Are you lucky enough to have killed off your inactive cells? what does your doctor think?
http://www.alphagalileo.org/ViewItem.aspx?ItemId=169983&CultureCode=en
For the first time, Tübingen neuroscientists were able to
differentiate between active and inactive cells in the brain
morphologically, i.e. based on the cells’ structure. Investigating
granule cells in the rat’s brain, they found a much larger proportion of
inactive than active cells.
Many things we think we know about the world have their origin in
popular culture, not science. The most well-known false ‘fact’ about the
brain is the misconception that we only use ten percent of the brain’s
overall capacity. This so-called ’ten percent myth’, while accepted as
such by neuroscientists, still regularly figures in advertisement, but
also in books and short stories as well as films. As with any myth,
however, there is a kernel of truth at the core of the matter: many
neurons remain dormant for most if not all of our life, even while their
direct neighbours show regular activity.
A team of neuroscientists led by Dr. Andrea Burgalossi of the Werner
Reichardt Centre for Integrative Neuroscience (CIN) at the University of
Tübingen have now taken an important step towards understanding why
some neurons are active and others are not: they can tell them apart
morphologically. To be able to do so, the investigators employed
so-called juxtacellular recordings in freely-moving rats. With this
technique, electrodes are inserted right next to individual, functioning
neurons in live organisms. This allows recording action potentials from
these neurons while they work, and while simultaneously identifying the
cells that the recordings are taken from for later analysis.
During this analysis, morphological traits of the analysed cells are
identified, most importantly their dendritic arbors, i.e. the filament
structures which receive input signals from other neurons. The cells
under investigation were granule cells (GCs) in the rat’s dentate gyrus
(DG). Dentate GCs have been shown to be intimately connected to
individual memories of places and individuals, and thus playing a
central role in memory tasks.
The researchers recorded from 190 GCs, only 27 of which they found to
be active (ca. 14 percent). While this seems to give credibility to the
‘ten percent myth’, the team actually expected this outcome, as the DG
is a brain structure where in any given task, only a very small
percentage of neurons take part, while their neighbours remain dormant,
waiting for their ‘cue’, as it were. Memory functions in the brain work
according to a principle that neuroscientists call ‘sparse coding’, i.e.
a comparatively small number of neurons encode complex information –
possibly to make overlap between different memories more unlikely.
Using a smaller subsample, the scientists looked for correlations
between active and passive functionality and the respective cells’
morphology. Their results show that active GCs have much more complex
dendritic arbors. They not only transfer and receive information from
many more neurons than the inactive ones, they also have better cellular
‘infrastructure’ to do so. Despite their as of yet limited sampling,
the scientists are positive that they can now tell apart active and
inactive GCs, mostly by merely looking at them. “Explaining the causes
of activity in some and inactivity in other neurons may still take a
long time”, cautions Burgalossi, leader of the research group. “But
finding a direct link between function and morphology is an important
step forward. It will be even more challenging to find evidence of
causality. But we are on the right track.”
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