volume changes in different brain areas including frontal and central regions of the brain, the hippocampus, cerebellum, and the motor cortex [3,5].…”

Measuring motor-training induced neuroplasticity using diffusion and functional MRI: a sensitive, pathology-robust approach

“…A related criticism is that task fMRI results can be variable, 181 and so could lead to differences in tractography that do not exist anatomically. We concede that single-participant activation maps based on a single time point are prone to such variability.…”

“…Head motion can often correlate with participant ability, 200 but was controlled for to the best of our ability in the present study. Task performance may also affect fMRI activation maps, 181 but we aimed to minimise any such effects by utilising a very simple task and ensuring adequate task performance for each participant. Activation volume and area did not correlate meaningfully with clinical scores, so are unlikely to have biased diffusion results.…”

“…180 Standard fMRI analyses include an appreciable amount of implicit and explicit smoothing, which can artificially increase the size of the detected activation beyond its true boundaries. 103,181 Additional smoothing also takes place when fMRI images are converted into dMRI seed images (i.e. reslicing and/or expanding activation ROI into WM).…”

“…In order to probe the biological changes subserving plasticity, brain stimulation and brain imaging techniques are required, each with their own relative advantages and disadvantages. 181 In the area of motor-skill learning, almost all studies investigating neuroplasticity have, so far, relied on animal models, cross-sectional data, or functional measures of brain change. 209 In rodents, motor learning appears to upregulate synaptic plasticity in the primary of motor cortex, 210 and may also be associated with altered neural recruitment in this area.…”