Top-Down and Bottom-Up Attention to Memory Are Dissociated in Posterior Parietal Cortex: Neuroimaging and Neuropsychological Evidence

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Abstract
Posterior parietal cortex is active during episodic memory retrieval, yet its role remains unclear. According to a recent proposal, dorsal parietal cortex (DPC) allocates top-down attention to memory retrieval, whereas ventral parietal cortex (VPC) mediates the bottom-up attentional capture by retrieved contents, i.e., the Attention-to-Memory (AtoM) hypothesis. Here, for the first time, functional magnetic resonance imaging (fMRI) and lesion techniques were combined in a single study to test the role of parietal cortex in episodic retrieval. Participants studied word pairs and then detected studied (target) words among new words. In some conditions, a studied word cued the upcoming target word, facilitating recognition performance. In line with the AtoM hypothesis, left DPC was engaged when participants searched for/anticipated memory targets upon presentation of relevant memory cues and predicted the ensuing behavioral advantage. In contrast, left VPC predicted efficacy and speed of target detection on noncued trials and was largest for memory targets that were invalidly cued. Consistent with fMRI evidence, patients with lesions in DPC did not benefit from memory cueing, whereas patients with lesions in VPC had problems recognizing unexpected memory targets. These results support the AtoM hypothesis that DPC and VPC mediate top-down and bottom-up attention to memory retrieval, respectively.

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