Jason C. K. Chan

Contextual processing in episodic future thought.

Remembering events from ones past (i.e., episodic memory) and envisioning specific events that could occur in ones future (i.e., episodic future thought) invoke highly overlapping sets of brain regions. The present study employed functional magnetic resonance imaging to test the hypothesis that one source of this shared architecture is that episodic future thought--much like episodic memory--tends to invoke memory for known visual-spatial contexts. That is, regions of posterior cortex (within posterior cingulate cortex [PCC], parahippocampal cortex [PHC], and superior occipital gyrus [SOG]) elicit indistinguishable activity during remembering and episodic future thought, and similar regions have been identified as important for establishing visual-spatial contextual associations. In the present study, these regions were similarly engaged when participants thought about personal events in familiar contexts, irrespective of temporal direction (past or future). The same regions, however, exhibited very little activity when participants envisioned personal future events in unfamiliar contextual settings. These findings suggest that regions within PCC, PHC, and SOG support the activation of well-known contextual settings that people tend to imagine when thinking about personal events, whether in the past or future. Hence, this study pinpoints an important similarity between episodic future thought and episodic memory.

The Testing Effect in Recognition Memory: A Dual Process Account.

The testing effect, or the finding that taking an initial test improves subsequent memory performance, is a robust and reliable phenomenon--as long as the final test involves recall. Few studies have examined the effects of taking an initial recall test on final recognition performance, and results from these studies are equivocal. In 3 experiments, we attempt to demonstrate that initial testing can change the ways in which later recognition decisions are executed even when no difference can be detected in the recognition hit rates. Specifically, initial testing was shown to enhance later recollection but leave familiarity unchanged. This conclusion emerged from three dependent measures: source memory, exclusion performance, and remember/know judgments.

Recalling a Witnessed Event Increases Eyewitness Suggestibility The Reversed Testing Effect

Peoples later memory of an event can be altered by exposure to misinformation about that event. The typical misinformation paradigm, however, does not include a recall test prior to the introduction of misinformation, contrary to what real-life eyewitnesses encounter when they report to a 911 operator or crime-scene officer. Because retrieval is a powerful memory enhancer (the testing effect), recalling a witnessed event prior to receiving misinformation about it should reduce eyewitness suggestibility. We show, however, that immediate cued recall actually exacerbates the later misinformation effect for both younger and older adults. The reversed testing effect we observed was based on two mechanisms: First, immediate cued recall enhanced learning of the misinformation; second, the initially recalled details became particularly susceptible to interference from later misinformation, a finding suggesting that even human episodic memory may undergo a reconsolidation process. These results show that real-life eyewitness memory may be even more susceptible to misinformation than is currently envisioned.

Impairing existing declarative memory in humans by disrupting reconsolidation

During the past decade, a large body of research has shown that memory traces can become labile upon retrieval and must be restabilized. Critically, interrupting this reconsolidation process can abolish a previously stable memory. Although a large number of studies have demonstrated this reconsolidation associated amnesia in nonhuman animals, the evidence for its occurrence in humans is far less compelling, especially with regard to declarative memory. In fact, reactivating a declarative memory often makes it more robust and less susceptible to subsequent disruptions. Here we show that existing declarative memories can be selectively impaired by using a noninvasive retrieval–relearning technique. In six experiments, we show that this reconsolidation-associated amnesia can be achieved 48 h after formation of the original memory, but only if relearning occurred soon after retrieval. Furthermore, the amnesic effect persists for at least 24 h, cannot be attributed solely to source confusion and is attainable only when relearning targets specific existing memories for impairment. These results demonstrate that human declarative memory can be selectively rewritten during reconsolidation.

Long-term Effects of Testing on the Recall of Nontested Materials

Testing, or memory retrieval, is a powerful way to enhance long-term retention of studied material. Recent studies have shown that testing can also benefit later retention of related but nontested material (a finding known as retrieval-induced facilitation, Chan, McDermott, & Roediger, 2006), but the long-term consequences of this benefit is unknown. In the current experiment three retention intervals—20 minutes, 24 hours, 7 days—were used to assess the effects of testing on subsequent recall of the nontested material. The results indicate that the magnitude of retrieval-induced facilitation, like that of the testing effect (i.e., the memorial benefit of testing on the tested material), increases with delay at the beginning (i.e., between 20 minutes and 24 hours) but asymptotes afterward (i.e., between 24 hours and 7 days). Theoretical and applied implications of this finding are discussed.

