Biology subjects

Estienne, P.

Publications and source records attributed to Estienne, P..

3 recordsLinked to original sources

bioRxiv2025

Problem-solving without a cortex: inferior lobe drives goal-directed object manipulation in cichlid fish

Goal-directed object manipulation and problem-solving, which are necessary to evolve tool use behaviors, have long been linked to the expansion of the telencephalon in mammals and birds. Here, we show that goal-directed object manipulation in cichlid fish is driven by a non-telencephalic brain structure, the inferior lobe. Using manganese-enhanced MRI (MEMRI) on an ultra-high field 17.2 Tesla MRI system, we show that the inferior lobe is activated during a puzzle-box opening task. Furthermore, magnetic resonance (MR)-guided High Intensity Focused Ultrasound (HIFU) lesions profoundly impair fine motor coordination during this task without affecting general locomotion or motivation. These results reveal that cortex-like cognitive functions can arise from non-telencephalic brain structures in teleosts. With no homolog in tetrapods, the inferior lobe is a critical hub for flexible behavior in teleost fish. Our findings highlight the existence of alternative neural architectures for the emergence of complex cognition.

neuroscience↗

bioRxiv2025

Functional Brain Imaging and Targeted Lesion Studies Using Manganese-Enhanced MRI and Focused Ultrasound in Non-Conventional ModelSpecies

Linking behavior to its neuroanatomical basis in non-conventional model species remains a significant challenge due to the scarcity of imaging and molecular tools. Commonly used approaches such as electrophysiological recordings rely on precise stereotaxic atlases or species-specific antibodies, while optogenetics requires transgenic lines which are largely unavailable beyond classical model organisms (e.g., mice, rats, zebrafish). Moreover, surgical lesion studies, a staple for verifying brain structure and behavior relationships, are logistically complex in species lacking atlases or living in aquatic environments. Here, we present a protocol integrating Manganese-Enhanced Magnetic Resonance Imaging (MEMRI) and MR-guided High-Intensity Focused Ultrasound (HIFU) to overcome these limitations, which we demonstrate in the convict cichlid (Amatitlania nigrofasciata), a teleost fish lacking conventional neuroscience tools. MEMRI enables non-invasive, sub-millimeter resolution mapping of brain activity during behavior, and HIFU facilitates precise, surgery-free lesioning of targeted regions, adaptable to species without stereotaxic atlases. This combined approach offers a versatile, broadly applicable framework for linking brain structure and behavior in non-model organisms, advancing evolutionary and comparative neuroscience.

neuroscience↗

bioRxiv2022

Different ways of evolving tool-using brains in teleosts and amniotes

In mammals and birds, tool-using species are characterized by a high degree of encephalization with a relatively large telencephalon containing a higher proportion of total brain neurons compared to other species. Some teleost species in the wrasse family have convergently evolved tool-using abilities. In this study, we compared the brains of tool-using wrasses with various teleost species from a broad phylogenetic range. Using the isotropic fractionator, we show that in the tool-using wrasses, the telencephalon and the ventral part of the forebrain and midbrain are significantly enlarged compared to other teleost species but do not contain a larger proportion of cells. Instead, we found with tract tracing and selective neuronal fiber visualization that this size difference is due to large fiber tracts connecting the dorsal part of the telencephalon (pallium) to the inferior lobe (IL), a ventral mesencephalic structure absent in amniotes. The high degree of connectivity between the IL and the pallium in tool-using wrasses suggests that this unique teleostean structure could contribute to higher-order cognitive functions. Given remarkable differences in their overall brain organization, we conclude that, unlike in amniotes, the evolution of non-telencephalic structures might have been key in the emergence of higher-order cognitive functions in teleosts.

neuroscience↗