Ultra-high Field fMRI Reveals Effect of Ketamine on Vocal Processing in Common Marmosets.

Ketamine, a drug that blocks NMDA receptors, broadly suppresses brain activity in auditory regions of awake marmoset monkeys, especially when they hear other marmosets' calls. Using ultra-high field fMRI at 9.4 T, the study compared brain responses to vocalizations, scrambled versions, and nonvocal sounds after a subanesthetic dose of ketamine versus saline. Ketamine caused widespread reduction of activations across auditory areas and produced distinct changes in the mediodorsal thalamus and anterior cingulate cortex during vocalization processing. These effects overlap with neural disruptions seen in schizophrenia, suggesting ketamine can model auditory processing deficits in this disorder.

Study at a glance

Abstract

Auditory deficits are a well-known symptom in neuropsychiatric disorders such as schizophrenia. The noncompetitive N-methyl-d-aspartate receptor antagonist ketamine has been used to model sensory and cognitive deficits in nonhuman primates, but its whole-brain effects remain largely unknown. Here we employed ultra-high field functional magnetic resonance imaging at 9.4 T in awake male and female marmoset monkeys (Callithrix jacchus) to compare brain activations to conspecific vocalizations, scrambled vocalizations, and nonvocal sounds following the administration of a subanesthetic dose of ketamine. Our findings reveal a broad suppression of activations across auditory regions following ketamine compared with saline. Additionally, we observed differential effects depending on the type of sound, with notable changes in the mediodorsal thalamus and anterior cingulate cortex, particularly during the processing of vocalizations. These findings suggest a potential overlap between the effects of ketamine and neural disruptions observed in schizophrenia, particularly affecting vocalization processing.