[lecture] Five senses
Mar. 30th, 2011 03:06 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
magidLast night I went to the third of this spring's four mini-med school lectures at Harvard's Longwood campus. The title was "From Vision to Touch: Exploring the five senses," and the handout is downloadable at the link (as are those from the two previous sessions, as well as videos). These are based on my notes; obviously, once the video is available, you can see how much I missed :-).
First up was Professor Datta (yes, pronounced "data," which is kind of fabulous), talking about sense in general, and about smell. He started talking about how all reality is virtual reality for the brain, since our senses extract information from our environment, but is not our environment, a map or spatial transformation of the environment (many visual examples of compressing information and mapping). Different species have different sense for extracting data, such as echolocation/sonar in bats or thermal sensing in (some?) snakes.
Smell is different from vision, hearing, and touch, because it is not topographically mappable in the same way. There are specialized olfactory sensory neurons, with each different smell triggering different combinations of receptors. Interestingly, a given smell has the same pattern of receptors in different individuals. However, the pattern is different in different parts of the brain, from the olfactory bulb to the other, farther back parts. Some of these parts are invariant, which might be part of innate odor information with behavioral consequences. (He showed a video in which a mouse's brain was stimulated in such a way that it thought it was smelling scent when it wasn't. (It was much more coherent than these notes imply, actually.)
Next was Dr. Livingstone (yes, presumed :-) talking about vision, especially about art, color, and luminance. There are two parts of the brain having to do with vision. One part is the 'what system,' dealing with object, face, and color recognition. The other part is the 'where system,' dealing with motion, depth, and spatial organization. She showed how the where system is colorblind. On the other hand, showing depth is related to luminance, in whatever color. On the other hand, color is coarse. Central vision is more detailed, while peripheral vision is more large, blurry. Face recognition focuses on extremes, not average stuff. The brain pays attention to extremes. Also, we're wired to recognize faces. Also, it's vision information processing, not image transformation. All of this was accompanied by visual demonstrations and art analysis, showing how visual artists know some of this, if perhaps instinctively rather than neurologically.
Third was Dr. Schlaug speaking about hearing, more specifically, the most complex sound we perceive, which is music. Music triggers emotions when we listen to it, and when making music, it can change the networks in the brain (and he had images comparing brains of musicians and non-musicians). Making music more frequently links the music and motor systems in the brain more. He talked (and showed slides) about how tone-deaf people lack a bit of connection in their brains between what is heard to a template of what it should be, lacking the right kinds of feedback to be able to change their sound (he has a test on tone deafness at his site, which has more detail about his studies on music). He studies how making music can connect the auditory and motor systems better, which can lead to improvement in neurological disorders. He showed video of how aphasic patients who could sing but not speak the same words, nonverbal (but comprehending) autistic-spectrum kids who had auditory-motor mapping training learning to speak, and patients with Parkinson's moved very differently when listening to favorite music with a beat close to their natural stride (rhythmic-auditory stimulation).
Fourth was Prof. Liberles talking about taste. Taste buds sense sweet (energy-rich sugars), sour (the taste of protons, of acids), salty (NaCl), bitter (a warning, often, also involved in caffeine, hops, and nicotine, that people can condition themselves to like), and savory (glutamate, amino acids that are part of proteins). Interestingly, bitter has more variety than sweet, which are all similar carbohydrates, so there is a wide range of bitter receptors, while all the sweet ones are similar. There are other influences on taste, including fat, metallic, and temperature (which included capsaicin and menthol, interestingly).
And last (but not least, of course) was Dr. Oaklander talking about touch, which is different from the other senses because it is perceived widely, mostly through the skin. Somatosensation, body sensation, is influenced by the nervous system, attention, memory, and emotion. The greatest sense of touch is on the face, especially the lips, and on the hands, especially the index finger. There's a variety of sensory receptors in the skin, reacting to thermal change, (light) touch, pain (in a variety of ways), and pressure. Interestingly, some touch receptors are involved in reacting to foods, which is why chilis are hot and mint is cool. Also, there are cold receptors on blood vessels (so 'one's blood can run cold' indeed). She had a theory about sensing itch which didn't seem convincing to me, about how our African/Middle Eastern ancestors lived in places where insects carried disease, so while pain triggers moving away from something (and is definitely useful, when not chronic and neuropathic), itch triggers moving towards and touching, to get the theoretical insect away. Which rang pretty false to me, especially since if one is too slow, then scratching would make the poison move more into the body.
