Posts Tagged ‘Neurobiology’

Cultural Neuroscience: An Intersection between Anthropology and Neurobiology

Tuesday, March 2nd, 2010

As we go about our day to day lives, it’s often easy to notice that people from different backgrounds think differently (an example would be the stereotypical Asian kid who has seemingly no difficulty in tackling math problems). However, it’s a bit harder to figure out exactly why these differences exist – and whether they are biologically or culturally based. Is there a “math gene” present in some people and not in others? Or is one’s intrinsic ability at a discipline the result of family values and upbringing?

Recent research suggests that the linkage between culture and biology determines the way that we view problems in the world. Eastern and Western subjects were asked the same questions while being examined through Functional Magnetic Resonance Imaging (fMRI) techniques – different regions of their brains were activated even when the subjects ultimately came up with the same response. For example, the Chinese subjects used one area of their brain to compute a basic math problem such as 3+4, while American subjects used a completely different region. Both groups ultimately arrived at the correct answer, of course, but these differences illuminate interesting biological phenomena about the influence that culture has on biology.

Of course, it is possible that these differences are due to a difference in biology all along – perhaps people from Eastern cultures simply have a different “math gene” than the rest of us. But consider the alternative – perhaps our cultural values and upbringing shape our neural development and perception. Further research may bring us closer to the truth.

Sleep on it!

Saturday, January 9th, 2010

During this January term at Harvard, most of us (hopefully) are catching up on all the missed sleep of this past semester and enjoying a period of rejuvenation and rest untroubled by thoughts of upcoming midterms and finals.  As the beginning of second semester looms ever closer, however, most of us are also mentally preparing ourselves for another period of sleep deprivation and cramming on Sunday nights to come.

But perhaps there is a way to cram facts into our head while we sleep, according to a recent study by Rudoy et al of Northwestern University.

The researchers performed a series of tests in which after subjects were taught the locations of certain pictures on the screen, they napped for 90 minutes while sounds related to certain pictures were played. The results showed that all subjects were able to recall the locations of those specific pictures much more efficiently than the pictures not reinforced by sound during sleep.  This would make sense, considering that it is speculated that memory consolidation occurs during sleep and rehearsal is known to be a good way to strengthen specific memories rather it be facts, names, or dates.

Looks like learning a fifth foreign language over J-term with those 1000 phrases on CD playing while you sleep may be an option after all!
And as for next semester, consider recording lectures and sleeping with headphones on – this may very well be the secret to the easy A that you’ve been missing all along! ;)

Musings on Time

Tuesday, January 5th, 2010

With the coming of a new year, we think about the time that has passed and what we have accomplished. We reflect on memories we have created, and the goals we hope to achieve in the coming years. But, how do we perceive time or rather how does the brain create time? An article in The New York Times (which I highly recommend reading), titled "Where did the Time Go? Do not ask the Brain,” led me to think about how the brain creates time.

During my research I learned that the way the brain creates time is still an enigma for many scientists. Moreover, extensive research has been done which has led us to believe that certain neurological diseases such as dyslexia are results of the brain’s distortion of time.  According to the research of Dean Buonomano, a neuroscientist at UCLA, and Warren Meck of Duke University, the brain has an internal clock which creates time. It does this through medium spiny neurons which send pulses that are read by the brain much like music.

In an effort to explain how we can skew the perception of time, Meck believes that neurotransmitters such as dopamine affect the pulses read by these neurons. As a result, watching a car crash can seem to us to have taken place a longer period of time than it actually was. However, on a daily basis, the brain makes time elastic, making certain events or actions seem much longer or shorter in time span. Moreover, emotions greatly affect our brain’s perception of time.  It is still debated where the brain stores memories of time and how we remember the amount of time that an action took to complete.

Perception of time is not dependent on one sensory organ but rather on many parts of the brain depending on the situation. For example, a sense of the length of an event is thought to originate in the medial temporal lobe, while sequencing events in their correct order comes from the prefrontal cortex.   Therefore, understanding how we perceive time has proven to be very complex. Einstein once said "…for us physicists believe the separation between past, present, and future is only an illusion, although a convincing one." Perhaps, Einstein knew more about our perception of time than we know today.

