Effects of prism adaptation on auditory spatial attention in patients with left unilateral spatial neglect: a non-randomized pilot trial.

A short period of adaptation to a prismatic shift of the visual field to the right briefly but significantly improves left unilateral spatial neglect. Additionally, prism adaptation affects multiple modalities, including processes of vision, auditory spatial attention, and sound localization. This non-randomized, single-center, controlled trial aimed to examine the immediate effects of prism adaptation on the sound-localization abilities of patients with left unilateral spatial neglect using a simple source localization test. Subjects were divided by self-allocation into a prism-adaptation group (n = 11) and a control group (n = 12). At baseline, patients with left unilateral spatial neglect showed a rightward deviation tendency in the left space. This tendency to right-sided bias in the left space was attenuated after prism adaptation. However, no changes were observed in the right space of patients with left unilateral spatial neglect after prism adaptation, or in the control group. Our results suggest that prism adaptation improves not only vision and proprioception but also auditory attention in the left space of patients with left unilateral spatial neglect. Our findings demonstrate that a single session of prism adaptation can significantly improve sound localization in patients with left unilateral spatial neglect. However, in this study, it was not possible to accurately determine whether the mechanism was a chronic change in head orientation or a readjustment of the spatial representation of the brain; thus, further studies need to be considered.

Somatosensory cortex excitability changes due to differences in instruction conditions of motor imagery.

Purpose Vivid motor imagery appears to be associated with improved motor learning efficiency. However, the practical difficulties in measuring vivid motor imagery warrant new analytical approaches. The present study aimed to determine the instruction conditions for which vividness in motor imagery could be more easily seen and the excitability of the sensory cortex as it relates to the motor image. Materials and methods In total, 15 healthy, right-handed volunteers were instructed to imagine grasping a rubber ball under a verbal-only instruction condition (verbal condition), a verbal + visual instruction condition (visual condition), and a verbal + execution (physically grasping a real ball) condition (execution condition). We analyzed motor imagery-related changes in somatosensory cortical excitability by comparing somatosensory-evoked potentials in each condition with the rest (control) condition. We also used a visual analogue scale to measure subject-reported vividness of imagery. Results We found the N33 component was significantly lower in the execution condition than in the rest condition (p < 0.05). The results suggested a gating effect via central efferent mechanisms that affected the excitability of areas 3b or 1 in the primary somatosensory cortex, but only in the execution condition. Conclusions These data suggest that experiencing a movement through actual motor execution immediately prior to performing mental imagery of that movement enhances the excitability of motor-related cortical areas. It is suggested that the excitability of the motor-related region increased as a result of the motor imagery in the execution condition acting on the corresponding somatosensory cortex.