Gamma frequency-range abnormalities to auditory stimulation in schizophrenia.
BACKGROUND
Basic science studies at the neuronal systems level have indicated that gamma-range (30-50 Hz) neural synchronization may be a key mechanism of information processing in neural networks, reflecting integration of various features of an object. Furthermore, gamma-range synchronization is thought to depend on the glutamatergically mediated interplay between excitatory projection neurons and inhibitory neurons utilizing gamma-aminobutyric acid (GABA), which postmortem studies suggest may be abnormal in schizophrenia. We therefore tested whether auditory neural networks in patients with schizophrenia could support gamma-range synchronization.


METHODS
Synchronization of the electroencephalogram (EEG) to different rates (20-40 Hz) of auditory stimulation was recorded from 15 patients with schizophrenia and 15 sex-, age-, and handedness-matched control subjects. The EEG power at each stimulation frequency was compared between groups. The time course of the phase relationship between each stimulus and EEG peak was also evaluated for gamma-range (40 Hz) stimulation.


RESULTS
Schizophrenic patients showed reduced EEG power at 40 Hz, but not at lower frequencies of stimulation. In addition, schizophrenic patients showed delayed onset of phase synchronization and delayed desynchronization to the click train.


CONCLUSIONS
These data provide new information on selective deficits in early-stage sensory processing in schizophrenia, a failure to support the entrainment of intrinsic gamma-frequency oscillators. The reduced EEG power at 40 Hz in schizophrenic patients may reflect a dysfunction of the recurrent inhibitory drive on auditory neural networks.
Kwon
J S
JS
Department of Psychiatry, Laboratory of Neuroscience, Harvard Medical School, Brockton Veterans Affairs Medical Center, MA 02401, USA.
O'Donnell
B F
BF
Wallenstein
G V
GV
Greene
R W
RW
Hirayasu
Y
Y
Nestor
P G
PG
Hasselmo
M E
ME
Potts
G F
GF
Shenton
M E
ME
McCarley
R W
RW
D000161:Acoustic Stimulation; D000328:Adult; D001306:Auditory Pathways / Q000502:physiology; D001307:Auditory Perception / Q000502:physiology*; D003344:Cortical Synchronization / Q000706:statistics & numerical data; D004569:Electroencephalography / Q000706:statistics & numerical data*; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D018079:Receptors, GABA / Q000502:physiology; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology; D012559:Schizophrenia / Q000175:diagnosis* / Q000503:physiopathology
D018079:Receptors, GABA; D016194:Receptors, N-Methyl-D-Aspartate