Biomedical subjects

Florin Dolcos

Publications and source records attributed to Florin Dolcos.

11 recordsLinked to original sources

PubMed2006

Role of the inferior frontal cortex in coping with distracting emotions.

The role of inferior frontal cortex in coping with emotional distracters presented concurrently with a working memory task was investigated using event-related functional magnetic resonance imaging. The study yielded two main findings: (i) processing of emotional distracters was associated with enhanced functional coupling between the amygdala and the inferior frontal cortex and (ii) the inferior frontal cortex showed a left-lateralized activation pattern discriminating successful from unsuccessful trials in the presence of emotional distraction. These findings provide evidence that coping with emotional distraction entails interactions between brain regions responsible for detection and inhibition of emotional distraction, and identified a hemispheric specialization in the inferior frontal cortex in controlling the impact of distracting emotions on cognitive performance (left hemisphere) vs. controlling the subjective feeling of being distracted (right hemisphere).

Adaptation, Psychological↗

PubMed2006

Brain systems mediating cognitive interference by emotional distraction.

Flexible behavior depends on our ability to cope with distracting stimuli that can interfere with the attainment of goals. Emotional distracters can be particularly disruptive to goal-oriented behavior, but the neural systems through which these detrimental effects are mediated are not known. We used event-related functional magnetic resonance imaging to investigate the effect of emotional and nonemotional distracters on a delayed-response working memory (WM) task. As expected, this task evoked robust activity during the delay period in typical WM regions (dorsolateral prefrontal cortex and lateral parietal cortex). Presentation of emotional distracters during the delay interval evoked strong activity in typical emotional processing regions (amygdala and ventrolateral prefrontal cortex) while simultaneously evoking relative deactivation of the WM regions and impairing WM performance. These results provide the first direct evidence that the detrimental effect of emotional distracters on ongoing cognitive processes entails the interaction between a dorsal neural system associated with "cold" executive processing and a ventral system associated with "hot" emotional processing.

Adolescent↗

PubMed2005

Remembering one year later: role of the amygdala and the medial temporal lobe memory system in retrieving emotional memories.

The memory-enhancing effect of emotion can be powerful and long-lasting. Most studies investigating the neural bases of this phenomenon have focused on encoding and early consolidation processes, and hence little is known regarding the contribution of retrieval processes, particularly after lengthy retention intervals. To address this issue, we used event-related functional MRI to measure neural activity during the retrieval of emotional and neutral pictures after a retention interval of 1 yr. Retrieval activity for emotional and neutral pictures was separately analyzed for successfully (hits) vs. unsuccessfully (misses) retrieved items and for responses based on recollection vs. familiarity. Recognition performance was better for emotional than for neutral pictures, and this effect was found only for recollection-based responses. Successful retrieval of emotional pictures elicited greater activity than successful retrieval of neutral pictures in the amygdala, entorhinal cortex, and hippocampus. Moreover, in the amygdala and hippocampus, the emotion effect was greater for recollection than for familiarity, whereas in the entorhinal cortex, it was similar for both forms of retrieval. These findings clarify the role of the amygdala and the medial temporal lobe memory regions in recollection and familiarity of emotional memory after lengthy retention intervals.

Adult↗

PubMed2004

Interaction between the amygdala and the medial temporal lobe memory system predicts better memory for emotional events.

Emotional events are remembered better than neutral events possibly because the amygdala enhances the function of medial temporal lobe (MTL) memory system (modulation hypothesis). Although this hypothesis has been supported by much animal research, evidence from humans has been scarce and indirect. We investigated this issue using event-related fMRI during encoding of emotional and neutral pictures. Memory performance after scanning showed a retention advantage for emotional pictures. Successful encoding activity in the amygdala and MTL memory structures was greater and more strongly correlated for emotional than for neutral pictures. Moreover, a double dissociation was found along the longitudinal axis of the MTL memory system: activity in anterior regions predicted memory for emotional items, whereas activity in posterior regions predicted memory for neutral items. These results provide direct evidence for the modulation hypothesis in humans and reveal a functional specialization within the MTL regarding the effects of emotion on memory formation.

Adult↗

PubMed2004

Dissociable effects of arousal and valence on prefrontal activity indexing emotional evaluation and subsequent memory: an event-related fMRI study.

