Saccadic adaptation in Chiari type II malformation.
BACKGROUND
Saccadic adaptation corrects errors in saccadic amplitude. Experimentally-induced saccadic adaptation provides a method for studying motor learning. The cerebellum is a major participant in saccadic adaptation. Chiari type II malformation (CII) is a developmental deformity of the cerebellum and brainstem that is associated with spina bifida. We investigated the effects of CII on saccadic adaptation.


METHODS
We measured eye movements using an infrared eye tracker in 21 subjects with CII (CII group) and 39 typically developing children (control group), aged 8-19 years. Saccadic adaptation was induced experimentally using targets that stepped horizontally 120 to the right and then stepped backward 3 degrees during saccades.


RESULTS
Saccadic adaptation was achieved at the end of the adaptation phase in participants in each group. Saccadic amplitude gain decreased by 6.9% in the CII group and 9.3% in the control group. The groups did not differ significantly (p = 0.27). Amplitude gain reduction was significantly less in the CII participants who had multiple shunt revisions. Regression analyses revealed no effects of spinal lesion level, presence of nystagmus, or cerebellar vermis dysmorphology on saccadic adaptation.


CONCLUSIONS
The neural circuits involved in saccadic adaptation appear to be functionally intact in CII.
Salman
Michael S
MS
Division of Neurology, The Hospital for Sick Children, Toronto, ON.
Sharpe
James A
JA
Eizenman
Moshe
M
Lillakas
Linda
L
To
Teresa
T
Westall
Carol
C
Steinbach
Martin J
MJ
Dennis
Maureen
M
D000222:Adaptation, Physiological / Q000502:physiology*; D000293:Adolescent; D001139:Arnold-Chiari Malformation / Q000503:physiopathology*; D002648:Child; D006801:Humans; D008279:Magnetic Resonance Imaging; D012438:Saccades / Q000502:physiology*