Neglect and Visual Recognition

Abstract

B.Q., a right-handed woman who had suffered a stroke affecting the right parietal region, showed visuospatial neglect and problems in recognizing seen objects and faces. Investigation of her visual recognition problems revealed a striking inability to identify the left sides of chimaeric objects and faces. Often, B.Q. would deny that the stimulus was chimaeric at all, and she was remarkably poor (though above chance) at discriminating chimaeric from normal faces. Even when left-sided details had been accurately traced or described, they were often either ignored in reporting the identities of the constituent parts of a chimaeric or assimilated in some way to the information from the right side. Neglect of the left side was more pronounced for chimaerics which approximated an individual face or object. It occurred regardless of the chimaeric's position in B.Q.'s field of vision, and was found with brief (200 ms) presentations of stimuli confined to her (perimetrically intact) right visual field. When chimaeric faces were inverted, B.Q. continued to neglect the side of the chimaeric falling to her left, which implies that the neglect did not operate in entirely object-centered coordinates. However, left-sided information could be used if it was critical in determining the identity of an object or a face. We suggest that this could explain B.Q.'s lack of neglect of individual words, for which left-sided (initial) letters are often crucial to successful recognition. An account of her deficit is proposed, involving an interaction between moderately defective pick-up of left-sided information in an object-based coding system and preserved access to stored representations of familiar visual stimuli.

Object-based attention: A tutorial review

“…Interestingly, when the shapes were tilted 45°to the right, she continued to show poor performance when the shapes differed on their left side even though the differences were now in her intact right side of space. Similar results were reported by a number of other researchers (e.g., Behrmann & Moscovitch, 1994;Caramazza & Hillis, 1990;Driver, Baylis, & Rafal, 1992;Marshall & Halligan, 1994;Young, Hellawell, & Welch, 1992). In all these studies, patients with neglect in their left visual field were less impaired in performance when the critical information was on the right side of the objects, even when the right side of the objects was in their impaired left side of space (cf.…”

Orienting of attention via observed eye gaze is head-centred

“…These effects suggest that the intrinsic head-centred representations of faces can affect the coding of stimuli on the face. That is, the left side of the face is encoded, at least in part, as the left side however it is oriented in space (see also, Young, Hellawell, & Welch, 1992). Indeed, some STS cells do code faces in object-centred coordinates (Hasselmo, Rolls, Baylis, & Nalwa, 1989;.…”

Modality-specific frontal and parietal areas for auditory and visual spatial localization in humans

“…IPL lesions, on the other hand, typically produce a hemispatial neglect syndrome with deficits in attention, response and orientation to stimuli in the contralesional part of space 30 . IPL lesions may also impair other perceptual processes such as object feature recognition and time perception 31,32 . Indeed, the human IPL has been described by some as a 'third stream' of visual processing where inputs from the dorsal stream in the SPL encoding spatial locations and from the ventral (occipitotemporal) stream regarding object identity are associated 30 .…”