Prefrontal cortex (PFC) activity associated with emotional evaluation and subsequent memory was investigated with event-related functional MRI (fMRI). Participants were scanned while rating the pleasantness of emotionally positive, negative, and neutral pictures, and memory for the pictures was tested after scanning. Emotional evaluation was measured by comparing activity during the picture rating task relative to baseline, and successful encoding was measured by comparing activity for subsequently remembered versus forgotten pictures (Dm effect). The effect of arousal on these measures was indicated by greater activity for both positive and negative pictures than for neutral ones, and the effect of valence was indicated by differences in activity between positive and negative pictures. The study yielded three main results. First, consistent with the valence hypothesis, specific regions in left dorsolateral PFC were more activated for positive than for negative picture evaluation, whereas regions in right ventrolateral PFC showed the converse pattern. Second, dorsomedial PFC activity was sensitive to emotional arousal, whereas ventromedial PFC activity was sensitive to positive valence, consistent with evidence linking these regions, respectively, to emotional processing and self-awareness or appetitive behavior. Finally, successful encoding (Dm) activity in left ventrolateral and dorsolateral PFC was greater for arousing than for neutral pictures. This finding suggests that the enhancing effect of emotion on memory formation is partly due to an augmentation of PFC-mediated strategic, semantic, and working memory operations. These results underscore the critical role of PFC in emotional evaluation and memory, and disentangle the effects of arousal and valence across PFC regions associated with different cognitive functions.

Adult↗

PubMed2004

Task-independent and task-specific age effects on brain activity during working memory, visual attention and episodic retrieval.

It is controversial whether the effects of aging on various cognitive functions have the same common cause or several different causes. To investigate this issue, we scanned younger and older adults with functional magnetic resonance imaging (fMRI) while performing three different tasks: working memory, visual attention and episodic retrieval. There were three main results. First, in all three tasks, older adults showed weaker occipital activity and stronger prefrontal and parietal activity than younger adults. The occipital reduction is consistent with the view that sensory processing decline is a common cause in cognitive aging, and the prefrontal increase may reflect functional compensation. Secondly, older adults showed more bilateral patterns of prefrontal activity than younger adults during working memory and visual attention tasks. These findings are consistent with the Hemispheric Asymmetry Reduction in Older Adults (HAROLD) model. Finally, compared to younger adults, older adults showed weaker hippocampal formation activity in all three tasks but stronger parahippocampal activity in the episodic retrieval task. The former finding suggests that age-related hippocampal deficits may have a global effect in cognition, and the latter is consistent with an age-related increase in familiarity-based recognition. Taken together, the results indicate that both common and specific factors play an important role in cognitive aging.

Adult↗

PubMed2004

Brain activity during episodic retrieval of autobiographical and laboratory events: an fMRI study using a novel photo paradigm.

Functional neuroimaging studies of episodic memory retrieval generally measure brain activity while participants remember items encountered in the laboratory ("controlled laboratory condition") or events from their own life ("open autobiographical condition"). Differences in activation between these conditions may reflect differences in retrieval processes, memory remoteness, emotional content, retrieval success, self-referential processing, visual/spatial memory, and recollection. To clarify the nature of these differences, a functional MRI study was conducted using a novel "photo paradigm," which allows greater control over the autobiographical condition, including a measure of retrieval accuracy. Undergraduate students took photos in specified campus locations ("controlled autobiographical condition"), viewed in the laboratory similar photos taken by other participants (controlled laboratory condition), and were then scanned while recognizing the two kinds of photos. Both conditions activated a common episodic memory network that included medial temporal and prefrontal regions. Compared with the controlled laboratory condition, the controlled autobiographical condition elicited greater activity in regions associated with self-referential processing (medial prefrontal cortex), visual/spatial memory (visual and parahippocampal regions), and recollection (hippocampus). The photo paradigm provides a way of investigating the functional neuroanatomy of real-life episodic memory under rigorous experimental control.

Adolescent↗

PubMed2003

Attention-related activity during episodic memory retrieval: a cross-function fMRI study.

