Neural substrates of long-term item and source memory for emotional associates: An fMRI study.

Since Tulving's influential work on the distinction between familiarity and recollection-based retrieval, numerous studies have found evidence for differential contribution of these retrieval mechanisms on emotional episodic memory. Particularly, retrieval advantage for emotional, compared to neutral, information has been related to recollection-, but not familiarity-mediated processes. Neuroimaging studies suggest that this recollection-based retrieval for emotional information is related to stronger engagement of regions in the medial temporal lobe (MTL), posterior parietal cortex (PPC), and prefrontal cortex (PFC). In the present study, we investigated neural correlates related to long-term memory of neutral information that has been associated with emotional and neutral contexts, using functional magnetic resonance imaging (fMRI). During encoding, different neutral objects integrated with emotional or neutral scenes were presented. One week later, the encoded objects were intermixed with new ones and participants had to indicate whether the objects were previously seen or not, using the Remember/Know procedure (item memory). Furthermore, memory for the correct scene background category was also tested (contextual source memory). First, replicating previous findings, we observed a preference for recollection-dependent memory retrieval versus familiarity-dependent memory retrieval for those neutral objects encoded in emotional compared to neutral contexts. Second, consistent with these behavioral effects, objects encoded with emotional, compared to neutral, scenes produced larger memory-related activity in recollection-sensitive brain regions, including PPC and PFC regions. Third, correctly retrieved emotional compared to neutral contextual information was associated with increased activity in these brain areas. Together, these results suggest that memory for information encoded in emotional contexts is remarkably robust over time and mediated by recollection-based processes.

Brain Activity and Network Interactions in the Impact of Internal Emotional Distraction.

Emotional distraction may come from the external world and from our mind, as internal distraction. Although external emotional distraction has been extensively investigated, less is known about the mechanisms associated with the impact of internal emotional distraction on cognitive performance, and those involved in coping with such distraction. These issues were investigated using a working memory task with emotional distraction, where recollected unpleasant autobiographical memories served as internal emotional distraction. Emotion regulation was manipulated by instructing participants to focus their attention either on or away from the emotional aspects of their memories. Behaviorally, focusing away from emotion was associated with better working memory performance than focusing on the recollected emotions. Functional MRI data showed reduced response in brain regions associated with the salience network, coupled with greater recruitment of executive prefrontal and memory-related temporoparietal regions, and with increased frontoparietal connectivity, when subjects focused on nonemotional contextual details of their memories. Finally, temporal dissociations were also identified between regions involved in self-referential (showing faster responses) versus context-related processing (showing delayed responses). These findings demonstrate that focused attention is an effective regulation strategy in coping with internal distraction, and are relevant for understanding clinical conditions where coping with distressing memories is dysfunctional.

Brain Activity and Network Interactions Linked to Valence-Related Differences in the Impact of Emotional Distraction.

Previous investigations showed that the impact of negative distraction on cognitive processing is linked to increased activation in a ventral affective system (VAS) and simultaneous deactivation in a dorsal executive system (DES). However, less is known about the influences of positive valence and different arousal levels on these effects. FMRI data were recorded while participants performed a working memory (WM) task, with positive and negative pictures presented as distracters during the delay between the memoranda and probes. First, positive distraction had reduced impact on WM performance, compared with negative distraction. Second, fMRI results identified valence-specific effects in DES regions and overlapping arousal and valence effects in VAS regions, suggesting increased impact of negative distraction and enhanced engagement of coping mechanisms for positive distraction. Third, a valence-related rostro-caudal dissociation was identified in medial frontal regions associated with the default-mode network (DMN). Finally, these DMN regions showed increased functional connectivity with DES regions for negative compared with positive distraction. Overall, these findings suggest that, while both positive and negative distraction engage partly similar arousal-dependent mechanisms, their differential impact on WM performance is linked to dissociations in the engagement of, and coupling between, regions associated with emotion processing and higher lever cognitive control.

Localized or diffuse: the link between prefrontal cortex volume and cognitive reappraisal.

Despite functional brain imaging research pointing to the role of prefrontal cortex in cognitive reappraisal, the structural correlates of habitual engagement of reappraisal are unclear. Functional imaging studies of reappraisal have shown broad engagement of bilateral middle frontal cortex (MFC) and left superior frontal cortex (SFC), and specific engagement of the right SFC. However, volumetric studies have not identified clear associations between reappraisal and these regions. This discrepancy between functional and structural studies suggests that broad functional engagement associated with reappraisal might not be detectable at a structural level using highly localized volumetric measures. This study addressed the discrepant structural findings by assessing the relation between reappraisal and grey matter volume, using methods that allow both region-level broad/diffuse assessments (surface-based morphometry), and voxel-level specific/localized (voxel-based morphometry) measures. Results were consistent with diffuse positive volumetric associations with reappraisal in the right MFC and left SFC, and a localized positive volumetric association in the right SFC, thus resolving the discrepancy between functional and structural studies. This study provides novel evidence supporting the idea that functional engagement related to transient manipulations of reappraisal can be linked to structural associations related to habitual engagement of similar operations, within the same brain regions.

