From hidden springs to endless oceans: exploring the complementary roles of the amygdala and hippocampus in phenomenal experience.

Consciousness is often thought to be centered on the self, with the insular cortex and subcortical regions supporting self-modeling and motivation. However, reports of minimal phenomenal experience (MPE) describe states without any self-referential content, challenging this ego-centric view. This theoretical paper proposes a dual-origin theory of cortical development to explain this duality. The 'Amygdala-System', expanding from the amygdala and olfactory system, supports interoceptive self-modeling and ego-centric processing. In contrast, the 'Hippocampus-System', centered on the hippocampus, supports allocentric cognition and selfless experiences, akin to an 'endless ocean'. MPE may be a fragile form of consciousness typically overshadowed by the Amygdala-System. Real-time fMRI neurofeedback could upregulate the Hippocampus-System to enable controlled study of MPE.

Study at a glance

Abstract

Current theories of consciousness often emphasize its ego-centric functions, highlighting the role of the insular cortex in interoceptive self-modeling and subcortical brain regions in qualitative experience and motivation, aptly described as the 'hidden spring' of consciousness. From ecological and pragmatic perspectives, conscious experience may facilitate the self-organization of complex organisms by optimizing goals that are typically parallel, multifaceted, and difficult to reconcile. However, the notion that all forms of conscious experience are ego-centric, or at least grounded in a minimal sense of self, is challenged by credible reports of minimal phenomenal experience (MPE), which occur without any self-referential content. I propose that this apparent duality in conscious experience can be explained by the dual-origin theory of cortical development. This theory suggests a gradual expansion of cortical cytoarchitecture from two distinct subcortical origins. The 'Amygdala-System' supports interoceptive self-modeling for habitual interactions with the body and the environment. It expands ventrally from the olfactory system and amygdala, enabling ego-centric processing. In contrast, the 'Hippocampus-System', centered on the hippocampus and expanding dorsally, supports allocentric cognition and experiences that are not constrained by self-referential processing. This complementary system allows for open-ended, selfless forms of experience, akin to an 'endless ocean'. In this framework, MPE may represent a fragile form of consciousness, typically overshadowed by the self-related interoceptive and exteroceptive functions of the Amygdala-System. Finally, I discuss how real-time functional magnetic resonance imaging (fMRI) neurofeedback could be used to upregulate the Hippocampus-System, potentially enabling the controlled study of MPE in neuroscientific settings.