Academic journal article Cognitive, Affective and Behavioral Neuroscience

Depressive Rumination and the C957T Polymorphism of the DRD2 Gene

Academic journal article Cognitive, Affective and Behavioral Neuroscience

Depressive Rumination and the C957T Polymorphism of the DRD2 Gene

Article excerpt

Published online: 15 July 2012

© Psychonomic Society, Inc. 2012

Abstract Previous recognition memory experiments have demonstrated that the ERPs elicited by correctly recognized test items differ according to whether the items were encoded in an emotionally arousing or an emotionally neutral context. It is not clear, however, whether these ERP differences depend on the explicit recognition of the items. We addressed this question in the present study by contrasting the ERPs elicited by test items encoded in emotionally negative or emotionally neutral study contexts, according to whether the items were correctly recognized or misclassified as new. Recognized items associated with emotional rather than neutral contexts elicited an early positive-going and a later negative-going effect that resembled the effects reported in prior studies. Relative to unrecognized items encoded in neutral contexts, unrecognized items encoded in emotional contexts elicited a sustained, frontal-maximum, positive-going effect that onset at about 200 ms poststimulus. This effect may reflect an influence of emotional arousal on the neural correlates of implicit memory.

Keywords Episodic memory . Implicit memory . Emotion . ERP . Priming

Considerable evidence has indicated that memory is enhanced for emotionally arousing relative to unarousing events (Christianson, 1992; Kensinger, 2007). Experiments investigating the neural mechanisms underlying this phenomenon have focused primarily on consolidation processes (Hamann, 2001), but recent neuroimaging and event-related potential (ERP) studies have investigated the effects of emotional arousal at the time of retrieval (Buchanan, 2007). Several of these studies have focused on information encoded in association with emotional contexts (Jaeger, Johnson, Corona, & Rugg, 2009; Maratos, Dolan, Morris, Henson, & Rugg, 2001; Maratos & Rugg, 2001; Smith, Dolan, & Rugg, 2004; Smith, Henson, Rugg, & Dolan, 2005; Smith, Stephan, Rugg, & Dolan, 2006).

One such study (Smith et al., 2004; see also Maratos & Rugg, 2001) demonstrated that ERPs elicited during recognition of objects that had been studied in association with emotional versus nonemotional pictorial contexts differed in two distinct ways. The first effect comprised a relatively earlyonsetting (circa 300-500 ms) temporal-maximum positivity for objects encoded in emotional versus neutral contexts. The second effect, which also took the form of a positive-going shiftin the ERPs for emotionally encoded objects, had a relatively late onset (circa 700 ms), was frontally distributed, and persisted for several hundred milliseconds.

The results reported by Smith et al. (2004) were extended by Jaeger et al. (2009), who contrasted ERPs elicited by recognized items that had been studied in association with emotionally negative versus emotionally neutral contexts either 10 min or 24 h earlier. In line with the findings of Smith et al. (2004), Jaeger et al. reported that after the shorter study- test delay, recognized items from emotional contexts elicited an early (circa 200 ms poststimulus) positivity, relative to items from neutral contexts. However, unlike the results reported by Smith et al. (2004), this positivity was sustained until about 1,100 ms post-stimulus-onset, rather than demonstrating distinct early and late phases. After the 24- h study-test delay, the effects of emotional context were reversed in polarity (i.e., items from emotional contexts elicited a more negative waveform than did items from neutral contexts) and were maximal over the posterior scalp. The polarity differences between short and long study-test delays were interpreted as evidence that emotion-specific consolidation mechanisms modulate the influence of emotion on retrieval-related neural activity.

Importantly, the onset latencies of the emotional context effects reported by Smith et al. (2004) and Jaeger et al. (2009) were similar to the onsets of ERP differences found for directly presented emotional and nonemotional items (Cuthbert, Schupp, Bradley, Birbaumer, & Lang, 2000; Keil, Bradley, Hauk, Rockstroh, Elbert, Lang, 2002; Schupp, Cuthbert, Bradley, Cacioppo, Ito, Lang, 2000). …

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