HIMP vs SHIMP comparison
Compare the two paradigms side-by-side across four clinical scenarios. The teaching narrative explains what each paradigm reveals that the other does not.
Clinical scenario:
HIMP
earth-fixed target
SHIMP
head-fixed laser target
HIMP gain
0.95 (Normal)
Saccades: none
SHIMP gain
0.92 (Normal)
Saccades: anti-comp
What this scenario teaches
Normal subject
HIMP shows preserved gain with no corrective saccades (eye tracks head perfectly opposite). SHIMP shows the same intact VOR, so a large anti-compensatory saccade is needed to catch up to the head-fixed laser target. Anti-compensatory saccades in healthy SHIMP are the signature of a working VOR.
How the two paradigms differ
HIMP
Patient fixates an earth-fixed target. Intact VOR → eye moves opposite head, gaze stays on target. Deficient VOR → eye lags, then a compensatory saccade brings gaze back.
SHIMP
Patient fixates a head-fixed laser target. Intact VOR → eye still moves opposite head, so an anti-compensatory saccade is needed to catch the head-fixed target. Deficient VOR → eye stays with head, no anti-compensatory saccade needed.