Composition of Complex Meaning

Language enables humans to communicate the most complex of thoughts, such that from patterns of sensory stimulation an interlocutor can reconstruct the message originating in a speaker’s brain. While every component of this remarkable process is a difficult problem, the fundamental starting point for this entire sequence of events is our ability to construct a complex meaning for the purpose of expression. Underlying this capacity is a generative system of meaning composition that sits in the interface of language and thought. Decades of research within philosophically based linguistics and in the psychology of concepts have characterized the nature of these complex semantic representations; however, this work has only recently begun to inform the brain science of semantic representation. In this chapter I bring together perspectives from theoretical linguistics, cognitive psychology, and neuropsychology to discuss what is currently known about the brain basis of complex meaning composition. Although differences in cognitive neuroscience techniques and experimental paradigms often result in more differences than similarities, a remarkable convergence arises from hemodynamic methods, magnetoencephalography (MEG), and neuropsychological data implicating the left anterior temporal lobe (LATL) as a core region for the construction of complex meaning. The focus of this chapter is on MEG data, on the basis of which the timing of LATL activity in comprehension has been characterized as relatively early, peaking at 200–250 ms after the onset of a composing word. Progress in our understanding of the computational contribution of this activity is only beginning to gain momentum, but I summarize an initial body of results suggesting that, crucially, the LATL supports automatic, task-insensitive composition in both comprehension and production and that its contribution is clearly semantic, as opposed to syntactic in nature.