Training of somatosensory discrimination after stroke: facilitation of stimulus generalization

Task-specific learning typifies perceptual training but limits rehabilitation of sensory deficit after stroke. We therefore investigated spontaneous and procedurally facilitated transfer of training effects within the somatosensory domain after stroke.

Ten single-case, multiple-baseline experiments were conducted with stroke participants who had impaired discrimination of touch or limb-position sense. Each experiment comprised three phases: baseline, stimulus-specific training of the primary discrimination stimulus, and either stimulus-specific training of the transfer stimulus or stimulus-generalization training. Both the trained and transfer stimuli were monitored throughout using quantitative, norm-referenced measures. Data were analyzed using individual time-series analysis and meta-analysis of intervention effects across case experiments.

Stimulus-specific training was successful for trained texture and proprioceptive discriminations, but it failed to show spontaneous transfer to related untrained stimuli in the same modality in seven of eight experiments in which this was possible. In contrast, intramodality transfer was obtained with stimulus-generalization training in four of five experiments that investigated stimulus-generalization training of texture discrimination. Findings were confirmed by meta-analysis.

Our findings demonstrate generalization of training within a somatosensory modality poststroke, provided that a program designed to enhance transfer is used. This has implications for the design of efficient rehabilitation programs.