Dysfunction of Ib (autogenic) spinal inhibition in patients with progressive supranuclear palsy.
We compared the activity of Ib spinal interneurons in five patients with progressive supranuclear palsy (PSP) with six age-matched control subjects. Stimulation of the medial gastrocnemius nerve at motor threshold intensity activated Ib afferents that in turn inhibit H reflexes from the soleus muscle. Maximum inhibition occurred at interstimulus intervals of 6 and 8 ms for both control subjects and PSP patients and was significantly greater in the PSP patients. Increased Ib activity of PSP patients may be caused by loss of inhibition of Ib interneurons through degeneration of the medullary reticulospinal pathway. The corticospinal pathways, unopposed by the medullary reticulospinal tract, may excessively activate Ib interneurons.
Neurology Service, Department of Veterans' Affairs Medical Center, State University of New York at Buffalo, 14215, USA.
E J
EJ
Fine
M
M
Hallett
I
I
Litvan
N
N
Tresser
D
D
Katz
D000344:Afferent Pathways / Q000473:pathology / Q000503:physiopathology; D000368:Aged; D000369:Aged, 80 and over; D001931:Brain Mapping; D004558:Electric Stimulation; D005260:Female; D006181:H-Reflex / Q000502:physiology; D006801:Humans; D007124:Immunoenzyme Techniques; D007395:Interneurons / Q000473:pathology / Q000502:physiology*; D008297:Male; D008465:Mechanoreceptors / Q000473:pathology / Q000503:physiopathology; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000294:innervation; D009433:Neural Inhibition / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D012154:Reticular Formation / Q000473:pathology / Q000503:physiopathology; D013116:Spinal Cord / Q000473:pathology / Q000503:physiopathology*; D013494:Supranuclear Palsy, Progressive / Q000175:diagnosis / Q000473:pathology / Q000503:physiopathology*