Gordon Johnson: Doctor, I’d like to continue with our brain anatomy lesson. We talked about the four basic overview parts of the brain, but I would now like to have you take us through some of the subparts of those brain and, and give it in a way that people can follow, both through your words and, and the demonstrative tools, what it is that we’re talking about.
Dr. Erin Bigler: Well, very good. I’m going to take this brain model here and this is one that I use in my neuro anatomy class, and it’s basically modeled after an adult, male brain. This is approximately the true size of an adult male brain. It would be approximately the size of my brain. I’ve already showed the four lobes, but I’ll just point that out again. So, we have the temporal lobe here, occipital lobe, here. Next up is the parietal and it comes to this point right here, where we see this sulcus so the the indentations are referred to as sulci and a single one is a sulcus.
Gordon Johnson: Can we rotate that a little bit better so we can see that.
Dr. Erin Bigler: So you can see that. So this is the central sulcus and in front of that is the frontal lobe. In back of that is the parietal lobe.
Gordon Johnson: So, we have four basic lobes.
Dr. Erin Bigler: Yes.
Gordon Johnson: We turn it this way, we have the frontal, the parietal, the occipital and the temporal. Is that correct?
Dr. Erin Bigler: That’s correct. And, I’m going stick with this for just a moment because at the cortical surface area, this back part of the frontal lobe is where motor cortex is.
Gordon Johnson: Now you used the term cortical surface. What do you mean?
Dr. Erin Bigler: So this is the cortical surface. It’s the outer surface of the brain. When I open this up, I’ll be able to explain that a little bit further. So, cortex is like the bark. In fact I, I think that’s the Latin term for it is bark. So, it’s like the bark of a tree that you’ve pulled off. This area here is the motor cortex. So, if someone has paralysis as a result of a surface injury to the brain, it’s likely that there’s damage here. Now, it’s organized in a way that the face and hand area is here and then the upper torso and then low and middle torso and then the legs are down in between, and we’ll look at that some more in, in a minute. Just behind this is the touch perception area so the front part of the parietal lobe is the touch perception area.
Gordon Johnson: Okay, so let me see if I can help with that. Moving my hand is going to be controlled by that portion of the frontal lobe, which is the motor area …
Dr. Erin Bigler: On the opposite side.
Gordon Johnson: Okay, so I’m moving my right hand, and somewhere up here, more or less, that is making that choice. But if I’m actually going to touch that and feel what the cortical area feels like, I’m not just using my motor area. I’m actually using my senses of touch –
Dr. Erin Bigler: Correct.
Gordon Johnson: To feel that texture.
Dr. Erin Bigler: Correct.
Gordon Johnson: And now that’s a little bit further back in the brain.
Dr. Erin Bigler: The touch part of it is further back but notice that you’ve actually moved so you actually have what’s called joint perception so your joints have receptors that fire off as you move and you’re guiding your hand with your vision. So, you’re engaging the occipital lobe back here. You’re engaging somatosensory cortex which is paying attention to joint position and what you’re feeling and then you’re moving, which involves this area. But even more importantly, you anticipated the question and then you started to initiate the movement. So that planning and organization happens up here in this premotor area and this motor and frontal association cortex. So all of a sudden you did something that was very, very simple and very, very basic, yet it shows the different networks and the way the brain interacts.
Gordon Johnson: And somewhere in there the cerebellum was involved, too?
Dr. Erin Bigler: Somewhere the cerebellum was involved but you’re in a sitting position and so you’re already maintaining postural control and the cerebellum does play a role because it is also connected to visual cortex and ocular movement and guidance of the hand. And notice when you were pointing here, you didn’t have tremor and you didn’t overshoot, which can be signs of cerebellar problems or another part of the brain that I’m going to point to in just a moment.
Gordon Johnson: And if you dropped that and I caught it, it would, may be all those years of playing Frisbee.
Dr. Erin Bigler: That’s correct. Yes, the motor learning and that motor memory just kicks right in, just like riding a bike when you haven’t done it in a long time.
Gordon Johnson: Okay.
Dr. Erin Bigler: So now, now if we turn the brain this way and we look at this part of the temporal lobe, this is where auditory perception begins.