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Picture 1Here is a heads up for a recent study demonstrating – again – that the amygdala is not merely a “fear centre” in the brain. I have previously blogged about the amygdala, first not being a single structure, and that it is not only involved in fear.

In 2007, a team of French researchers demonstrated that direct stimulation of the amygdala did evoke emotional responses, but that there was a difference between which hemisphere was stimulated. Right amygdala stimulations induced aversive responses, in particular fear and sadness. In contrast, left hemisphere stimulation induced either positive (happiness) or negative emotions (fear, anxiety, sadness). As the abstract reads:

Very few studies in humans have quantified the effect obtained after direct electrical stimulation of the amygdala, in terms of both emotional and physiological responses. We tested patients with drug-resistant partial epilepsies who were explored with intracerebral electrodes in the setting of presurgical evaluation. We assessed the effects of direct electric stimulations in either the right or the left amygdala on verbally self-reported emotions (Izard scale) and on psychophysiological markers of emotions by recording skin conductance responses (SCRs) and by measuring the electromyographic responses of the corrugator supercilii (EMGc). According to responses on Izard scales, electrical stimulations of the right amygdala induced negative emotions, especially fear and sadness. In contrast, stimulations of the left amygdala were able to induce either pleasant (happiness) or unpleasant (fear, anxiety, sadness) emotions. Unpleasant states induced by electrical stimulations were accompanied by an increase in EMGc activity. In addition, when emotional changes were reported after electrical stimulation, SCR amplitude for the positively valenced emotions was larger than for the negative ones. These findings provide direct in vivo evidence that the human amygdala is involved in emotional experiences and strengthen the hypothesis of a functional asymmetry of the amygdala for valence and arousal processing.

Interestingly, there is more to say about this study. First, it may be that there is a systematic bias introduced by the way the researchers did the study. By using high-frequency (50 Hz) stimulation in 1 second, they might have induced one characteristic response of the amygdala. This structure is often seen as having quick “on-off” responses. Thus, one second pulse trains is actually a long duration for the amygdala. So a pulse of 20 milliseconds could be hypothesised to produce different responses. Also, the researchers found that GSR responses were actually larger for positive emotions, when they were reported. As the amygdala has often been implicated in unconscious emotional responses (mostly aversive responses) one may speculate that the left-hemisphere amygdala involvement in positive emotions may be related to conscious emotions.

As always, new findings leads to numerous novel questions, ideas and hypotheses. Which is why science is so much fun. But it is important to note the change we see today the role of the amygdala in emotional responses. We are moving away from the LeDouxian paradigmatic focus on fear (and some aversion)as the sole emotion of the brain, and more towards a balanced view towards a similar focus on positive emotions and (hopefully) more complex human emotions. Through this development, we can see that novel findings are breaking down the old ideas of neo-phrenology, breaking single structures into smaller parts, and into parts of a larger network of convergence and divergence structures. Keep your eyes open, more is on the way.

-Thomas

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I just found this through mindhacks, and thought it was nice how well this illustrates the amazement one can get from witnessing neurological injury and disease. Through my early clinical practices, I’ve seen several kinds of unilateral neglect, blindsight, amnesias, aphasias, weird dementias (Wernicke-Korsakoff, fronto-polar, Parkinson Plus), and youtube may be the place to find good illustrations of this to the general public.

-Thomas

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-Thomas

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I’m having the pleasure of reading The brain that changes itself by Norman Doidge, as a reviewer for a potential translation here in Denmark. Brain plasticity, or neuroplasticity, has always been a hot topic, from it’s (re)birth in modern neuroscience, and all the way up until today, where researchers are still fiercely debating how plastic the brain is and how functions relate to brain structures – aka the debate of modularism. In its early days, the neuroscientific community strongly believed that the modularity of the brain was established during childhood, and that little, if any, change could occur later on. Researchers suggesting otherwise were eschewed, heavily criticized on the ground that their data/ideas did not fit into the existing model. The land did not fit onto the map, so to say. This book is dedicated to the idea of neuroplasticity.

The book introduces brain plasticity in a very vivid and close-up manner, as Doidge tells the story from the inside, through some of the biggest names in this research, including the late Paul Bach-y-Rita, Michael Merzenich, and Gerald Edelman. Not only is the book very interesting to read as a historical background, but it also takes a look behind the scenes in two ways. Doidge has talked the researchers himself, and bring their experience of how plasticity came to go from a ignored (and carreer risky business) field, to a scientifically acceptable and highly influential topic. Even today, one may claim that we do not fully comprehend or apply the insights from this research.

