James A. Waltz, PhD

1. Waltz, J.A., Brown, J.K., Gold, J.M., Ross, T.J., Salmeron, B.J., Stein, E.A. (2015). Probing the dynamic updating of value in schizophrenia using a Sensory-specific Satiety Paradigm. Schizophrenia Bulletin. Epub 2015 April 1. PMID: 25834028.
2. Waltz, J.A., Kasanova, Z., Ross, T.J., Salmeron, B.J., McMahon, R.P., Gold, J.M., Stein, E.A. (2013). The roles of reward, default, and executive control networks in set-shifting impairments in schizophrenia. PLoS-ONE, 8, e57257. Epub 2013 Feb 27. PMID: 23468948. PMCID: PMC3584128.
3. Simpson, E.H., Waltz, J.A., Kellendonk, C., Balsam, P.D. (2012). Schizophrenia in Translation: Dissecting Motivation in Schizophrenia and Rodents. Schizophrenia Bulletin, 38, 1111-1117. Epub 2012 Sep 26. PMID: 23015686.
4. Waltz, J.A., Frank, M.J., Wiecki, T.V., Gold, J.M. (2011).  Altered probabilistic learning and response biases in schizophrenia: Behavioral evidence and neurocomputational modeling.  Neuropsychology, 25, 86-97. PMID: 21090899.
5. Waltz, J.A., Schweitzer, J.B., Ross, T.J., Kurup, P.K., Salmeron, B.J., Rose, E.J., Gold, J.M., Stein, E.A. (2010). Abnormal responses to monetary outcomes in cortex, but not in the basal ganglia, in schizophrenia. Neuropsychopharmacology, 35, 2427-39. Epub 2010 Aug 18. PMID: 20720534; PMCID: PMC2955756.
6. Gold, J.M., Hahn, B., Strauss, G.P., Waltz, J.A. (2009).  Turning it upside down: areas of preserved cognitive function in schizophrenia.  Neuropsychology Review, 19, 294-311.
7. Waltz, J.A., Schweitzer, J.B., Gold, J.M., Kurup, P.K., Ross, T.J., Salmeron, B.J., Rose, E.J., McClure, S.M., Stein, E.A. (2009). Patients with Schizophrenia have a Reduced Neural Response to Both Unpredictable and Predictable Primary Reinforcers. Neuropsychopharmacology, 34, 1567-77.
8. Haenschel, C., Bittner, R., Waltz, J.A., Haertling, F., Wibral, M., Singer, W., Linden, D.E.J., and Rodriguez, E. (2009).  Cortical oscillatory activity is critical for working memory as revealed by deficits in early onset schizophrenia.  Journal of Neuroscience, 29, 9481-89.
9. Pipa, G., Städtler, E.S., Rodriguez, E.F., Waltz, J.A., Muckli, L.F., Singer, W., Goebel, R., Munk, M.H. (2009). Performance- and stimulus-dependent oscillations in monkey prefrontal cortex during short-term memory. Frontiers in Integrative Neuroscience, 3, 25. Epub 2009 Oct.
10. Waltz, J.A., Frank, M.J., Robinson, B.M., and Gold, J.M. (2007). Selective reinforcement learning deficits in schizophrenia support predictions from computational models of striato-cortical dysfunction. Biological Psychiatry 62, 756-764. 
11. Waltz, J.A., and Gold, J.M. (2007). Probabilistic reversal learning impairments in schizophrenia: further evidence of orbitofrontal dysfunction. Schizophrenia Research 93, 296-303. 

My major current scientific interest is in understanding how abnormalities in learning and decision making relate to the symptoms of psychotic illness. My work makes use of findings and techniques from the basic cognitive neuroscience literature, including computational modeling and functional neuroimaging techniques, in conjunction with experimental reinforcement learning paradigms. We have observed an inverse relationship between clinical ratings of motivational deficits in SZ and experimental variables capturing the ability to precisely represent value and flexibly update these representations in the brain. This set of findings helps us to potentially arrive at better mechanistic understandings of both the positive and negative symptoms of SZ.

The work described above was motivated by findings from a related line of work, examining neural responses to experienced rewards, as well as the signaling of mismatches between expected and obtained outcomes, called “Reward Prediction Errors (RPEs)”, in psychiatric illness. Based on the established role for brain dopamine systems in both psychosis and RPE signaling, my colleagues and I tested the idea that RPE-signaling in schizophrenia would be disrupted, perhaps in a manner relating to symptom severity. The work below produced several unexpected findings: 1) schizophrenia patients showed relatively intact brain responses to negative outcomes, and appropriately signaled when outcomes were worse than expected (negative RPEs); 2) schizophrenia patients showed relatively disrupted brain responses to positive outcomes, and attenuated brain signals when outcomes were better than expected (positive RPEs; a similar observation was made in cocaine-dependent subjects); 3) in cross-sectional studies, schizophrenia patients gave pleasant stimuli hedonic ratings in line with those given by controls, though they failed to normatively modulate ratings of pleasant food stimuli within a session, as a consequence of sensory-specific satiety. These findings argue that motivational deficits in schizophrenia are less likely to be a consequence of sensitivity to outcomes, and more likely to result from a reduced ability to use prediction errors signals to adjust value representations.

Another related line of work, in which I have engaged, has examined the potential role of aberrant effort-cost estimation in cost/benefit decision making in schizophrenia. In the context of cost/benefit decision making, an individual may decline to carry out an action, either because the prospective reward of the action is judged to be insufficient, or because the prospective cost of the action is judged to be too high, in terms of effort. Recent work in basic neuroscience has shown that effort-cost estimation relies on fronto-striatal circuits and their modulation by dopamine systems. Given evidence of fronto-striatal dysfunction in SZ, especially with regard to motivational deficits, my colleagues and I hypothesized that motivational deficits in schizophrenia would relate to estimates of effort-cost. In the case of a task dependent on the estimation of physical effort-cost, we observed this to be true. In the case of a task dependent on the estimation of mental effort-cost, however, we observed that patients did not avoid high-effort conditions, because they had greater difficulty in detecting differences in cognitive effort demands.

Honors and Awards

1994 – 1995                University Fellowship, University of California

1996 – 1997                Ursula Mandel Fellowship, University of California

1998 – 1999                National Research Service Award, National Institutes of Health

1998 – 1999                Predoctoral Fellowship, John Douglas French Foundation for

Alzheimer's Research

1999                            Joseph A. Gingerelli Award for the Distinguished Dissertation,

Psychology Dept, UCLA

1999                            Postdoctoral Fellowship, Alexander von Humboldt Foundation

(declined)

1999 – 2000                Postdoctoral Fellowship, John Douglas French Foundation for

Alzheimer's Research

1999 – 2003                Postdoctoral Fellowship, McDonnell-Pew Program in Cognitive

Neuroscience

2003 – 2004                Postdoctoral Fellowship, Max Planck Institute for Brain Research

2004 – 2006                Postdoctoral Fellowship, UMSOM/MPRC

2009                            H. McKee Jarboe Award for Outstanding Research in Psychiatry, UMSOM

2013                            Young Investigator Mentor, International Congress on Schizophrenia

Research

Professional Memberships

1995 – present            Society for Neuroscience

1995 – present            Cognitive Neuroscience Society

2008                                American Psychological Society

2015 – present            American College of Neuropsychopharmacology (Associate Member)

Lab website: http://www.waltzlab.org