Neural signatures of the response to emotional distraction: a review of evidence from brain imaging investigations.

Prompt responses to emotional, potentially threatening, stimuli are supported by neural mechanisms that allow for privileged access of emotional information to processing resources. The existence of these mechanisms can also make emotional stimuli potent distracters, particularly when task-irrelevant. The ability to deploy cognitive control in order to cope with emotional distraction is essential for adaptive behavior, while reduced control may lead to enhanced emotional distractibility, which is often a hallmark of affective disorders. Evidence suggests that increased susceptibility to emotional distraction is linked to changes in the processing of emotional information that affect both the basic response to and coping with emotional distraction, but the neural correlates of these phenomena are not clear. The present review discusses emerging evidence from brain imaging studies addressing these issues, and highlights the following three aspects. First, the response to emotional distraction is associated with opposing patterns of activity in a ventral "hot" affective system (HotEmo, showing increased activity) and a dorsal "cold" executive system (ColdEx, showing decreased activity). Second, coping with emotional distraction involves top-down control in order to counteract the bottom-up influence of emotional distraction, and involves interactions between the amygdala and the prefrontal cortex. Third, both the response to and coping with emotional distraction are influenced by individual differences affecting emotional sensitivity and distractibility, which are linked to alterations of both HotEmo and ColdEx neural systems. Collectively, the available evidence identifies specific neural signatures of the response to emotional challenge, which are fundamental to understanding the mechanisms of emotion-cognition interactions in healthy functioning, and the changes linked to individual variation in emotional distractibility and susceptibility to affective disorders.

Diethylaminoethanol action in the arthritis with Freund adjuvant, in rats.

The authors have studied the action of diethylaminoethanol on Freund adjuvant arthritis, induced in female Lewis rats. They worked on 3 groups, each one including 14 rats, weighing 110-130 g: group I = control; group II = rats injected intracutaneous with 0.1 ml Freund adjuvant; group III = rats injected with Freund adjuvant and treated with diethylaminoethanol i.m. (10 mg/kg body weight), and gel application (2.5%) on paws and tail, daily. During the experiment clinical observations and measurements were made and when the animals were killed, blood was sampled for haematological and immunological assays (CD4, CD8, CD25 T cells and NK cells, antinuclear autoantibody and immune complexes). While in all the rats from group II (without treatment) inflammatory processes developed at the level of the peripheral joints, in group III (diethylaminoethanol treated), these ones were present in only 64% of the rats and by much more reduced forms, followed by a short period of involution. The paw volume, measured with an electronic plethysmometer, was more reduced in the treated rats (7.1-14.2%) than in the non treated ones (27.7-29.3%). The haematologic examination showed an increased number of neutrophiles in both groups with FA injecting. The immunological investigations revealed: a decrease of CD4 cells and an increase of CD8 T cells and NK cells in both groups, a much more decreased level (13.2%) of circulatory immune complexes in treated rats, as compared to the non-treated ones (71.7%). No differences were found regarding the CD25 cells and antinuclear antibodies. The histo-pathological examination showed that the intensity and the extension area of the joint lesions (granulation tissue with fibrous change, cartilage invasion and dilaceration, bone atrophy) were much more reduced in the treated rats. The authors put forward the hypothesis that these effects might be due to diethylaminoethanol antiinflammatory properties.

The involvement of endogenous opiates in emotional-cognitive interaction in stress.

Stress system is very important in the co-ordination of the generalised stress response, which takes place when a stressor of any kind exceeds a threshold. In our experiments we have analysed aspects of opiate involvement in the interactions among the emotional, motivational and cognitive processes, as well as aspects concerning the relations between physiological and behavioural mechanisms, both in normal conditions and under stress. We also analysed aspects of the interaction between stress system and endogenous opioid systems (e.o.s.). As emotional states interfere with perception and cognition, in our experiments we used suitable variants of the open-field test, which evaluates the exploratory drive and emotional reactivity. We used 30 Wistar male rats, 18 months old, weighing 350-400 g, divided into three groups, of 10 animals each. In order to assess the behaviour of the animals, we have analysed exploratory (cognitive) and non-exploratory (emotional) parameters. In order to evaluate the manner in which endogenous opioid systems are involved in these aspects, different groups of rats were treated with an opiate agonist (codeine syrup, 0.117, 5 ml/kg to approximately 0.5 mg/kg morphine as active compound, p.o.) and an antagonist (naloxone 0.4 mg/kg i.p.), before testing in open-field. To distinguish between the effect of habituation and the effect of the opiate agonist and antagonist, the placebo treatment and the test/retest method were used. At these doses, the opiate agonist has stimulated the exploratory behaviour, while the antagonist has inhibited the cognitive behaviour and enhanced the emotional response. Our experimental data together with data from literature allowed us to present an interactive model that points out a general manner of interaction between emotions and cognition, in relation to the interactions between physiological and behavioural mechanisms.