Training of Somatosensory Discrimination After Stroke: Facil- of Australia Project Grant (191214)

Art: 162531 4:48 05/11/3 10؍balt5/z79-phm/z79-phm/z7900505/z792796-05a browncm S Authors: Leeanne M. Carey, PhD Thomas A. Matyas, PhD Stroke Affiliations: From the National Stroke Research Institute, Heidelberg West, Victoria, Australia (LMC); and the Schools of RESEARCH ARTICLE Occupational Therapy (LMC) and Psychological Sciences (TAM), LaTrobe University, Bundoora, Victoria, Australia. Training of Somatosensory Disclosures: Discrimination After Stroke Supported, in part, by a LaTrobe University Faculty of Health Sciences Facilitation of Stimulus Generalization Research Grant, an Australian Research Council small grant, a Research Development Grant from the Department of Health and ABSTRACT Human Services, and a National Health and Medical Research Council Carey LM, Matyas TA: Training of somatosensory discrimination after stroke: Facil- of Australia project grant (191214). itation of stimulus generalization. Am J Phys Med Rehabil 2005;84:000–000. Presented, in part, at the 11th Objective: Task-specific learning typifies perceptual training but limits rehabilitation of International Congress of the World sensory deficit after stroke. We therefore investigated spontaneous and procedurally Federation of Occupational facilitated transfer of training effects within the somatosensory domain after stroke. Therapists, London, UK, and at the Third Annual Perception for Action Design: Ten single-case, multiple-baseline experiments were conducted with Conference, Melbourne, Australia. stroke participants who had impaired discrimination of touch or limb-position sense. Each experiment comprised three phases: baseline, stimulus-specific Correspondence: training of the primary discrimination stimulus, and either stimulus-specific train- All correspondence and requests for ing of the transfer stimulus or stimulus-generalization training. Both the trained reprints should be addressed to and transfer stimuli were monitored throughout using quantitative, norm-refer- Leeanne M. Carey, PhD, National Stroke Research Institute, Level 2, enced measures. Data were analyzed using individual time-series analysis and Neurosciences Building, Austin meta-analysis of intervention effects across case experiments. Health, Banksia Street, Heidelberg West, Victoria, Australia 3081. Results: Stimulus-specific training was successful for trained texture and proprioceptive discriminations, but it failed to show spontaneous transfer to related untrained 0894-9115/05/8405-0001/0 stimuli in the same modality in seven of eight experiments in which this was possible. American Journal of Physical In contrast, intramodality transfer was obtained with stimulus-generalization training in Medicine & Rehabilitation Copyright © 2005 by Lippincott four of five experiments that investigated stimulus-generalization training of texture Williams & Wilkins discrimination. Findings were confirmed by meta-analysis. DOI: 10.1097/01.PHM.0000159971.12096.7F Conclusions: 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. Key Words: Sensation, Rehabilitation, Cerebrovascular Accident, Transfer of Training May 2005 Training of Somatosensory Discrimination 1 ؆●●●؆؍؆●●●؆ PPL؍؆5؆ PPF؍؆84؆ ISS؍؆May 2005؆ VID؍؆Stroke؆ DATE؍؆Research Articles؆ DOCSUBJ؍ARTICLE DOCTOPIC> <؆10.1097/01.PHM.0000159971.12096.7F؆؍DOI Art: 162531 4:48 05/11/3 10؍balt5/z79-phm/z79-phm/z7900505/z792796-05a browncm S tasks and processing activities are highly similar, it Generalization of intervention effects to un- is unknown whether these conditions are adequate trained tasks is central to sensorimotor neuroreha- for individuals in whom the perceptual system is bilitation. Task-specific training, although effec- damaged. Furthermore, the potential for transfer tive, has the potential to be very costly, and novel of training under different training conditions has tasks will present continuing problems. Discovery not been systematically investigated within the so- of effective training methods also able to achieve matosensory domain after stroke. transfer of gains to novel tasks is thus essential. We have focused our research on rehabilitation Furthermore, investigation of the boundaries of of somatosensory deficits, particularly touch and transfer is increasingly regarded as a key ingredient proprioceptive discrimination. These deficits are to a proper understanding of learning effects in the characteristic of the loss experienced and are re- sensorimotor system.1 In the sensory domain, in- ported in approximately 50% of stroke patients.12 vestigation of stimulus-generalization effects could Such deficits pose substantial difficulties in recep- help clarify what is encoded about the stimuli dur- tion