Abstract
Reach-to-grasp is an evolutionarily conserved motor function that is adversely impacted following stroke and traumatic brain injury (TBI). Non-invasive brain stimulation (NIBS) methods, such as transcranial magnetic stimulation and transcranial direct current stimulation, are promising tools that could enhance functional recovery of reach-to-grasp post-brain injury. Though the rodent literature provides a causal understanding of post-injury recovery mechanisms, it has had a limited impact on NIBS protocols in human research. The high degree of homology in reach-to-grasp circuitry between humans and rodents further implies that the application of NIBS to brain injury could be better informed by findings from pre-clinical rodent models and neurorehabilitation research. Here, we provide an overview of the advantages and limitations of using rodent models to advance our current understanding of human reach-to-grasp function, cortical circuitry, and reorganization. We propose that a cross-species comparison of reach-to-grasp recovery could provide a mechanistic framework for clinically efficacious NIBS treatments that could elicit better functional outcomes for patients.
Highlights
Reach-to-grasp is an essential task that requires precise spatial and temporal integration of sensory and motor systems
Given the wealth of evidence of widespread changes to cortico-cortical interactions governing motor control after brain injury, there is a need to investigate whether other nodes in the parietofrontal system are suitable stimulation targets for improving reach-to-grasp behavior. Supporting this notion, Lotze et al [213] found that stimulating contralesional M1, PMd, and superior parietal lobule (SPL) each led to deficits in performance of a complex sequential motor task in wellrecovered stroke patients, suggesting that all three areas play a role in compensatory reorganization
We present the idea that the reach-tograsp movement is an impaired motor function following acquired brain injury, such as traumatic brain injury or stroke
Summary
Reach-to-grasp is an essential task that requires precise spatial and temporal integration of sensory and motor systems Damage to these systems following stroke or traumatic brain injury (TBI), commonly leads to long-term deficits in reach-to-grasp function [1, 2]. Rodents exhibit a similar laminar organization of their M1 cortex compared to primates, and proximal and longitudinal connectivity patterns are known to be mostly conserved [10] In addition to their comparable dexterity and homology to human cortical representation, rodent models offer several translational advantages—such as the availability of transgenic lines, feasibility of invasive function modulation, and imaging tools that can be exploited to study circuit function and behavioral outcomes under highly controlled environments [11, 12].
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