Perceptual difficulty in source memory encoding and retrieval: Prefrontal versus parietal electrical brain activity

Abstract

It is well established that source memory retrieval -remembering relationships between a core item and some additional attribute of an event -engages prefrontal cortex (PFC) more than simple item memory. In event-related potentials (ERPs), this is manifest in a late-onset difference over PFC between studied items which mandate retrieval of a second attribute, and unstudied items which can be immediately rejected. Although some sorts of attribute conjunctions are easier to remember than others, the role of source retrieval difficulty on prefrontal activity has received little attention. We examined memory for conjunctions of object shape and color when color was an integral part of the depicted object, and when monochrome objects were surrounded by colored frames. Source accuracy was reliably worse when shape and color were spatially separated, but prefrontal activity did not vary across the object-color and frame-color conditions. The insensitivity of prefrontal ERPs to this perceptual manipulation of difficulty stands in contrast to their sensitivity to encoding task: deliberate voluntary effort to integrate objects and colors during encoding reduced prefrontal activity during retrieval, but perceptual organization of stimuli did not. The amplitudes of ERPs over parietal cortex were larger for frame-color than object-color stimuli during both study and test phases of the memory task. Individual variability in parietal ERPs was strongly correlated with memory accuracy, which we suggest reflects a contribution of visual working memory to long-term memory. We discuss multiple bottlenecks for source memory performance. KeywordsSource memory; Prefrontal cortex; Object-based; Difficulty; Working memory Episodic memory is defined as inherently relational, or as Schacter and Tulving (1994, p. 28) put it, consisting of "multifeature representations in which numerous different kinds of information -spatial, temporal, contextual, and so forth -are bound together". However, different memory tests require retrieval of more or less information for successful performance. At one extreme are old/new recognition tests that require only an assessment of whether a stimulus was presented sometime in the laboratory experiment. In contrast, source memory tests are those that probe relational information more closely: what voice spoke a word, where was an object viewed, what color was a picture, was an action executed or only imagined, etc. (Johnson, Hashtroudi, & Lindsay, 1993). In these tests, memory for the core event -the word, object, or picture -is considered item memory, and source accuracy is defined by accurate retrieval of the additional information associated with that item. Introspection suggests that the * Corresponding author at: Department of Psychology, University of Arizona, Tucson, AZ 85721, United States. E-mail address: cvanpett@binghamton.edu (C. Van Petten). NIH Public Access Author ManuscriptNeuropsychologia. Author manuscript; available in PMC 2009 July 1. Published in final edited form as:Neuropsych...

After the P3: Late executive processes in stimulus categorization

“…Similar late prefrontal positive components have been observed in source memory tests that require participants to judge conjunctions of stimulus attributes as studied or unstudied, for instance whether a test word occurred in a previously studied list and whether it was spoken by the same voice (Kuo & Van Petten, 2006, 2008; Senkfor & Van Petten, 1998; Trott, Friedman, & Ritter, 1997; Van Petten, Senkfor, & Newberg, 2000; Wilding & Doyle, 1996). These episodic memory tasks share some formal properties of the categorization rule used here: 1) single stimulus attributes do not signal the correct response, which must be based on attribute conjunctions, and 2) single attributes are associated with multiple responses (i.e., studied words may require a response of “old same voice” or “old different voice”, just as the presence of a horse-like body shape here may require a “mog” or a “nib” response, depending on the other stimulus features).…”

Pharmacological Modulation of the Short-Lasting Effects of Antagonistic Direct Current-Stimulation Over the Human Motor Cortex

“…These results are similar to the data published by Kuo et al (2008). The combined application of cathodal-anodal tDCS and d -CYC within independent experimental sessions, were examined in conjunction with mechanisms of homeostatic plasticity during a motor learning task.…”

“…By these means, the verum drugs were able to induce a stable plasma level (Deleu et al, 2002) and produce prominent effects in the CNS (Nitsche et al, 2004a, 2006; Kuo et al, 2008). To avoid interference of plasticity induction by cumulative drug effects, each experimental session was separated by at least 1 week.…”

Parietal Contributions to Visual Working Memory Depend on Task Difficulty

“…Within the cortex, tDCS modulates synaptic strength and likely stimulates neurons in the cortex, pyramidal neurons, and interneurons (Stagg and Nitsche, 2011). Several neuromodulators such as GABA (Stagg et al, 2009), Na + and Ca 2+ channel blockers (Nitsche et al, 2004), l -DOPA (Kuo et al, 2008), and the D 2 receptor agonists (Nitsche et al, 2006; Monte-Silva et al, 2009) also have an effect on increasing and/or decreasing the effects of tDCS stimulation (for more see Stagg and Nitsche, 2011). Some progress in linking DNA genotypes with cognitive performance is underway.…”