Fighting fire with fire

Tuesday, November 17th, 2009

Well that's what Nworah Ayogu, a Senior concentrating in Neurobiology, is doing in the Rabkin Lab at the Massachusetts General Hospital.  Targeting brain tumors with viruses may seem like something out of a science fiction movie, but Ayogu has been working to use mutant viruses to trigger the immune response against cancer cells, in what is called tumor vaccination.  One type of primary brain tumors in the central nervous system, known as gliomas, is extremely malignant, with a median survival time of twelve to fifteen months.  Researchers have been studying two particular types of treatments in an attempt to combat this deadly disease.  One, known as immunotherapy, attempts to elicit an immune response against tumor cells, while the other, which uses oncolytic herpes viruses, is what Ayogu is especially interested in.  These herpes implex viruses (HSV), modified so that they will only replicate in tumor cells, are dependent for replication on certain factors only seen in rapidly proliferating cancer cells.  HSV replication in the body normally triggers an immune response, which we more commonly recognize as either cold sores or genital Herpes, so when the HSV in tumor cells replicate and lyze, it is proposed that an anti-tumor response will be generated indirectly.  Using the HSV strain G47delta, Ayogu has established a mouse model to study whether G47delta can activate the dendritic cell response. He found that the dendritic cells matured after exposure to virally-infected tumor cells, indicating that tumor vaccination had been achieved in the mice studied.  Ayogu admits that there is still work to be done and is currently furthering this line of research as we speak.  I, for one, would love to see this succeed.  Not only would break-throughs in this field help to combat brain tumors, but it would also be incredibly cool to fight cancer with mutant viruses.

Ayogu presented this work, entitled "Establishment of a Gliomal Model for Tumor Vaccination Using Virally Infected Tumor Cells,"
at the Harvard Undergraduate Research Symposium (HURS) this past weekend.

Janet

Through the Looking Glass

Monday, November 2nd, 2009

MIT Technology Review has a set of stunning images of the brain. The slideshow traces the ways we have visualized neurons from Santiago Ramón y Cajal's 19th century sketches to Brainbow to MRI. To find out more about how some of these techniques work, check out "Project BrainSTORM" in our last issue.

Dopamine? Dope!

Monday, November 2nd, 2009

The same week the New York Times ran Natalie Angier's excellent article on dopamine neurons, we discussed Nature papers on dopamine in my neurobiology class. Classically, the neurotransmitter dopamine has been associated with pleasure and reward, but recent research suggests that dopamine neuron firing is more closely related to drive and motivation. Is this a real difference, or as one student asked, is this just a matter of semantics? Quipped another,  "Just look at half the kids at Harvard — they’re driven but far from happy." Yikes, maybe.

Moviemakers Use Brain Scans to Improve Films

Wednesday, October 7th, 2009

Movies, at their core, are attempts at mind control. Filmmakers want us to laugh at the funny parts, jump at the scary parts, and cry at the sad parts. Eliciting these emotions through cinematographic techniques is their art.

But now, science is playing its hand.

MindSign Neuromarketing is a firm attempting to apply the principles of neuroscience to movies. The firm showed producer Peter Katz"s recent horror film, "Pop Skull," to an individual in an fMRI machine. This machine allows researchers to determine which parts of the brain were activating during which scenes. They specifically focused on the amygdala, the emotional center of the brain. It controls "fear, anger, rage, anything that's fight or flight," as one researcher explains in Peter Katz's video on the project. These are all emotions specifically targeted during a horror film.

The subject was shown 2 scenes from the film, and her amygdala was highly active during both. The researchers can pinpoint exactly when the subject's brain was activated, right down to the specific action: the scariest moment in the scene is exactly when the hand reaches around the corner. This is a wealth of knowledge for the filmmaker.

