Bridging Phenomenology and Neural Mechanisms of Inner Speech: ALE Meta-Analysis on Egocentricity and Intentionality in a Dual-Mechanistic Framework

Abstract

The neural mechanisms of inner speech remain unclear despite its importance in a variety of cognitive processes and its implication in aberrant perceptions such as auditory verbal hallucinations. Previous research has proposed a corollary discharge model in which inner speech is a truncated form of overt speech, relying on speech production-related regions (e.g. left inferior frontal gyrus). This model does not fully capture the diverse phenomenology of inner speech and recent research suggesting alternative perception-related mechanisms of generation. Therefore, we present and test a framework in which inner speech can be generated by two separate mechanisms, depending on its phenomenological qualities: a corollary discharge mechanism relying on speech production regions and a perceptual simulation mechanism within speech perceptual regions. The results of the activation likelihood estimation meta-analysis examining inner speech studies support the idea that varieties of innerspeech recruit different neural mechanisms.

Distinct neural mechanisms support inner speaking and inner hearing

“…4 By contrasting inner speaking and inner hearing of non-speech sounds, Chu et al (2023) recently showed a clear dissociation in the involvement of the motor-based and memory-based networks, further supporting the distinction between these two processes. Overall, our results are also compatible with the framework recently provided by Pratts et al (2023), in which inner speech can be generated by two separate mechanisms similar to those postulated by the dual stream prediction model, according to the intentionality and egocentricity constraints of the task.…”