Words without mind.
A woman (LR), unconscious for 20 years, spontaneously produces infrequent, isolated words unrelated to any environmental context. Fluorodeoxy-glucose-positron emission tomography (FDG-PET) imaging coregistered with magnetic resonance imaging (MRI) revealed a mean brain metabolism equivalent to deep anesthesia. Nevertheless, PET imaging demonstrated islands of modestly higher metabolism that included Broca's and Wernicke's areas. Functional brain imaging with magnetoencephalographic (MEG) imaging, a technique providing a temporal resolution of better than 1 msec, identified preserved dynamic patterns of spontaneous and evoked brain activity in response to sensory stimulation. Specifically, we examined spontaneous gamma-band activity (near 40 Hz) and its reset or modification during early auditory processing, a measure that correlated with human perception of sensory stimuli (Joliot, Ribary, & Llinás, 1994). Evidence of abnormal and incomplete gamma-band responses appeared in the left hemisphere only in response to auditory or somatosensory stimulation. MEG single-dipole reconstructions localized to the auditory cortex in the left hemisphere and overlapped with metabolically active regions identified by FDG-PET. The observation demonstrates that isolated neuronal groups may express well-defined fragments of activity in a severely damaged, unconscious brain. The motor fixed-action pattern character of her expressed words supports the notion of brain modularity in word generation.
Schiff
N
N
Department of Neurology and Neuroscience, New York Hospital-Cornell Medical Center, 1300 York Avenue, NY, NY 10021, USA. nschiff@mail.med. cornell.edu
Ribary
U
U
Plum
F
F
Llinás
R
R
D000161:Acoustic Stimulation; D001306:Auditory Pathways / Q000503:physiopathology; D001921:Brain / Q000000981:diagnostic imaging / Q000473:pathology; D005260:Female; D005385:Fingers / Q000503:physiopathology; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008279:Magnetic Resonance Imaging; D015225:Magnetoencephalography; D008875:Middle Aged; D018458:Persistent Vegetative State / Q000175:diagnosis / Q000503:physiopathology / Q000523:psychology*; D010812:Physical Stimulation; D014055:Tomography, Emission-Computed; D014705:Verbal Behavior
D019788:Fluorodeoxyglucose F18