Understanding in an instant: Neurophysiological evidence for mechanistic language circuits in the brain

Abstract

How long does it take the human mind to grasp the idea when hearing or reading a sentence? Neurophysiological methods looking directly at the time course of brain activity indexes of comprehension are critical for finding the answer to this question. As the dominant cognitive approaches, models of serial/cascaded and parallel processing, make conflicting predictions on the time course of psycholinguistic information access, they can be tested using neurophysiological brain activation recorded in MEG and EEG experiments. Seriality and cascading of lexical, semantic and syntactic processes receives support from late (latency ∼1/2 s) sequential neurophysiological responses, especially N400 and P600. However, parallelism is substantiated by early near-simultaneous brain indexes of a range of psycholinguistic processes, up to the level of semantic access and context integration, emerging already 100–250 ms after critical stimulus information is present. Crucially, however, there are reliable latency differences of 20–50 ms between early cortical area activations reflecting lexical, semantic and syntactic processes, which are left unexplained by current serial and parallel brain models of language. We here offer a mechanistic model grounded in cortical nerve cell circuits that builds upon neuroanatomical and neurophysiological knowledge and explains both near-simultaneous activations and fine-grained delays. A key concept is that of discrete distributed cortical circuits with specific inter-area topographies. The full activation, or ignition, of specifically distributed binding circuits explains the near-simultaneity of early neurophysiological indexes of lexical, syntactic and semantic processing. Activity spreading within circuits determined by between-area conduction delays accounts for comprehension-related regional activation differences in the millisecond range.

Using the readiness potential of button-press and verbal response within spoken language processing

“…Further evidence for this assumption comes from the famous shadowing task by Marslen-Wilson (1973, 1985, in which people were able to repeat another speaker's sentences with a time delay of only 250 ms. Finally Pulvermüller resumes that early indexes of lexical, syntactic and semantic processes have been found after 100-250 ms in written and spoken language processing which reflects almost parallel processes (Pulvermüller, 2005;Pulvermüller et al, 2009). Both behavioural studies (Marslen-Wilson, 1985) as well as the results of the underlying functional neuroanatomical studies are therefore roughly comparable to the observed behavioural inter-turn delays of about 120-250 ms.…”

Lexical and sublexical orthographic processing: An ERP study with skilled and dyslexic adult readers

“…From a dual-route perspective of reading (Coltheart, 2007;Coltheart, Rastle, Perry, Langdon, & Ziegler, 2001), less effort was expected in order to find a fitting orthographic representation for familiar words in the orthographic lexicon, whereas the search should be prolonged and unsuccessful in case of unfamiliar word-forms, resulting in enhanced N1-amplitudes to pseudohomophones and pseudowords as found by us. Here the finding that lexical variables affect the brain response very early in processing fits better within frameworks where word recognition is accomplished by early near-simultaneous (cascaded) or partially overlapping stages and the underlying processes can be interactive (e.g., o Grainger & Holcomb, 2009;Pulvermüller, Shtyrov, & Hauk, 2009). Accordingly, in a study using a multiple regression design Hauk, Davis et al (2006) reported an early lexical frequency effect around 110 ms that closely follows and partly overlaps with the earlier bigram frequency effect.…”

Stimulus onset asynchrony and the timeline of word recognition: Event-related potentials during sentence reading

“…The interaction, though, was relatively weak in the global analyses and occurred only in a brief interval on a deflection that was absent in Experiments 1 and 2. Yet, there are reasons to take this finding serious: First, it is well known that effects in early time ranges are generally small and focal, so that rather mild amplitude modulations are expected (Penolazzi et al, 2007;Pulvermüller, Shtyrov, & Hauk, 2009). Second, the effect is only weak in a conservative analysis including all channels, whereas post-hoc tests on averaged channels PO7/8 revealed a very robust pattern.…”