ERP correlates of the incidental retrieval of emotional information: Effects of study-test delay

Abstract

Prior studies indicate that, in tests of recognition memory, ERPs elicited by correctly recognized test items differ according to whether the items were encoded in an emotionally arousing or an emotionally neutral study context. These prior studies employed only a relatively brief (ca. 10 min) retention interval, however. The present study contrasted the ERP correlates of incidental emotional retrieval as a function of study-test delay. Pictures of emotionally neutral objects were encoded in association with either emotionally negative or emotionally neutral scenes. In a repeated measures design (N=19), half of the objects were subjected to a recognition memory test 10 min after completion of the study phase, whereas the remainder were tested 24 hrs later. After the short delay, ERPs elicited by objects paired with emotional vs. neutral backgrounds differed from around 200 ms post-stimulus, the objects paired with the emotional scenes eliciting the more positive-going waveforms. After 24 hrs, differences between the ERPs elicited by the two classes of object were still apparent from around 200 ms post-stimulus. Strikingly, these effects differed from those obtained 10 min after study in both their polarity and scalp distribution. The early onset of these ERP effects suggests that they may reflect a form of memory independent of the conscious recollection of the associated study contexts. The qualitative differences in the effects at the two retention intervals raises the possibility that the encoded objects were subjected to consolidation processes that differed according to the emotional attributes of their study contexts.

Binding neutral information to emotional contexts: Brain dynamics of long-term recognition memory

“…In accordance with this suggestion, in behavioral research it has been observed that recognition of emotional contextual cues compared to neutral ones is enhanced after long (such as 1 or 7 days), but not after short delays (Pierce & Kensinger, 2011;. Recently, two ERP studies have investigated emotional contextual binding (Jaeger et al, 2009;Jaeger & Rugg, 2012) on a delayed test (24 hours). However, Jaeger and colleagues found no better memory for neutral objects encoded in emotionally unpleasant background scenes compared to those neutral objects associated with neutral scenes, indicating that beneficial effects of contexts may occur after longer consolidation periods (c.f., Pierce & Kensinger, 2011).…”

“…computer monitor located 150 cm in front of the participant. In contrast to previous studies (e.g., Jaeger et al, 2009;Jaeger & Rugg, 2012;Smith, Dolan, et al, 2004, Smith, Henson, Dolan, & Rugg, 2004Smith, Henson, Rugg, & Dolan, 2005), in which objects were visually separated (white background and/or yellow frame), here objects were presented with transparent background and without frame to facilitate object-scene binding. Objects were presented in one of four quadrants of the screen.…”

“…Participants were presented with one of six encoding lists (for list construction, see Jaeger et al, 2009;Smith, Dolan, et al, 2004), each consisting of 144 object/background pairs, with no more than two pictures from the same valence presented consecutively. Each neutral object set was paired with a neutral background scene in one list, an unpleasant background in another, a pleasant background scene in a third, and was available as a novel object set for the remaining three lists.…”

“…The identification of sensor clusters representative for maximal old/new effects were based on visual inspection of the waveforms and based on previous studies (Jaeger et al, 2009;Jaeger & Rugg, 2012;Maratos & Rugg, 2001;Smith, Dolan, et al, 2004;Weymar et al, 2009Weymar et al, , 2010bWeymar, Löw, Modess, et al 2010a;Wirkner et al, 2013Wirkner et al, , 2015. Because recent studies observed context effects at earlier (<300 ms) stages of processing (Curran & Dien, 2003;Tsivilis, Otten, & Rugg, 2001;Voss & Paller, 2009), especially for emotionally arousing events (Jaeger et al, 2009;Jaeger & Rugg, 2012;Schaefer et al, 2011;Smith, Dolan, et al, 2004), we also examined ERP differences in an early time window. Mean ERP amplitudes were analyzed in a 180 to 220 ms and 300 to 500 ms time window over frontal brain regions (EGI HydroCel sensors 5, 6, 7, 8, 14, 15, 16, 22, 23, and 29), and in a 400 to 700 ms time window over centro-parietal brain regions (EGI HydroCel sensors 9, 45, 80, 81, 89, 90, 130, 131, 132, 186, and 257).…”

“…Smith, Dolan, and Rugg (2004) explored ERPs related to immediate recognition of emotionally neutral objects associated with emotional and nonemotional background scenes. These authors found no ERP old/ new differences between context categories in early frontal or late parietal regions (replicated by Jaeger, Johnson, Corona, & Rugg, 2009). Similarly, Maratos and Rugg (2001) also did not observe ERP old/new differences when source information (contextual pairings) was tested for neutral words encoded in emotionally arousing sentences compared to emotionally neutral sentences.…”