The influence of rightward and leftward spatial deviations of spatial attention on emotional picture recognition.

OBJECTIVES: Several studies have reported that positive emotions are primarily mediated by the left hemisphere and negative emotions by the right hemisphere. Since each hemisphere primarily allocates attention toward the contralateral hemispace, we wanted to learn how inducing a spatial attentional orienting bias to right and left egocentric hemispace might influence the recognition and perception of visually presented emotional scenes.

METHOD: Participants were 42 healthy, right-handed young adults. To induce a directional change in spatial attention, we used a horizontal prism adaptation (PA) method that trains participants to allocate attention in the opposite direction to the prism-induced deviation. After each PA, participants evaluated a set of affective (positive/neutral/negative) pictures from the Nencki Affective Picture System. Responses in each emotional category and reaction times were recorded and analyzed.

RESULTS: There was no PA effects on reaction times between the experimental conditions. However, when compared to the control condition, both rightward and leftward PA resulted in a reduction of correctly recognized positive emotions as well as altering the perception of neutral and positive pictures as more emotionally negative.

CONCLUSIONS: The results do not support the proposed left-right spatial attentional valence hypothesis. The reason why PA in both directions negatively altered emotion perception is not known. However, a portion of the dorsal visual stream, the parietal lobes, and especially the right parietal lobe, are critical for mediating horizontal egocentric spatial attention. The right hemisphere also mediates negative emotions, and the activation of this right hemispheric attention network may have induced the changes in perception found in this study. However, future studies are needed to further test this hypothesis.