That Neuroscience Guy - Neuroscience Bites-The Primary Sensory Cortex

Episode Date: May 26, 2023

For this week's neuroscience bite, we discuss the primary sensory cortex, a brain area important for how integrate sensory information from our environment. 

Hi, my name is Olaf Kregolsen, and I'm a neuroscientist at the University of Victoria. And in my spare time, I'm that neuroscience guy. Welcome to another neuroscience bite. So on season five, we're going to continue with what we did in season four, which is some of the bites are going to be about neuroanatomy. Some of them are going to be book reviews or things I think are interesting, and some are going to be topical. So pick the ones you like and listen to them. Hopefully you listen to them all. On today's bite, I'm going to continue with neuroanatomy and specifically the somatosensory cortex or the primary sensory cortex. We've talked about it a lot across various episodes, but I just want to focus in on the neuroanatomy and how it works specifically.

So the somatosensory cortex, or the primary sensory cortex, is a region of the brain. It's just behind the central sulcus. So the central sulcus sort of is a dividing region. Now, you have a whole bunch of sulci, but one of the biggest ones is the central sulcus, and it goes left to right across your brain, and it separates the frontal cortex from the parietal cortex. And the somatosensory cortex is just posterior to the central sulcus. It's the first or most anterior part of the parietal cortex, and basically it's where all sensory information comes, at least in terms of somatosensation

or proprioception. So what do I mean by that? Touch, temperature, pain, you know, obviously not vision, hearing, smell or taste, but this is where all of those body sensations come. And let's just do a quick experiment to explain how it works. If you take the index finger of your right hand and you start tapping the palm of your left hand, you should be able to feel that. If you can't, you should see your doctor. But what's happening when you sense this? Well, underneath the skin on the palm of your left hand, there's a whole bunch of what we call sensory receptors. Now, these are actually just neurons, all right? The dendrite of the neuron, if you remember back to previous episodes, the dendrites where information comes in,

well, at the end of it, it's got a very specific receptor that is literally sensitive to the pressure when you touch the hand, just as a cold receptor in your hand would be sensitive to cold, a heat receptor would be sensitive to heat, a pain receptor is receptive to things that cause pain. So when you tap your hand, you're actually firing a neuron. You're firing a bunch of neurons because the end of your finger is very big, but you're firing a neuron. And that neuron, when it fires, the information flows up the axon to the spinal cord. It attaches to another neuron.

That flows up to the thalamus where it attaches to another neuron, and then it goes up to the primary sensory cortex. And the primary sensory cortex is arranged a lot like the primary motor cortex. We call it a humunculus, which is basically just a representation of the body. So there's a sensory region for the palm of your hand, but there's also for your biceps, muscle, your triceps, your face, your shoulder, your feet, every part of your body is represented there. And if you go to the blog on olivkrigolson.com or thatneuroscienceguide.com, I'll put a post and show you where it is and write a little blurb about it. But basically when you tap the palm of your hand, your brain is receiving that. And this is how your body knows what's going on, or at least your brain

knows what's going on with your body. Right now, as you're listening, these sensory receptors across your entire body are firing, conveying all of that information to the primary sensory cortex. And what the primary sensory cortex does with it is just receive it. It doesn't do a lot of processing. It's just a mirror replication of what you're sensing in the world. What it does do is pass that information to what are called sensory association areas. And I'm going to talk more about that in future episodes. But what those sensory association areas do is they integrate the information into a representation of your body and its current sensations.

All right, there's a little bite on the primary sensory cortex or the somatosensory cortex. Like I said, if you check out my blog, olafkrigolson.com or thatneuroscienceguy.com, they link to the same place. All right, I'll put up a map and a little blurb about the primary sensory cortex. And of course, I'm not going to go through it all, but please check out the website, thatneuroscienceguy.com, links to Etsy and Patreon. Of course, DM us ideas and follow me on Twitter at thatneuroscienceguy. And thank you so much for listening to the podcast, and please subscribe if you can. My name is Olof Kregolsen, and I'm that neuroscience guy. Thanks for listening to this neuroscience bite, and I'll see you in a few days

for another full episode of the podcast.