Dendritic Forests and Purkinje Cell Trees

Dendritic Forests and Purkinje Cell Trees

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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

Ref: The Purkinje Neuron Acts as a Central Regulator of Spatially and Functionally Distinct Cerebellar Precursors (2013). Fleming et al., See news story here:

Another installment in the occasional series on #excyting  cell types for #ScienceSunday .

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19 Responses to Dendritic Forests and Purkinje Cell Trees

  1. So intricate. Explains those millions of years.

  2. Rajini Rao says:

    R Prakash Prakash , yes indeed! To quote from the link in the post, “the ones in your brain are the same shape as the ones in the brain of a fish, bird, reptile or the earliest vertebrate” (quote from Dr. James Bower).

  3. Thanks Rajini Rao I am probably among those living in the best of times.

  4. Amber Peall says:

    I have to apologize. I saw the first image, saw the caption “little brain”, and my first thought was about penises.

    Thanks though, it is very interesting reading…

  5. Rajini Rao says:

    Amber Petchey , lol. A good topic for future post. 

  6. Kathryn Kure says:

    Rajini Rao did you see that interesting recent medical science story as to why a few MDs hypothesise James Bond prefers his martinis shaken, not stirred?

    From the evidence presented in the novels, seems Mr Bond is highly likely to be one of those people suffering from a persistent hand tremor.

    The MDs speculated James Bond would probably only make 59 if he were a real person. Interestingly enough, Ian Fleming, the author, who it seemed IRL was a hard-drinking, heavy smoker, just like Bond, only made it to 56 before clocking out.

    Three people independently read all of his novels (bar two – one was short stories only and one was eliminated since Bond only appears 2/3 way through). They counted number of drinks and number of days … the total is astounding, but would definitely cause a hand tremor.

  7. Rajini Rao says:

    Kathryn Kure , yes I did see that story. It turns out that the science behind Bond’s martinis is a popular topic and comes up in the news regularly. The last time it did, I wrote a post on “shaken not stirred”

    We do romanticize alcoholism, as we do cigarette smoking, in books and movies. No doubt there is a high price to pay for that. 

  8. Jim Carver says:

    Rajini Rao “Resistance is futile”, said the superconductor. 😉

  9. Jim Donegan says:

    Great topic, this. I can remember many years ago at university considering the computational complexity involved in handling even a simple act like touching one’s own nose with a finger. After a hour or so we couldn’t even estimate the algorithm involved at the level of cells like purkinje cells. Believe me it’s stupendously complex (adopting a mathematical/computational model). And yet our brains manage far more complex tasks.

    The day that someone figures this out I hope there is something even better than a Nobel handed out! It’s just possible now to trace the activity of individual axons using MRI so maybe – just maybe – some better understanding is coming along soon.

  10. Rajini Rao says:

    Jim Donegan , well said. The computing mechanism (what we know of it) of the cerebellum alone is incredibly complex: thousands of noisy/weak parallel spikes superimposed on to slow but strong stimulus.

  11. We’re all made of fractals!  :^D

  12. Rajini Rao says:

    Shaker Cherukuri , I agree..not the entire brain, which is unlikely to have any unique solution to a given problem or stimulus. More like sections of it, such as decoding vision or computing movement. Event that seems quite far from a tractable problem at this time. 

  13. Hemant Dave says:

    Rajini Rao “It is thought that an imbalance in these two opposing functions can underlie psychiatric and neurodevelopmental disorders including schizophrenia and autism spectrum disorders.” Does yoga help in restoring the balance of the opposing functions? I firmly believe that with a given frame of mind, one can have required chemicals generated in body! Please tell what you think about it. Others are also well come!

  14. Very informative post help to understand the brain function to be mimiced in A I machines in near future.

  15. merci beaucoup par votre responsabilité!

  16. Rashid Ellis says:

    Hi Rajini! Would you happen to know how electric eels generate their electricity? Is it like nervous system potentiality or different mechanism?

  17. Rajini Rao says:

    Rashid Ellis electric eels generate electricity using stacks of specialized muscle cells, each of which has packed ion channels similar to the ones found in the nervous system. 

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