Measurements | PD | AD | ALS | HD |
|---|
| | | OFF | ON | | | |
|---|
Single-pulse | MEP threshold | â—‹ | â—‹ | - | -/+b
| + |
MEP amplitude | + | + | + | + | - |
Silent period | - | â—‹/+ | - | - | - |
Paired-pulse | SICI | - | -/â—‹ | - | - | - |
ICF | ○ | ○ | ○ | + | × |
LICI | - | - | × | × | × |
SAI | ○ | - | - | × | - |
LAI | - | - | × | × | × |
IHI | −c
| × | - | - | × |
Cortical plasticity | LTP-like effectd
| −e
| â—‹e
| - | × | - |
LTD-like effectd
| × | × | -/○ | × | - |
-
Abbreviations: AD Alzheimer’s disease, ALS amyotrophic lateral sclerosis, HD Huntington’s disease, PD Parkinson’s disease, OFF off dopaminergic medication, ON on dopaminergic medication
- + increase; - decrease; × not tested; ○ normal
-
ICF intracortical facilitation, IHI interhemispheric inhibition, LAI long latency afferent inhibition, LICI long interval intracortical inhibition, LTD long-term depression, LTP long-term potentiation, MEP motor evoked potential, SAI short latency afferent inhibition, SICI short interval intracortical inhibition
- Notes:
-
aTMS measurements with different stimulus parameters may lead to different results in testing cortical circuits in neurodegenerative diseases. We only list the most consistent findings in the literatures. Detailed discussion is in the main text of the review
-
bMEP threshold increased in ALS but could be decreased at early stage of the disease
-
cOnly long latency IHI was decreased in PD patients with mirror movement. Such abnormality was found from both the less affected to more affected side and from the more affected to less affected side. Short latency IHI does not change
-
dLTP-like effects are tested by facilitatory repetitive stimulation protocols including high-frequency repetitive transcranial magnetic stimulation, intermittent theta burst stimulation and paired associative stimulation while LTD-like effects are tested by inhibitory repetitive stimulation protocols including low-frequency repetitive transcranial magnetic stimulation and continuous theta burst stimulation
-
eLTP-like cortical plasticity tested with paired associative stimulation is impaired in PD patients off medication. Dopaminergic medications restore the plasticity in non-dyskinetic patients but not in the dyskinetic patients
