Attention Therapy in Neglect: Behavioral and Imaging data

Introduction: Spatial neglect subsequent to right hemisphere lesions is closely associated with non spatial deficits of attention like intrinsic alertness and sustained attention. Several studies have shown that the degree to which sustained attention is impaired is a strong predictor for the persistence of neglect. A postulated interaction between the anterior alerting and the posterior spatial attention network directly leads to the hypothesis that an alertness training may improve spatial neglect in right hemisphere stroke patients.

Impact of alertness vs. OKS training on neglect: We examined the effect of the computerized alertness training AIXTENT in a group of 7 chronic neglect patients by means of fMRI (Thimm et al., 2006). Following the training, the group showed a significant improvement in the performance of a neglect test battery over and above any improvement during a four week baseline phase. Improvements in the neglect tasks were accompanied by an increase of right hemisphere neural activity in frontal cortex, anterior cingulate cortex, precuneus, and angular gyrus, areas previously associated with alertness and spatial attention. A similar pattern of increased neural activity was found for the left hemisphere. Four weeks after the end of the training, the patients' neglect test performance had mostly returned to baseline, while the increases in neural activity bilaterally in frontal areas, in the anterior cingulate cortex and in the left temporoparietal cortex remained. The data show that a three-week computerised alertness training can improve performance in neglect tests and that these behavioural improvements are associated with functional reorganisation in areas associated with alerting and visuospatial attention. In a similar approach, the impact of a three-week optokinetic stimulation training (OKS) on neglect was studied. Behaviourally, OKS caused both a short and long-term (4 weeks) improvement of performance. This amelioration of neglect symptoms was associated with increases of neural activity during an fMRI spatial attention task bilaterally in the middle frontal gyrus and in the precuneus. Additional left hemisphere increases in neural activity were observed in the cingulate gyrus, angular gyrus, middle temporal gyrus and occipital cortex. This pattern of activation represents a combination of areas normally involved in spatial attention plus a compensatory recruitment of left hemisphere areas. These results were then compared with data from our alertness training study. After OKS training there was bilaterally more activation in the precuneus than after AIXTENT training (fig. a). In contrast, after AIXTENT training there was more activation bilaterally in several frontal areas (fig. b).

Conclusion: The results show that amelioration of neglect can be induced by both OKS and alertness training. The data furthermore suggest that the differential activation of frontal or parietal areas may reflect the specific impact of the two types of training either on an anterior system for the control of attention intensity (AIXTENT) or on the posterior system of spatial attention (OKS).

References: Sturm, W., Thimm, M., Kust, J., Karbe, H., & Fink, G. R. (2006b). Alertness-training in neglect: behavioral and imaging results. Restor. Neurol. Neurosci, 24, 371–384; Thimm, M., Fink, G. R., Kust, J., Karbe, H., & Sturm, W. (2006). Impact of alertness training on spatial neglect: A behavioural and fMRI study. Neuropsychologia, 44, 1230–1246.

Fig. 1