Self-organising coordinate transformation with peaked and monotonic gain modulation in the primate dorsal visual pathway

Abstract

We study a self-organising neural network model of how visual representations in the primate dorsal visual pathway are transformed from an eye-centred to head-centred frame of reference. The model has previously been shown to robustly develop head-centred output neurons with a standard trace learning rule [1], but only under limited conditions. Specifically it fails when incorporating visual input neurons with monotonic gain modulation by eye-position. Since eye-centred neurons with monotonic gain modulation are so common in the dorsal visual pathway, it is an important challenge to show how efferent synaptic connections from these neurons may self-organise to produce head-centred responses in a subpopulation of postsynaptic neurons. We show for the first time how a variety of modified, yet still biologically plausible, versions of the standard trace learning rule enable the model to perform a coordinate transformation from eye-centred to head-centred reference frames when the visual input neurons have monotonic gain modulation by eye-position. Author summaryCoordinate transformations are an essential aspect of behaviour. For instance, sensory information encoded in the coordinates of the retina needs to be transformed to relevant coordinates for planning and movement. Particularly, head-centred coordinates are essential for accurate motor behaviours and required to compute more complex coordinate transformations for sensorimotor integration [2]. Head-centred coordinates are obtained by combining information about the the retinal location of visual stimuli and the position of the eye. Previous work did not address the influence of different forms of gain modulation by eye position, albeit a variety of forms being widely reported for several cortical areas. Here we show how a biologically plausible model that successfully self-organised head-centred responses [1,3] fails when the visual input units have a commonly observed form of eye-position gain modulation, i.e. monotonic modulation. Our work makes an important contribution to understanding how head-centred responses may develop in the brain through an unsupervised process of visually-guided learning using a set of more sophisticated, and yet still biologically

Spatial coordinate transforms linking the allocentric hippocampal and egocentric parietal primate brain systems for memory, action in space, and navigation

“…It is proposed in this paper that this memory trace learning principle could be applied at a number of stages of processing involving different coordinate transforms in the dorsal visual system. Some progress has been made in applying this to one stage of processing, that involved in forming head‐centered representations (Navarro, Mender, Smithson, & Stringer, ).…”