Gordon Johnson: Doctor, let’s talk more specifically about the temporal area.
Dr. Erin Bigler: So the temporal lobe here, on this lateral surface, this outer surface, this area here the very top is called the superior temporal gyrus. So, the sort of lumps that you see here, these are gyri, singular is gyrus. So the superior temporal gyrus houses some of the auditory receptive areas of the brain.
Gordon Johnson: Okay, let’s see if I can help the memory of those watching a little bit from a trick I learned. The gyri, I like to think of them as the little hills that gyrate around the surface of the brain.
Dr. Erin Bigler: Correct.
Gordon Johnson: Is that basically the source of that term?
Dr. Erin Bigler: That is correct.
Gordon Johnson: Now, the sulcus, I’m not sure, I haven’t come up with a trick for that one. The sulcus are the little valleys.
Dr. Erin Bigler: They’re the indentations or valleys.
Gordon Johnson: And, what’s the latin derivative – how did valleys get to be sulcus? Any ideas?
Dr. Erin Bigler: I could look it up. There’s a whole index that gives you all that but I can’t think of it off the top of my head.
Gordon Johnson: Can we take this apart so we can see the temporal lobes?
Dr. Erin Bigler: Yes. The only thing is to take it fully apart, I have to go all the way through, so.
Gordon Johnson: Well, I just sort of stretched it apart and that is, in fact, you can sort of see.
Dr. Erin Bigler: So, if we pull that, this is what’s referred to as the –
Gordon Johnson: Reflexes.
Dr. Erin Bigler: – you did, great. This is the sylvian fissure that’s in here and then this is an insulated part of the cortex. And, so this is called insular cortex.
Gordon Johnson: And, is that part of the temporal lobes?
Dr. Erin Bigler: Well, some of it is part of the temporal lobe and some of it is part of the frontal lobe.
Gordon Johnson: Is it actually in real life as distinct from the part I caught when this part as it seems to be in the model?
Dr. Erin Bigler: Absolutely. This is the thing that’s really remarkable when you actually have a real postmortem brain. Note that I can stick my finger all the way down the whole length of my finger until I hit the top of the corpus callosum.
Gordon Johnson: And, when you’re talking about postmortem, you’re talking about a brain that would be autopsied.
Dr. Erin Bigler: That’s correct. So what I’m showing you here is in many respects that we have two brains in one. See, we isolate this here and I can take the inferior part of the frontal lobe and –
Gordon Johnson: The lower part.
Dr. Erin Bigler: The lower part and notice that we literally have two hemispheres here that are connected by this structure right here, the corpus callosum. Now we’re looking at the temporal lobe here. And, if I turn the temporal lobe up, eventually we’re going to get to a structure that’s right in here. So this is the medial part of the temporal lobe.
Now, while I’m pointing to this right here, a very important aspect of understanding some of what goes on in head injury I think occurs by this anatomical positioning of the medial part of the temporal lobe to this lateral part of the upper brain stem. So, the upper brain stem as I pointed out earlier has that reticular activating system. So if you are stretching or twisting this part of the brain stem, you may lose consciousness but that may also be an indication that this inner aspect of the temporal lobe is also being stretched or mechanically deformed or hitting bone. And, right in here is where the hippocampus is. And, the hippocampus is this critical brain structure that I’ll show in a minute on memory.
Gordon Johnson: Now, before we leave this area and we’ve got our model kind of half falling apart here. Maybe you’re better in putting it back together than I am, but I’d like to match up what you just showed us in terms of the brain stem and the lower part of that, you called it the medial –
Dr. Erin Bigler: The medial temporal lobe.
Gordon Johnson: – temporal lobe.
Dr. Erin Bigler: Well, the problem is that this model is too big for this brain. So, this is actually a female skull and this is a model of a male brain. So, it, I, but I can use a different model to show.
Gordon Johnson: But, essentially what that part, the brain stem would come back out.
Dr. Erin Bigler: Yes.
Gordon Johnson: And, these areas that you’re concerned about in the medial temporal lobe, the lower part of the temporal lobe it’s these.
Dr. Erin Bigler: So, what I used was my thumb as the analogy. So, if you look at the thumb, the thumb is basically sitting in the position of the brain stem and then the medial temporal lobe is right there. This is where the hippocampus sits. Right in this position right here. And, you can see all of these bony structures here and then there’s also an element of the meninges, the dura, that comes along right there and that’s what it hits.