How problem solving changes affect adult neurogenesis in Octopus vulgaris

Octopus vulgaris has a complex and centralized nervous system, located around oesophagus, with a hierarchical organization. It is considered the most intelligent invertebrate due to its advanced cognitive capability, as learning and memory, and complex behaviour that results in an enormous capability of problem solving. “Problem solving” is the capability to use cognitive processing to find a solution to a problematic situation. Several behavioural experiments show that octopus has this kind of skill (FINN et al., 2009). Neural plasticity and synaptic remodelling are the base of adult neurogenesis that occur in organisms that have complex and centralized nervous system, as teleosts, amphibians, reptiles, birds and mammals, and among invertebrates, decapods and insects. Recently, our group demonstrated its occurrence also in O. vulgaris brain, resulting the first demonstration across Lophotrochozoa clade. The experimental data have been obtained by problem solving behavioural experiments and the evaluation of the Oct-Pax6 expression. Pax6 gene is known as neurogenic marker during cephalopod brain development (NAVET et al., 2017). Specimens of O. vulgaris were divided into two experimental groups: challenged and control. After the acclimatization period, the standard housing condition was altered adding jars containing food providing a cognitive challenge. During experimental days, octopuses had not feeding opportunities except to open the jars to reach the food. Control animals were not challenged and they were fed regularly without any task. At last, challenged and control octopuses were scarified as described in POLESE et al. (2014) and their brains were dissected out to be processed for RNA extraction with Trizol. cDNA obtained was used to evaluate the amount of Oct-Pax6 through a semi-quantitative PCR, using -tubulin as normalizer. PCR products were analysed on 2% agarose gel at the Bio-Rad ChemiDoc, and quantified using ImageJ. Our data show that octopuses challenged with problem solving tasks vs. unchallenged animals result in up- regulation of Oct-Pax6 in areas of the brain previously described as sites of adult neurogenesis (BERTAPELLE et al., 2017). In conclusion, these results support that intellectual, physical and sensory challenges increase neural plasticity and synaptic remodelling through adult neurogenesis.