Week 3. Chemical Senses and Visual System

This week we were been learning about the somatic system, particularly the chemical senses and the sight. I think perception is one of the most important brain functions, as it allows us to get information from the world, and from our own systems, to make decisions and act accordingly. This means that perception is necessary for our survival, our creativity and creation ability and for our social way of living.

 Chemical Senses

Olfaction and Taste are the most studied and known chemical senses, even if there are some others. These senses are possible because of the chemoreceptors: specialized receptor cells that are sensitive to some chemical substances; once the concentration of those substances reaches threshold, neurotransmitters are released. In taste, there are also electrical synapses when tasting saltiness and sourness.

The other common mechanism between olfaction and taste is the “processing” of the sensed data. Even if all the chemoreceptors are more sensitive to a particular molecule (taste or odorant), they will respond in some way to any substance. So, there is not a direct relation between sensor type and molecule sensed, but a population coding. This mean, that a certain pattern of several responses from different receptor cells to the same molecule will form the stimulus to be processed by the brain. This population coding mechanism has been difficult to “decode” in order to get a deeper understanding of the chemical senses functioning.

The Central Visual System

The sight is probably the most studied human sense, as there is some hegemony of visual information in our way of living and in consequence, the disabilities and illnesses related to visual perception have been deeply addressed. It is also very interesting to know that even if it is the most studied sense, we still know very little about it. There is this general understanding that sight is the perception of images, so, if we understand an image as the reconstruction of light reflected in objects, then we know enough about the phenomenon. But in reality the visual system is not a photo camera, and the reconstruction of images is just the beginning of the brain processing of visual information. There are specialized neurons to process color, shapes, movement, directions, even faces. The quantity of information we get from one glance is enormous, and we only know that all that information is being processed in different brain areas, we have an idea of the specialization of those areas but we are completely unaware of how is the brain capable to process and give meaning to the very complex visual world.

Posted by Gloria Mendoza Franco

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