The effect of monocular viewing on heartbeat discrimination.

In monocular viewing conditions, an activational imbalance between the cerebral hemispheres was assumed to develop, the direction of which depends on the side of the viewing eye. This assumption was based on the morphological differences between the nasal and the temporal hemiretinas and on physiological data. It was assumed that the hemisphere receiving visual information via the nasal optic fibers, that is, the hemisphere contralateral to the viewing eye, would be the more activated one. Because heartbeat perception is regarded as a predominantly right hemispheric function, it was predicted that during right hemispheric activation created by left monocular viewing heartbeat discrimination performance would be better than during left hemispheric activation created by right monocular viewing. This hypothesis was tested on 30 male right-handed university students who performed a Whitehead-type heartbeat discrimination task while viewing only with the left or with the right eye. Heartbeat perception was more accurate when viewing with the left eye. Additionally, respiratory manipulation during heartbeat discrimination improved performance on this task.