Tag Archives: neuroplasticity

Neurophysiology of Meditation, 2 of 2

These articles have taken steps to identify and understand physiological differences in well-focused minds compared to lay people, it is analogous to a study showing that professional athletes have more muscle mass, in a manner communicating to those of us who seek to perform better at either a physical sport or become better problem solvers, that the mind, like the body must be trained and shaped to overcome difficult challenges. The papers in these two posts converge in that both studies show meditation increases activity and over long-term practice, cause structural changes in regions associated with focus and concentration.

Fig 1 Larger GM volumes in meditators (co-varied for age). Views of the right orbito-frontal cortex, right thalamus, and left inferior temporal gyrus, where GM is larger in meditators compared to controls. The color intensity represents T-statistic values at the voxel level.

Where the last post attempts to capture a snapshot of the mind during a meditative act the paper in the following post attempts to show structural changes caused by long-term, regular meditation. The underlying anatomical correlates of long-term meditation-Larger hippocampal and frontal volumes of gray matter, by Luders, et al., asked a simple question: does regular meditation over many years cause any neuroanatomical changes in the meditator.

Image from National Geographic magazine

To find the answer the authors took 22 meditators with mean meditation experience of 24.18 years and acquired images of their brains using MRI. The images were then passed through Voxel-based GM volume analysis, at a local and global level. Next the images passed through Parcellated volume analysis software, combined the various software analysis would help to distinguish grey matter volume differences between the 22 long-term meditators and 22 control subjects with no meditation experience. As a result, this would to some degree, help the authors identify regions with grey matter (GM) differences, however it is not so clear how those changes can be specifically attributed to meditation alone. The data in figure 1 reveals increased GM differences in areas shown as activated by meditation in previous studies. The authors believe the results of this study provides enough positive data to continue to examine the relationship between meditation and GM volume, they nevertheless do acknowledge that on a global level there was no GM difference, only on a local level.

The future for neurophysiological research of focus and the clarity of thought relies significantly on better imaging technology; we must be able to see what pathways are becoming activated, when and during which thoughts. With increased complexity in our everyday lives, less time and more tasks to complete, being able to focus on the everyday problems and the overarching issues that are inherent with existence will become more relevant, research such as this may help to aid individuals and societies alike.

Citations:
Luders E, Toga AW, Lepore N, & Gaser C (2009). The underlying anatomical correlates of long-term meditation: larger hippocampal and frontal volumes of gray matter. NeuroImage, 45 (3), 672-8 PMID: 19280691

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Filed under Meditation, Neuroimaging, Neurophysiology, Neuroscience

Practice makes perfect: Dendritic Pruning & LTP

Dendritic trees

It was about two years ago today, when I began to get a clearer picture of how the cells of the brain physically change as a result of our thoughts, experiences and actions. The mind is a result of a network of billions of individual brain cells, neurons, that exchange information with each other; much of the communication between neurons occurs through structures known as dendrites. These tree-like structures emerge from the main body of a neuron, the tips of each branch exchanging information with other neurons. As we develop habits & recurring thoughts, the neurons who communicate the most with each other begin to strengthen the dendritic branches that connect them. Simultaneously, the connections between neurons who don’t often speak with one another begins to atrophy, the dendrites start to prune themselves. These processes together encompass the much larger idea of neuroplasticity, the idea that our brain physically changes and adapts.

Dendritic Pruning

One of the best examples of this concept can be seen when drendritic trees of young mammals are compared with adults, we see extensive branching on the younger brains relative to the adults, supporting the idea that with experience unused connections are pruned off. One proposed mechanism by which the brain is capable of such adaptability is long term potentiation (LTP). The speed of neural communication is largely attributed to the electro-chemical nature of the transmission, allowing for large chunks of information to be rapidly shared across networks of millions of cells every second. LTP is a specific pattern of signaling between neurons where hundreds of bursts of electrical currents of a particular frequency are sent between two neurons; resulting in enhanced communication between the two neurons and strengthening of the dendrites involved, from that point onward. There’s a decent amount of speculation currently, looking to LTP as the mechanism by which our neurons prune their dendritic trees. What this means for you & me: the more we repeat an action or thought, the more the neurons involved in that process communicate with one other, resulting in a streamlining & strengthening of the connections between them; by the same token, routine will cause the number of neurons who can communicate with each other to degrade, possibly limiting what we can learn and understand as we age.

A: Neuron of Child | B: Neuron of Adult

More than ever before, we can observe how our physical minds change as a result of our actions and have a measurable candidate for the mechanism behind this adaptability. If the 20th century belonged to physics, the last several decades to genomics, it may not be a stretch to see the recent future of science be dominated with answering the questions of neuroplasticity and our minds as a physical structure.

Citations:
Yi Zuo, Guang Yang, Elaine Kwon & Wen-Biao Gan (2005). Long-term sensory deprivation prevents dendritic spine loss in primary somatosensory cortex Nature, 436 : 10.1038/nature0371
Kelly D. Hartle, Matthew S. Jeffers, Tammy L. Ivanc (2010). Changes in dendritic morphology and spine density in motor cortex of the adult rat after stroke during infancy. Synapse, 9999 (9999A) : 10.1002/syn.20767
Daniel McGowan (2006). Pruning processes Nature Reviews Neuroscience : 10.1038/nrn1997

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Filed under Neurophysiology, Neuroscience