Prof. Peter Gärdenfors, mentioned in the previous post by Matti, has written an excellent book called Conceptual Spaces: The Geometry of Thought (MIT Press 2000). One of the strengths of the book is that there is no jump to the symbolic level of representation through some kind of magical leap like in many traditional theories of semantics and cognition. Gärdenfors' book should be read by all who are interested in the intellectual battle between proponents of symbolic and connectionist representations.
During my visit to California, I had a chance to visit Prof. Jerome A. Feldman at University of California Berkeley. Jerry Feldman is Professor of Electrical Engineering and Computer Science at UC Berkeley and a member of the Institute for Cognitive and Brain Sciences. Feldman's book From Molecule to Metaphor is an important contribution related, for example, to the question "where does the meaning come from". In From Molecule to Metaphor, Feldman proposes a theory of language and thought that treats language not as an abstract symbol system but as a human biological ability that can be studied as a function of the brain. In the preface, he mentions "virtually everyone agrees that the scientific explanation for human language and cognition will be based on our bodies, brains, and experiences." He continues by mentioning Noam Chomsky as the major exception. However, Chomsky focuses on linguistic form and Feldman deals first with meaning that is something that Chomsky has hard time to deal with.
In his book, Feldman discusses, among other things, embodied language, neural computing, and computational modeling. He continues to explore learning concrete words, spatial relation words, action words, and further understanding stories. Feldman concludes that even though cognitive science can not yet address all mysteries of the mind, an enormous amount has been achieved and the outlook for continuing progress is excellent. The years of research has made him confident to even state "I have been able to assemble a picture of language and thought that must be right in its essentials."
Feldman leaves, though, some questions open. As remaining mysteries he mentions the origins of language, and the nature of subjective experience. Interestingly enough, Gärdenfors has touched upon the question of the origins of language in his research and has authored a book called "How Homo Became Sapiens: On the Evolution of Thinking". The nature of subjective experience is an issue that has multiple facets. Personally, I have approached it from the point of view of subjectivity and intersubjectivity of understanding language.
with Mathias Creutz, Jouko Salo (Tekes) and Janne Hukkinen.