Mirror Neurons Discovered in Birds

A new paper by Prather et al. identifies song-specific neurons in the swamp sparrow that are active during song perception and song performance. These properties suggest that the neurons might be part of mirroring system analagous to those identified in primates. As far as I can tell, this is the first paper on mirror neurons that Nature has published, though its sibling journals have been kinder to the emerging field (see here and here; note the infamous Iacaboni is an author on both). Because mirror neurons have received extraordinary media attention, sometimes it’s hard to separate the facts from the hype. This Nature paper lends credibility to the field by establishing a small-animal model for future investigation.

Prather et al. measured action potential activity using motorized microdrives that precisely positioned electrodes in the telencephalic nucleus HVC, a brain region known to be involved in singing and song perception. They found that the pattern activity in these regions was nearly identical for auditory perception and song vocalization (see figure below). The authors do note one difference between the neural correlates of action and perception: HVC neurons fired single action potentials during song perception but fired in bursts during song vocalization.

The authors also prove that activity during song vocalization cannot be explained in terms of auditory feedback. For instance, the authors show that HCV activity is not influenced by auditory distractions while a bird is singing. This suggests that activity during singing reflects a corollary discharge from motor systems.

I think the most exciting aspect of this research is the translational potential. Now that we have a small-animal model, it will be easier to test the effects of genetic and pharmacological manipulations on mirror neuron systems. Further research might provide important insights about language acquisition and how it is disrupted in certain pathologies (i.e. autism).

Encephalon 36

Welcome to Encephalon, the bi-weekly neuroscience blog carnival. In the 36th Edition, you will learn what STDs have to do with Alzheimer’s, how rats plan their decisions in a maze and why kids start speaking in nouns. Thanks for all the great submissions.

Brain Disease

Zachary Tong at Distributed Neuron reports on new evidence that neural progenitor cells migrate towards the site of strokes. Researchers injected progenitor cells into mouse brains and then induced artificial strokes in half the subjects. They tracked the progenitor cells and found direct migration of labeled cells in the animals with brain injury.

Zachary also investigates the diverse genetic causes for epilepsy. New research demonstrates that disparate mutations associated with the disease can cancel each others’ negative effects when co-expressed.

Evil Monkey at Neurotopia provides yet another reason to practice safe sex: avoiding Alzheimer’s Disease (AD). Herpes virus HSV-1 is a risk factor for AD and may accelerate the formation of amyloid plaques associated with cognitive decline.

Relatedly, Sandra Kiume at Channel N links to videos about memory loss from a conference at the University of British Columbia. The videos discuss tips for healthy aging in the context of cutting edge neuroscience research.

Computational Neuroscience

Jake Young at Pure Pedantry highlights a great paper in J. Neuroscience about how spatial information is encoded in the hippocampus. The authors made electrophysiogical recordings from rats as they chose between two alternative arms of a maze. These recordings revealed transient activation of neurons associated with each path, even before the rat embarked on either of them. This research proves that hippocampal maps are not solely for real-time encoding of spatial location but also for projections about future position.

In a related — albeit more theoretical — vein, Michael introduces his new blog Shared Symbolic Storage with a post about embodied cognition. Michael mentions a paper co-authored by Benoit Hardy-Vallée, an Encephalon contributor.

Imaging Studies

Ed Yong at Not Exactly Rocket Science reviews new research showing that the brains of children with attention deficit hyperactivity disorder (ADHD) exhibit delayed maturation of the prefrontal cortex and accelerated maturation of the primary motor cortex. The findings are encouraging because they suggest that the brains of patients with ADHD eventually catch with those of nonaffected individuals.

The Neurocritic has a great two part takedown of the New York Times’ latest foray into pseudoscience. He links to several rebuttals and contributes a healthy dose of common sense with this rhetorical question: “Did we really need fMRI to tell us that Mrs. Clinton should try to soften the negative responses of swing voters?”

