Humans are innately social beings and, in almost all cultures, vocal communication is the dominant mode for social interactions. It is, therefore, not surprising that voices became the most salient auditory signal. We often use voices to communicate verbal information but voices are much more than that: they convey a wealth of socially relevant information about the speaker (e.g., age, sex, emotional state, social traits), which can be decoded from the briefest of utterances. Voices are, therefore, fundamental for social experience.
My research is focused on understanding how humans make sense of and use vocal information to communicate with each other. I am particularly interested in how these mechanisms, when altered, may explain the characteristic symptoms of schizophrenia, such as auditory verbal hallucinations. The investigation of language and communication in schizophrenia during my PhD convince me of the importance of looking at voice perception mechanisms to understand the experience of hearing voices without matching external acoustic input. I pursued the investigation of these mechanisms during my Post-Doctoral studies at Harvard Medical School, and later as director of the Voice, Emotion & Speech Laboratory at the University of Lisbon.
Auditory verbal hallucinations remain one of the most puzzling phenomena of human experience: they are self-generated but are typically experienced as a form of communication from another (or other) speaker(s). They are one of the most troubling symptoms in psychosis and thus contribute to significant suffering. However, hallucinations may also be reported in the general population without need for psychiatric care. Despite many efforts to explain this puzzling phenomenon, the underlying pathophysiology is still poorly understood. My studies suggest that auditory verbal hallucinations co-opt the neurocognitive mechanisms underpinning voice generation and perception. For example, we documented disrupted voice feedback processing in both adult psychotic patients and nonclinical voice hearers, which may link to dysfunctional cerebellar circuitry. Based on these findings, we put forward a framework that accentuates the role of the cerebellum in voice feedback processing and auditory verbal hallucinations. These findings add to prior studies showing that predictive processing dysfunction is at the basis of auditory verbal hallucinations. We also showed that hallucination proneness is associated with hypersalient responses in voice-sensitive regions of the cerebral cortex to acoustic features coding speaker identity.
Auditory verbal hallucinations are associated with greater risk of conversion to psychosis compared to other types of hallucinations, contribute transdiagnostically to psychopathology in adolescents, and predict poor functional outcome in schizophrenia. Detecting early alterations at the neurophysiological or behavioral levels before the development of full-blown psychotic symptoms could radically modify the risk trajectory. Voice processing could be a strong candidate for differentiating between vulnerability, risk, and clinical profiles. This is an innovative concept and of high relevance as voice-sensitive tasks are relatively cheap and reliable measures that could be implemented in larger samples with a longitudinal outlook. Our ongoing studies are testing this hypothesis.
This work has been a collaborative effort and I have been extremely lucky to have found brilliant mentors who continue to inspire me, including Margaret Niznikiewicz or Sonja Kotz. I am also deeply grateful for all the learning and collaboration opportunities I have found as a SIRS member since early in my graduate training, and especially honored to have received the 2022 SIRS Rising Star Award.
My ongoing studies continue the quest for a mechanistic understanding of auditory verbal hallucinations aiming to inform future preventive strategies. Investigating vocal communication might prove especially informative to clarify why hallucinated voices are typically experienced as social entities and why they may acquire an emotional quality.
