Spatial Binding Impairments in Visual Working Memory following Temporal Lobectomy

Abstract

Disorders of the medial temporal lobe (MTL) adversely affect visual working memory (vWM) performance, including feature binding. It is unclear whether these impairments generalise across visual dimensions or are specifically spatial. To address this issue, we compared performance in two tasks of thirteen epilepsy patients, who had undergone a temporal lobectomy, and fifteen healthy controls. In the vWM task, participants recalled the color of one of two polygons, previously displayed side by side. At recall, a location or shape probe identified the target. In the perceptual task, participants estimated the centroid of three visible disks. Patients recalled the target color less accurately than healthy controls because they frequently swapped the non-target with the target color. Moreover, healthy controls and right temporal lobectomy patients made more swap errors following shape than space probes. Left temporal lobectomy patients, showed the opposite pattern of errors instead. Patients and controls performed similarly in the perceptual task. We conclude that left MTL damage impairs spatial binding in vWM, and that this impairment does not reflect a perceptual or attentional deficit.

Significance Statement

This study examined color recall in temporal lobectomy patients and healthy controls, to determine whether patients show differential impairments binding color and shape vs color and location of memorised objects. Left temporal lobectomy patients were less accurate recalling color, especially when the target object was identified by the location, rather than the shape it had in the initial display. We found no group difference in a task, which required estimating the centroid of three circles, indicating that the memory impairment was not accounted by perceptual or attentional difficulties. Our findings indicate that lateralised medial temporal circuits are crucial for binding visual features to the location where they had appeared, thus ensuring the primacy of space in organising declarative memories.