Doidge also does a great job in describing patient cases of brain plasticity, including:

(…) a woman born with half a brain that rewired itself to work as a whole, a woman labeled retarded who cured her deficits with brain exercises and now cures those of others, blind people learning to see, learning disorders cured, IQs raised, aging brains rejuvenated, painful phantom limbs erased, stroke patients recovering their faculties, children with cerebral palsy learning to move more gracefully, entrenched depression and anxiety disappearing, and lifelong character traits altered.

(from the book cover)

The stories from both researchers and patients are written in a most vivid and entertaining way, and the first 100 pages alone makes the book a page-turner. The book as a whole is filled with these fantastic descriptions and stories that equal great writers such as Oliver Sacks.

So how about the sex part? Yes, this is where I got a little puzzled, too. Going from the insights of neuroplasticity, Doidge turns his attention to sexual disorders and abberations. This is, of course, both a very interesting, challenging and risky choice, but it is also a topic that Doidge is intimately close to through his clinical work. In much the same manner as the description of neuroplasticity cases, we are presented to patients of Doidge (or his peers) that suffer from psychological illnesses, in particular sex related problems. Interestingly, it seems that the insights from plasticity can be applied to these disorders and problems, and Doidge does a great job in presenting and discussing these issues.

My quarrel, however, is with Doidge’s theoretical position — psychoanalysis. Is it not itself strange to combine the insights from the edgy yet stringent scientific approaches of neuroplasticity with the unscientific theoretical (armchair) century old approach? Doidge does use the suggestions from Freud to interpret the psychological cases he presents. This includes the interpretation of dreams, a business receiving a lot of criticism, too. At best, I think this part of the book becomes an anachronism. The problem lies in why, at all, Doidge needs to invoke a theoretical position like psychoanalysis at all in order to understand what is going on. This is where science becomes fiction, and where the book breaks down. But not totally. If one is aware of the problems associated with psychoanalysis and science, the book is still a wonderful read.

-Thomas

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amygdalaoid.jpegThat almond-shaped structure we call amygdala is typically thought of as solely (or mainly) involved in negative affect. However, some studies have suggested that the amygdala is also involved in other processes, such as novelty (of faces). It should come as a big surprise, however, to many researchers that this structure is also involved in positive emotions. It runs counter to many ideas and interpretations of amygdala activation in, e.g., fMRI studies.

Even more so, in a recent paper in TICS, Elisabeth Murray from the NIH put forth three distinct claims regarding amygdala function (and structure):

  1. amygdala plays a role in positive affect, and therefore not exclusively — or even mainly — in negative affect
  2. contrary to an influential model, recent evidence points to a distinction between emotion and reward and contradicts previous conclusions about the role of the amygdala in reward processing
  3. the amygdala is not a single “thing” but a conglomerate of structures playing different roles in emotional and non-emotional processes

The research reviewed is, as always in the case of Murray, well supported and yet controversial. To anyone studying emotions and reward, it’s a must-read. But even to people studying other functions and regions, it’s a principal discussion and a well-needed lesson in the still-present oversimplified neo-phrenology seen in cognitive neuroscience.

So next time you see the amygdala light up during a brain scan, resort from interpreting it as a sign of anxiety or fear.

-Thomas

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kandel150.jpgThis year’s annual question at Edge was, “What are you optimistic about?”. Now, Brockman has asked Eric Kandel to outline the four neuroscience breakthroughs made in 2006 that makes him optimistic about our future possibility of understanding the brain. The first breakthrough is research into the role of microRNAs in the formation of synapses. The second is research into the encoding of external space in the hippocampus and the entorhinal cortex. Kandel’s third choice is research into social interaction, including Rebecca Saxe’s imaging studies of Theory of Mind, and Barry Dickson’s discovery that if the male form of the protein fruitless is expressed in female Drosophila, the females will display male courship behaviour. And his fourth is the possibility, through neuroimaging and other new techniques, of understanding the effects of psychotherapy on psychiatric diseases.

All four advances are clearly great causes for optimism. But maybe there are other breakthroughs worth mentioning? What about research into decision-making, or comparative genetic studies casting light on the evolution of the hominid brain? I bet that you readers have your own suggestions. Please share them with us in the comments section.

-Martin

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figure1.jpgIs binding the single most important concept in neuroscience? I think it is, even without making the concept too general or vague. On the contrary, binding seems to be a general concept to understand the workings of the brain. No more need for modules of perception, cognition, memory and action. Binding is the solution.

More specifically, what is binding? Or, to reframe the question 100%: what happens when the brain works? To many, the brain binds information together at all levels throughout the brain. If you perceive an object, that particular object is a mixture between colour, form, position, movement etc., that is bound together. Because of you look at the early sensory processes in the brain, we know that the features of an object are treated by separate processes in the brain. Accordingly, they can be lesioned separately, leading to e.g. acquired colour blindless but with intact movement perception.

(more…)

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