The Selectivity of Neurons in the Macaque Fundus of the Superior Temporal Area for Three-Dimensional Structure from Motion

Abstract

Motion is a potent cue for the perception of three-dimensional (3D) shape in primates, but little is known about its underlying neural mechanisms. Guided by recent functional magnetic resonance imaging results, we tested neurons in the fundus of the superior temporal sulcus (FST) area of two macaque monkeys (Macaca mulatta, one male) using motion-defined surface patches with various 3D shapes such as slanted planes, saddles, or cylinders. The majority of the FST neurons (Ͼ80%) were selective for stimuli depicting specific shapes, and all the surfaces tested were represented among the selective FST neurons. Importantly, this selectivity tolerated changes in speed, position, size, or between binocular and monocular presentations. This tolerance demonstrates that the 3D structure-from-motion (3D-SFM) selectivity of FST neurons is a higher-order selectivity, which cannot be reduced to a lower-order speed selectivity. The 3D-SFM selectivity of FST neurons was unaffected by removal of the opposed-motion cue that supplemented the speed gradient cue in the standard stimuli. When tested with the same standard stimuli, fewer neurons in the middle temporal/visual 5 (MT/V5) area were selective than FST neurons. In addition, selective MT/V5 neurons represented fewer types of surfaces and were less tolerant of stimulus changes than FST neurons. Overall, these results indicate that FST neurons code motion-defined 3D shape fragments, underscoring the central role of FST in processing 3D-SFM.

Tolerance of Macaque Middle STS Body Patch Neurons to Shape-preserving Stimulus Transformations

“…First, the gross responses of each cell were tabulated in an m × n matrix M, with m and n corresponding to the different stimuli (e.g., the five stimuli of the position test) and the transformation variable (e.g., position), respectively. The predicted response, assuming separability of the stimuli and the transformation variable, was then computed as the product of the first principal components of the singular value decomposition of M (see Mysore, Vogels, Raiguel, Todd, & Orban, 2010). The separability index equals the squared Pearson correlation (r 2 ) between the actual and the predicted responses and could range between 0 (no separability) and 1 ( perfect separability).…”

What you see depends on what you saw, and what else you saw: The interactions between motion priming and object priming

“…While there are general agreements about the early (the computation of motion from V1 to MT/V5) and late (the neural representations of 3-D objects at ventral occipitotemporal region) stages of SFM processing – similar to the field of static object recognition – what is largely unknown is the neural representations and computations at the intermediate levels, i.e., the neural mechanisms transferring 3-D motion to 3-D structure. The location of these potential intermediate neurons are also controversial – studies have proposed candidate regions like superior lateral occipital region (sLO) (Kau et al, 2013; Murray, Olshausen, & Woods, 2003; Peuskens et al, 2004, see also data from patients with lesion, Matheson & McMullen, 2010), ventral part of MT/V5 (or human analogues of hMT+) (Kolster, Peeters, & Orban, 2010; Kourtzi, Bülthoff, Erb, & Grodd, 2002; Mysore, Vogels, Raiguel, Todd, & Orban, 2010; Peuskens et al, 2004), anterior superior temporal polysensory area (STPa) (Anderson & Siegel, 2005), and parts of parietal region (Durand et al, 2007; Kau et al, 2013). To reconcile with these different results, Orban and colleagues have proposed a two-stage model of 3-D SFM processing (Mysore et al, 2010; Orban, 2011), the first step involves the extraction of linear gradients at MT/V5, and the second step involves the extraction of second-order gradients at FST, followed by further projections to regions like STPa, IPS, and sLO (Orban, 2011).…”

The ventral visual pathway: an expanded neural framework for the processing of object quality

“…The MT/MST/FST complex is sensitive to many aspects of motion (see[300] for a review) and depth[301] and contains many neurons selective for shapes defined by motion (e.g. [302]). It is likely that this complex, in concert with areas in intraparietal sulcal cortex, provide the depth and motion information needed to generate the selectivity for 3D (e.g.…”