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The Basal Ganglia: Your internal puppet master

Have you ever left your house in the morning and wondered whether you locked the door or remembered to close the window? Have you ever arrived at your destination and realised you had no recollection of the journey? Have you ever completed any mundane task, whilst thinking about, well… nothing? If you have, it’s not the case that your memory is leaving you or that something is wrong with the inside of your head. In fact, things are probably working better than you think.

Every one of us is perpetually bombarded with an assortment of stimuli. You are constantly seeing, hearing, smelling, tasting and touching. There are also the less recognised senses such as balance, proprioception (your sense of your “body position”) and changes in temperature. Whilst you are not consciously aware of most of these sensations, under the bonnet your brain works through this huge array of information and sorts the important stuff from the chaff. Even when you are asleep, you might awaken only to critical sounds such as a baby crying in the next room but not, say, a car driving past the window.

But your brain doesn’t just subconsciously extract the interesting stuff. It takes this information and combines it with your internal body state (Hungry? Tired? Bored?) and uses this to decide how you should act. This processing allows you to interact with your environment, seamlessly performing the most complex or the most humble of tasks.

An example: you are sitting in a chair in a room and the window is open. There is a cold draft so you get up to close the window. You probably don’t think about how to rise out of the chair. When you walk over to the window, you aren’t aware of the hundreds of muscles working in concert to move you. You aren’t considering the position of your legs, how balanced you are or the sense of touch on the soles of your feet. But your brain takes these sensations and executes movements. It all happens automatically without any need for you to be consciously aware of the process.

Below is a different example. This man is playing music on his guitar. He has to make a series of movements that are precise in both time and space. He does this in response to the sound of the notes and feeling and seeing the position of his hands. As he progresses, the subsequent sensations trigger the movements for the next section of the piece. It’s not entirely automatic but he wouldn’t be able to play this piece without having practiced and learned it first.

So why is such concentration required for playing a guitar but not for walking? From your brain’s perspective, any movement that you repeat can be considered “practice”. The more you do something, the better you become and the less you actively think about it. Therefore, it’s simply the case that you spend a rather huge amount of time “practicing” walking but not playing a guitar. Even the greatest Rock God doesn’t spend as much time swinging his axe as he does putting one foot in front of the other. If you picked up a completely new instrument, how much time do you think you would need to learn how to play it? A month? Two months? And how long was it before you learned to walk properly?

Regular guitar playing is also known to result in questionable fashion choices.

Practicing, learning and then reciting these movements is part of your procedural memory. Unlike other forms of memory which are governed by the hippocampus, procedural memory is controlled mainly by the basal ganglia, with a bit of tweaking by the cerebellum. In a previous post, Sarah wrote of HM, an individual who suffered damage to his hippocampi resulting in permanent amnesia. Despite this, he could still be taught mirror writing when encouraged by the scientists working with him. When prompted, he was able to write in reverse with no effort, despite insisting he had no knowledge of ever having done it before!

Players such as Dan Carter are notorious for quick, incisive actions that are beyond that of many of their contemporaries.

Learning a new skill requires a large amount of effort and attention. However, through repetition, the effort and attention required to perform the task can be reduced. For some the practice of complex motor skills consumes their entire lives. In particular, sportsmen and women have huge demands placed upon them during matches, both physical and mental. Whilst the activity of the basal ganglia and procedural memory is certainly not the brain’s only toil, players that are quick thinking and can dictate play are thought to have greater automation of their movement skills, thus freeing up their conscious mind to analyse the game around them.

Even for everyday souls like us this system is utterly indispensable. Below is a man with Parkinson’s disease, which primarily damages the basal ganglia. He is still able to move his limbs, but coordinating himself is a huge challenge.  In the second part of the video he is given a common treatment, L-DOPA, which provides temporary respite. However, eventually even this will not restore normality.

Illnesses such as Parkinson’s highlight why the basal ganglia, like so many parts of the brain, are fundamental to our everyday lives. Helping to treat such disorders is the primary reason for scientific research in this area. However, if it also helps us to understand why sometimes we don’t pay attention when we pack our bags in the morning or lock our front doors, then I think that can be quite interesting too.

Post by: Chris Logie

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