Proc Natl Acad Sci U S A. 2017 Jun 6;114(23):E4530-E4538. doi: 10.1073/pnas.1620669114. Epub 2017 May 22.

Spatiotemporal dynamics of word retrieval in speech production revealed by cortical high-frequency band activity.

Riès SK^1,², Dhillon RK², Clarke A^3,⁴, King-Stephens D⁵, Laxer KD^5,⁶, Weber PB⁵, Kuperman RA⁷, Auguste KI^6,⁷, Brunner P^8,⁹, Schalk G^8,⁹, Lin JJ¹⁰, Parvizi J¹¹, Crone NE¹², Dronkers NF^13,^14,¹⁵, Knight RT².

Author information

1: School of Speech, Language, and Hearing Sciences, San Diego State University, San Diego, CA 92182; sries@sdsu.edu.
2: Helen Wills Neuroscience Institute and Department of Psychology, University of California, Berkeley, CA 94720-3190.
3: University of California Davis Center for Neuroscience, Davis, CA 95618.
4: Centre for Speech, Language and the Brain, Department of Psychology, University of Cambridge, Cambridge CB2 3EB, United Kingdom.
5: California Pacific Medical Center, San Francisco, CA 94115.
6: University of California San Francisco Medical Center, San Francisco, CA 94143.
7: Children's Hospital and Research Center, Oakland, CA 94609.
8: New York State Department of Health, Wadsworth Center, Albany, NY 12208.
9: Department of Neurology, Center for Medical Science, Albany, NY 12208.
10: Department of Neurology, School of Medicine, University of California, Irvine, CA 92697.
11: Stanford Human Intracranial Cognitive Electrophysiology Program, Stanford University, Stanford, CA 94305.
12: Department of Neurology, The Johns Hopkins University School of Medicine, Baltimore, MD 21287.
13: Center for Aphasia & Related Disorders, Veterans Affairs Northern California Health Care System, Martinez, CA 94553.
14: Department of Neurology, University of California, Davis, Sacramento, CA 95817.
15: Neurolinguistics Laboratory, National Research University Higher School of Economics, Moscow, Russian Federation, 101000.

Abstract

Word retrieval is core to language production and relies on complementary processes: the rapid activation of lexical and conceptual representations and word selection, which chooses the correct word among semantically related competitors. Lexical and conceptual activation is measured by semantic priming. In contrast, word selection is indexed by semantic interference and is hampered in semantically homogeneous (HOM) contexts. We examined the spatiotemporal dynamics of these complementary processes in a picture naming task with blocks of semantically heterogeneous (HET) or HOM stimuli. We used electrocorticography data obtained from frontal and temporal cortices, permitting detailed spatiotemporal analysis of word retrieval processes. A semantic interference effect was observed with naming latencies longer in HOM versus HET blocks. Cortical response strength as indexed by high-frequency band (HFB) activity (70-150 Hz) amplitude revealed effects linked to lexical-semantic activation and word selection observed in widespread regions of the cortical mantle. Depending on the subsecond timing and cortical region, HFB indexed semantic interference (i.e., more activity in HOM than HET blocks) or semantic priming effects (i.e., more activity in HET than HOM blocks). These effects overlapped in time and space in the left posterior inferior temporal gyrus and the left prefrontal cortex. The data do not support a modular view of word retrieval in speech production but rather support substantial overlap of lexical-semantic activation and word selection mechanisms in the brain.