Functional motor compensation in amyotrophic lateral sclerosis

Abstract

The present study investigated the fMRI correlates of functional compensation/neural reorganization of the motor system in patients with amyotrophic lateral sclerosis (ALS). The hypothesis was that ALS patients would recruit additional brain regions compared with controls in a motor task and that activity in these regions would vary as a function of task difficulty. Patients and controls executed a motor task with two sequences (a simple and a more difficult one) of consecutive button presses. Patients and controls both activated brain regions known to be involved in motor execution and control. Activity in ipsilateral motor areas as well as difficulty-related activity in the left cerebellum could only be observed in patients. The behavioral data indicated that the motor task was much more difficult for patients than for controls. At nearly equal difficulty the observed patterns of hemodynamic activity in controls were very similar to those observed in ALS. The findings suggest that functional compensation in ALS relies on existing resources and mechanisms that are not primarily developed as a consequence of the lesion.

Altered cortical beta‐band oscillations reflect motor system degeneration in amyotrophic lateral sclerosis

“…The abnormalities in this characteristic motor system rhythm displayed by ALS patients (amplified beta desychronization and attenuated beta rebound) may reflect or even contribute to an excitotoxic degeneration of neural microcircuitry, particularly given the apparent correlation with rate of disease progression. A more simplistic explanation of the beta desychronization difference in ALS patients might be the relative cognitive demands and task difficulty in comparison to healthy controls [Schoenfeld et al, 2005]. However, this fails to account for the corresponding abnormalities seen in high‐performing AGCs and the lack of excess beta desychronization within equally disabled PLS patients.…”

Neuroimaging in Amyotrophic Lateral Sclerosis

“…Increased sensorimotor activation has also been reported in the brain ipsilateral to the movement [80]. In addition, reduced activation in the dorsolateral prefrontal cortex has been observed, providing further evidence for the existence of frontal lobe function deficits in patients with ALS [81].…”

“…A general pattern of cortical reorganization was found for motor function in patients with ALS when compared with that seen in normal subjects [24], with increased activation of the contralateral sensorimotor cortex, supplementary motor area, basal ganglia, and cerebellum demonstrated on fMR images during motor tasks [24,25,80,81]. Increased sensorimotor activation has also been reported in the brain ipsilateral to the movement [80].…”

Neuroimaging as a New Diagnostic Modality in Amyotrophic Lateral Sclerosis

“…Functional MRI Functional MRI (fMRI) studies of motor function complement earlier PET results by demonstrating increased recruitment of cortical regions associated with motor processing, suggesting that the ALS brain attempts to compensate for functional loss [70,71]. Recently, abnormalities of prefrontal activation to letter fluency have been reported in both patients with PMA and ALS [72].…”