The representation continues through to size- and viewpoint-invariant representations of shape in higher cortical regions, such as the lateral occipital cortex (Grill-Spector, Kourtzi, & Kanwisher, 2001 Kourtzi & Kanwisher, 2000 Sawamura, Georgieva, Vogels, Vanduffel, & Orban, 2005 Silson et al., 2013) and inferior temporal cortex (Afraz & Cavanagh, 2009).

The resulting visual representation is then processed through a hierarchy of cortical areas (Op de Beeck, Torfs, & Wagemans, 2008), each with increasing receptive field sizes (Felleman & Van Essen, 1991 Grill-Spector & Malach, 2004 Lennie, 1998 Wilson & Wilkinson, 2015). The processing of local orientation information, critical for detecting shape boundaries, begins in area V1 of the visual cortex (Blakemore & Campbell, 1969 Ferster & Miller, 2000 Hubel & Wiesel, 1968 Loffler, 2008). The human visual system is capable of efficiently processing the visual information in a scene to reliably recognize critical objects. Additionally, this study shows that the perceptual characteristics and neuroanatomical substrates can be detected using electrophysiological measures. These findings suggest that corners contain vital information for the discrimination of shapes. Source localization on the N170 and N220 components was conducted in Experiment 2, and a source in cortical area V4 was identified. In Experiment 2, we confirm the primary effect of the presence of corners on the amplitude of the posterior N220 component and extend the stimuli to include shapes defined by texture. An enhanced negativity (posterior N220) over the occipital lobe was elicited following the presentation of an RF with three modulation cycles (RF3) but not following a circle, suggesting that the posterior N220 is sensitive to variation in curvature on a contour. The results showed that the angle separating corners was more critical than the overall number of corners for discrimination performance. In Experiment 1, event-related potentials were recorded while participants discriminated between two radial frequency (RF) patterns with the same maximum local curvature defining corners but varying arrangements of those corners.

The aim of the current study was to examine the relative contribution of the number of corners and the angle between corners to shape discrimination in complex visual scenes as well as to determine the time course and neural substrates of global shape processing based on the presence or absence of these specific features. Turning point is attested by 1640s in a figurative sense 'point at which a decisive change takes place ' literal sense 'point on which a thing turns point at which motion in one direction ceases and that in another or contrary direction begins' is from 1660s.The number of corners on the boundary of a closed contour is thought to be particularly critical for shape detection and discrimination. To turn up one's nose as an expression of contempt is attested from 1779. To turn the stomach 'nauseate' is recorded from 1620s. Turn in 'go to bed' is attested from 1690s, originally nautical. Turn down (v.) 'reject' first recorded 1891, American English. To turn (something) loose 'set free' is recorded from 1590s. Turn about 'by turns, alternately' is recorded from 1640s. Use in expression to turn (something) into (something else) probably retains the classical sense of 'to shape on a lathe.' To turn up 'arrive, make an appearance' is recorded from 1755. Late Old English turnian 'to rotate, revolve,' in part also from Old French torner 'to turn away or around draw aside, cause to turn change, transform turn on a lathe' (Modern French tourner), both from Latin tornare 'to polish, round off, fashion, turn on a lathe,' from tornus 'lathe,' from Greek tornos 'lathe, tool for drawing circles,' from PIE root *tere- (1) 'to rub, turn.' Transitive sense in English is from c.

Contour definition in shape