, 1972, Fujita et al., 1992, Gallant et al., 1993, Kobatake and Tanaka, 1994, Janssen

et al., 2000a, Rollenhagen and Olson, 2000, Tsunoda et al., 2001, Baker et al., 2002, Hung et al., 2005, Leopold et al., 2006, Tsao et al., 2006, Freiwald et al., 2009 and Freiwald and Tsao, 2010), there has been no way to distinguish whether they are driven specifically by internal medial axis shape. In fact, studies have consistently shown that ventral pathway neurons represent external boundary shape fragments, either 2D contours or 3D surfaces, which require less computation to derive from visual images (Pasupathy and Connor, 1999, Pasupathy and Connor, 2001, Brincat and Connor, 2004, Yamane et al., 2008 and Carlson et al., 2011). Here, we addressed this buy Sunitinib theoretical/experimental gap by testing for medial axis coding directly and comparing medial axis and surface coding. We studied 111 visually responsive neurons recorded from central and anterior IT cortex (13–19 mm anterior to the interaural line) in two awake, fixating monkeys. We used adaptive

shape sampling algorithms (Yamane et al., 2008 and Carlson et al., 2011) for efficient exploration of neural responses in the medial axis and surface domains. We used metric shape analyses to characterize neural tuning in both domains. We found that many IT neurons explicitly Dasatinib mw encode medial axis information, consistently responding to configurations of 1–12 axial components. We found that this configural medial axis tuning exists on a continuum with surface tuning, Cytidine deaminase and that most cells are tuned for shape configurations combining both axial and surface elements. We used an adaptive stimulus strategy guided by online neural response feedback. Compared to random or systematic sampling, adaptive sampling makes it possible to study much larger domains of more complex shapes, by

focusing sampling on the most relevant regions within those larger domains. To optimize sampling in both the axial and surface domains, it was necessary to use two different adaptive paradigms simultaneously. This is because complex surface shape and complex axial shape are geometrically exclusive. Elaborate skeletal shape is only perceptible if surfaces are shrunk around the medial axes, limiting surface complexity on a visible scale. Conversely, elaborate surface shape requires surface expansion, which eliminates and/or obscures complex skeletal structure. An example of the medial axis adaptive sampling paradigm is shown in the left column of Figure 1A. The first generation of medial axis stimuli (M1.1) comprised 20 randomly constructed shapes with 2–8 axial components that varied in orientation, curvature, connectivity, and radius (see Experimental Procedures and Figure S1A, available online, for stimulus generation details). These shapes were presented on a computer screen for 750 ms each, in random order, at the center of gaze while the monkey performed a fixation task.