Lexeme (in neurocognitive linguistics)

In neurocognitive linguistics, a lexeme or lexical item is understood not as a unit but as a subnetwork, a functional web (Pulvermueller's term) within the linguistic information system. For most lexemes, the functional web is quite large, especially if we include all of the nodes that together represent its meaning -- including nodes in the visual cortex (representing what the thing in question looks like), the auditory cortex, etc. Most such nodes are shared by other lexemes and indeed they often come into play in extra-linguistic activity. But there is one node at the logical top of the functional web, the cardinal node, the lemma node. For most, if not all, noun lexemes it is probably in the angular gyrus, in the lower part of the parietal lobe close to Wernicke's area, that has connections to the phonological node (in Wernicke's area) and to these three sensory-perceptual networks as well as to various items of abstract information. As this cardinal node is unique to the functional web of the lexeme in question, we can also refer just to it as the internal representation of the lexeme. Note that whenever it is activated it activates the rest of the functional web -- connections to meaning nodes and to phonological nodes and graphic nodes.

Comments
A lexeme is what it is not just as occupier of a particular position within the network. What it is depends upon the other nodes and links to which it is connected. Every lexeme has its connection to the grammatical tactics. And it connects downwards to expression in some cases as a simple connection; for example, the lexeme "dog" coincides with the morpheme "dog". Others are more complicated; for example, "German Shepherd" connects to the combination of morphemes "German" and "shepherd."

There is another aspect to the structure of the usual entry in a dictionary and that is the definition, the specification of what the meaning is, and that involves conceptual relationships or semological structure. Any lexeme connects upwards to the sememic or conceptual system. Now in the case where it relates to several concepts, we have an upward OR node which allows one line to go to each of the different concepts which the lexeme can represent. So this part of the structure, as you can see, is purely relational.

Another dimension of lexemes is entrenchment. A lexeme becomes more entrenched with more use: the neurocognitive pathways which support it become stronger the more they are traveled.

Many linguists suppose that lexemes have meanings. In what sense of have can this notion be viewed as realistic? The fact that exercises of deriving one meaning from another can be successfully conducted does not constitute evidence. As Lamb has had students demonstrate in his cognitive linguistics class, it is possible to derive any meaning (of any word chosen at random) from any other meaning (of another word chosen at random by another student).

Subtypes
There are simple lexemes and complex lexemes. The latter shouldn't be conflated with idioms, which are complex lexemes whose meaning is not clear from the meanings of their constituents -- so a lexeme can be transparent or opaque or anywhere in between. Transparent lexemes can be interpreted via the constituents or via the whole. This is no problem for a network approach, in which lexemes and their constituents are all activated in parallel.

It is surprising how much ordinary English text is made up of complex lexemes. Stored in memory as units, complex lexemes don't have to be constructed for their production or understanding.

When one or more elements of a complex lexeme is variable, the lexeme is said to be mutable.

Origin
The term "lexeme" was introduced by Benjamin Whorf in the 1930s and used subsequently by Morris Swadesh and Harold Conklin and others. It was brought into neurocognitive linguistics under the influence of Conklin.

Polysemy
See lexeme.