Body patterning and cognition in cephalopods - a literature review

Abstract: Cephalopods are a valuable model for studying the evolution of cognition due to their distinctive brain structure, organisation, and connectivity patterns compared to vertebrates. The development of large brains and behavioural complexities are believed to be triggered by evolutionary pressures stemming from factors like heightened predation, more demanding foraging conditions, and intense mating competition. While the differences between corvid and mammals are less pronounced, the cephalopod brain is closer to the vertebrate brain in terms of encephalisation of ganglionic masses observed by nerve cell clusters. The cerebral ganglion in cephalopods is similar to the vertebrate forebrain and midbrain, while the vertical lobe is similar to the vertebrate cerebral cortex and hippocampus formation, which are involved in learning and memory. These brain regions function in a hierarchical system and are intimately connected with their eyes and optic lobes where visual inputs are processed, motor commands are transmitted to the lower motor centre. Chromatophores are skin elements and the physiological control of body patterning and are visually driven and light sensitive. This sets cephalopods apart from their molluscan families such as gastropods and bivalves. Recent studies have revealed that the opsins present in the skin are like those occurring in the retina. This infers that the connection between visual processing and body patterns is not exclusively innate. Expanding on Macphail's Null Hypothesis which posits no significant qualitative or quantitative differences in intelligence across vertebrates, this study seeks to explore the link between body patterning and cognitive abilities across cephalopod species. By comparing patterns of similarities and differences in cognitive abilities, this study aims to investigate whether body patterning can serve as an indicator of cognitive capacity. In conclusion, the study finds the presence of interindividual variations within species and disparities across different species in both body patterning and cognitive abilities. There are associations between cognitive capacity and body patterns. However, establishing a direct and conclusive connection between high-level cognitive abilities and the expression of body patterns remains elusive, as concrete evidence supporting such a relationship is lacking.