Verbal and nonverbal emotional memory following unilateral amygdala damage

Abstract

The amygdala is involved in the normal facilitation of memory by emotion, but the separate contributions of the left and right amygdala to memory for verbal or nonverbal emotional material have not been investigated. Fourteen patients with damage to the medial temporal lobe including the amygdala (seven left, seven right), 18 brain-damaged, and 36 normal controls were exposed to emotional and neutral pictures accompanied by verbal narratives. Memory for both narratives and pictures was assessed with a free recall test 24 h later. Subjects with left amygdala damage failed to show the normally robust enhancement of memory for verbal and nonverbal emotional stimuli. The group with right amygdala damage showed the normal pattern of facilitation of memory by emotion for both verbal and nonverbal stimuli despite an overall reduction in memory performance. Furthermore, subjects with left amygdala damage were disproportionately impaired on memory for emotional narratives as compared with memory for emotional pictures. The latter finding offers partial support for a lateralized and material-specific pattern of the amygdala's contribution to emotional memory.

Figure 1

Ratings of picture valence and arousal. (A) Mean (±standard error) ratings of valence (pleasantness) are shown from all subjects across the three emotion categories. The scale represents maximum pleasantness at 9 and maximum unpleasantness at 0. (B) Mean (±standard error) ratings of arousal from all subjects across the three emotion categories. The scale represents maximum arousal at 9 and minimum arousal at 0.

Figure 2

Free recall for narratives and pictures across valence categories. (A) Mean (±standard error) of correctly recalled narratives across all subjects from each valence category. (B) Mean (±standard error) of correctly recalled pictures across all subjects from each valence category.

Figure 3

Free recall for narratives and pictures across arousal categories. (A) Mean (±standard error) of the proportion of correctly recalled narratives across all subjects from low and high arousal categories. (B) Mean (±standard error) of the proportion of correctly recalled pictures across all subjects from low- and high-arousal categories.