Neglect dyslexia: whole-word and within-word errors with parafoveal and foveal viewing

Abstract

Patients with left-sided neglect dyslexia often omit whole words positioned on the left, termed whole-word errors, or commit errors on the left-sided letters of words, termed unilateral paralexias. In addition, the errors have been shown to be exacerbated by simultaneously presented distractors, which has been interpreted as a failure of selective attention. In two experiments, we examined the dependency of these error types on parafoveal versus foveal viewing. The first experiment used a paradigm with parafoveal targets and distractors; the second a paradigm with foveal targets and parafoveal distractors. This enabled a separate evaluation of the influences of stimulus position within an egocentric frame, a two-word allocentric frame, and a within-word allocentric frame. First, regarding whole-word errors, we found the expected spatial and distractor effects with parafoveal targets and distractors. With foveal targets and parafoveal distractors, however, the spatial effect was effectively eliminated. Surprisingly, intrusions from the distractor word were common in distractor conditions. This is consistent with an egocentric account and not a two-word allocentric account. Second, we found that unilateral paralexias remained largely consistent regardless of spatial position or the presence of a distractor. Thus, there is a contrast in spatial and distractor effects between whole-word errors and unilateral paralexias. These results are consistent with three distinct deficits: an egocentric deficit across space resulting in whole-word errors, a failure of selective attention that results in whole-word intrusion errors, and a within-word allocentric deficit resulting in unilateral paralexias.

Dissociation between Selecting and Orienting Attentional Reading Deficits: A Study in Adults with Epilepsy

“…Other spatial dyslexia can occur because the lesion produces a pathological bias affecting the orienting of attention, producing asymmetric performance. For example, in spatial neglect, a deficit in which patients ignore stimuli located on the contralesional side, patients make frequent errors reading words located in the contralesional space in a text or in a two-word bilateral display [ 13 , 14 , 15 ], or reading letters located in the contralesional part of a single word, mainly involving letter omission and substitution errors [ 16 , 17 ]. This type of deficit, namely neglect dyslexia, is frequent after lesions of the posterior part of the brain, and can sometimes occur without spatial neglect for nonverbal stimuli [ 18 , 19 ].…”

“…In the present study, we were particularly interested in egocentric deficits, because they show the importance of some orienting process to shift attention from one word to the other. Rich and Palmer [ 13 ] found that not only patients made word omission errors when two words, one in each visual hemifield, were presented and only one cued word had to be reported, but they sometimes replaced the target word by the distractor word located on the right ipsilesional side. These intrusion errors were interpreted by the authors as a mislocalization of the contralesional cue or of the contralesional word in the two-word pair.…”