The contribution of the parietal cortex to episodic memory is a fascinating scientific puzzle. On one hand, parietal lesions do not normally yield severe episodic memory deficits, but on the other hand, parietal activations are seen frequently in functional neuroimaging studies of episodic memory. A review of these two categories of evidence suggests that the answer to the puzzle requires us to distinguish between dorsal and ventral parietal regions and between top-down vs. bottom-up attention as they are applied to memory.If twenty years ago a neurologist had been asked if the parietal cortex played an important role in episodic memory, the answer probably would have been negative. Such an answer would have been quite reasonable given the fact that parietal lesions do not yield severe episodic memory deficits, such as the ones associated with damage to the medial temporal lobe (MTL). During the last two decades, however, numerous studies using event-related potentials (ERPs), 1 positron emission tomography (PET), and functional MRI (fMRI) 2 have shown that the parietal cortex is one of the regions most frequently activated during episodic memory retrieval. Thus, the contribution of parietal regions to episodic memory constitutes an intriguing scientific puzzle. Potential answers to this problem have begun to emerge only recently. First, the development of event-related fMRI methods has allowed imaging researchers to specify the types of memory processes that are associated with activations in different parietal subregions. Second, a few neuropsychological studies have demonstrated that parietal lesions do impair certain episodic memory processes. Finally, memory researchers have started focusing on the contributions of the parietal cortex and have proposed several hypotheses with clear, testable predictions. As result, a new domain of cognitive neuroscience research has emerged with a critical mass of empirical evidence and a set of testable hypotheses.The goal of the present article is to provide a concise overview of this new domain of inquiry. We begin by summarizing accepted ideas regarding the anatomy and function of the parietal cortex. This is followed by a review of recent findings from neuropsychology and neuroimaging studies that link parietal function to episodic retrieval. This review is intended for the general neuroscience audience; more detailed reviews intended for memory experts can be found in other related publications. 72,73 Finally, we review the potential explanations for these findings and discuss our attention-based hypothesis. We end by considering several open questions about the contribution of parietal lobe to episodic memory. Anatomy and Functions of Parietal CortexThe parietal cortex includes a strip posterior to the central sulcus that is specialized for somatosensory function (Brodmann areas [BAs] 1, 2, 3, and 5) as well as regions posterior to that strip that are known as posterior parietal cortex and may be grossly divided into a medial and a lateral portion. The media...

No abstract

Although ventral parietal cortex (VPC) activations can be found in a variety of cognitive domains, these activations have been typically attributed to cognitive operations specific to each domain. In this article, we propose a hypothesis that can account for VPC activations across all the cognitive domains reviewed. We first review VPC activations in the domains of perceptual and motor reorienting, episodic memory retrieval, language and number processing, theory of mind, and episodic memory encoding. Then, we consider the localization of VPC activations across domains, and conclude that they are largely overlapping with some differences around the edges. Finally, we assess how well four different hypotheses of VPC function can explain findings in various domains, and conclude that a bottom-up attention hypothesis provides the most complete and parsimonious account.

Recent fMRI evidence has detected increased medial prefrontal activation during contemplation of personal moral dilemmas compared to impersonal ones, which suggests that this cortical region plays a role in personal moral judgment. However, functional imaging results cannot definitively establish that a brain area is necessary for a particular cognitive process. This requires evidence from lesion techniques, such as studies of human patients with focal brain damage. Here, we tested 7 patients with lesions in the ventromedial prefrontal cortex and 12 healthy individuals in personal moral dilemmas, impersonal moral dilemmas and non-moral dilemmas. Compared to normal controls, patients were more willing to judge personal moral violations as acceptable behaviors in personal moral dilemmas, and they did so more quickly. In contrast, their performance in impersonal and non-moral dilemmas was comparable to that of controls. These results indicate that the ventromedial prefrontal cortex is necessary to oppose personal moral violations, possibly by mediating anticipatory, self-focused, emotional reactions that may exert strong influence on moral choice and behavior.

Choices are often intertemporal, requiring tradeoff of short-term and long-term outcomes. In such contexts, humans may prefer small rewards delivered immediately to larger rewards delivered after a delay, reflecting temporal discounting (TD) of delayed outcomes. The medial orbitofrontal cortex (mOFC) is consistently activated during intertemporal choice, yet its role remains unclear. Here, patients with lesions in the mOFC (mOFC patients), control patients with lesions outside the frontal lobe, and healthy individuals chose hypothetically between small-immediate and larger-delayed rewards. The type of reward varied across three TD tasks, including both primary (food) and secondary (money and discount vouchers) rewards. We found that damage to mOFC increased significantly the preference for small-immediate over larger-delayed rewards, resulting in steeper TD of future rewards in mOFC patients compared with the control groups. This held for both primary and secondary rewards. All participants, including mOFC patients, were more willing to wait for delayed money and discount vouchers than for delayed food, suggesting that mOFC patients' (impatient) choices were not due merely to poor motor impulse control or consideration of the goods at stake. These findings provide the first evidence in humans that mOFC is necessary for valuation and preference of delayed rewards for intertemporal choice.