of sensory information and exploration of the ing the training experience. environment and have detrimental effects on spon- “Generalization of training” or “transfer of taneous use of hands, object manipulation, and learning” to an unpracticed task has been investi- precision grip. Moreover, sensory loss has a nega- gated with healthy subjects in various domains, tive effect on personal safety, functional outcome, including perception.2 Empirical investigations in and quality of life, and it influences length of stay the perceptual learning literature suggest that in the hospital (see Carey12 for review), highlight- transfer is possible in some instances.3,4 However, ing the functional importance of training these discrimination training is often highly specific to capacities. the task.2,3,5 A general finding is that similarity This investigation of generalization effects fol- between the trained and transfer tasks is an impor- lowed our initial findings that stroke-induced im- tant determinant of positive transfer.2 pairments of texture discrimination and limb-posi- The dimensions of similarity that seem to mat- tion senses are trainable.8 Improvements were ter include whether the novel transfer task is specific to the stimuli trained2 and confirmed the within the same perceptual dimension as the expected independence of tactile and propriocep- trained task, the similarity of the required re- tive performance.8 Although lack of transfer across sponse, and the similarity in method of processing tactile and proprioceptive discrimination was ex- the information.2–4 Body location, density of recep- pected, those data do not address transfer across tors, and organization of the somatosensory cortex stimuli of the same type, such as textures with may also affect transfer of learning in somatosen- different distinctive features of roughness. Efficient sory discrimination.2–4 The training conditions retraining of somatosensory discrimination abili- under which transfer might be expected also need ties requires an understanding of the similarity to be considered. Principles that may enhance required to achieve successful transfer. transfer of training have been identified in the We therefore conducted a series of ten con- motor-learning literature.1 However, exposure and trolled, multiple-baseline, single-case experi- feedback may be adequate for perceptual transfer, ments13 to investigate transfer across stimuli at least for unimpaired subjects.3–6 within the same sensory-perceptual dimension us- Generalization of training within the same ing either SST or stimulus-generalization training perceptual dimension or sensory modality has re- (SGT). The design permitted training the primary ceived only limited investigation in stroke patients. discrimination stimuli while simultaneously mon- Spontaneous improvement in related visual func- itoring the influence of this treatment on the tions was found in a controlled study that trained a transfer stimuli, and the design delayed introduc- single visual function of patients with cerebral tion of generalization-enhanced training to after blindness.7 In contrast, we found stimulus-specific this control phase. Study 1 investigated spontane- training (SST) effects across tactile and propriocep- ous transfer of training effects within tactile and tive discrimination tasks poststroke.8 Studies that proprioceptive domains after SST. Study 2 investi- have trained multiple modalities simultaneously, gated transfer to novel stimuli within the tactile used objects with multisensory demands,9 or em- dimension using a program modified to facilitate ployed sensorimotor tasks10,11 have reported im- SGT. provement in untrained sensory tasks, suggesting Transfer tasks were selected to require the the potential for generalized somatosensory effects. same sensory-perceptual dimension and body loca- These results are consistent with findings of spon- tion as the trained task, as these features of simi- taneous transfer across multidimensional tasks in larity seem to be important in perceptual learn- healthy subjects.2 Although spontaneous transfer ing.2,3 Tactile stimuli were two types of textured may be achieved by unimpaired subjects when surfaces: plastic grids and fabrics. These stimuli 2 Carey and Matyas Am. J. Phys. Med. Rehabil. ● Vol. 84, No. 5 Art: 162531 4:48 05/11/3 10؍balt5/z79-phm/z79-phm/z7900505/z792796-05a browncm S require processing within the same tactile domain lidity and normative standards have also been es- and are both explored with the fingertip but have tablished for these tests.14,16 different surface characteristics. The propriocep- tion tasks involved discrimination of imposed wrist Procedure positions in

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