In our latest publication in NeuroImage we investigate the similarity of visual field maps in the cortex in a twin design. Identical (monozygotic, MZ) twins share 100% of their genes while fraternal (dizygotic, DZ) twins only share about 50% on average. This genetic profile allows researchers to make inferences about whether (and to what extent) particular traits are genetically influenced. Previous research has already shown that many aspects of brain structure are more similar in MZ twins. However, we wanted to know if this translates also into greater similarity in the organisation and functional properties of retinotopic maps. There is converging evidence to suggest that functional map organisation is related to brain structure – but this alone does not necessarily mean that retinotopic maps are also more similar in MZ twins. Our results now demonstrate that this is indeed the case: at the coarsest scale, the general spatial configuration of population receptive field maps in early visual cortex is more similar in MZ twins. Investigating maps for pRF parameters separately, we find a larger difference between MZ and DZ for polar angle estimates and pRF size, than for eccentricity (and thus arguably cortical magnification). In part this could be because in general the gradient of eccentricity maps is very consistent between people. It will be interesting to further investigate the consequences of this heritability in brain organisation on perceptual processing. While we conducted preliminary experiments on this as part of our project, answering such questions requires much larger sample sizes. These findings were therefore not included in the present study but could form the basis of future work.
This project is the culmination of many years of work. The actual research was conducted as part of my ERC grant project back at University College London, critically the hard work by my postdoc at the time, Nonie Finlayson, a research project student, Shwe Ei, and including a long list of collaborators, Ivan Alvarez, Benjamin de Haas, and John Greenwood. Due to several of us authors moving across the globe and many other technical challenges we must solve, it took a number of years until these findings could finally see the light of day.
Alvarez, I, Finlayson, NJ, Ei, S, de Haas, B, Greenwood, JA, & Schwarzkopf, DS (2021). Heritable functional architecture in human visual cortex. NeuroImage 239: 118286.