Recognition of faces expressing emotions in patients with unilateral brain damage

The experiment concerned the functional specialization of brain hemispheres in recognizing faces expressing emotions in patients with focal brain damage of the left and right hemispheres and in persons without damage of the central nervous system. Three types of faces were presented: happy i.e. expressing positive emotions, sad i.e. expressing negative emotions and neutral. The task of the subject was to recognize the test face exposed for 20 ms in the left or right visual field and point to the correct face on the response-card which contained three different faces. The errors made in recognizing of faces exposed in the right visual field (addressing the left hemisphere) and in the left one (addressing the right hemisphere) were analyzed. The patients with left hemisphere damage showed a similar pattern of hemispheric differences to that observed in the controls. In case of neutral and sad faces fewer errors were made in the left visual field exposures, in case of happy faces no significant differences between the two fields were stated. The results in patients with right hemispheric damage were different from both the other groups. In processing all the three types of faces, fewer errors were made in the left visual field presentations independently of the localization of the damage within the right hemisphere. Similar recognition level of different types of faces was also found in patients with left or right hemisphere damage as well as in controls. The above results suggest the crucial role of the right hemisphere in processing both positive and negative emotions expressed in faces.