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Morris RW, Vercammen A, Lenroot R, Moore L, Langton JM, Short B, Kulkarni J, Curtis J, O'Donnell M, Weickert CS, Weickert TW. Disambiguating ventral striatum fMRI-related BOLD signal during reward prediction in schizophrenia. Mol Psychiatry. 2012 Mar ; 17(3):235, 280-9. Pubmed Abstract

Comments on News and Primary Papers


Primary Papers: Disambiguating ventral striatum fMRI-related BOLD signal during reward prediction in schizophrenia.

Comment by:  Patricio O'Donnell, SRF Advisor
Submitted 14 July 2011
Posted 15 July 2011
  I recommend this paper

Primary Papers: Disambiguating ventral striatum fMRI-related BOLD signal during reward prediction in schizophrenia.

Comment by:  René Kahn, SRF Advisor
Submitted 20 July 2011
Posted 20 July 2011

In their paper, Morris et al. investigate whether schizophrenia is associated with altered neural responses in the ventral striatum to rewards, surprise, or prediction errors. Sixteen patients and 16 matched, healthy controls performed a modified reward task. This task contains standard reward trials (a monetary reward after a correct or fast response) and omission trials (no reward). These trials are standard in that participants can more or less predict (expect) if they will receive a reward or not. Interestingly—and this is what makes the paradigm stand out from the more basic reward tasks—a small number of trials participants unexpectedly receive or fail to receive a reward. In this way, the impact of prediction error and surprise could be disentangled from standard reward processing.

While the above approach is interesting, some weaknesses should be noted that prevent the results from being fully convincing. First, the statistical analysis resulted in clusters of above 1,000 voxels, suggesting that the threshold was too low. Second, the definition of the ventral striatum including a large dorsal region is questionable. Third, the patients in the study were all on medication. This makes it difficult to interpret the results. Not only are there known effects of medication at a neuronal level (dopamine suppression in the primary region of interest), but also possible cardiovascular changes. Finally, the study would benefit greatly from a (far) larger sample of participants, which would allow between-subject testing based on genes or even symptoms. In this way, the vast heterogeneity within the patient population would be better addressed, which is of crucial importance for increasing our understanding of how the brain is affected by schizophrenia.

View all comments by René Kahn