Cognitive–motor interference during the suppression head impulse paradigm

Objective The vestibulo-ocular reflex (VOR) is critical for stabilizing vision during head motion and for daily multitasking activities. The suppression head impulse paradigm (SHIMP) complements the head impulse paradigm (HIMP) and is considered more sensitive for residual vestibular function. This study examined the impact of cognitive and motor dual-tasking on SHIMP in healthy adults. Methods Twenty-two participants performed single-task HIMP and SHIMP alongside two cognitive dual-task SHIMP (serial subtraction, map navigation) and one motor dual-task SHIMP (counter clicking). Outcomes included VOR gain and anti-compensatory saccade parameters (number, latency, amplitude, duration, and peak velocity). Results VOR gain was lower in SHIMP than HIMP (0.827 ± 0.140 vs 0.941 ± 0.123; p < 0.001). Cognitive dual-task markedly affected anti-compensatory saccade, reducing saccade number (15–22%), prolonging latency (39–47%), decreasing amplitude (20%), shortening duration (∼5%), and reducing peak velocity (∼10%) (all p < 0.05). Motor dual-task modestly increased gain (0.868 ± 0.131 vs 0.827 ± 0.140; p = 0.025) but only increased anti-compensatory saccade latency by 17% ( p < 0.05). Conclusions Dual-tasking exerted distinct effects on SHIMP outcomes. VOR gain remained largely preserved, whereas anti-compensatory saccades were substantially impaired. These findings highlight the contribution of central and attentional mechanisms to anti-compensatory saccade generation and suggest that these parameters may provide complementary information to VOR gain during SHIMP testing.