Lecture 1: Sensation vs. Perception

Welcome back to the course Brain, Behaviour, and Dentistry. Now we continue the first session of the course, which will focus on the issues of perception and attention, and some clinical implications in dental practice. After this course, you will learn how to differentiate the concepts of sensation and perception, the key concepts of perceptual processing, and to learn some interesting features of visual perception. Imagine we all gain a new superpower, i.e., to put our mind into another person’s body. I wonder if I take control of the body of some, well, famous politicians, and I would use their bodies to say something very stupid. That’s really fun.

And of course, because you are using their bodies, so you are using their eyes to see things. For example, you can still see a red thing through their eyes.

Here we got a problem: what if the host has colour blindness so that he cannot see red things?

Now I am using his eyes to see things. Does that mean I can only see grey? The body-exchange experiment is weird, but it tells us that, to be honest, it is very difficult to ‘feel’ something in the patient’s place. The formation of ‘feeling’ is very subjective and that subjectivity is associated with the ownership of the body.

Now let’s move back to our own bodies. We have some definitions here and they are very important. When I said that I can see red things through my eyes, we mainly focus on the mental process ‘sensation’. Simply speaking, the sensation is about collecting external stimuli and translating the stimuli into neural signals, via our sensory receptors. Here these ‘signals’ are all information, i.e., the information of the shape of things, the colour and motion of things. Now, perception is the mental process associated with the integration of information. In visual perception, we combine the information of size, shape, colour, and so on, to form new information. The new information is merging in our conscious mind and then I know what I see.

And therefore ‘perception’ is subjective, but I want to add more on this: what we perceive from the world is subjective because ‘we’ personally organize and form this experience. What matters is the process of how we organize and form the experience from the information collected from the sensory pathway.

In fact, not just vision but audition and gustation, i.e., hearing and tasting, are follows the same pathway of information processing. For hearing, the receptors in the eardrum translate sound waves to neural signals, and for tasting, the taste buds translate chemical stimuli to neural signals. And then information is integrated. The integration of the raw signals happens in our brain, mostly in the primary sensory cortices, such as the visual cortex for vision and the auditory cortex for the audition. It should be noted that the more complicated processing happens, the more brain regions take part in it. For example, to identify what an object is, both the temporal lobe and the visual cortex take part in the process of visual perception.

Therefore, from the point of cognitive neuroscience, the concepts of sensation and perception are not isolated. They are all part of the stream of information processing.