Fig. 7: Summary of LIP intrinsic connectivity, the wider cortical network and the proposed circuit for processing perceptual decisions about 3D motion in macaques.

A This diagram summarises the key findings of the intrinsic connectivity pattern between LIPd and LIPv from this study. LIPv, previously shown to be topographically organised²⁵, sends a point-to-point projection to LIPd (blue arrows). In turn, each point in LIPv receives inputs from a number of different regions within LIPd (white arrows). Within both compartments, there is widespread connectivity. B Illustration of selected, previously established cortico-cortical in- and outputs to LIPv and LIPd. Extrastriate visual area V5/MT projects exclusively to LIPv, not LIPd, while ventral stream visual area V4 has a stronger projection to LIPd^9,13. The frontal eye fields (FEF) send a feedforward-type projection to LIPd, and a feedback-type projection to LIPv¹⁵. These connections with FEF are reciprocal. C Illustration of the proposed processing scheme for perceptual decisions about 3D structure-from-motion stimuli, based on input of perceptual evidence represented in area V5/MT^49,50 projected in a topographic fashion to LIPv. This input can convey perceptual signals about direction of motion and 3D depth localised to specific locations in the visual field. The intrinsic network between LIPv and LIPd can map one input (topographically mapped in LIPv) to other potential visual field locations through the connectivity loop with LIPd. The specific association between the sensory RF and saccade MF might be achieved gradually in a recurrent network. Interconnected with a feedforward connection into LIPd and receiving input from LIPv, FEF signals could support an attentional shift from stimulus to choice target representations and thus facilitate the association of the stimulus with a specific choice target. The map of planned saccade target locations in FEF is thus connected to the visual perceptual map in V5/MT through the circuitry in LIP. The specific associations of RF and MF in single neurons we found could be the product of the daily visual experience of the animals directing saccades to salient visual features and the specific training the animals underwent to learn to make perceptual decisions about 3D structure-from-motion objects. Arrows intrinsic connectivity: blue – projection to LIPd injection site, white – to LIPv injection site; arrows inter-area connectivity: black – feedforward, grey – feedback.