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If you're in the field of neuroscience and for some crazy reason haven't heard of channel rhodopsin-2 (ChR2) yet, you will. It has got to be the sexiest contemporary technique available for the neuroscientist, and one that will probably earn Karl Deisseroth a trip to Stockholm in the future.
A relatively new technique, ChR2 allows for tight temporal control of neuronal activation via photostimulation (optically mediated inhibition can be induced via the halorhodopsin channel). The ability to express ChR2 in specific cell populations via genetic targeting make it far superior to previous methods of neuronal activation. Thus far, ChR2 has mainly been used to study synaptic plasticity and to map functional connections between neurons. However, a new paper in Science is the first to show that ChR2 activation can actually drive behavioral changes in adult mammals. While this result is not all that surprising, it's surely a milestone in the field and a harbinger for many, many studies to come. comments
Jeremy Biane 1 June 2009
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A New Role for "Vitamin P"
For many years, selective serotonin reuptake inhibitors (SSRIs) such as prozac have been a favorite pharmalogical treatment for depression. Interestingly, it is often weeks before the psychological effects of these drugs kick in, the cause of this lag period being largely unknown. As the drug is known to increase neurogenesis, some believe this upregulation of newborn cells - and the gradual time it takes for this process to occur - underlies the delayed impact of SSRIs.
In a "recent" study published in Science magazine, Vetencourt et al throw another interpretation into the hat. Their study indicates that under the influence of fluoxetine (aka prozac), the adult rat visual cortex can undergo levels of reorganization typically restricted to developmental periods of life.
Whatever the case, given what we already know about plasticity and sensory processing, you might consider increasing your vitamin p intake next time you take on a new language (I hear the side effects are pretty tolerable). Full Article
Jeremy Biane 19 May 2009
It's Not the Ink!
Do you want to post your Powerpoint lecture notes online? If you post published material online, legally, you should buy the copyright permissions; these run anywhere from $30 – $200 bucks per figure, graph, or table. It's somewhat ridiculous that we were buying back “our” own research after the publishing companies appropriate the rights to everything. It’s important to consider - under this system, all the research and all the funding eventually ends up in the hands of the publishing companies. Oh, and the 400 dollar a year price tag on some of these journals? It’s not the ink! Read Full Article
The publishing process is broken. We aim to fix it.
“In this section, we discuss existing research into red-black trees, vacuum tubes, and courseware. On a similar note, recent work by Takahashi suggests a methodology for providing robust modalities, but does not offer an implementation...” - David Phillips and Andrew Kent, Center for Research in Applied Phrenology, Ithaca, New York.
The excerpt at the top of this article comes from a paper submitted by Philip Davis and Kent Anderson to The Open Information Science Journal. If you find the prose confusing, then you probably went one step further than the publishing company/reviewers – you actually read it. The entire paper, in fact, was constructed using software that creates grammatically correct but nonsensical text. Read Full Article
Reconsidering the value of dopamine
Consult any introductory neuroscience text on the topic of dopamine, and you’re likely to be regaled with how dopaminergic neurons of the midbrain code for the rewarding value of a stimulus. According to this generally accepted theory, midbrain dopamine neurons increase their firing rate in response to a) an unexpected reward; or b) a stimulus that predicts delivery of reward. Conversely, firing rate decreases if reward is withheld following presentation of a reward-predicting stimulus. However, results regarding the response of dopamine neurons in response to adverse stimuli have been conflicting, with some experiments showing increased firing, and others depressed firing. In this week’s edition of Nature, Matsumoto and Hikosaka recorded from distinct classes of dopaminergic neurons that differ based on their response to adverse stimuli – in essence showing that both response patterns exist in the same animal. Interestingly, these separate populations were largely confined to distinct regions of the midbrain, with neurons excited by adverse stimuli found mostly in the dorsolateral midbrain, while those inhibited by adverse stimuli located in ventromedial regions.
While all recorded neurons showed the well-established excitatory response to rewarding stimuli, this study is the first concrete evidence that dopaminergic neurons of the midbrain may not be as homogenous as previously thought, with one population encoding the rewarding value of a stimulus (neurons excited by reward and inhibited by “punishment”), and the other seemingly encoding motivational salience (neurons excited by both rewarding and adverse stimuli).
The authors point out that, based on their location in the midbrain, these distinct populations of neurons can also be differentiated based on their primary target of axonal projection, which may account for the unique information carried by these different classes of neuron. It will also be interesting to see whether the type of dopamine receptors contacted differs by class.
Matsumoto and Hikosaka are quick to point out that their boundaries for classification are rather arbitrary, and in reality there probably exist many distinct categories based on more subtle criteria. Still, the study is a landmark in the reward signaling field, and provides fertile ground for reexamining our rather simple view of dopaminergic signaling.
Jeremy Biane 11 June 2009