A particular difficulty in discriminating between mirror images

Abstract

We investigated the selective impairment of mirror image discrimination in a patient with bilateral parieto-occipital lesions (FIM). We report a difficulty with the discrimination between mirror images more selective than has been previously reported (Turnbull OH, McCarthy RA. Failure to discriminate between mirror-image objects: a case of viewpoint-independent object recognition? Neurocase 1996;2:63). FIM was asked to judge, in five same/different experiments, whether pairs of simultaneously presented line drawings of objects were identical. FIM demonstrated only a minor impairment in discriminating between orientations in the picture plane but was at chance in making discrimination between mirror images. An experiment with normal observers established that our results were not due to differences in task difficulty. Two further experiments investigated the effects of rotation on the discrimination of letters and geometric shapes. FIM's impairment extended to geometric shapes but not to letters. These results would be consistent with the preservation of an abstract representation for object recognition that did not code the difference between mirror image views.

Hierarchical Processing of Face Viewpoint in Human Visual Cortex

“…A similar approach was recently used to show tuning for gratings' orientation in the striate cortex (Serences et al, 2009) and to investigate the representation of scenes in the PPA (Walther et al, 2009;Park et al, 2011). Using classification error rates, we revealed evidence for partial view invariance for mirror-symmetric views (mirror confusion), which has been reported in behavioral and neurophysiological studies in both humans and animals (Mach, 1914;Sutherland, 1960;Nickerson and Adams, 1979;Logothetis and Sheinberg, 1996;Davidoff and Warrington, 2001). The high-level faceselective areas (FFA and STS) and the LO object area all showed a characteristic inverted bell-shaped tuning curve, indicating that the highest confusion was between mirror-symmetric profiles compared with all other views.…”

Breaking the symmetry: Mirror discrimination for single letters but not for pictures in the Visual Word Form Area

“…Indeed, neuropsychological data suggest that, in expert readers, the visual recognition of mirror images involves distinct neural systems for letters and written words than for other non-linguistic visual objects. Some patients, following parieto-occipital lesions, suffer from a specific visual leftright orientation agnosia, i.e., they become unable to distinguish the left-right orientation of objects, even though they are still able to recognize them (Turnbull and McCarthy, 1996;Davidoff and Warrington, 2001;Priftis et al, 2003;Vinckier et al, 2006). Remarkably, mirror discrimination of letters/words is perfectly intact in these patients.…”

“…Inter-hemispheric connections through the corpus callosum, linking symmetrically regions of each hemisphere point by point, would operate in such a way that a "b" in one hemisphere would become a "d" in the other (Corballis and Beale, 1976;Dehaene, 2009). Others authors (Rollenhagen and Olson, 2000;Davidoff and Warrington, 2001) stress that mirror discrimination, for identification purposes, does not represent any evident advantage in a natural world when the vast majority of living and non-living forms do not change category under mirror symmetry. It is therefore plausible that the orientation information is simply not coded at all, so that separate representations of original and mirror representations do not exist, which seems coherent with single neuron monkey data (Logothetis et al, 1995;Rollenhagen and Olson, 2000).…”

Mirror-image relations in category learning

“…Previous work has considered mirror-image-discrimination mainly as an existing skill, the presence (or absence) of which being indicative either of the status of cognitive development (Rudel & Teuber, 1963;Bornstein, Gross & Wolf, 1978), or of a particular perceptual deficit within neurological patient populations (Turnbull & McCarthy, 1996;Davidoff & Warrington, 2001, Priftis et al 2003). The present study transcends this perspective by focussing on the learning of mirrorimage discrimination skills in normal adult observers, and on the way in which such skills are embedded into the process of pattern categorization -the cognitive backbone of visual perception (Bruner, 1957;Rosch, 1978).…”

“…This finding, and the fact that practice does reduce plane rotation costs in object naming but not in left/right orientation judgements (Jolicoeur, 1989), indicate that object identification does not necessarily imply the ability to distinguish between mirror images. In fact, neuropsychological evidence shows that mirror-image discrimination may be selectively impaired, leaving object recognition skills spared (Turnbull & McCarthy, 1996;Davidoff & Warrington, 2001, Priftis et al 2003. 3 Adopting an evolutionary perspective, Gross & Bornstein (1976) argue that the tendency to confuse mirror images may reflect an adaptive mode of processing rather than a perceptual limitation.…”