Smell and taste is one of the most interesting topics of sensation and perception. These senses are stimulated chemically. In other words, for example when chemicals stimulate the receptors inside of the taste buds in mouth, we start to feel the sense of taste. These buds are in papillae. We are able to taste from our tongue, throat and inside part of the cheeks. However, the most sensitive part is our tong. The front edge of the tong is very sensitive for sweet tastes and the upper sides of the front tong tastes salty very well. Also, tong's middle sides are sensitive for sour tastes mostly where the spicy tastes are sensed mostly at the back of the tong. However, it is an unavoidable fact that the entire tong itself is able to sense and detect every kind of tastes at any parts because receptors and taste buds are everywhere on the tong. For example, one can easily taste a very spicy pepper from his/her front edge of the tong. The thing is, different types of tastes have different and specific spots on the tong.
Another chemical sense it the smell. While we breathe, we also inhale some chemicals that are in the air and some of them stimulate the receptors which are located in the nasal passage. After these receptors are notified by these chemicals, the message is ready to be sent to the brain. These chemicals could be from flowers, food, perfume or even a person's own smell.
These senses are not only for us to detect things but also remind us how we felt during the times that we have interacted with specific tastes or smells. As the interview which is recorded in video with Dr. Stuart Firestein, from Columbia University, says that the connection between taste and smell, and memory is still unexplainable. There are theories that could bring an explanation to this issue and one of them says that they are processing in intimate locations of the brain; hence, they might be affecting each other. They both connect to memory but the strongest sense that triggers memory is the smell.
In my opinion, it is very interesting to remember exact emotion when I smell something even though that memory belongs to many years ago. For example, couple weeks ago I smelled someone's perfume and it reminded me my childhood because my mother used to use the same perfume.
All in all, it is obvious that smell and taste are very important chemical senses for us and have really strong connection to memory, especially the smell, even though scientists have not figured out why.
For the interview and video: http://bigthink.com/ideas/25252