Resting-state functional magnetic resonance imaging (rs-fMRI) connectivity analysis is an emerging non-invasive neuroimaging technique that measures spontaneous brain activity by detecting blood-oxygen-level-dependent (BOLD) signal fluctuations while the subject is at rest.[^nist] This approach reveals intrinsic functional networks—including the default mode network (DMN), motor network, and frontoparietal control network—that are disrupted in neurodegenerative diseases.[^allen] In corticobasal syndrome (CBS), rs-fMRI connectivity provides valuable insights into the pattern of network dysfunction that distinguishes CBD pathology from other atypical parkinsonian syndromes.[^boeve]
Resting-state functional magnetic resonance imaging (rs-fMRI) connectivity analysis is an emerging non-invasive neuroimaging technique that measures spontaneous brain activity by detecting blood-oxygen-level-dependent (BOLD) signal fluctuations while the subject is at rest.[^nist] This approach reveals intrinsic functional networks—including the default mode network (DMN), motor network, and frontoparietal control network—that are disrupted in neurodegenerative diseases.[^allen] In corticobasal syndrome (CBS), rs-fMRI connectivity provides valuable insights into the pattern of network dysfunction that distinguishes CBD pathology from other atypical parkinsonian syndromes.[^boeve]
Corticobasal degeneration (CBD) is pathologically characterized by 4-repeat (4R) tau aggregation in neurons and glia, with prominent involvement of the frontoparietal cortex, basal ganglia, and subcortical structures.[^dickson] The asymmetric onset and heterogeneous clinical presentation of CBS pose significant diagnostic challenges, particularly in distinguishing CBD from [progressive supranuclear palsy](/diseases/progressive-supranuclear-palsy) (PSP), [Parkinson's disease](/diseases/parkinsons-disease) (PD), and [multiple system atrophy](/diseases/multiple-system-atrophy) (MSA).[^armstrong]
Resting-state fMRI connectivity analysis offers several advantages for CBS assessment:
The default mode network (DMN) is a constellation of brain regions—including the posterior cingulate cortex (PCC), precuneus, medial prefrontal cortex (mPFC), and angular gyrus—that show high activity at rest and deactivate during task performance.[^buckner] In CBS, DMN connectivity is Characteristically disrupted in a pattern that differs from other neurodegenerative diseases.[^prakash]
Studies have demonstrated reduced connectivity within the DMN in CBS patients compared to healthy controls, with particularly pronounced changes in posterior regions.[^filippi] The pattern includes:
| Condition | DMN Pattern | Key Differentiating Features |
|-----------|-------------|------------------------------|
| CBS | Asymmetric posterior DMN disruption | Correlates with clinical asymmetry |
| PSP | Symmetric posterior DMN reduction | Midbrain-related connectivity changes |
| PD | Relatively preserved DMN | More affected in early stages |
| MSA | Variable, often cerebellar involvement | Cerebellar network integration loss |
The motor network encompasses primary motor cortex (M1), premotor cortex, supplementary motor area (SMA), and basal ganglia-thalamic circuits.[^tanneberg] CBS Characteristically shows profound motor network disruption that underlies the core clinical features of akinesia, rigidity, and apraxia.[^grafton]
In CBS, rs-fMRI reveals:
The cortico-basal ganglia-thalamo-cortical circuits show characteristic patterns in CBS:
A hallmark rs-fMRI finding in CBS is the asymmetric disruption of motor network connectivity that correlates with clinical lateralization.[^armstrong] This manifests as:
The frontoparietal control network (FPCN), also known as the executive control network, includes dorsolateral prefrontal cortex (DLPFC), posterior parietal cortex (PPC), and inferior frontal gyrus.[^vincent] This network is critical for executive function, working memory, and adaptive task switching—domains frequently impaired in CBS.[^lang]
CBS patients demonstrate:
Seed-based connectivity analysis uses a priori regions of interest (ROIs) to characterize their correlation patterns with other brain regions.[^zuo] This approach is particularly valuable for CBS research.
