Grounded symbols in the brain

What is the nature of symbols in human brain-mind? Is it amodal, like logical statements, like arithmetic, or is it grounded in perceptions? We describe a mathematical technique modeling grounded symbols, based on neural modeling fields (MFT) and dynamic logic (DL), which have overcome limitations of classical artificial intelligence and connectionist approaches. The paper relates these difficulties to classical logic, discusses why logic could not have overcome these difficulties, and how DL overcomes past limitations. We apply MFT-DL to one aspect of symbolic operations, learning higher-level sign-symbols from lower level ones. We relate MFT-DL to essential mechanisms of concepts and grounding. Experimental neuroimaging evidence for DL in brain imaging is discussed as well as future research directions.