fMRI study of graduated emotional charge for detection of covert activity using passive listening to narratives.

Detection of awareness in patients with consciousness disorders is a challenge that can be facilitated by functional neuroimaging. We elaborated a functional magnetic resonance imaging (fMRI) protocol to detect covert activity in altered states of consciousness. We hypothesized that passive listening to narratives with graduated emotional charge triggers graduated cerebral activations. The fMRI protocol was designed in healthy subjects for further clinical applications. The emotional charge was graduated using voice familiarity and long-term declarative memory content: low emotional charge, unknown person telling general semantic memory; mean emotional charge, relative telling the same narratives; high emotional charge, same relative telling autobiographical memory. Autobiographical memory was subdivided into semantic autobiographical memory and episodic autobiographical memory. The protocol proved efficient at triggering graduated cerebral activations: low emotional charge, superior temporal gyri and sulci; mean emotional charge, same as low emotional charge plus bilateral premotor cortices and left inferior frontal gyrus; high emotional charge, cingulate, temporal, frontal, prefrontal and angular areas, thalamus and cerebellum. Semantic autobiographical memory revealed larger activations than episodic autobiographical memory. Independent ROI analysis confirmed the preponderant contribution of narratives with autobiographical memory content in triggering cerebral activation, not only in autobiographical memory-sensitive areas, but also in voice-sensitive, language-sensitive and semantic memory-sensitive areas.