 Hi, welcome back to the video course biological psychology and in this video video 3.6 We're going to take a look at the perception of touch Touch or sometimes called somatic sensation is not really one thing Touch is not really one sense in the way that for example hearing is one sense rather touches sensitivity to various ways in which Various forms of contact essentially with our skin for example Sensitivity to pressure to heat temperature itch pain tickle and also sometimes Special touch a particular kind of slow slow stroking of the skin that we experienced as being very pleasant is also considered a specific form of touch All right, so touch refers to all those different things that we can be sensitive to now And there were many different Receptors mostly located in the skin that allow us that sense these different aspects of touch, right? So I'll walk you through them. This is a list. This is not a list that I would normally know by heart It's just a list that you can look up in the textbook of the different kinds of photos Oh, not photoreceptor skin receptors For example Meissner's corpuscles, which are sensitive to pressure and local frequency vibration Merkel's discs Also sensitive to light pressure Raffini corpuscles stretch, right? So it's sort of a bending of the skin Pesinion corpuscles short-term pressure high frequency vibration Free nerve endings sensitive for example to temperature and pain so all these all these different receptors are located in the skin and Support different aspects of touch From these very different touch receptors the signals right? So these these are that's the sensation of touch and the signals travel up through the spinal cord to our brain and Then in our brain Touch is primarily processed by the somatosensory cortex, which is part of the parietal lobe Now so we've seen for for vision if you've seen the video on visual perception that we have a primary visual cortex in the back of our brain, right? V1 in our video about Hearing we've seen that we have a primary auditory cortex where auditory information is processed And in the same way we have a primary somatosensory cortex as I said for part of the parietal cortex Where where where touch is processed? Now and we've already taken a look at the the concept of topography in the context of vision and audition, right? So in for vision the retinal topography is preserved the kind of spatial topography for for hearing The topography of pitch so high versus low pitch sound is preserved And the somatosensory cortex also has a topography very literal topography No, namely it has a somatotopic representation of the body So what it means that adjacent parts of the body are Processed by adjacent neurons in your in your somatosensory cortex And that's what you see in this picture on the right So you see for example, right if we zoom in on a particular You see that for example your forearm is processed by a region of of your cortex here And then right next to it there would be a region that is that is that processes touch of your wrist, right? So those are very close together You also see that Not only is the top sort of the topography of your body preserved in the sense that neighboring body parts are represented by neighboring parts of the somatosensory cortex But in addition to that you see that parts of your your your body that you that you are very sensitive in right? Things like your nose your like your face in general, right? But also your your hands, right? You're very sensitive to touch on your hands Are represented by larger parts of your somatosensory cortex than the parts of your The parts of your body that you're not so sensitive to right? So also kind of your sensitivity in a way is is represented in the somatosensory cortex Now and if you you may notice these these sort of images of sort of a neanderthal looking figure with very large hands and very big lips That is the sensory homunculus and that is essentially a doll that is skilled based on how how Strongly different parts are represented in the somatosensory cortex For example the very big hands of the homunculus are supposed to represent the fact that our hands occupy a very large part of the Somatosensory cortex so if you see that image then then now you know what it what it sort of colloquially represents Pain is also a sensation right and it is processed in the somatosensory cortex just like just like other forms of touch But pain also has a very strong emotional component right that normal touch doesn't really have in the same way Maybe pleasant touch has kind of a Emotional component, but most forms of touch are not inherently emotional in the same way that pain is and This is the fact that Pain has a link with with with emotion is also reflected by the fact that pain is also represented Processed by the limbic system and specifically the amygdala, which as we will see in the the lecture on emotion Is a very important brain area in the in the processing of emotions mostly negative emotions So pain is is a special kind of touch that is has an emotional component and the emotional component of pain is also evident in the fact that pain Is processed differently than normal touch So the amygdala and the hypothalamus the singulate cortex the hippocampus all of those areas are part of the limbic system But the amygdala is especially involved in the processing of negative emotions Now what is quite interesting is that the limbic system is also involved in mental pain So right you should not over over interpret that that phenomenon, I suppose But in a way it shows that negative things whether regardless of whether they are mentally negative Or whether they're physically negative are processed in similar ways, right? With that let's move on to the next video video 3.7 in which we're going to take a look at taste and smell