Parietal lobe and episodic memory: bilateral damage causes impaired free recall of autobiographical memory

Abstract

Does the parietal lobe have a critical role in memory? The neuroimaging literature indicates that it has an important role, especially in episodic memory. However, the neuropsychological literature suggests that its role is more limited to attentional, spatial, or imagery aspects of memory. Here, we present data to adjudicate this disagreement. Two patients with bilateral parietal lobe damage received detailed assessments of their autobiographical memories. The results show that although both patients easily recalled various memories, their freely recalled memories were relatively impoverished, lacking in detail. This deficit was ubiquitous, and not limited to spatial or perceptual aspects of memory. The memory deficit disappeared when memory was specifically probed by asking pointed questions. Additional tests show that it is unlikely that their free recall deficit can be explained by general mental imagery problems. In sum, the parietal lobe appears to have a critical role in recollection aspects of episodic memory.

Figure 1.

Patient lesion traces. Lesions are shown on T2 fluid-attenuated inversion recovery images in which the lesions appear as white higher intensity patches in parietal regions. The right is on the left.

Figure 2.

Internal and external details retrieved during free recall of memories (top) and when specifically probed (bottom). Internal details refer to details pertaining to the probed event. External details refer to details that were irrelevant to the probed event. Error bars represent SEM. Asterisks denote significant differences between the control and patient groups.

Figure 3.

Free recall performance. Top, Number of internal details. Middle, External details. Bottom, Memory ratings for different categories retrieved during the free recall condition. The axes for the top and middle graphs reflect the total number of details tallied for each memory. The axes for the bottom graph reflect the scale of 0–6 for episodic richness and 0–3 for the remaining categories. Error bars represent SEM. Asterisks denote significant differences between the control and patient groups.

Figure 4.

Specific probe performance. Top, Number of internal details. Middle, External details. Bottom, Memory ratings for each category in retrieved during the specific probe condition. The axes for the top and middle graphs reflect the total number of details tallied for each memory. The axes for the bottom graph reflect the scale of 0–6 for episodic richness and 0–3 for the remaining categories. Error bars represent SEM. Asterisks denote significant differences between the control and patient groups.