An evaluation of how connectopic mapping reveals visual field maps in V1

Abstract

Functional gradients, in which response properties change gradually across the cortical surface, have been proposed as a key organising principle of the brain. However, the presence of these gradients remains undetermined in many brain regions. Resting-state neuroimaging studies have suggested these gradients can be reconstructed from patterns of functional connectivity. Here we investigate the accuracy of these reconstructions and establish whether it is connectivity or the functional properties within a region that determine these “connectopic maps”. Different manifold learning techniques were used to recover visual field maps while participants were at rest or engaged in natural viewing. We benchmarked these reconstructions against maps measured by traditional visual field mapping. We report an initial exploratory experiment of a publicly available naturalistic imaging dataset, followed by a preregistered replication using larger resting-state and naturalistic imaging datasets from the Human Connectome Project. Connectopic mapping accurately predicted visual field maps in primary visual cortex, with better predictions for eccentricity than polar angle maps. Non-linear manifold learning methods outperformed simpler linear embeddings. We also found more accurate predictions during natural viewing compared to resting-state. Varying the source of the connectivity estimates had minimal impact on the connectopic maps, suggesting the key factor is the functional topography within a brain region. The application of these standardised methods for connectopic mapping will allow the discovery of functional gradients across the brain. Protocol registration The stage 1 protocol for this Registered Report was accepted in principle on 19 April 2022. The protocol, as accepted by the journal, can be found at https://doi.org/10.6084/m9.figshare.19771717.

Gradient organisation of functional connectivity within resting state networks is present from 25 weeks gestation in the human fetal brain

“…For the primary visual network, both a principal connectopic gradient with an inferiorsuperior organisation and a secondary connectopic gradient with an anteriorposterior organisation were identified in the fetal cortex (Fig. 2A), consistent with connectopic mapping work in adults where two distinct gradients representing polar angle and eccentricity of vision are seen (Haak et al, 2018;Watson & Andrews, 2022). Assessing the global spatial similarity of each gradient across gestational age showed that the connectopic maps were remarkably replicable and symmetrical in topography, both across hemispheres and gestation, despite being derived independently (Fig.…”

“…Globally, this organisation remains largely stable across the studied age range, suggesting that the organisation of these RSNs is shaped early in gestation and is intrinsically determined. This was most evident in the primary sensory and motor networks, which showed remarkably consistent connectopies across our study period of 25-37 GW that are already comparable to the canonical topographic organisation of functional connectivity in corresponding cortical regions in the mature adult brain (Haak et al, 2018;Ngo et al, 2021;Park et al, 2021;Watson & Andrews, 2022). Within this, we have identified local clusters of age-related differences in the gradient values, suggesting an on-going refinement of their connectivity structure.…”

“…Our results demonstrate that in the human fetal cortex, finer grain organisations of RSNs are indeed present from 25 GW. Furthermore, the topographies of the fetal functional gradients we have identified here are remarkably reminiscent of the functional organisation present in the mature lateral and medial motor gradients, principal and secondary visual gradients, and somatosensory gradient (Haak et al, 2018;Ngo et al, 2021;Park et al, 2021;Watson & Andrews, 2022).…”

Linking functional and structural brain organisation with behaviour in healthy adults

“…For instance, it has long been known that the brain has behaviourally relevant topographic organisations and regions may have multiple overlapping functional organisations (Kaas 1997; Jbabdi, Sotiropoulos, and Behrens 2013). Recently, various methods have been developed to investigate the ‘gradual’ organisation of the brain, see (Watson and Andrews 2022) for an overview and comparison of methods. These methods are termed ‘connectopic mapping’.…”