Motor Extinction in Distinct Reference Frames: A Double Dissociation

Jennifer Heidler-Gary,Melissa Newhart,Mikolaj Pawlak,Cameron Davis,Edward H Herskovits,Argye E Hillis,Lydia A Trupe

doi:10.1155/2013/181903

Abstract

Objective:Test the hypothesis that right hemisphere stroke can cause extinction of left hand movements or movements of either hand held in left space, when both are used simultaneously, possibly depending on lesion site.Methods:93 non-hemiplegic patients with acute right hemisphere stroke were tested for motor extinction by pressing a counter rapidly for one minute with the right hand, left hand, or both simultaneously with their hands held at their sides, or crossed over midline.Results:We identified two distinct types of motor extinction in separate patients; 20 patients extinguished left hand movements held in left or right space (left canonical body extinction); the most significantly associated voxel cluster of ischemic tissue was in the right temporal white matter. Seven patients extinguished either hand held in left space (left space extinction), and the most significantly associated voxel cluster of ischemic tissue was in right parietal white matter.Conclusions:There was a double dissociation between left canonical body extinction and left space motor extinction. Left canonical body extinction seems to be associated with more dorsal (parietal) ischemia, and left canonical body extinction seems to be associated with more ventral (temporal) ischemia.

Highlights

Left-sided extinction with double simultaneous stimulation occurs when a patient can detect a stimulus on the side contralateral to the lesioned hemisphere, but fails to detect the same stimulus when presented simultaneously on the side ipsilateral to the lesion
We hypothesized that, depending on the lesion site, right-hemisphere ischemic stroke can cause extinction of either left hand movements or movements of either hand held in left space when both hands are moving simultaneously
There are dissociable types of left motor extinction, distinguished by reference frame– one in which the patient extinguishes movements of the left hand, irrespective of the location of the hand, and one in which the patient extinguishes the either hand held in left space

Summary

Introduction

Left-sided extinction with double simultaneous stimulation occurs when a patient can detect a stimulus on the side contralateral to the lesioned hemisphere, but fails to detect the same stimulus when presented simultaneously on the side ipsilateral to the lesion. We reported the surprising finding that left motor extinction (failure to move the left hand or early discontinuation of left hand movements only when the right hand was moving simultaneously) in patients with acute right hemisphere stroke was associated with infarct and/or hypoperfusion (tissue dysfunction) in right superior temporal cortex [14]. This area has been reported as frequently associated with hemispatial neglect [20,22], or stimulus/object-centered hemispatial neglect but not viewer-centered neglect [16], it was surprising that superior temporal cortex ischemia was associated with motor extinction rather than visual or tactile extinction. We speculated that motor extinction reflected extinction of the canonical left side of the body (a specific type of object-centered or allocentric neglect), irrespective of where the hand was placed in space relative to the midline of the viewer (or person) making the movements

Methods

Discussion

Conclusion