In the second study, pregnant rat dams were injected with a cytokine inducer to activate the maternal immune response during the prenatal period [48•] because epidemiological studies have linked maternal immune activation (MIA) during pregnancy to an increased risk of schizophrenia in offspring [49]. Coherence between the hippocampus and prefrontal cortex was significantly reduced in the delta (2–4 Hz), theta (4–12 Hz), beta (12–30 Hz), and low frequency gamma (30–48 Hz) bands in rats that were prenatally exposed to MIA. In accordance, mPFC neurons in MIA rats were significantly less phase-locked to hippocampal theta and gamma oscillations. Additionally, reductions in low frequency gamma mPFC–hippocampal coherence were correlated with deficits in prepulse inhibition to startle, a widely used measure of sensorimotor gating that is impaired in schizophrenics. These findings suggest that deficient oscillatory synchrony between the hippocampus and prefrontal cortex may contribute to the sensory gating deficits associated with schizophrenia.
