That doughnut shape decorated with bright green spots, some connected by red pathways, amidst sky blue neighbors could be an artist's creation, but is the result of a creative scientific attempt to grow an active brain in a dish, complete with memories. Really.
Researchers at the University of Pittsburgh published this stunning study in the journal Lab on a Chip {the full paper can be accessed here.} When I first learned how to grow cells in a lab, the technique of tissue culture, the idea of even growing brain cells was a far-fetched dream, much less brain cells capable of forming networks, complete with biological signals.
How did they do it?
To produce the models, the Pitt team stamped adhesive proteins onto silicon discs. Once the proteins were cultured and dried, cultured hippocampus cells from embryonic rats were fused to the proteins and then given time to grow and connect to form a natural network. The researchers disabled the cells' inhibitory response and then excited the neurons with an electrical pulse.Zeringue and his colleagues were able to sustain the resulting burst of network activity for up to what in neuronal time is 12 long seconds. Compared to the natural duration of .25 seconds at most, the model's 12 seconds permitted an extensive observation of how the neurons transmitted and held the electrical charge, Zeringue said.
From the paper's Abstract: {excerpted for clarity}
Persistent activity in the brain is involved in working memory and motor planning. The ability of the brain to hold information 'online' long after an initiating stimulus is a hallmark of brain areas such as the prefrontal cortex. Recurrent network loops such as the thalamocortical loop and reciprocal loops in the cortex are potential substrates that can support such activity. However, native brain circuitry makes it difficult to study mechanisms underlying such persistent activity. Here we propose a platform to study synaptic mechanisms of such persistent activity by constraining neuronal networks to a recurrent loop like geometry. Using a polymer stamping technique, adhesive proteins are transferred onto glass substrates in a precise ring shape. Primary rat hippocampal cultures were capable of forming ring-shaped networks containing 40-60 neurons. Calcium imaging of these networks show evoked persistent activity in an all-or-none manner. Blocking inhibition leads to an increase in the duration of persistent activity. These persistent phases were abolished by blockade of asynchronous neurotransmitter release by ethylene glycol tetraacetic acid.
This is amazing. I wonder what the "memory" could be - could be a good subject for a science fiction story.
Source: Scienceblogs
