8/02/2012

Functional connectivity of dorsal vs. ventral posterior parietal cortices during top-down vs. bottom-up attention to memory


In previous neuroimaging studies, the human posterior parietal cortex has been identified as one intimately involved in attentional processes. Dorsal aspects of the posterior parietal cortex have been associated with “top-down” attention (i.e., focusing attention on external stimuli based on internal goals of the subject) and ventral aspects of the posterior parietal cortex have been associated with “bottom-up” attention (i.e., externally presented unexpected stimuli capturing one’s attention). Whilst studying attention to externally applied stimuli is experimentally convenient, focusing attention on internal events (e.g., conducting memory searches) is equally important. One might assume that the posterior parietal cortex governs attention to memorized items similarly as in the case of externally applied stimuli, however, it has not been systematically tested whether the posterior parietal cortex is functionally segregated into dorsal and ventral areas during cued vs. non-cued recognition memory trials.

In their recent study, Burianov√° et al. (2012) tested, by presenting cued vs. non-cued recognition memory trials during functional magnetic resonance imaging, whether dorsal aspects of the posterior parietal cortex are more involved in top-down memory searches and whether ventral aspects of the posterior parietal cortex are more involved in non-cued bottom-up recognition memory. The authors observed spatially dissociable networks of brain areas that overlapped only in precuneus. During cued recognition memory trials (“top-down”), dorsal posterior parietal cortex was functionally connected with areas comprising the dorsal attention network as well as with memory-related brain areas; there was further a significant correlation between cued memory recognition performance and this network activity. In contrast, during uncued trials, ventral posterior parietal cortex was functionally connected with the ventral attention system and with relevant memory areas. These findings thus disclose a nice double-dissociation of roles between dorsal and ventral posterior parietal cortical areas in recognition memory that closely resembles the distinct roles that these areas play in top-down vs. bottom-up attention.

Reference: Burianov√° H, Ciaramelli E, Grady CL, Moscovitch M.  Top-down and bottom-up attention-to-memory: mapping functional connectivity in two distinct networks that underlie cued and uncued recognition memory. Neuroimage (2012) e-publication available prior to publication. http://dx.doi.org/10.1016/j.neuroimage.2012.07.057

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