Until now, producers have had to rely on exit polling of test audiences for feedback on their movies. However, after a 2-hour film, subjects are unlikely to remember how exactly they felt during a particular scene. They also feel pressured to write down positive responses on the report. However, brain scans will show exactly when the subject was bored or uninterested.

NYU neuroscientists researched the effects of film on the brain over a variety of genres. They played clips from Sergio Leone's "The Good, the Bad, and the Ugly," Alfred Hitchcock's "Bang! You're Dead," and Larry David's""Curb Your Enthusiasm." Then they played a 10-minute, unedited clip from a concert, to establish a control. They then measured the level of activity in the neocortex, the area of the brain involved in perception and conscious thought. The Hitchcock episode involved 65% of the neocortex, which indicates rapt attention; "The Good, the Bad, and the Ugly" evoked 45%;"Curb Your Enthusiasm" came in at a low 18%. The concert video was less than 5%.

http://www.wired.com/geekdad/2009/09/neurocinema-aims-to-change-the-way-movies-are-made/

http://www.neurosciencemarketing.com/blog/articles/movie-mind-control.htm

"Coming Closer": approach sensitivity and understanding visual circuits

Tuesday, October 6th, 2009

This month in Nature Neuroscience, it was demonstrated that the retinal circuits underlying day and night vision share at least one of the same components. In their article "Approach sensitivity in the retina processed by a multifunctional neural circuit,” Münch, et al demonstrate that the mouse AII amacrine cell, in addition to its known role in the dim light, rod-driven (scotopic) pathway, underlies the approach sensitivity of PV5 retinal ganglion cells (RGC), which project from the retina to the brain.

In brief, they demonstrate that these RGC respond to approaching dark stimuli, independent of luminance (dim vs. bright) effects, but do so selectively, ignoring departing dark stimuli. This is relevant in nature when one considers than approaching predator will appear as an approaching dark stimulus, and in fact, this analog between predators and dark stimuli is utilized by many behavioral tests. For instance, in the zebrafish, in a behavior known as the escape response, fish will swim away from an approaching black stripe.

This selective response can be understood in terms of the inputs of RGC, bipolar cells, which come in two varieties: ON and OFF, responding to light or its absence, respectively. One can imagine that as a dark stimulus of fixed size moves into the receptive field of a PV5 cell, OFF bipolars become more excited, while ON bipolars are unaffected. However, as a dark stimulus departs from the PV5 receptive field, OFF bipolar cells are excited, but this excitation is balanced by inhibitory input from ON bipolars. This inhibitory signal is mediated through AII amacrine cells, which become activated through electrical synapses (very fast synapses) with ON bipolars.

Interestingly, the AII amacrine cell conducts excitatory, rather than inhibitory signals, between rod bipolar cells (like ON bipolar cells, but connected to rods instead of cones) and ON bipolar cells in scotopic conditions. Thus, this cell is important to both day and night visual circuits, but conducts opposite signals. How this is possible has yet to be determined.

With discoveries such as these, we become closer to understanding mouse retinal function, in particular its role in discerning complicated features of the visual scene. While it was previously assumed that night and dark pathways were distinct, leaving each neuron with one role, it seems that these circuits are more complicated than anticipated, overlapping and even potentially interacting with one another.

Love and Sex and Magic

Tuesday, October 6th, 2009

The concept of the "love potion” has been one of great fascination throughout history and, more recently, in popular media such as the magical Harry Potter series.  Without a doubt, many have stopped to think, "Would it be possible to brew love in a bottle?”

Before you scoff at such nonsense, however, consider this: recent studies show that love may depend immensely on the chemistry experienced not only between a couple, but within the complex pathways of their brains.

A classic example of "love” chemicals in action is the vole romance.  When prairie voles mate, the hormones oxytocin and vasopressin are released. If these hormones are inhibited, vole sex becomes merely a promiscuous affair not unlike the nondiscriminatory sex often witnessed in animals. When the voles receive these hormones by injection, however, and are prevented from mating, the voles still form a fairly monogamous preference for their partner. In essence, it would appear that scientists could make prairie voles fall in love with a single injection, not far off from the concept of a love potion.

