Reviews and perspectivesMemory retrieval and the parietal cortex: A review of evidence from a dual-process perspective
Section snippets
Recognition memory
There is substantial evidence that recognition memory judgments are not ‘process-pure’, but rather are supported by at least two sources of information about past occurrence (Rugg & Yonelinas, 2003). This evidence has motivated a number of ‘dual-process’ accounts of recognition memory (e.g., Atkinson & Juola, 1974; Mandler, 1980; Yonelinas & Jacoby, 1995; for review see Yonelinas, 2002). Common to all of these accounts is the proposal that recognition can be supported both by an
Meta-analysis of fMRI studies of recollection and familiarity
We conducted a review of published event-related fMRI studies where contrasts were employed that allowed retrieval-related activity associated with recollection- and familiarity-driven recognition judgments to be separately identified. We restricted our analysis to studies requiring judgments on individually presented test items that differed in their study histories (that is, tests employing judgments on ‘old’ vs. ‘new’ items). Among these studies, we further narrowed our selection to those
Findings from specific studies
In this section, we discuss specific findings that we consider especially relevant to the understanding of the functional significance of retrieval-related activity in the parietal cortex. In light of the findings of the above meta-analysis, we focus on lateral, and especially left lateral, cortex. We consider results from some of the studies listed in Table 1 along with findings from additional studies where relevant.
Superior parietal cortex
We turn first to the possible significance of the ‘familiarity’ effects localized to superior lateral parietal cortex in the vicinity of the IPS. Although the findings reported in Table 1 suggest that activity in this region co-varies with familiarity strength, this does not necessarily lead to the conclusion that the region specifically supports processes underlying familiarity-driven recognition. Indeed, the evidence suggests otherwise. In the first place, not only does this region
Inferior parietal cortex
The meta-analysis of the findings listed in Table 1 shows that retrieval-related effects in parietal cortex inferior to the IPS emerge mainly from contrasts aimed at identifying neural correlates of recollection. The question arises whether these inferior effects are indicative of a specific role for lateral parietal cortex in recollective processing, or whether, as appears to be the case for superior parietal cortex, they index the engagement of processes confounded with, but not directly
Timing of recollection-related neural activity—evidence from ERPs
Information about the time-course of the recollection effects in inferior parietal cortex would be very helpful in constraining their functional interpretation. For example, if it turned out that the onset latency of the effects exceeded the latency of recollection-based behavioral responses, this would invalidate any interpretation that linked the effects to processes directly supporting successful retrieval. Unfortunately, the low temporal resolution of the BOLD signal means the precise
Recollection and the functions of inferior parietal cortex
Before proposing a specific role for inferior parietal cortex in recollection, it would seem sensible to ask whether any of the functions already proposed for this region might accommodate its involvement in recollective processing. There is no shortage of potential functions to choose from (for reviews see Culham & Valyear, 2006; Husain & Nachev, 2006; Jackson & Husain, 2006). Among the more prominent are control of visuospatial attention, attention switching, the temporary storage of
Alternatives to dual-process interpretations of retrieval-related parietal activity
As was previously, dual-process interpretations of retrieval-related neural activity (whether in the parietal cortex or elsewhere) depend on the twin assumptions that recollection and familiarity provide independent bases for recognition decisions, and that recollection has a thresholded (‘all-or-none’) character. These assumptions are challenged by models proposing that recognition decisions are based on a continuous, unidimensional memory signal (e.g., Dunn, 2004). For example, in one recent
Hemispheric asymmetry of lateral parietal contributions to retrieval
Both neuropsychological and functional neuroimaging evidence suggest that parietal cortex is functionally lateralized, with particularly striking asymmetries of function in the cases of visuospatial attention, organization of action, and language (Husain & Nachev, 2006). The fact that retrieval-related parietal activity is more frequently observed in the left than the right hemisphere, and the predominant finding of a left-sided distribution of recollection-related parietal ERP effects (see
Medial parietal cortex
Medial parietal cortex (BA 7) – often referred to as the precuneus – has been implicated in retrieval since the earliest functional imaging studies, and is frequently held to be a key component of a cortical network subserving episodic retrieval (e.g., Cavanna & Trimble, 2006). Consistent with this view, the precuneus, along with inferior parietal cortex, was identified as a region demonstrating strong functional interconnectivity with the hippocampal formation in the study of Vincent et al.
Retrieval tests other than recognition
As already noted, the overriding majority of studies investigating the neural correlates of retrieval success have employed variants of recognition memory tests. This raises the question whether the findings reported in such studies generalize to other kinds of memory test. If recollection-driven recognition does indeed rely on the same core retrieval operations that support episodic retrieval more generally, then the recollection-sensitive inferior parietal regions identified with recognition
Effects of parietal lesions on memory
As we noted previously, functional neuroimaging findings suggesting a role for parietal cortex in memory were unanticipated given the lack of neuropsychological evidence for long-term memory deficits following parietal damage. However, while clinical observation unquestionably suggests that long-term memory is largely unaffected following parietal lesions, there are only a few published studies in which memory performance of parietal patients has been studied formally. In one such study (Simons
Concluding comments
Event-related fMRI findings have amply confirmed earlier suspicions that neural activity in lateral and medial parietal cortex is sensitive to retrieval success. The findings further point to a functional dissociation between superior and inferior lateral parietal regions, with the latter showing strong evidence of a direct role in episodic memory retrieval. We conjecture that this role involves the maintenance or representation of retrieved information in something like the episodic buffer
Acknowledgements
K. Vilberg was supported by NSF Graduate Research Fellowship Award D/DGE-0234621. Preparation of this article, and some of the research reported within it, were supported by NIMH grant 5R01MH072966.
References (81)
The episodic buffer: A new component of working memory?
Trends in Cognitive Sciences
(2000)- et al.
Effective connectivity in target stimulus processing: A dynamic causal modeling study of visual oddball task
NeuroImage
(2007) - et al.
Human parietal cortex in action
Current Opinion in Neurobiology
(2006) - et al.
Support for an auto-associative model of spoken cued recall: Evidence from fMRI
Neuropsychologia
(2007) - et al.
Emotion-attention network interactions during a visual oddball task
Brain Research Cognitive Brain Research
(2004) - et al.
ERP ‘old/new’ effects: Memory strength and decisional factor(s)
Neuropsychologia
(2002) - et al.
The functional neuroanatomy of episodic memory
Trends in Neurosciences
(1997) - et al.
The posterior parietal cortex in recognition memory: A neuropsychological study
Neuropsychologia
(2008) - et al.
Probability effects on the neural correlates of retrieval success: An fMRI study
NeuroImage
(2004) - et al.
Visuomotor functions of the posterior parietal cortex
Neuropsychologia
(2006)