Investigating Default Mode and Sensorimotor Network Connectivity in Amyotrophic Lateral Sclerosis

Area of Science:

• Neuroscience
• Neuroimaging
• Neurology

Background:

• Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease affecting motor neurons.
• Resting state networks (RSNs) reflect spontaneous brain activity and may be disrupted in neurodegenerative conditions.
• Previous studies on RSNs in ALS have yielded conflicting results, with limited investigation into the role of upper motor neuron (UMN) degeneration.

Purpose of the Study:

• To investigate functional connectivity within the default mode network (DMN) and sensorimotor network (SMN) in ALS patients.
• To explore the relationship between RSN connectivity and clinical measures, including UMN burden, disability, and disease progression.
• To determine if UMN degeneration influences RSN connectivity in ALS.

Main Methods:

• Resting state functional magnetic resonance imaging (fMRI) was performed on 21 ALS patients and 40 healthy controls using a 4.7 tesla MRI scanner.
• ALS patients were categorized into UMN+ and UMN- groups based on an UMN score.
• Connectivity of the DMN and SMN was compared between groups, and correlations with clinical assessments (ALSFRS-R, progression rate, UMN score, finger tapping) were analyzed.

Main Results:

• No significant differences in DMN or SMN connectivity were found between ALS patients and healthy controls, irrespective of UMN burden.
• Increased DMN connectivity correlated with greater patient disability and faster disease progression rates.
• Reduced SMN connectivity was associated with increased motor impairment in ALS patients.

Conclusions:

• While overall RSN connectivity did not differ between ALS patients and controls, specific network alterations correlate with disease severity and progression.
• Increased DMN connectivity in more disabled patients may reflect compensatory mechanisms or disease-related changes.
• Reduced SMN connectivity in patients with motor impairment aligns with the known impact of neurodegeneration on sensorimotor processing.
• Findings suggest that RSN alterations in ALS are linked to clinical manifestations, potentially related to changes in inhibitory interneuron function.