Left Tactile Agnosia Amelioration by Prism Adaptation Sustains Unilateral Spatial Neglect-Based Hypothesis

Abstract

Objective: Left tactile agnosia has never been described as part of the neglect syndrome so far. We observed two patients with left tactile agnosia, following a right hemisphere stroke and test if impairment in their unilateral tactile object recognition could be due to Unilateral Spatial Neglect. Method: patients were submitted to three different experimental tests assessing the tactile recognition of micro and macro structural characteristics of shapes, the number of hands' explorative movements and the effects of prism adaptation on tactile object recognition impairment. Results: patients showed a left tactile agnosia, which was neither related to impairment in microstructural nor macrostructural recognition of shapes. Similarly to controls, patients performed more exploratory movements with the left hand, which resulted to be impaired in object recognition, suggesting that tactile apraxia was not the cause of this tactile agnosia. After 10 days treatment with prism adaptation procedure, both neglect symptoms and left tactile agnosia improved. Conclusions: The absence of other causes of left tactile agnosia and the efficacy of prism adaptation on it, support the functional relation between tactile agnosia and tactile neglect.