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Archive for October 2008

Brain’s ‘Hate Circuit’ Identified

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People who view pictures of someone they hate display activity in distinct areas of the brain that, together, may be thought of as a ‘hate circuit’, according to new research by scientists at UCL (University College London).

The study, by Professor Semir Zeki and John Romaya of the Wellcome Laboratory of Neurobiology at UCL, examined the brain areas that correlate with the sentiment of hate and shows that the ‘hate circuit’ is distinct from those related to emotions such as fear, threat and danger – although it shares a part of the brain associated with aggression. The circuit is also quite distinct from that associated with romantic love, though it shares at least two common structures with it.

The results are an extension of previous studies on the brain mechanisms of romantic and maternal love from the same laboratory. Explaining the idea behind the research, Professor Zeki said: “Hate is often considered to be an evil passion that should, in a better world, be tamed, controlled, and eradicated. Yet to the biologist, hate is a passion that is of equal interest to love. Like love, it is often seemingly irrational and can lead individuals to heroic and evil deeds. How can two opposite sentiments lead to the same behaviour?”

To compare their present results with their previous ones on romantic love, Zeki and Romaya specifically studied hate directed against an individual. Seventeen subjects, both female and male, had their brains scanned while viewing pictures of their hated person as well as that of neutral faces with which they were familiar. Viewing a hated person showed activity in distinct areas of the brain that, together, may be thought of as a ‘hate circuit’.

The ‘hate circuit’ includes structures in the cortex and in the sub-cortex and has components that are important in generating aggressive behaviour, and translating this into action through motor planning, as if the brain becomes mobilised to take some action. It also involves a part of the frontal cortex that has been considered critical in predicting the actions of others, probably an important feature when one is confronted by a hated person.

The subcortical activity involves two distinct structures, the putamen and insula. The former, which has been implicated in the perception of contempt and disgust, may also be part of the motor system that is mobilised to take action, since it is known to contain nerve cells that are active in phases preparatory to making a move.

Professor Zeki added: “Significantly, the putamen and insula are also both activated by romantic love. This is not surprising. The putamen could also be involved in the preparation of aggressive acts in a romantic context, as in situations when a rival presents a danger. Previous studies have suggested that the insula may be involved in responses to distressing stimuli, and the viewing of both a loved and a hated face may constitute such a distressing signal.

“A marked difference in the cortical pattern produced by these two sentiments of love and hate is that, whereas with love large parts of the cerebral cortex associated with judgment and reasoning become de-activated, with hate only a small zone, located in the frontal cortex, becomes de-activated. This may seem surprising since hate can also be an all-consuming passion, just like love. But whereas in romantic love, the lover is often less critical and judgmental regarding the loved person, it is more likely that in the context of hate the hater may want to exercise judgment in calculating moves to harm, injure or otherwise extract revenge.

“Interestingly, the activity in some of these structures in response to viewing a hated face is proportional in strength to the declared intensity of hate, thus allowing the subjective state of hate to be objectively quantified. This finding may have legal implications in criminal cases, for example.”

Unlike romantic love, which is directed at one person, hate can be directed against entire individuals or groups, as is the case with racial, political, or gender hatred. Professor Zeki said that these different varieties of hate will be the subject of future studies from his laboratory.

Zeki S, Romaya JP (2008) Neural Correlates of Hate. PLoS ONE 3(10): e3556. doi:10.1371/journal.pone.0003556

Abstract

In this work, we address an important but unexplored topic, namely the neural correlates of hate. In a block-design fMRI study, we scanned 17 normal human subjects while they viewed the face of a person they hated and also faces of acquaintances for whom they had neutral feelings. A hate score was obtained for the object of hate for each subject and this was used as a covariate in a between-subject random effects analysis. Viewing a hated face resulted in increased activity in the medial frontal gyrus, right putamen, bilaterally in premotor cortex, in the frontal pole and bilaterally in the medial insula. We also found three areas where activation correlated linearly with the declared level of hatred, the right insula, right premotor cortex and the right fronto-medial gyrus. One area of deactivation was found in the right superior frontal gyrus. The study thus shows that there is a unique pattern of activity in the brain in the context of hate. Though distinct from the pattern of activity that correlates with romantic love, this pattern nevertheless shares two areas with the latter, namely the putamen and the insula.

