Positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) have been extensively used to explore the functional neuroanatomy of cognitive functions. Here we review 275 PET and fMRI studies of attention (sustained, selective, Stroop, orientation, divided), perception (object, face, space/motion, smell), imagery (object, space/motion), language (written/spoken word recognition, spoken/no spoken response), working memory (verbal/numeric, object, spatial, problem solving), semantic memory retrieval (categorization, generation), episodic memory encoding (verbal, object, spatial), episodic memory retrieval (verbal, nonverbal, success, effort, mode, context), priming (perceptual, conceptual), and procedural memory (conditioning, motor, and nonmotor skill learning). To identify consistent activation patterns associated with these cognitive operations, data from 412 contrasts were summarized at the level of cortical Brodmann's areas, insula, thalamus, medial-temporal lobe (including hippocampus), basal ganglia, and cerebellum. For perception and imagery, activation patterns included primary and secondary regions in the dorsal and ventral pathways. For attention and working memory, activations were usually found in prefrontal and parietal regions. For language and semantic memory retrieval, typical regions included left prefrontal and temporal regions. For episodic memory encoding, consistently activated regions included left prefrontal and medial temporal regions. For episodic memory retrieval, activation patterns included prefrontal, medial temporal, and posterior midline regions. For priming, deactivations in prefrontal (conceptual) or extrastriate (perceptual) regions were consistently seen. For procedural memory, activations were found in motor as well as in non-motor brain areas. Analysis of regional activations across cognitive domains suggested that several brain regions, including the cerebellum, are engaged by a variety of cognitive challenges. These observations are discussed in relation to functional specialization as well as functional integration.

A model of the effects of aging on brain activity during cognitive performance is introduced. The model is called HAROLD (hemispheric asymmetry reduction in older adults), and it states that, under similar circumstances, prefrontal activity during cognitive performances tends to be less lateralized in older adults than in younger adults. The model is supported by functional neuroimaging and other evidence in the domains of episodic memory, semantic memory, working memory, perception, and inhibitory control. Age-related hemispheric asymmetry reductions may have a compensatory function or they may reflect a dedifferentiation process. They may have a cognitive or neural origin, and they may reflect regional or network mechanisms. The HAROLD model is a cognitive neuroscience model that integrates ideas and findings from psychology and neuroscience of aging.

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Emotional events often attain a privileged status in memory. Cognitive neuroscientists have begun to elucidate the psychological and neural mechanisms underlying emotional retention advantages in the human brain. The amygdala is a brain structure that directly mediates aspects of emotional learning and facilitates memory operations in other regions, including the hippocampus and prefrontal cortex. Emotion-memory interactions occur at various stages of information processing, from the initial encoding and consolidation of memory traces to their long-term retrieval. Recent advances are revealing new insights into the reactivation of latent emotional associations and the recollection of personal episodes from the remote past.

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...