Somatosensory Cortex

The study involved 26 experienced Buddhist meditators and 40 control subjects. Scans of their brains while they played the "ultimatum game," in which the first player proposes how to divide a sum of money and the second can accept or reject the proposal, revealed that the two groups engaged different parts of the brain when making these decisions.

Consistent with earlier studies, controls showed increased activity in the anterior insula (involved in disgust and emotional reactions to unfairness and betrayal) when the offers were unfair. However the Buddhist meditators showed higher activity instead in the posterior insula (involved in interoception and attention to the present moment). In other words, rather than dwelling on emotional reactions and imaginary what-if scenarios, the meditators concentrated on the interoceptive qualities that accompany any reward, no matter how small.

The meditators accepted unfair offers on more than half of the trials, whereas controls only accepted unfair offers on a quarter of the trials.

Moreover, those controls who did in fact play the game ‘rationally’ (that is, mostly accepting the unfair offers) showed activity in the dorsolateral prefrontal cortex, while rational meditators displayed increased activity in the somatosensory cortex and posterior superior temporal cortex.

The most intriguing thing about all this is not so much that regular meditation might change the way your brain works (although that is undeniably interesting), but as a more general demonstration that we can train our brain to work in different ways. Something to add to the research showing how brain regions shift in function in those with physical damage to their brains or sense organs (eg, in those who become blind).

As I’ve discussed on many occasions, a critical part of attention (and working memory capacity) is being able to ignore distraction. There has been growing evidence that mindfulness meditation training helps develop attentional control. Now a new study helps fill out the picture of why it might do so.

The alpha rhythm is particularly active in neurons that process sensory information. When you expect a touch, sight or sound, the focusing of attention toward the expected stimulus induces a lower alpha wave height in neurons that would handle the expected sensation, making them more receptive to that information. At the same time the height of the alpha wave in neurons that would handle irrelevant or distracting information increases, making those cells less receptive to that information. In other words, alpha rhythm helps screen out distractions.

In this study, six participants who completed an eight-week mindfulness meditation program (MBSR) were found to generate larger alpha waves, and generate them faster, than the six in the control group. Alpha wave activity in the somatosensory cortex was measured while participants directed their attention to either their left hand or foot. This was done on three occasions: before training, at three weeks of the program, and after the program.

The MBSR program involves an initial two-and-a-half-hour training session, followed by daily 45-minute meditation sessions guided by a CD recording. The program is focused on training participants first to pay close attention to body sensations, then to focus on body sensations in a specific area, then being able to disengage and shifting the focus to another body area.

Apart from helping us understand why mindfulness meditation training seems to improve attention, the findings may also explain why this meditation can help sufferers of chronic pain.

If our brains are full of clusters of neurons resolutely only responding to specific features (as suggested in my earlier report), how do we bring it all together, and how do we switch from one point of interest to another? A new study using resting state data from 58 healthy adolescents and young adults has found that the intraparietal sulcus, situated at the intersection of visual, somatosensory, and auditory association cortices and known to be a key area for processing attention, contains a miniature map of all the things we can pay attention to (visual, auditory, motor stimuli etc).

Moreover, this map is copied in at least 13 other places in the brain, all of which are connected to the intraparietal sulcus. Each copy appears to do something different with the information. For instance, one map processes eye movements while another processes analytical information. This map of the world may be a fundamental building block for how information is represented in the brain.

There were also distinct clusters within the intraparietal sulcus that showed different levels of connectivity to auditory, visual, somatosensory, and default mode networks, suggesting they are specialized for different sensory modalities.

The findings add to our understanding of how we can shift our attention so precisely, and may eventually help us devise ways of treating disorders where attention processing is off, such as autism, attention deficit disorder, and schizophrenia.

[1976] Anderson JS, Ferguson MA, Lopez-Larson M, Yurgelun-Todd D. Topographic maps of multisensory attention. Proceedings of the National Academy of Sciences [Internet]. 2010 ;107(46):20110 - 20114. Available from: http://www.pnas.org/content/107/46/20110.abstract

Older news items (pre-2010) brought over from the old website

November 2005

What we perceive is not what we sense

Perceiving a simple touch may depend as much on memory, attention, and expectation as on the stimulus itself. A study involving macaque monkeys has found that the monkeys’ perception of a touch (varied in intensity) was more closely correlated with activity in the medial premotor cortex (MPC), a region of the brain's frontal lobe known to be involved in making decisions about sensory information, than activity in the primary somatosensory cortex (which nevertheless accurately recorded the intensity of the sensation). MPC neurons began to fire before the stimulus even touched the monkeys' fingertips — presumably because the monkey was expecting the stimulus.

Lafuente, V. & Romo, R. 2005. Neuronal correlates of subjective sensory experience. Nature Neuroscience, 8, 1698-1703.

http://www.eurekalert.org/pub_releases/2005-11/hhmi-tsi110405.php

February 2003

Another step in understanding how memories are formed

The electrical activity of individual neurons in the brains of two adult rhesus monkeys was monitored while the monkeys played a memory-based video game in which an image pops up on the computer screen with four targets—white dots—superimposed on it. The monkeys’ task was to learn which target on which image was associated with a reward (a drop of their favorite fruit juice). Dramatic changes in the activity of some hippocampal neurons, which the scientists called "changing cells", paralleled their learning, indicating that these neurons are involved in the initial formation of new associative memories. In some of the cells, activity continued after the animal had learned the association, suggesting that these cells may participate in the eventual storage of the associations in long-term memory.

Wirth, S., Yanike, M., Frank, L.M., Smith, A.C., Brown, E.N. & Suzuki, W.A. 2003. Single Neurons in the Monkey Hippocampus and Learning of New Associations. Science, 300, 1578-1581.

http://www.eurekalert.org/pub_releases/2003-06/nyu-fir060503.php
http://tinyurl.com/ftob