There was a Q&A session after, which I crocheted through. I realized only later that I would have been interested to hear what they would have said about how some people taste cilantro differently (guess who's included in this group :-). And how people's tastes change over time, too.
First up was Professor Datta (yes, pronounced "data," which is kind of fabulous), talking about sense in general, and about smell. He started talking about how all reality is virtual reality for the brain, since our senses extract information from our environment, but is not our environment, a map or spatial transformation of the environment (many visual examples of compressing information and mapping). Different species have different sense for extracting data, such as echolocation/sonar in bats or thermal sensing in (some?) snakes.
Smell is different from vision, hearing, and touch, because it is not topographically mappable in the same way. There are specialized olfactory sensory neurons, with each different smell triggering different combinations of receptors. Interestingly, a given smell has the same pattern of receptors in different individuals. However, the pattern is different in different parts of the brain, from the olfactory bulb to the other, farther back parts. Some of these parts are invariant, which might be part of innate odor information with behavioral consequences. (He showed a video in which a mouse's brain was stimulated in such a way that it thought it was smelling scent when it wasn't. (It was much more coherent than these notes imply, actually.)
Next was Dr. Livingstone (yes, presumed :-) talking about vision, especially about art, color, and luminance. There are two parts of the brain having to do with vision. One part is the 'what system,' dealing with object, face, and color recognition. The other part is the 'where system,' dealing with motion, depth, and spatial organization. She showed how the where system is colorblind. On the other hand, showing depth is related to luminance, in whatever color. On the other hand, color is coarse. Central vision is more detailed, while peripheral vision is more large, blurry. Face recognition focuses on extremes, not average stuff. The brain pays attention to extremes. Also, we're wired to recognize faces. Also, it's vision information processing, not image transformation. All of this was accompanied by visual demonstrations and art analysis, showing how visual artists know some of this, if perhaps instinctively rather than neurologically.
Third was Dr. Schlaug speaking about hearing, more specifically, the most complex sound we perceive, which is music. Music triggers emotions when we listen to it, and when making music, it can change the networks in the brain (and he had images comparing brains of musicians and non-musicians). Making music more frequently links the music and motor systems in the brain more. He talked (and showed slides) about how tone-deaf people lack a bit of connection in their brains between what is heard to a template of what it should be, lacking the right kinds of feedback to be able to change their sound (he has a test on tone deafness at his site, which has more detail about his studies on music). He studies how making music can connect the auditory and motor systems better, which can lead to improvement in neurological disorders. He showed video of how aphasic patients who could sing but not speak the same words, nonverbal (but comprehending) autistic-spectrum kids who had auditory-motor mapping training learning to speak, and patients with Parkinson's moved very differently when listening to favorite music with a beat close to their natural stride (rhythmic-auditory stimulation).
Fourth was Prof. Liberles talking about taste. Taste buds sense sweet (energy-rich sugars), sour (the taste of protons, of acids), salty (NaCl), bitter (a warning, often, also involved in caffeine, hops, and nicotine, that people can condition themselves to like), and savory (glutamate, amino acids that are part of proteins). Interestingly, bitter has more variety than sweet, which are all similar carbohydrates, so there is a wide range of bitter receptors, while all the sweet ones are similar. There are other influences on taste, including fat, metallic, and temperature (which included capsaicin and menthol, interestingly).
And last (but not least, of course) was Dr. Oaklander talking about touch, which is different from the other senses because it is perceived widely, mostly through the skin. Somatosensation, body sensation, is influenced by the nervous system, attention, memory, and emotion. The greatest sense of touch is on the face, especially the lips, and on the hands, especially the index finger. There's a variety of sensory receptors in the skin, reacting to thermal change, (light) touch, pain (in a variety of ways), and pressure. Interestingly, some touch receptors are involved in reacting to foods, which is why chilis are hot and mint is cool. Also, there are cold receptors on blood vessels (so 'one's blood can run cold' indeed). She had a theory about sensing itch which didn't seem convincing to me, about how our African/Middle Eastern ancestors lived in places where insects carried disease, so while pain triggers moving away from something (and is definitely useful, when not chronic and neuropathic), itch triggers moving towards and touching, to get the theoretical insect away. Which rang pretty false to me, especially since if one is too slow, then scratching would make the poison move more into the body.
There was a Q&A session after, which I crocheted through. I realized only later that I would have been interested to hear what they would have said about how some people taste cilantro differently (guess who's included in this group :-). And how people's tastes change over time, too.