Language

Michael at Shared Symbolic Storage offers a three part review of Baboon Metaphysics, a new book by Dorothy Cheny and Robert Seyfarth. The authors propose that social cognition preceded and made possible the emergence of language, instead of vice versa. Michael argues that this proposal neglects the mechanisms though which language can in turn influence our thought.

“Mama,” “Cookie,” “Nap.” Why do children learn nouns like these before other parts of speech? Dave Munger at Cognitive Daily reports on a creative study in which infants learning their first language were compared to older children learning a second language. This allowed researchers to figure out whether the early abundance of nouns is a function of age or an necessary feature of language acquisition.

That wraps it up for this issue of Encephalon. Bora at A Blog Around the Clock hosts Encephelon #37 on December 3rd. Email your posts to encephalon{dot}host{at}gmail{dot}com or submit using the online form.

Pinker on Grammar, Swears and Innuendo

In case you haven’t heard, Harvard psychology professor Steven Pinker is touring the country in a thinly veiled campaign to sell his new book, The Stuff of Thought. Yesterday I heard him speak at the Philadelphia Free Library. It was very entertaining, though in retrospect, perhaps not super cohesive.

The first third of the lecture was about language as a window into human cognition. For instance, Pinker discussed how verb tenses reveal a primitive theory of physics. Things can either be determined and unchangeable, present and part of conscious experience, or undetermined and changeable. Though this tripartition does not really supervene on scientific truths, conventional use of tenses does allow us to communicate our ideas effectively. Pinker also stressed how we compartmentalize time with spatial metaphors; for instance, we are relieved when a difficult exam is ‘behind’ us. Pinker suggests that spatial metaphors help us separate events conceptually, but that some ambiguity remains. As an example, he asked whether “9/11” refers to one event (a terrorist attack) or two (each plane as a separate event). This question seems besides the point, until you realize that the owner of the World Trade Center was supposed to receive 3.5 billion dollars for each destructive event that befell his property. In case you are wondering, a jury decided that it was only one event.

The second third of the lecture was filled with gratuitous swears. I’m not kidding. Pinker was trying to make a point about how language can serve as a window into our emotions, though in reality this point may have been obscured by the furious laughter that erupted every time the the distinguished professor uttered words like “fuck” or “doo-doo.” He delineated five contexts in which we swear, devoting most of his discussion to cathartic swearing. Pinker dismissed the so-called hydraulic theory in which we swear to “let off steam.” Instead, he suggested that crude interjections are analogous to situations in which lower-order animals let out a yelp or squeal to startle attackers. According to Pinker, swearing is mediated by the same primitive rage circuits, but over time these circuits have hijacked our language systems to produce expletives. He stressed the automaticity of these outcries, suggesting that they may have evolved to alert bystanders about our misfortunes.

Lastly, Pinker discussed how our use of innuendo might reveal interesting information about how we navigate social relationships. He brought up an example from the movie Fargo, in which Steve Buscemi’s character hands over his wallet to a cop who pulls him over and asks for his driver’s license. Buscemi lets a fifty dollar bill peak out of the wallet and suggests, “I was just thinking we could take care of it right here, in Brainerd.” Buscemi’s character hopes to bribe to cop, but chooses to veil his offer. Pinker examined this situation through the lens of Game Theory. While failing to offer a bribe brings about a moderately negative outcome no matter what (paying a fine) an overt bribe carries a high risk if the cop is honest (arrest). Innuendo provides a third option, in which Buscemi’s character preserves a degree of plausible deniability while successfully suggesting a tit for tat. Thus, the cop is allowed to choose between a relationship of domination and one of reciprocity.

The lecture was very clean and well-rehearsed. In fact, it seems like the same one that he gave in New York. My summary leaves much to be desired, so I highly recommend checking out His Highness for yourself. Perhaps the most engaging part of the lecture was also the least scripted: Pinker does a fantastic job of answering questions pitched from all levels of sophistication.

You can find the schedule for his lecture tour here.

UPDATE: Pinker has a piece in The New Republic that explains his theory of swearing much better than I could ever hope to do.