It turns out that prairie voles have receptors for oxytocin and vasopressin in brain pathways associated with reward and reinforcement, and such receptors are also present in the human brain.

But how can one achieve higher oxytocin levels and a better love life without resorting to needles? Do what the voles do.

Oxytocin levels rise during both foreplay and orgasm in both men and women, boosting trust and creating a deeper sense of attachment.  A good illustration of how important oxytocin is in maintaining trust in a relationship is a laboratory investment game devised by neuro-economist Ernst Fehr at the University of Zurich in Switzerland. It turns out that almost half the people playing the role of an "investor” would hand over all their money to an anonymous trustee, with no guarantee of its return, only if they sniffed an oxytocin spray beforehand! In this sense, sex may very well be the all-natural love potion.

There is still much to learn about the chemical workings of love, and man may never be able to brew the true love potion of fairy tales and myths, but perhaps enough is now known to make you believe in love and sex and magic.

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Anderson, Alun, and Lucy Middleton.. "What is this thing called love?." New Scientist 190.2549 (29 Apr. 2006): 32-34.

Cocking an ear to tonal languages

Tuesday, October 6th, 2009

A cochlear implant (illustration) can give a deaf person a representation of their auditory surroundings in enough detail to understand speech. Still, the current technologies for recording, processing, and transmitting sound directly to the auditory nerve are still in their infancy. For instance, we cannot replicate the tonal qualities of speech through electrical signals. How then can a deaf child use a cochlear implant to learn a tonal language such as Mandarin, where a slight tone difference can distinguish two completely unrelated words? (Demonstration of different tones)

This is precisely the question that Michael Chi-Fai Tong and Kathy Yuet-Sheung Lee at the University of Hong Kong are asking. Current models of cochlear implants are designed primarily to mimic frequency and volume of incoming sound. They achieve this by processing sound picked up by a microphone into electrical signals. To bypass the damaged hair cell pathway, electrodes are implanted directly into the cochlea, transmitting the electrical signals to the auditory nerve in patterns determined by the sound’s frequency.

The cochlear implant design takes advantage of what we understand best about the auditory system: the organization in the ear and brain that separates sounds by frequency. So-called "tonotropic” pathways are roughly analogous to the organization for processing small elements of light information in the visual system. We know that the patterned organization in the visual system depends on the animal’s ability to see – does the development and maintenance of the tonotropic pathway require a child to hear? More importantly, can a cochlear implant sufficiently replace normal auditory input so that a deaf child develops normal acuity in auditory processing?

Although children given cochlear implants at a very young age can develop remarkable hearing, few studies have closely examined the brain for changes in neural connections and organization. How to establish and maintain a tonotropic pathway is a critical question when we think about adding tone quality to the repertoire of a cochlear implant. Imagine that 20 years from now we invent the technology for encoding tone in an electrical signal. Will infants who receive today’s limited cochlear implants have enough auditory experience for the brain to develop the organization that can process tone? If given a futuristic implant in 20 years, will they hear tone immediately, or be able to learn to hear it?

Of course, the importance of these questions is emphasized by the fact that it is incredibly difficult to learn to produce sounds that you cannot hear. Try learning Mandarin from silent videos. It is no wonder that so many people have hope for cochlear implants that can reproduce tones.

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Illustration of cochlear implant.

Tones

Holguin, Kirsten. "Cochlear Implant Outcomes in China to be Researched.” House Ear Institute. 15 January 2009. 5 October 2009.

Robinson, K. (1998). "Implications of developmental plasticity for the language acquisition of deaf children with cochlear implants.” Int J Pediatr Otorhinolaryngol. 46(1-2):71-80.
Squire L, Berg D., Bloom FE, du Lac S, Ghosh A, Spitzer NC. Fundamental Neuroscience. 3rd Ed. Pp. 609-636. Burlington, MA: Elsevier (2008).
Tong MC & Lee KY. (2009). "Do Chinese speakers need a specialized cochlear implant system?” Otorhinolaryngol Relat Spec. 71(4):184-6. Epub 2009 Aug 26.