The early auditory gamma-band response is heritable and a putative endophenotype of schizophrenia.
BACKGROUND
Reduced power and phase locking of the early auditory gamma-band response (EAGBR) have been reported in schizophrenia, but findings are equivocal. Further, little is known about genetic (heritability) and environmental influences on the EAGBR or its potential as an endophenotype of schizophrenia. The present study used a twin design to examine whether EAGBR power and phase locking are heritable and reduced in schizophrenic patients and their unaffected co-twins and thus putative endophenotypes of schizophrenia.


METHODS
The study sample included a total of 194 individuals, consisting of 15 monozygotic [MZ] twin pairs concordant for schizophrenia, 9 MZ twin pairs discordant for schizophrenia, and 42 MZ and 31 dizygotic (DZ) control pairs. Evoked power and phase-locking factor of the EAGBR were computed on Morlet wavelet-transformed electroencephalogram responses to standard tones during an auditory oddball target detection task. Structural equation modeling was applied to estimate heritability and genetic and environmental correlations with schizophrenia for the EAGBR measures.


RESULTS
Both evoked power and phase-locking phenotypes were heritable traits (power: h(2) = 0.65; phase locking: h(2) = 0.63). Impaired EAGBR measures were significantly associated with schizophrenia. Patients with schizophrenia and their unaffected identical co-twins exhibited significantly reduced EAGBR power compared with control subjects. In each phenotype, shared genetic factors were likely the source of the observed associations with schizophrenia.


CONCLUSIONS
Our results support EAGBR measures as putative endophenotypes of schizophrenia, likely reflecting an ubiquitous local cortical circuit deficit.
Hall
Mei-Hua
MH
Cognitive Neuroscience Laboratory, Harvard Medical School, McLean Hospital, 115 Mill Street, Belmont, MA 02478, USA. mhall@mclean.harvard.edu
Taylor
Grantley
G
Sham
Pak
P
Schulze
Katja
K
Rijsdijk
Fruhling
F
Picchioni
Marco
M
Toulopoulou
Timothea
T
Ettinger
Ulrich
U
Bramon
Elvira
E
Murray
Robin M
RM
Salisbury
Dean F
DF
D000161:Acoustic Stimulation; D000328:Adult; D001288:Attention; D058256:Brain Waves / Q000235:genetics*; D004200:Diseases in Twins / Q000175:diagnosis / Q000235:genetics* / Q000523:psychology; D004569:Electroencephalography; D058068:Endophenotypes; D005072:Evoked Potentials, Auditory / Q000235:genetics*; D005260:Female; D005819:Genetic Markers / Q000235:genetics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012042:Registries; D012559:Schizophrenia / Q000175:diagnosis / Q000235:genetics*; D012565:Schizophrenic Psychology; D012815:Signal Processing, Computer-Assisted; D012931:Social Environment; D014429:Twins, Dizygotic / Q000235:genetics / Q000523:psychology; D014430:Twins, Monozygotic / Q000235:genetics / Q000523:psychology; D055815:Young Adult
D005819:Genetic Markers