I have piles of fascinating intentions on my desk(s). Lotsa interesting science news comes by that I’d like to abstract for this blog. And rarely get to. This one is unique and too important to be put off. It’s about human glial cells…and how, when grown in mouse brains, the mice get smarter. Reminds me of the Pigoons in Margaret Atwood’s great MADADAM trilogy–the pigoons are pigs with human cell components that are more than a match for their human competitors. This particular neuroscience story, from Science News, August 22, 2015, heralds a shifting paradigm in neuroscience. Glial cells do more than “protect and serve” neurons in the brain, they facilitate the connectivity itself. After reviewing the Science News article, I will draw a connection between glial cells and neurofeedback as we apply it in practice. The article, with the long title and summarizing subtitle, Rethinking which cells are the conductors of learning and memory: Brain cells called glia may be center stage when it comes to how humans learn and remember is by Ashley Yeager. The article is posted online and is available to subscribers and university community. It begins with a story and a couple of paragraphs of context:
A mouse scurries across a round table rimmed with Dixie cup–sized holes. Without much hesitation, the rodent heads straight for the hole that drops it into a box lined with cage litter. Any other hole would have led to a quick fall to the floor. But this mouse was more than lucky. It had an advantage — human glial cells were growing in its brain.
Glia are thought of as the support staff for the brain’s nerve cells, or neurons, which transmit and receive the brain’s electrical and chemical signals. Named for the Greek term for “glue,” glia have been known for nearly 170 years as the cells that hold the brain’s bits together. Some glial cells help feed neurons. Other glia insulate nerve cell branches with myelin. Still others attack brain invaders responsible for infection or injury. Glial cells perform many of the brain’s most important maintenance jobs.
But recent studies suggest they do a lot more. Glia can shape the conversation between neurons, speeding or slowing the electrical signals and strengthening neuron-to-neuron connections. When scientists coaxed human glia to grow in the brains of baby mice, the mice grew up to be supersmart, navigating tabletops full of holes and mastering other tasks much faster than normal mice. This experiment and others suggest that glia may actually orchestrate learning and memory, says neuroscientist R. Douglas Fields.
The Science News review is important for pointing us non-neuroscientists toward a new way of understanding the function of glial cells in the brain. The paradigm shift begins as we understand that “the neuron is [not] the only active cell type in the central nervous system” and that “learning and cognition are [not] solely the domain of neurons.” All glial cell types appear to have a role in brain plasticity. Reviewing the known functions of the three major known glial cell types, microglia seem to have the least effect on information processing. RD Fields summarized that microglia
- Travel and respond to nervous system injury and infection
- Monitor electrical activity in neurons and prune synaptic connections
- Their dysfunction is involved in almost all nervous system diseases and in certain psychiatric conditions, including obsessive-compulsive disorder
Astrocytes and oligodendrocytes are more interesting in terms of information processing and signal control. Each seems to have a role in “helping neurons keep their electrical signals flowing at a healthy rhythm.” We have long-known that oligodendrocytes are associated with myelin production of the “insulation” around neurons. Now we are finding the process is far more active than simple insulation of electrical impulse flow in neurons’ axons. Fields’ group has shown that “myelin speeds the transmission time of electrical signals along axons. It takes a signal 30 milliseconds to cross from the left to the right side of the brain on myelinated axons. A similar signal takes about 300 milliseconds on un-myelinated axons. Slight changes in the thickness of myelin layers on axons may tweak the timing of the brain’s electrical signals just enough to bolster learning and memory or do damage.”. MRI brain scans revealed structural changes in the myelin-wrapped white matter in children, teens and adults learning to play piano and in adults who learned to juggle. The jugglers’ brains showed increased white matter at the back of their right intraparietal sulcus — a crease at the back of the brain that helps with visually guided grasping of objects. Individuals who weren’t learning the new skill showed no changes. As an adult learns a new skill like juggling, the brain may be churning out new oligodendrocytes, which then wrap extra myelin around the axons of the neuronal circuits being built.” [quotations from the Science News article]. Oligodendrocytes
- Form myelin around neurons, substantially increase signal speed
- Provide vital metabolic support for axons
- Problems with these cells are implicated in multiple sclerosis, amyotrophic lateral sclerosis and inhibition of repair after spinal cord injury [Fields].
Research on astrocytes has made major contributions as we are developing the new paradigm. Now we know that it is known that they use chemical mediation (glutamate release) to maintain the organizing gamma rhythms (25-60 surges per second) that in mice are responsible for healthy curiosity and adaptation to new environments. It is known that in flies, astrocytes “nudge neurons’ electrical signals along or slow them down.” Equally intriguing (to me) are the findings that some types of astrocytes are very long and appear to be involved in long-range signaling across the cerebral cortex. This finding reminds me of Karl Pribram’s discovery of communication patches in the cortex associated with chemical signaling; these patches are sensitive to local field changes capable of wavelet communication consistent with holonomic brain theory. Astrocytes
- Wrap around synapses, influencing signaling and nerve birth and growth
- Respond to injury by producing proteins
- When dysfunctional, implicated in many neurological and psychiatric disorders, such as epilepsy and schizophrenia [Fields]
In short, we are learning that glia have a major role in the brain’s information processing functions. Where is this leading? Karl Pribram (1919-2015) was decades ahead of us when he teamed up with theoretical physicist David Bohm to model non-linear dynamic communication and the application of wavelet analysis in the brain. Contemporary neuroscience is beginning to have the observational tools to delineate the role that the various glial cells play in mental function. The developing paradigm of harmonic system emergence–which we can hazily see that glia are part of– will help us out of the modern dependence on nerve structure/function for an explanation of mental phenomena. Undoubtedly, we are coming to a new scientific way of thinking about the neuroscience of thinking. One must remain skeptical, however, that there is an imaginable way to use science, in any paradigm’s perspective, to “see” thought in its non-materialist manifestation and generation.
I touched briefly on the topic of glial cells and neurofeedback in a blogpost October 28, 2013, entitled Neurofeedback WORKS–how?. I noted then-recent research about the association of glial activity and a kind of cyclic “brainwashing” in which glial cells swell when the brain is active, and shrink during sleep, basically controlling the chronobiology of cerebral spinal fluid. I also referenced a helpful blogpost by David Kaiser PhD that described research from Mario Beauregard’s laboratory about brain changes with neurofeedback–changes that point to glial influences with strengthened connections between brain areas (mediated by the Central Executive Network, the CEN). Kaiser discussed EEG biofeedback (called “Endogenous Neuromodulation”) in an article with Siegfried Othmer and others, published in Seminars in Pediatric Neurology December 2013; that article explores how neurofeedback modulates Neural Networks and brain plasticity. These articles do not speculate about the function of glial cells in the dynamics of the key control networks, the Default Mode Network, the CEN, and the Salience Network; rather they discuss dynamics of plasticity that we now realize are mediated by glial activity. Although I have seen reports claiming that EEG neurofeedback is effective because it is directly mediated by feedback loops including glial cell activity, that is a leap to which we as yet have no coherent evidence.
The brain activities of glial cells are like dark matter, black holes, and quantum particles; we know just enough to project on to them all sorts of functions that we really do not have the tools to comprehend. Yet we see that glia are involved in the exciting observations about brain plasticity and information processing. The new paradigm is not quite visible, but it is taking shape to be seen by those will keep looking toward the emergent/deteriorating edges of what we think we know and visualize.