Features of the Brain Connectome are Predictive of Grip Strength
The functional connectome is a map of connections between brain regions, produced via MRI imaging. Features tend to be fairly distinct from individual to individual, and change over time. Researchers here show that the functional connectome can be used to predict handgrip strength in patients exhibiting age-related frailty, which is quite interesting. One tends to think of loss of hand strength as emerging from degeneration of local musculature and local neuromuscular junctions. The results suggests that there is a component of physical frailty localized in the brain, though it is also possible that this reflects downstream issues resulting from the underlying mechanisms of aging occurring distinctly in both locations.
Physical frailty, which refers to a decline in physical strength and energy, is prevalent in older adults and has been attributed to impaired cognitive function and adverse health outcomes. The strength of a contraction on a handgrip, known as isometric handgrip strength, has been used as a marker of physical frailty. While handgrip strength can partially be explained by muscle properties (e.g., cross-sectional area and architecture), it may also be influenced by neural adaptations, such as intermuscular and intramuscular coordination.
There is a growing use of imaging-derived data from different modalities to predict clinical phenotypes and disease risk. In this context, handgrip strength has been attributed to resting-state functional connectivity within motor and salience networks. For example, within healthy older adults, researchers found that higher functional connectivity of the motor cortex to putamen, insula, and cerebellum was associated with higher handgrip strength. Another study investigated whole-brain functional connectivity (i.e., connectome) and observed that higher handgrip strength was associated with greater functional segregation of the salience ventral attention network in older adults at rest.
Because the connectome is unique for each person, akin to a "brain fingerprint", it may also serve as a personalized marker that can be used to predict their individual behavioral measures. A predictive model can be developed using connectomes from tasks involving motor components. Such tasks shift the brain into a more alert, motor-relevant state, offering greater sensitivity to motor-related conditions like frailty compared to resting-state connectivity. In this study, we focused on healthy older adults and had them perform two perceptual discrimination tasks on two different functional MRI sessions, both of which involved a non-dominant handgrip manipulation. We aimed to test the identifiability of the task-based connectomes across the sessions and identify the key functional connections (FCs).
We measured participants' maximum isometric voluntary contraction (MVIC) of their non-dominant hand as an indicator of frailty and neuromuscular health. We identified FCs predictive of MVIC, which may partly explain motor-related impairments in frail older adults. Finding such brain-based biomarkers for grip strength could identify potential target sites for motor rehabilitation programs.