Effects of repetition on memory for pragmatic inferences

Social interaction requires active inferential processing on the part of the listener. Such inferences can affect memory. For example, after hearingthe karate champion hit the cinder block, one might erroneously recollect having heard the verbbroke (Brewer, 1977)—a reasonable inference, but one not logically necessitated. The mechanisms behind this type of erroneous recollection have not been much explored. Experiments in the present article assessed the influence of repetition, response deadline, and age (cf. Jacoby, 1999), in an effort to demonstrate the dual contributions of familiarity and recollection underlying this phenomenon. For older adults, repetition at encoding increased the later likelihood of erroneously recognizing pragmatic inferences. For younger adults, repetition exerted the opposite effect. Both age groups, however, benefited from a second study-test trial. Experiment 2 demonstrated a similar interaction on a cued recall test for younger adults, whereby repetition exerted different influences as a function of time permitted during retrieval. Implications for theories of memory and discourse processing are considered.

The importance of material-processing interactions in inducing false memories

Deep encoding, relative to shallow encoding, has been shown to increase the probability of false memories in the Deese/Roediger-McDermott (DRM) paradigm (Thapar & McDermott, 2001; Toglia, Neuschatz, & Goodwin, 1999). In two experiments, we showed important limitations on the generalizability of this phenomenon; these limitations are clearly predicted by existing theories regarding the mechanisms underlying such false memories (e.g., Roediger, Watson, McDermott, & Gallo, 2001). Specifically, asking subjects to attend to phonological relations among lists of phonologically associated words (e.g.,weep, steep, etc.) increased the likelihood of false recall (Experiment 1) and false recognition (Experiment 2) of a related, nonpresented associate (e.g.,sleep), relative to a condition in which subjects attended to meaningful relations among the words. These findings occurred along with a replication of prior findings (i.e., a semantic encoding task, relative to a phonological encoding task, enhanced the likelihood of false memory arising from a list of semantically associated words), and they place important constraints on theoretical explanations of false memory.

Proteins of rat serum V: adjuvant arthritis and its modulation by nonsteroidal anti-inflammatory drugs.

The effect of adjuvant arthritis (AA) on the pattern of rat serum proteins includes the upregulation of haptoglobin, orosomucoid, α2‐macroglobulin, serine protease inhibitor‐3, thiostatin, α1‐antitrypsin, C‐reactive protein, and the downregulation of kallikrein‐binding protein, α1‐inhibitor III, apolipoprotein A‐I, α2‐HS‐glycoprotein, albumin, apolipoprotein A‐IV, transthyretin and transferrin. Minor changes (± 20%) are observed for Gc‐globulin, ceruloplasmin, and α1‐macroglobulin. AA thus grossly resembles the acute inflammatory response elicited by the injection of turpentine, although the changes in the levels of negative acute‐phase proteins (APP) are smaller in acute inflammation. Indomethacine and ibuprofen inhibit the effects of arthritis on the synthesis of rat serum proteins in different ways: The former is, on average, three times as effective as the latter. Each drug interferes differently with different proteins. In animals without AA, both nonsteroidal anti‐inflammatory drugs (NSAID) mimick the inflammatory pattern to a certain extent, with more effect on the negative than on the positive APPs. Overall, the shifts in serum protein levels parallel changes in inflammatory parameters such as joint swelling and serum interleukin‐6 (IL‐6) activity. Protein quantitation after two‐dimensional electrophoresis (2‐DE) reveals some effects of the drugs per se which escape detection by other routine tests.

Retrieval Enhances Eyewitness Suggestibility to Misinformation in Free and Cued Recall

Immediately recalling a witnessed event can increase peoples susceptibility to later postevent misinformation. But this retrieval-enhanced suggestibility (RES) effect has been shown only when the initial recall test included specific questions that reappeared on the final test. Moreover, it is unclear whether this phenomenon is affected by the centrality of event details. These limitations make it difficult to generalize RES to criminal investigations, which often begin with free recall prior to more specific queries from legal officials and attorneys. In 3 experiments, we examined the influence of test formats (free recall vs. cued recall) and centrality of event details (central vs. peripheral) on RES. In Experiment 1, both the initial and final tests were cued recall. In Experiment 2, the initial test was free recall and the final test was cued recall. In Experiment 3, both the initial and final tests were free recall. Initial testing increased misinformation reporting on the final test for peripheral details in all experiments, but the effect was significant for central details only after aggregating the data from all 3 experiments. These results show that initial free recall can produce RES, and more broadly, that free recall can potentiate subsequent learning of complex prose materials.

The effects of frontal lobe functioning and age on veridical and false recall.

Washington University, St. Louis, Missouri Older adults’ heightened susceptibility to false memories has been linked to compromised frontal lobe functioning as estimated by Glisky and colleagues’ (Glisky, Polster, & Routhieaux, 1995) neuropsychological battery (e.g., Butler, McDaniel, Dornburg, Price, & Roediger, 2004). This conclusion, however, rests on the untested assumption that young adults have uniformly high frontal functioning. We tested this assumption, and we correlated younger and older adults’ frontal scores with veridical and false recall probabilities with prose materials. Substantial variability in scores on the Glisky battery occurred for younger (and older) adults. However, frontal scores and age were independent contributors to recall probabilities. Frontal functioning is not the sole cause of older adults’ heightened susceptibility to false memories.