Poster A46, Saturday, March 24, 1:30–3:30 pm, Exhibit Hall C
Left temporal lesions affect inner speech monitoring in language production: an electroencephalography and neuropsychological study
Stephanie Ries1,2, Alexa Cavalea1, Chase Tengberg1, Kathleen Y. Haaland3, Robert T. Knight4, Nina F. Dronkers5,6,7; 1School of Speech, Language, and Hearing Sciences, San Diego State University, 2Center for Clinical and Cognitive Neuroscience, San Diego State University, 3Department of Psychiatry and Behavioral Sciences, and Department of Neurology, University of New Mexico, Albuquerque, 4Department of Psychology and Helen Wills Neuroscience Institute, University of California, Berkeley, California, 5Center for Aphasia and Related Disorders, Veterans Affairs Northern California Health Care System, Martinez, California, 6Department of Neurology, University of California, Davis, California, 7Neurolinguistics Laboratory, National Research University Higher School of Economics, Moscow, Russian Federation
Healthy adults only err about once every thousand words produced, while patients with left posterior temporal brain lesions make frequent production errors. We tested whether these errors were associated with impaired speech monitoring abilities. Medial frontal and posterior superior temporal regions (pSTG, with stronger activations on the left) have been associated with different aspects of speech monitoring. The medial frontal activity, reflected in the error negativity (Ne, larger in error than correct trials), has been associated with a monitoring mechanism engaged before speech output. The pSTG activity, on the other hand, has been associated with a monitoring mechanism dependent on auditory feedback. Whether these mechanisms interact to enable speech monitoring is unknown. We investigated the effect of stroke-induced brain lesions encompassing the left pSTG on medial frontal monitoring. We recorded scalp electroencephalography in four chronic stroke patients with lesions involving the left pSTG during a picture naming task. The results show a dramatically reduced amplitude difference between errors and correct trials on the Ne in these patients. This contrasts with previous reported results using the same paradigm in chronic stroke patients with lesions outside of the pSTG (in the lateral prefrontal cortex, PFC). PFC patients showed an intact Ne pattern, suggesting a normal speech monitoring mechanism in simple picture naming. The present results suggest interactions between the left pSTG and the medial frontal cortex are necessary for speech monitoring, and begin to shed light on the physiological underpinnings of abnormal speech monitoring in patients with left pSTG brain lesions.
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