Kinesthetic Alexia due to Left Parietal Lobe Lesions

Abstract

To investigate the neuropsychological mechanisms of kinesthetic alexia, we asked 7 patients who showed kinesthetic alexia with preserved visual reading after damage to the left parietal region to perform tasks consisting of kinesthetic written reproduction (writing down the same letter as the kinesthetic stimulus), kinesthetic reading aloud, visual written reproduction (copying letters), and visual reading aloud of hiragana (Japanese phonograms). We compared the performance in these tasks and the lesion sites in each patient. The results suggested that deficits in any one of the following functions might cause kinesthetic alexia: (1) the retrieval of kinesthetic images (motor engrams) of characters from kinesthetic stimuli, (2) kinesthetic images themselves, (3) access to cross-modal association from kinesthetic images, and (4) cross-modal association itself (retrieval of auditory and visual images from kinesthetic images of characters). Each of these factors seemed to be related to different lesion sites in the left parietal lobe.

Multimodal alexia: Neuropsychological mechanisms and implications for treatment

“…She often reverted to guessing “A, R, S, T” when she could not immediately name the letter. Taken together, these results suggested that ST’s kinesthetic alexia was caused by a kinesthetic-verbal disconnection similar to some of the cases described in the Japanese literature (Fukatsu et al, 1998; Ihori et al, 2000; 2002). The kinesthetic-verbal disconnection was not evident in the patient control group, however, prompting a closer examination of the lesion profile in ST relative to the PCA stroke group and the cases of kinesthetic alexia reported in the literature.…”

“…Kinesthetic reading requires intact somatosensory perception, retrieval of “kinesthetic images” (Ihori et al, 2002) for letters stored in graphic motor programs (Rapcsak & Beeson, 2002), and the activation of the corresponding letter name codes. ST’s kinesthetic alexia could not be attributed to impaired somatosensory perception of letter shape information or defective activation of graphic motor programs, as we have shown that she was able to write letters accurately with both hands based on kinesthetic input.…”

“…Accurate completion of these tasks required letter-shape recognition from kinesthetic input, activation of corresponding graphic motor programs, and access to letter name codes (cf. Ihori et al, 2002). …”

“…Relevant to this issue is the fact that there are some individuals for whom this skill is selectively impaired. A cohort of Japanese individuals with “kinesthetic alexia” who were unable to name letters or read words via the kinesthetic modality have been described by several investigative teams (Fukatsu, Fujii & Yamadori, 1998; Ihori, Kawamura, Fukuzawa & Kamaki, 2000; Ihori, Kawamura, Araki & Kawachi, 2002). Despite having intact visual reading and somatosensory function, some of these individuals demonstrated a kinesthetic-verbal disconnection attributed to damage to left parietal cortex and underlying white matter.…”

“…Considered relative to the visual alexia literature, these observations suggest an apparent double dissociation between visual and kinesthetic impairments of reading. Specifically, damage to left occipito-temporal cortex results in defective visual identification of letters and words with preserved kinesthetic reading (e.g., Lott et al 1994; Maher et al, 1998), whereas the opposite pattern is observed in patients with left parietal lesions (Fukatsu et al, 1998; Ihori et al, 2000; 2002). …”