Language processing more than A-B-C

NYU (US) — Neural processing that goes into deciphering simple two-word phrases is different from what happens when decoding complete sentences and other more complex linguistic expressions.

To better understand how the brain functions during simple language processing, native English speakers were shown simple nouns presented either by themselves or preceded by a simple adjective.

Results of the study are reported in the Journal of Neuroscience.

Brain activity during the processing of the nouns was gauged using magnetoencephalography (MEG), a technique that maps neural activity by recording magnetic fields produced by the electrical currents produced by the brain.

During the experiment, subjects were shown common nouns (“boat”) that were either part of a simple noun phrase (“red boat”), or preceded by an unrelated noun (“cup, boat”) or non-pronouncable consonant string (“xhl boat”).

By comparing neural activity generated during the phrases with the control conditions, it was possible to isolate brain activity that increased during basic combinatorial processing (i.e., the adjective and the noun) compared to when no linguistic combination was present.

To make sure the subjects were processing the words correctly, they had to assess whether a following colored shape (e.g., a red boat) matched the words they had just seen.

The regions of the brain typically identified with the processing of complex linguistic expressions—”Broca’s” and “Wernicke’s” areas—appeared to play no role in the comprehension of such basic phrases.

Instead, the MEG results revealed increased activity in the left anterior temporal lobe (LATL), followed by increased activity in the ventromedial prefrontal cortex (vmPFC) region of the brain during the processing of simple adjective-noun phrases.

While these parts of the brain have previously been shown to be involved in the processing of more complex linguistic expressions, the new findings suggest they play a pivotal role in the most fundamental aspects of language processing.

This result, in conjunction with the absence of increased activity in Broca’s and Wernicke’s areas, indicates that traditional neural models of language processing must be expanded in order to encompass a wider network of brain areas than are typically included.

“Surprisingly, direct investigations into the neural underpinnings of basic combinatorial processing in language have been virtually nonexistent,” write Liina Pylkkänen, associate professor of psychology at New York University and graduate student Douglas Bemis.

“This research introduces a powerful method for directly investigating these operations by allowing the linguistic expressions under consideration to be reduced to the absolute minimum: a simple adjective composed with a noun.”

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