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Written by huehueteotl

October 30, 2008 at 8:45 am

Posted in Neuroscience

Been There, Done That: Brain Mechanism Predicts Ability To Generalize

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A new study reveals how the brain can connect discrete but overlapping experiences to provide a rich integrated history that extends far beyond individually experienced events and may help to direct future choices. The research also explains why some people are good at generalizing from past experience, while others are not.

Decisions are often guided by drawing on past experiences, perhaps by generalizing across discrete events that overlap in content. However, how such experiences are integrated into a unified representation is not clear, and fundamental questions remain regarding potential underlying brain mechanisms. It is likely that such mechanisms involve the hippocampus, a brain structure closely linked with learning and memory. The midbrain may also play a role, as its projections modulate activity in the hippocampus, and activity in both regions has been shown to facilitate encoding of individual episodes.

Dr. Daphna Shohamy from the Department of Psychology at Columbia University was interested in examining how past experiences might be integrated within the brain to create generalizations that guide future decisions. “We hypothesized that generalization stems from integrative encoding that occurs while experiencing events that partially overlap with previously encoded events and that such integrative encoding depends on both the hippocampus and midbrain dopamine regions. Further, we anticipated that greater hippocampal-midbrain engagement during integrative encoding enables rapid behavioral generalization in the future,” offers Dr. Shohamy.

Dr. Shohamy and her collaborator, Dr. Anthony Wagner from the Department of Psychology at Stanford University, used functional magnetic resonance imaging to study participants engaged in an associative learning and generalization task. They found that activity in the hippocampus and midbrain during learning predicted generalization and observed a cooperative interaction between the hippocampus and the midbrain during integrative encoding.

“By forming a thread that connects otherwise separate experiences, integrative encoding permits organisms to generalize across multiple past experience to guide choices in the present,” explains Dr. Shohamy. “In people who generalize successfully, the brain is constantly building links across separate events, creating an integrated memory of life’s episodes. For others, although the brain may accurately remember each past event, this integration does not occur, so that when confronted with a new situation, they are unable to flexibly apply what they learned in the past.”

Neuron, Volume 60, Issue 2, 378-389, 23 October 2008

doi:10.1016/j.neuron.2008.09.023

Integrating Memories in the Human Brain: Hippocampal-Midbrain Encoding of Overlapping Events

Daphna Shohamy and Anthony D. Wagner

Summary

Decisions are often guided by generalizing from past experiences. Fundamental questions remain regarding the cognitive and neural mechanisms by which generalization takes place. Prior data suggest that generalization may stem from inference-based processes at the time of generalization. By contrast, generalization may emerge from mnemonic processes occurring while premise events are encoded. Here, participants engaged in a two-phase learning and generalization task, wherein they learned a series of overlapping associations and subsequently generalized what they learned to novel stimulus combinations. Functional MRI revealed that successful generalization was associated with coupled changes in learning-phase activity in the hippocampus and midbrain (ventral tegmental area/substantia nigra). These findings provide evidence for generalization based on integrative encoding, whereby overlapping past events are integrated into a linked mnemonic representation. Hippocampal-midbrain interactions support the dynamic integration of experiences, providing a powerful mechanism for building a rich associative history that extends beyond individual events.

Written by huehueteotl

October 24, 2008 at 7:54 am

Posted in Neuroscience

Musicians Use Both Sides Of Their Brains More Frequently Than Average People

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Supporting what many of us who are not musically talented have often felt, new research reveals that trained musicians really do think differently than the rest of us. Vanderbilt University psychologists have found that professionally trained musicians more effectively use a creative technique called divergent thinking, and also use both the left and the right sides of their frontal cortex more heavily than the average person.

