Online research in philosophy

The following questions are addressed concerning how a theory of lexical access can be realized in the brain: (1) Can a brainlike device function without inhibitory mechanisms? (2) Where in the brain can one expect to find processes underlying access to word semantics, syntactic word properties, phonological word forms, and their phonetic gestures? (3) If large neuron ensembles are the basis of such processes, how can one expect these populations to be connected? (4) In particular, how could one-way, reciprocal, and numbered connections be realized? and, (5) How can a neuroscientific approach for multiple access to the same word in the course of the production of a sentence? Footnotes1 This commentary originally appeared in the Levelt et al. treatment in BBS 22(1) (pp. 52–54).

The theory of lexical selection presented by Levelt, Roelofs & Meyer addresses the mechanisms of semantic activation that lead to the selection of isolated words. The theory does not appear to extend naturally to the referential use of words (particularly pronouns) in coherent discourse. A more complete theory of lexical selection has to consider the semantics of discourse as well as lexical semantics.

There are perceptual states whose representational content cannot even in principle be conceptual. If that claim is true, then at least some perceptual states have content whose semantic structure and psychological function are essentially distinct from the structure and function of conceptual content. Furthermore the intrinsically “orientable” spatial character of essentially non-conceptual content entails not only that all perceptual states contain non-conceptual content in this essentially distinct sense, but also that consciousness goes all the way down into so-called unconscious or subpersonal mental states. Both my argument for the existence of essentially non-conceptual content and my theory of its structure and function have a Kantian provenance.

It has recently been pointed out that perceptual nonconceptualism admits of two different and logically independent interpretations. On the first (content) view, perceptual nonconceptualism is a thesis about the kind of content perceptual experiences have. On the second (state) view, perceptual nonconceptualism is a thesis about the relation that holds between a subject undergoing a perceptual experience and its content. For the state nonconceptualist, it thus seems consistent to hold that both perceptual experiences and beliefs share the same (conceptual) content, but that for a subject to undergo a perceptual experience, the subject need not possess the concepts involved in a correct characterization of such content. I argue that the consistency of this position requires a non-Fregean notion of content that fails to capture the way the subject grasps the world as being. Hence state nonconceptualism leaves perceptual content attribution unsupported. Yet, on a characterization of content along the relevant (neo-Fregean) lines, this position would become incoherent, as it would entail that a subject could exercise cognitive abilities she doesn’t possess. I conclude that, given the notion of content demanded by the debate, the state view does entail the content view after all.

The cell assembly model of language posits that words are laid down in the cortex by discrete sets of neurons distributed over specific parts of the brain. The strong internal links of these “word webs” may not only bind articulatory and acoustic knowledge of a lexical item, they may also link word and meaning; for example, by connecting neuron populations related to word forms to those of actions and perceptions to which the words refer. Therefore, the cortical activation elicited by words should reflect aspects of word meaning, a postulate that has received strong support from recent work using neurophysiological and metabolic imaging. Segalowitz & Lane make the point that this neurobiological model can also be used to predict reaction times in behavioral experiments, using the behavioral distinction between content and function words as an example. We acclaim their view, but warn that response times might be related to different mechanisms at the neuronal level, including the cortical distribution and internal connectivity of cell assemblies along with their mutual connections in the grammatical (syntactic and semantic) network.

Pulvermüller traces the differences in brain activity associated with function and content words. The model considers words displayed primarily in isolation. Research on letter detection suggests that what distinguishes function from content words are their roles in text. Hence a model that fails to consider context effects on the processing of words provides an insufficient accounting of word representation in the brain.

We urge caution in generalising from content words to function words, in which lexical-to-phonemic feedback might be more likely. Speech perception involves more than word recognition; feedback might be outside the narrow logic of word identification but still be present for other purposes. Finally, we raise the issue of evidence from imaging studies of auditory hallucination.

The literature contains a disconnect between accounts of how humans learn lexical semantic representations for words. Theories generally propose that lexical semantics are learned either through perceptual experience or through exposure to regularities in language. We propose here a model to integrate these two information sources. Specifically, the model uses the global structure of memory to exploit the redundancy between language and perception in order to generate inferred perceptual representations for words with which the model has no perceptual experience. We test the model on a variety of different datasets from grounded cognition experiments and demonstrate that this diverse set of results can be explained as perceptual simulation (cf. Barsalou, Simmons, Barbey, & Wilson, 2003) within a global memory model.

Speakers retrieve words to use them in sentences. Errors in incorporating words into sentential frames are revealing with respect to the lexical units as well as the lexical retrieval mechanism; hence they constrain theories of lexical access. We present a reanalysis of a corpus of spontaneously occurring lexical exchange errors that highlights the contact points between lexical and sentential processes.

Word class-specific differences in brain evoked potentials (EP) are discussed for connotative meaning and for function versus content words. A well-controlled experiment found matching lexical decision times for function and content words, but clear EP differences (component with maximum near 550 msec) among function words, content words, and nonwords that depended on brain site. Another EP component, with a 480 msec maximum, differentiated words (either function or content) from nonwords.