[MUSIC] Let's remind ourselves of the primary areas in cortex. So if we're looking now here at the left side of the brain, you can see the spinal cord down here, you can see the cerebellum here and then the rest of this is the left hemisphere of the brain. And we're going to show where four areas are. So, remember that this is the frontal lobe, and in the frontal lobe is a strip, which is motor cortex, and right behind that strip is a sulcus, that we call the central sulcus. And then the gyrus right behind the central sulcus is somatosensory cortex, primary somatosensory cortex. So we call primary motor cortex, we can call that M1 and primary somatosensory cortex we can call that S1, saves me a lot of writing. Down here in the temporal lobe right around here, is A1, that's auditory cortex, primary auditory cortex and back here is visual cortex. And remember most of visual cortex peeks around on the medial surface of the hemisphere, so most of it's not visible from right here. So the hemispheres are specialized because this, the left hemisphere primary motor cortex in left hemisphere is not going to move the left hand. It's going to move the right hand, but they're not specialized in the sense that it's analogous. The left motor cortex moves the right hand and the right motor cortex moves the left hand. The somatosensory, again, somatosensory information comes in so the left cortex gets information from the right side of the body, the right cortex gets information from the left side of the body. The situations are a little bit different for auditory and visual cortex. Auditory cortex, we basically get input from both ears. There might be a predominance for the contralateral ear, for the ear on the other side, but for the most part it's a minor predominance. So auditory cortex is not the other side of the other ear, it's not serving the other ear. Visual cortex is serving, not the other side's eye, but the other side of the world. So my left visual cortex sees everything that's on the right, whether that's coming from my right eye or my left eye. So it sees the other side of the visual world, which we call the visual field. Now, that's essentially a symmetrical distinction. So the left hemisphere is seeing the right world and the right hemisphere is seeing the left world. Is there anything that is different? And the thing that's really different is language. Language is in the left hemisphere and it's not in the right hemisphere. So what we're going to do now is look at aphasia. We're going to look at aphasia, which is a disorder of language, and it is a disorder of the left hemisphere. [MUSIC]