The research by Crystal Gibson, Bradley Folley and Sohee Park is currently in press at the journal Brain and Cognition.

“We were interested in how individuals who are naturally creative look at problems that are best solved by thinking ‘out of the box’,” Folley said. “We studied musicians because creative thinking is part of their daily experience, and we found that there were qualitative differences in the types of answers they gave to problems and in their associated brain activity.”

One possible explanation the researchers offer for the musicians’ elevated use of both brain hemispheres is that many musicians must be able to use both hands independently to play their instruments.

“Musicians may be particularly good at efficiently accessing and integrating competing information from both hemispheres,” Folley said. “Instrumental musicians often integrate different melodic lines with both hands into a single musical piece, and they have to be very good at simultaneously reading the musical symbols, which are like left-hemisphere-based language, and integrating the written music with their own interpretation, which has been linked to the right hemisphere.”

Previous studies of creativity have focused on divergent thinking, which is the ability to come up with new solutions to open-ended, multifaceted problems. Highly creative individuals often display more divergent thinking than their less creative counterparts.

To conduct the study, the researchers recruited 20 classical music students from the Vanderbilt Blair School of Music and 20 non-musicians from a Vanderbilt introductory psychology course. The musicians each had at least eight years of training. The instruments they played included the piano, woodwind, string and percussion instruments. The groups were matched based on age, gender, education, sex, high school grades and SAT scores.

The researchers conducted two experiments to compare the creative thinking processes of the musicians and the control subjects. In the first experiment, the researchers showed the research subjects a variety of household objects and asked them to make up new functions for them, and also gave them a written word association test. The musicians gave more correct responses than non-musicians on the word association test, which the researchers believe may be attributed to enhanced verbal ability among musicians. The musicians also suggested more novel uses for the household objects than their non-musical counterparts.

In the second experiment, the two groups again were asked to identify new uses for everyday objects as well as to perform a basic control task while the activity in their prefrontal lobes was monitored using a brain scanning technique called near-infrared spectroscopy, or NIRS. NIRS measures changes in blood oxygenation in the cortex while an individual is performing a cognitive task.

“When we measured subjects’ prefrontal cortical activity while completing the alternate uses task, we found that trained musicians had greater activity in both sides of their frontal lobes. Because we equated musicians and non-musicians in terms of their performance, this finding was not simply due to the musicians inventing more uses; there seems to be a qualitative difference in how they think about this information,” Folley said.

The researchers also found that, overall, the musicians had higher IQ scores than the non-musicians, supporting recent studies that intensive musical training is associated with an elevated IQ score.

Brain Cogn. 2008 Aug 22. [Epub ahead of print]
Enhanced divergent thinking and creativity in musicians: A behavioral and near-infrared spectroscopy study.
Gibson C, Folley BS, Park S.

Empirical studies of creativity have focused on the importance of divergent thinking, which supports generating novel solutions to loosely defined problems. The present study examined creativity and frontal cortical activity in an externally-validated group of creative individuals (trained musicians) and demographically matched control participants, using behavioral tasks and near-infrared spectroscopy (NIRS). Experiment 1 examined convergent and divergent thinking with respect to intelligence and personality. Experiment 2 investigated frontal oxygenated and deoxygenated hemoglobin concentration changes during divergent thinking with NIRS. Results of Experiment 1 indicated enhanced creativity in musicians who also showed increased verbal ability and schizotypal personality but their enhanced divergent thinking remained robust after co-varying out these two factors. In Experiment 2, NIRS showed greater bilateral frontal activity in musicians during divergent thinking compared with nonmusicians. Overall, these results suggest that creative individuals are characterized by enhanced divergent thinking, which is supported by increased frontal cortical activity.

