Pints and Plasticity

On Tuesday afternoon in New York City, science enthusiasts gathered at Ryan’s Daughter, a bar on the upper east side. It is also one of the many locations of “A Pint of Science,” an annual science festival that takes place for three days in May, in various locations around the country. The premise of the festival is to give adults an outlet for learning about science in a fun and casual environment.

pintofscience aoki

The evening’s focus was on brain plasticity, which is the brains ability to adapt and change throughout life. Chiye Aoki, professor of neural science and biology at NYU, explained her work concerning learning and synapse formation. Synapses play a role in the connectivity of neurons. Synapse formation happens throughout life, and is a key component in learning.

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Tales from the Lab: Behavioral Adaptations

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Grace Lindsay, a neuroscience graduate student from Columbia University, is guest blogging about neuroplasticity for our “Tales from the Lab” series. This is Grace’s third and final blog post.

Adaptation is crucial to survival: in a world where only the fittest survive, changing circumstances call for changing responses. While some bodily adaptations to the environment occur over long, evolutionary timescales, the brain has two key features that allow for behavioral adaptations to occur much faster: complexity and plasticity. The immense number of cells in the brain means that there are many ways that those cells could connect to each other, and plasticity allows for re-wiring that can sample some of these connection possibilities. When inputs to the brain cause re-wiring, the brain’s response to a future input will be different—and hopefully more beneficial to the animal–than it was before. Acquiring a new physical skill, learning to avoid places associated with danger, and figuring out how to extract relevant information in a new environment are all adaptive behaviors that rely on this ability.

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Tales from the Lab: Plasticity in Response to Injury–a Blessing and a Curse

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Grace Lindsay, a neuroscience graduate student from Columbia University, is guest blogging about neuroplasticity for our “Tales from the Lab” series. This is Grace’s second blog post.

Plasticity is a necessary and powerful force in the developing brain. By adulthood, however, things have mostly settled down. But every now and then, there are events that can upturn the relative stability of the adult brain, forcing a rearrangement of its otherwise consistent connections.

Stroke is one such event. The cutoff of blood to brain tissues leads to the death of neurons, disrupting the neural network in and around the affected region. In a frantic and somewhat messy attempt to salvage what remains, the brain responds by releasing a molecular cocktail to encourage the growth of new cells and of new axons on existing cells, trying to reestablish the lost connections. But this attempt to reconnect is largely random and time sensitive; it rarely is able to restore the brain to the way it was before the stroke. Scientists are studying how to best intervene to enhance the brain’s natural response to injury and improve stroke outcomes.

Facemap

   Photo courtesy of Peter W. Halligan, Cardiff University

But the brain’s natural response to trauma is not always helpful. Take, for example, the problem of “referred phantom sensation.” When a person loses a limb, the cortical area that normally processes sensory signals from that limb no longer receives its normal input. Yet a large fraction of amputees report feeling sensation in their phantom limb on a regular basis. What’s more, some patients actually feel sensation in their phantom limbs in response to being touched in another part of the body. For example, a case study from Oxford University describes how an amputee felt sensation in her amputated right arm when certain parts of the right side of her face were touched. The responses were somatotopically mapped –that is, nearby areas of the face corresponded roughly to nearby areas of the arm (see figure below). It appears that, because it’s lacking its own input, the region assigned to the now-missing limb is overtaken by inputs from another region. In most people, the area of cortex representing the head is located directly next to that representing the arm, so perhaps it is unsurprising that the arm area would be overtaken by head inputs. It’s assumed that plasticity, either in the cortex or the subcortical structures which feed into it (or both), is responsible for this phenomenon. But exactly how–either through the strengthening of existing synapses or the sprouting of new ones into the affected area–is not clear.

 

While this ability of the cortex to rearrange itself can be damaging, it can also be utilized. Prosthetic devices such as cochlear implants rely on it. Over time and use, the brain learns how to properly process inputs it gets from the implant, allowing a person to improve in important areas such as speech perception. The double-edged nature of the brain’s dramatic response to dramatic change can be fully appreciated.

– Grace Lindsay

Grace Lindsay is a first-year Ph.D. student in the Neurobiology and Behavior Program at Columbia University. She got her BS in neuroscience from the University of Pittsburgh in 2011 and then spent a year doing research at the Bernstein Center in Freiburg, Germany. She blogs about all things neuroscience at neurdiness.wordpress.com.

Tales from the Lab: Developmental Plasticity and the Effect of Genetic Disorders

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Over the next three months, the Dana Foundation blog is pleased to host a new blog series, “Tales from the Lab,” featuring two neuroscience graduate student guest bloggers: Tim Balmer from Georgia State University and Grace Lindsay from Columbia University. Tim’s contributions will focus on life as a neuroscience graduate student and Grace will focus on neuroplasticity. This is Grace’s first blog in the series.

Infancy is a tumultuous time for the brain. A set of neurons with connections in constant flux are working to process an onslaught of sensory signals; yet the connections themselves are guided by the very signals they’re processing. Despite the apparent chaos, we all end up with roughly the same hardware: an occipital lobe for seeing, a temporal lobe for hearing, parietal lobe for sensing touch, etc. 

But what happens when those brain-shaping signals can’t get into the brain? For example, in the case of Leber’s congenital amaurosis (LCA), a genetic mutation disrupts the function of cells in the eye, leaving people with LCA essentially blind from birth. This lack of visual input throws a wrench into the brain’s normal plan of development, and it shows in the brain anatomy of adults with these kinds of disorders. Without visual information to process, the occipital lobe is reassigned to other tasks. PET and fMRI studies of congenitally blind humans have shown activation of the occipital lobe during processing of sounds, smells, and touch (such as braille). Such activation is not seen when imaging the brains of sighted people, or even those who lost their vision later in life. These findings demonstrate the remarkable plasticity of the developing brain to adapt its activity and structure in order to best process the signals it receives.

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Blindness and Sensory Perception

Ever since studying Oedipus Rex and The Odyssey in tenth-grade English class, I’ve been exposed to the idea of the blind seer. From at least the heyday of ancient Greece, people have thought that with loss of sight comes a heightening of other senses (which, in literature, means extraordinary perception and foresight, usually resulting in tragedy. Oedipus, do you really want Tiresias to tell you who killed your father?).

Recent research has found that many blind people do, in fact, experience a heightened sense of touch. But this may not occur merely due to blindness, but from increased use.  

Scientists at McMaster University tested 28 profoundly blind people and compared them to 55 seeing adults. When asked to identify the textured patterns pushed against their fingertips, blind participants performed better than sighted participants. Braille readers performed better still, especially when researchers tested their reading finger.

But when the textured patterns were pushed against the participants lower lips, there was no difference in the performance of participants. Therefore, concludes the study authors, use improves skill.

How can blindness impact the other senses?

Let’s look at smell: A study from researchers at the University of Copenhagen compared the olfactory responses of normally sighted study subjects to those blind from birth. Functional magnetic resonance imaging revealed more blood flow to primary and secondary olfactory areas in the congenitally blind subjects. A study from the University of Montreal—comparing odor detection abilities of 11 congenitally blind and 14 normally sighted study subjects—concluded that the blind participants had better senses of smell only in areas relating to environmental assessment.

Compensatory sensory perception appears to result from use, which can lead the brain’s connections to change and reorganize. A “third eye” of the blind may therefore exist in some neuroplastic fashion—but not in the way presented by Sophocles and Homer.

–Johanna Goldberg

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