Dendritic Forests and Purkinje Cell Trees
● The Little Brain: Tucked under and in the back of our two major brain hemispheres is the cerebellum (Latin for “little brain”). Best known for coordinating fine motor skills, the cerebellum receives signals from the spinal cord and other parts of the brain to refine and compute an output that lets us reach out and precisely touch an object with the tip of our finger. All of this output is made by a single type of cell: the Purkinje neuron. Not surprisingly, they have been described as, “the only source of news, the sole TV network, the cerebellar state-controlled media”.
● A Primer on Purkinje Neurons: These are among the largest and earliest neuron types to be described (by Czech anatomist Jan Evangelista Purkyně in 1837). Arranged in a domino-like layer (image 1-2) in the cerebellum, each neuron has a distinctive tree-like shape (image 3), with elaborate branches called dendrites which make contact with other neuron types. Each Purkinje cell makes >200,000 contacts with other cells, receiving enormously noisy informational input which is then selectively suppressed and sculpted by a complex algorithm that is not fully understood.
● Sentinel Circuit: New research shows that Purkinje neurons release factors that trigger development of two very different cell types (excitatory and inhibitory) in the cerebellum. Curiously, these cells then regulate the activity of the Purkinje cells themselves. Why? This may be an elaborate means of self regulation. It is thought that an imbalance in these two opposing functions can underlie psychiatric and neurodevelopmental disorders including schizophrenia and autism spectrum disorders.
A great pop-sci read titled Purkinje World: http://goo.gl/nJiS1J
Ref: The Purkinje Neuron Acts as a Central Regulator of Spatially and Functionally Distinct Cerebellar Precursors (2013). Fleming et al., http://goo.gl/lmf0Kq. See news story here: http://goo.gl/gJILgo
Another installment in the occasional series on #excyting cell types for #ScienceSunday .