A new study published in Science reveals that zebrafish organize and combine sensory information through a hierarchical system similar to features found in mammalian brains, according to findings announced on Jul. 31 by researchers led by Prof. Emre Yakşi of the Norwegian University of Science and Technology and Koç University Research Center for Translational Medicine.
The research team examined how young zebrafish responded to visual stimuli and vibrations using advanced neural imaging and circuit-mapping methods. They tracked how these signals entered the forebrain and changed as they moved through different brain regions. The study identified the preglomerular complex, or PG, as the main source of visual and vibrational information reaching the zebrafish pallium, which is an evolutionarily related counterpart of the vertebrate cerebral cortex.
According to the researchers, “The PG and its projections to the pallium were organized according to both sensory modality and spatial location. Visual and vibrational signals initially followed distinct pathways and reached different regions of the pallium.”
As information progressed within the pallium, organization became more complex: some neurons responded specifically to one type of input while others responded to multiple types. The team also identified neurons with nonlinear responses that remained inactive when presented with either light or vibration alone, but responded strongly when both stimuli occurred together. The researchers said this activity may help determine whether separate sensory signals belong to a single event.
The findings show a spatially organized hierarchy in the zebrafish forebrain where neurons responding only to individual inputs are found alongside those capable of integrating information from different senses. This transition from specific responses toward multimodal integration resembles hierarchical processing observed in mammalian thalamocortical systems.
While anatomical structures differ between fish and mammals, both appear to use similar computational logic: initially separating, then progressively integrating sensory data for perception and adaptive behavior. The results suggest hierarchical sensory processing could be a convergent organizational principle across vertebrate brains. Researchers plan further studies into cellular identities within these circuits as well as their influence on learning, decision-making, and adaptive behavior.
