Posterior parietal cortex and episodic retrieval: Convergent and divergent effects of attention and memory

  1. J. Benjamin Hutchinson1,3,4,
  2. Melina R. Uncapher1,3 and
  3. Anthony D. Wagner1,2
  1. 1Department of Psychology, Stanford University, Stanford, California 94305-2130, USA;
  2. 2Neuroscience Program, Stanford University, Stanford, California 94305-2130, USA
    1. 3 These authors contributed equally to this work.

    Abstract

    Functional neuroimaging studies of humans engaged in retrieval from episodic memory have revealed a surprisingly consistent pattern of retrieval-related activity in lateral posterior parietal cortex (PPC). Given the well-established role of lateral PPC in subserving goal-directed and reflexive attention, it has been hypothesized that PPC activation during retrieval reflects the recruitment of parietal attention mechanisms during remembering. Here, we evaluate this hypothesis by considering the anatomical overlap of retrieval and attention effects in lateral PPC. We begin by briefly reviewing the literature implicating dorsal PPC in goal-directed attention and ventral PPC in reflexive attention. We then discuss the pattern of dorsal and ventral PPC activation during episodic retrieval, and conclude with consideration of the degree of anatomical convergence across the two domains. This assessment revealed that predominantly divergent subregions of lateral PPC are engaged during acts of episodic retrieval and during goal-directed and reflexive attention, suggesting that PPC retrieval effects reflect functionally distinct mechanisms from these forms of attention. Although attention must play a role in aspects of retrieval, the data reviewed here suggest that further investigation into the relationship between processes of attention and memory, as well as alternative accounts of PPC contributions to retrieval, is warranted.

    Footnotes

    • 4 Corresponding author.

      E-mail jbhutchi{at}stanford.edu; fax (650) 725-5699.

    • 5 Use of the term “lateral parietal” or “lateral PPC” in the present review is in keeping with prior publications in the episodic memory literature, and refers to those aspects of the posterior parietal cortex that fall lateral to the mesial aspect of BA 7 (also referred to as “medial PPC,” or the precuneus). Lateral parietal cortex therefore comprises both dorsal and ventral regions of PPC, with the dorsal component consisting of the superior parietal lobule (SPL; the lateral extent of BA 7) and the ventral encompassing the inferior parietal lobule (IPL), including the supramarginal gyrus and temporoparietal junction (SMG and TPJ; BA 40), as well as angular gyrus (AnG; BA 39).

    • 6 Although the number of foci are limited, and thus strong conclusions cannot be drawn at this point, it may be notable that the majority of the dorsal PPC foci elicited under conditions of reflexive orienting fall lateral to the dorsal PPC foci elicited under conditions of goal-directed attentional allocation (Fig. 4). Future within-subject comparison is required to determine whether this possible anatomic divergence is real.

    • 7 Interestingly, in this same study, there also was a left IPL focus that was more responsive during the episodic retrieval than during the cued attention paradigm, and bilateral TPJ/SMG foci were observed to be more responsive to the cued attention than the episodic retrieval paradigm. Interpretation of these data, as well as the IPS/SPL response that was common to the attention and retrieval paradigms, is complicated, however, because the retrieval activations consisted of a comparison to a low-level baseline, rather than a comparison between retrieval conditions. Thus, it is unclear in this study whether these IPL, TPJ/SMG, and IPS/SPL regions demonstrated an old/new or recollection effect.

    • Article is online at http://www.learnmem.org/cgi/doi/10.1101/lm.919109.

      • Received October 23, 2008.
      • Accepted March 25, 2009.
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