Background: Individuals with schizophrenia who engage in targeted cognitive training (TCT) of the auditory system show generalized cognitive improvements. The high degree of variability in cognitive gains maybe due to individual differences in the level of engagement of the underlying neural system target. Method: 131 individuals with schizophrenia underwent 40 hours of TCT. We identified target engagement of auditory system processing efficiency by modeling subject-specific trajectories of auditory processing speed (APS) over time. Lowess analysis, mixed models repeated measures analysis, and latent growth curve modeling were used to examine whether APS trajectories were moderated by age and illness duration, and mediated improvements in cognitive outcome measures. Results: We observed significant improvements in APS from baseline to 20 hours of training (initial change), followed by a flat APS trajectory (plateau) at subsequent time-points. Participants showed interindividual variability in the steepness of the initial APS change and in the APS plateau achieved and sustained between 20 and 40 hours. We found that participants who achieved the fastest APS plateau, showed the greatest transfer effects to untrained cognitive domains. Conclusions: There is a significant association between an individual's ability to generate and sustain auditory processing efficiency and their degree of cognitive improvement after TCT, independent of baseline neurocognition. APS plateau may therefore represent a behavioral measure of target engagement mediating treatment response. Future studies should examine the optimal plateau of auditory processing efficiency required to induce significant cognitive improvements, in the context of interindividual differences in neural plasticity and sensory system efficiency that characterize schizophrenia.
Bibliographical noteFunding Information:
The cognitive training software used in these studies was supplied to the last author free of charge by Posit Science. Vinogradov is a site PI on an SBIR grant to Posit Science, a company with a commercial interest in the cognitive training software used in these studies. Biagianti is a post-doctoral research fellow partially funded through Posit Science. None of the other authors have any financial interest in Brain Plasticity Inc. or Posit Science. Vinogradov serves on an advisory board for Forum pharmaceuticals. This work was supported by National Institute of Health grants R01MH82818-01A2, MH068725-06A2 and by the Stanley Foundation grant 06TAF-972
© 2016 American Psychological Association.
- Auditory processing
- Cognitive training
- Target engagement