Editors' ChoiceRehabilitation

The Changing Brain

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Science Translational Medicine  01 Jun 2011:
Vol. 3, Issue 85, pp. 85ec83
DOI: 10.1126/scitranslmed.3002690

Scientists and clinicians are exploring various frontiers to treat spinal cord injury (SCI) or alleviate functional deficits caused by SCI. One example is spinal cord regeneration through molecular and cellular mechanisms; another is brain–computer interface systems. However, a key factor that should be taken into consideration by all of these approaches is the potential change in cortical organization owing to injury-related interruption of sensory and motor pathways to and from the brain.

In a recent study, Freund et al. recruited patients with injury to the cervical (neck) spinal cord and able-bodied control patients. They examined five different metrics; the first was hand function, in which subjects performed timed hand movement tasks, such as placing pegs in small holes and grasping and transporting objects of different sizes. They also examined cord area above the injury level, gray and white matter volume, cortical thickness, and cortical activity (measured as blood oxygenation level–dependent signals) during motor (hand grip) and sensory (nerve stimulation) tasks. The authors demonstrated that compared with control subjects, the SCI subjects exhibited reduced cord area, smaller gray matter volume, and reduced cortical thickness in the leg area of the primary motor and sensory cortices. Furthermore, functional magnetic resonance imaging data revealed cortical reorganization after SCI, as evidenced by increased activation of the leg area of primary motor cortex during a hand movement task. These structural and functional changes were correlated with degrees of disability that had been measured with hand function tests. Taken together, Freund et al. concluded that SCI leads to spinal cord and cortex atrophy as well as reorganization of the sensorimotor cortices, the latter of which is linked to degree of disability.

This study further suggests that SCI rehabilitation researchers need to be fully aware of cortical changes after spinal cord injury when developing new therapeutics. For example, for direct brain interface systems the cortical electrode design and cortical signal processing algorithms need to accommodate changes in cortical thickness and in the activity of cortical areas that are used to govern the motor and sensory functions of the paralyzed limbs.

P. Freund et al., Disability, atrophy and cortical reorganization following spinal cord injury. Brain 134, 1610–1622 (2011). [Full Text]

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