Errors of somatosensory localisation in a patient with right-hemisphere stroke

Abstract

Following a right-hemisphere stroke, Patient NG could detect somatosensory stimulation that she was unable to localise. With vision precluded, NG systematically mislocalized touch on the little and ring finger of her affected left hand, and reported feeling this touch on the neighbouring rightward finger. This pattern of mislocalization occurred not only when the Examiner administered touch but also when touch was self-administered. We manipulated the relative position of NG's two hands during sensory assessment of the affected hand. When NG's right hand was positioned to the left of her affected hand, NG exhibited improved localisation. Theoretical and clinical implications are discussed.

The role of self-touch in somatosensory and body representation disorders after stroke

“…A recent report demonstrated a righthemispheric stroke patient who was able to detect somatosensory stimulation on the left-hand but was not able to localize the stimulus [78]. This suggests that the patient had an impaired representation of the affected hand.…”

“…(b) Self-touch and body representation Although there is considerable evidence for modulation of tactile perception by self-touch, less is known about self-touch modulation and higher order somatosensory processing. A recent report demonstrated a righthemispheric stroke patient who was able to detect somatosensory stimulation on the left-hand but was not able to localize the stimulus [78]. This suggests that the patient had an impaired representation of the affected hand.…”

Commentary: An Adaptation-Induced Repulsion Illusion in Tactile Spatial Perception

“…For instance, stroke patients with damage to somatosensory areas of the brain mislocalize touch toward the middle of the hand (Rapp et al, 2002 ; White et al, 2010 ). This distortion likely arises from a reduced cortical representation of the hand, leading to more uncertainty (Rapp et al, 2002 ; White et al, 2010 ). If sustained tactile stimulation does improve perception then it might be viable as a treatment for these patients.…”

A New Method for Assessing Self-Touch Enhancement of the Foot in Stroke Patients with Mobility Problems

“…This phenomenon, termed 'self-touch enhancement' (STE), has been investigated in five studies. Self-touch enhancement can occur when the patient administers self-touch without Examiner assistance (van Stralen et al 2011) and when the patient is guided by the Examiner to administer touch (Valentini et al 2008;Weiskrantz and Zhang 1987;White et al 2010aWhite et al , 2010b. Possible explanations for how STE occurs include: (1) proprioceptive information, the patient infers touch based on the relative position of the patient's administering hand and the affected body part; (2) spatial attention, the patient's administering hand provides a spatial cue that directs attention toward the affected body part; (3) temporal expectation, the action of the patient's administering hand provides a temporal cue that focuses attention as touch is administered.…”