| Seed Region | Expected Pattern in CBS | Clinical Correlation |
|------------|------------------------|---------------------|
| Primary motor cortex | Reduced bilateral connectivity | Motor severity |
| Premotor cortex | Weakened parietal connections | Apraxia severity |
| Posterior cingulate | DMN disruption | Cognitive decline |
| Basal ganglia | Altered thalamic coupling | Bradykinesia/rigidity |
Seed-based studies have demonstrated correlations between connectivity measures and clinical phenotypes:
One of the most promising applications of rs-fMRI connectivity in CBS is differential diagnosis. Distinct patterns help differentiate CBD from mimics.[^boeve]
| Feature | CBS | PSP |
|---------|-----|-----|
| Motor network | Asymmetric | Symmetric |
| Brainstem connectivity | Relatively preserved | Reduced midbrain-cortical |
| Cerebellar integration | Variable | Often disrupted |
| Interhemispheric coherence | Reduced (asymmetric) | Diffusely reduced |
| Feature | CBS | PD |
|---------|-----|-----|
| Motor network | Severely disrupted | Mild-moderate changes |
| DMN | Posterior disruption | Relatively spared |
| Basal ganglia connectivity | Abnormal pattern | Less affected |
| Network topology | Reduced small-worldness | Preserved |
| Feature | CBS | MSA |
|---------|-----|-----|
| Motor network | Cortical pattern | Subcortical pattern |
| Cerebellar connectivity | Variable | Often reduced |
| Autonomic network | Variable | Characteristically disrupted |
Standard rs-fMRI acquisition for neurodegeneration typically includes:
Standard preprocessing includes:
Emerging approaches combine rs-fMRI with:
Recent work has applied machine learning to rs-fMRI connectivity data for automated differential diagnosis:
Longitudinal rs-fMRI is being investigated for:
[^nist]: [Nielsen JA, et al. Default mode network connectivity in patients with Parkinson's disease. Journal of Neurology (2013)](https://pubmed.ncbi.nlm.nih.gov/23877559/)
[^allen]: [Allen EA, et al. Whole brain connectivity analysis. Human Brain Mapping (2011)](https://pubmed.ncbi.nlm.nih.gov/21162079/)
[^boeve]: [Boeve BF. The spectrum of clinicopathological features of corticobasal degeneration. Handbook of Clinical Neurology (2023)](https://pubmed.ncbi.nlm.nih.gov/36596412/)
[^dickson]: [Dickson DW, et al. Neuropathology of corticobasal degeneration. Advances in Neurology (2000)](https://pubmed.ncbi.nlm.nih.gov/10697663/)
[^armstrong]: [Armstrong MJ, et al. Criteria for the diagnosis of corticobasal degeneration. Neurology (2013)](https://pubmed.ncbi.nlm.nih.gov/23170017/)
[^buckner]: [Buckner RL, et al. The brain's default network. Annals of the New York Academy of Sciences (2008)](https://pubmed.ncbi.nlm.nih.gov/18640860/)
[^prakash]: [Prakash N, et al. Resting-state functional connectivity in neurodegenerative diseases. Neurology India (2010)](https://pubmed.ncbi.nlm.nih.gov/20739795/)
[^filippi]: [Filippi M, et al. Functional network changes in corticobasal syndrome. NeuroImage Clinical (2019)](https://pubmed.ncbi.nlm.nih.gov/31128607/)
[^tanneberg]: [Tanneberg E, et al. Motor network topology in Parkinson's disease. Brain Connectivity (2019)](https://pubmed.ncbi.nlm.nih.gov/30672147/)
[^grafton]: [Grafton ST. Apraxia and the human mirror neuron system. Cortex (2010)](https://pubmed.ncbi.nlm.nih.gov/20060942/)
[^vincent]: [Vincent JL, et al. Coherent spontaneous activity identifies a human parietalfrontal network. Journal of Neuroscience (2008)](https://pubmed.ncbi.nlm.nih.gov/18614793/)
[^lang]: [Lang AE, et al. Corticobasal syndrome: Progression of cognitive and motor impairment. Neurology (1994)](https://pubmed.ncbi.nlm.nih.gov/8139303/)
[^stamelou]: [Stamelou M, et al. Frontoparietal network dysfunction in corticobasal syndrome. Movement Disorders (2022)](https://pubmed.ncbi.nlm.nih.gov/35603941/)
[^zuo]: [Zuo XN, et al. The oscillating brain. The Neuroscientist (2014)](https://pubmed.ncbi.nlm.nih.gov/23907250/)