Written by huehueteotl

October 6, 2008 at 7:44 am

Posted in Neuroscience

Independent Brain Pathways Generate Positive Or Negative Reappraisals Of Emotional Events

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Scientists now have a better understanding of how the human brain orchestrates the sophisticated pathways involved in the regulation of emotions. The research identifies brain pathways that underlie reinterpretation of aversive images in ways that reduce or enhance their negative emotional intensity.

“If our emotions are a duet played between the self and the environment, then our ability to regulate them keeps us in harmony with the outside world,” says senior study author Dr. Tor D. Wager from the Department of Psychology at Columbia University. “Although the failure to successfully regulate emotions is thought to contribute to several psychiatric disorders, we do not fully understand how the brain regions involved interact with one another to orchestrate an emotional response and what makes attempts at regulation less successful in some individuals.”

Recently developed brain-based models of emotion regulation identify the prefrontal cortex (PFC) as a key player in the cognitive regulation of emotion. Specifically, brain imaging studies have demonstrated increased activity in the ventrolateral, dorsolateral, and dorsomedial prefrontal cortices (vlPFC, dlPFC, and dmPFC) when individuals are asked to make use of cognitive strategies, such as reappraisal, to alter the emotional impact of a stimulus.

Scientists think that these brain regions are involved in bringing feelings into line with what the situation demands—for example, avoiding feeling or expressing anger during a conflict with a boss. However, there is relatively scant evidence on how the PFC interacts with nuclei deep in the brain that are critical for generating the visceral emotional responses that sometimes cause us to get carried away.

To examine this potential interaction, Dr. Wager and colleagues developed a novel mechanism that enabled them to identify multiple brain regions that serve as mediators of successful reappraisal and to examine how they are organized into functional networks. “We looked for evidence on how PFC activity leads to successful reappraisal, and whether it does so by affecting evolutionarily older subcortical systems critical for emotional experience and emotional learning,” explains Dr. Wager.

The researchers correlated activity in the right vlPFC with reduced negative emotional experience during cognitive reappraisal of aversive images. They went on to use their new mapping strategy to identify two separate pathways that linked activity of the vlPFC with regulation of negative emotion during reappraisal. One pathway, which involved the nucleus accumbens, predicted greater reductions in negative emotion during reappraisal while the other pathway, linked with the amygdala, predicted reduced reappraisal success and, therefore, an increase in negative emotion.

“These results provide evidence that vlPFC is involved in both the generation and regulation of emotion through different subcortical pathways and indicate that the prefrontal cortex is involved in both creating and mitigating negative emotion, depending on the contents of thought,” concludes Dr. Wager. “Our findings also suggest that the existence of multiple prefrontal-subcortical pathways should be considered when examining how emotion is dysregulated in psychiatric disorders.”

Neuron. 2008 Sep 25;59(6):1037-50.
Prefrontal-subcortical pathways mediating successful emotion regulation.
Wager TD, Davidson ML, Hughes BL, Lindquist MA, Ochsner KN.

Department of Psychology, Columbia University, New York, NY 10027, USA. tor@psych.columbia.edu

Although prefrontal cortex has been implicated in the cognitive regulation of emotion, the cortical-subcortical interactions that mediate this ability remain poorly understood. To address this issue, we identified a right ventrolateral prefrontal region (vlPFC) whose activity correlated with reduced negative emotional experience during cognitive reappraisal of aversive images. We then applied a pathway-mapping analysis on subcortical regions to locate mediators of the association between vlPFC activity and reappraisal success (i.e., reductions in reported emotion). Results identified two separable pathways that together explained approximately 50% of the reported variance in self-reported emotion: (1) a path through nucleus accumbens that predicted greater reappraisal success, and (2) a path through ventral amygdala that predicted reduced reappraisal success (i.e., more negative emotion). These results provide direct evidence that vlPFC is involved in both the generation and regulation of emotion through different subcortical pathways, suggesting a general role for this region in appraisal processes.

Written by huehueteotl

October 1, 2008 at 7:50 am

Posted in Neuroscience