Neuropsychological evidence that somatic stimuli are spatially coded according to multiple frames of reference in a stroke patient with tactile extinction.

A right-brain damaged patient with pure tactile extinction was asked to report series of single or double light, brief touches delivered to both hands, the thumb or the pinkie of a single hand, the sides of a single index. The stimulated hand was positioned palm up or palm down, in front of or behind the patient, in anatomic or crossed position. In double touch conditions, stimuli coded as left-sided were extinguished not only when delivered to both hands, but also when delivered on a single hand or a single finger. The findings suggest that tactile stimuli may be coded as left or right according to multiple body anchors that are dynamically scaled from the corporeal midline, to axes centered on a single hand or finger.