The effect of vision on top.down modulation of hand blink reflex

Objective: The magnitude of hand blink reflex (HBR) increases when a threatening stimulus is positioned in the peripersonal space (PPS) compared with stimulus in the extrapersonal space (EPS). We hypothesized that the reflex increase in PPS might change depending on whether the stimulus was seen. We aimed to investigate the alterations in HBR response to understand the effects of vision on cortical modulation of HBR. Methods: The HBR was recorded from 11 healthy volunteers while the hand was far away from the face (EPS), close to the face with eyes open (PPS-eyes open), and close to the face with eyes closed (PPS-eyes closed). Changes in the response magnitudes were compared between the three conditions. Results: HBR was obtained in all subjects. As expected, there was an increase in the reflex magnitude in the PPS-eyes open condition relative to EPS. In the PPS-eyes closed condition, the duration and latency were shorter and the area under the curve was significantly smaller compared with the PPS-eyes open condition. Conclusion: The enhancement of HBR in PPS is attributed to tonic top-down modulation. Our study provides evidence for the special sensory modulation of the PPS effect on HBR and may suggest cortical modulation of top-down modulation of brainstem neural circuits.