In functional neuroimaging studies of episodic retrieval (ER), activations in prefrontal, parietal, anterior cingulate, and thalamic regions are typically attributed to episodic retrieval processes. However, these activations are also frequent during visual attention (VA) tasks, suggesting that their role in ER may reflect attentional rather than mnemonic processes. To investigate this possibility, we directly compared brain activity during ER and VA tasks using event-related fMRI. The ER task was a word recognition test with a retrieval mode component, and the VA task was a target detection task with a sustained attention component. The study yielded three main findings. First, a common fronto-parietal-cingulate-thalamic network was found for ER and VA, suggesting that the involvement of these regions during ER reflects general attentional processes. This idea is compatible with some of the interpretations proposed in the ER literature (e.g. postretrieval monitoring), which may be rephrased in terms of attentional processes. Second, several subregions were differentially involved in ER versus VA. For example, the frontopolar cortex and the precuneus were more activated for ER than for VA, possibly reflecting retrieval mode and processing of internally generated stimuli, respectively. Finally, the study yielded an unexpected finding: some medial temporal lobe regions were similarly activated for ER and VA. This finding suggests that the medial temporal lobes may be involved in indexing representations within the focus of consciousness, regardless of whether they are mnemonic or perceptual. Overall, the present results suggest that many of the activations attributed to specific cognitive processes, such as episodic memory, may actually reflect more general cognitive operations.

Adult↗

PubMed2002

Similarities and differences in the neural correlates of episodic memory retrieval and working memory.

Functional neuroimaging studies have shown that different cognitive functions activate overlapping brain regions. An activation overlap may occur because a region is involved in operations tapped by different cognitive functions or because the activated area comprises subregions differentially involved in each of the functions. To investigate these issues, we directly compared brain activity during episodic retrieval (ER) and working memory (WM) using event-related functional MRI (fMRI). ER was investigated with a word recognition test, and WM was investigated with a word delayed-response test. Two-phase trials distinguished between retrieval mode and cue-specific aspects of ER, as well as between encoding/maintenance and retrieval aspects of WM. The results revealed a common fronto-parieto-cerebellar network for ER and WM, as well as subregions differentially involved in each function. Specifically, there were two main findings. First, the results differentiated common and specific subregions within the prefrontal cortex: (i) left dorsolateral areas were recruited by both functions, possibly reflecting monitoring operations; (ii) bilateral anterior and ventrolateral areas were more activated during ER than during WM, possibly reflecting retrieval mode and cue-specific ER operations, respectively; and (iii) left posterior/ventral (Broca's area) and bilateral posterior/dorsal areas were more activated during WM than during ER, possibly reflecting phonological and generic WM operations, respectively. Second, hippocampal and parahippocampal regions were activated not only for ER but also for WM. This result suggests that indexing operations mediated by the medial temporal lobes apply to both long-term and short-term memory traces. Overall, our results show that direct cross-function comparisons are critical to understand the role of different brain regions in various cognitive functions.

Adult↗

PubMed2002

Hemispheric asymmetry and aging: right hemisphere decline or asymmetry reduction.

We review evidence for two models of hemispheric asymmetry and aging: the right hemi-aging model, which proposes that the right hemisphere shows greater age-related decline than the left hemisphere, and the hemispheric asymmetry reduction in old adults (HAROLD) model, which proposes that frontal activity during cognitive performance tends to be less lateralized in older than in younger adults. The right hemi-aging model is supported by behavioral studies in the domains of cognitive, affective, and sensorimotor processing, but the evidence has been mixed. In contrast, available evidence is generally consistent with the HAROLD model, which is supported primarily by functional neuroimaging evidence in the domains of episodic memory encoding and retrieval, semantic memory retrieval, working memory, perception, and inhibitory control. Age-related asymmetry reductions may reflect functional compensation or dedifferentiation, and the evidence, although scarce, tends to support the compensation hypothesis. The right hemi-aging and the HAROLD models are not incompatible. For example, the latter may apply to prefrontal regions and the former to other brain regions.

Aging↗

PubMed2002

Event-related potentials of emotional memory: encoding pleasant, unpleasant, and neutral pictures.

Emotional events tend to be remembered better than nonemotional events. We investigated this phenomenon by measuring two event-related potential (ERP) effects: the emotion effect (more positive ERPs for pleasant or unpleasant stimuli than for neutral stimuli) and the subsequent memory effect (more positive ERPs for subsequently remembered items than for subsequently forgotten items). ERPs were measured while subjects rated the emotional content of pleasant, unpleasant, and neutral pictures. As was expected, subsequent recall was better for pleasant and unpleasant pictures than for neutral pictures. The emotion effect was sensitive to arousal in parietal electrodes and to both arousal and valence in frontocentral electrodes. The subsequent memory effect at centroparietal electrodes was greater for emotional pictures than for neutral pictures during an early epoch (400-600 msec). This result suggests that emotional information has privileged access to processing resources, possibly leading to better memory formation.

Adult↗