Rewarding Systems

Project lead: Prof. Dr. Andreas Luft, Department of Neurology, University Hospital Zurich


Being informed about good performance usually leads to positive emotions whereas information about bad
performance can worsen one’s mood considerably. But vice verca, emotional states influence how we perform
motor activities and how we perceive errors. Motor skill learning is likely to be achieved through long-term potentiation
(LTP) like processes within the primary motor cortex (M1)[1], which could be mediated my Dopamine (DA)[2]. Animal
models prove that DA is released into the M1 from the brain’s reward centers in the mesencephalon[3], promoting
synaptic plasticity and thus motor learning[4]. These findings lead to the hypothesis that rewarding stimuli (e.g.,
positive feedback with/without monetary reward) influence motor cortex plasticity and lead to more efficient motor skill
learning.

The project is testing this hypothesis in healthy joung adulty as well as in patients with motor impairments after stroke.
The patient population is particularly important, since motor rehabilitation just as motor learning relies on M1
plasticity[5-8]. Furthermore, the DA-system in stroke patients may be disturbed.

Therefore, several experiments are going to be performed:

1. Motor skill learning under different reward conditions in healthy subjects: An arc pointing task [9] will be trained within
an fMRI environment, allowing to assess activity of the midbrain reward system under three conditions: A) Performance
feedback about a random selection of trials, B) Performance fedback about the trials performed better than a sliding
median, and C) Performance feedback together with monetary reward.


2. Assessment of reward system activity in stroke patients: The same task will be presented in a modified form,
allowing to adapt the difficulty level to a patient’s skill. Without testing for learning effects, a short session will be
performed, giving performance dependent monetary reward in a subset of trials in order to evoke activity of the
participant’s reward system. This activity will be quantified and compared to normal values.

3. Armeo-Senso Arm Training with/without rewarding gaming features A training developped for arm rehabilitation will
be adopted to create a version free of features which act as „task intrinsic rewards“ like explosions, upgrades, etc.
Training performance will be compared between users of the different versions.



References

  1. Rioult-Pedotti, M.S., D. Friedman, and J.P. Donoghue, Learning-induced LTP in neocortex. Science, 2000.
    290(5491): p. 533-6.
  2. Kuo, M.F., W. Paulus, and M.A. Nitsche, Boosting focally-induced brain plasticity by dopamine. Cereb Cortex,
    2008. 18(3): p. 648-51.
  3. Hosp, J.A., et al., Dopaminergic modulation of receptive fields in rat sensorimotor cortex. Neuroimage, 2011.
    54(1): p. 154-60.
  4. Molina-Luna, K., et al., Dopamine in motor cortex is necessary for skill learning and synaptic plasticity.
    PLoS One, 2009. 4(9): p. e7082.
  5. Abe, M., et al., Reward improves long-term retention of a motor memory through induction of offline memory
    gains. Curr Biol, 2011. 21(7): p. 557-62.
  6. Nudo, R.J., Adaptive plasticity in motor cortex: implications for rehabilitation after brain injury. J Rehabil Med,
    2003(41 Suppl): p. 7-10.
  7. Ramanathan, D., J.M. Conner, and M.H. Tuszynski, A form of motor cortical plasticity that correlates with
    recovery of function after brain injury. Proc Natl Acad Sci U S A, 2006. 103(30): p. 11370-5.
  8. Luft, A.R., et al., Repetitive bilateral arm training and motor cortex activation in chronic stroke: a randomized
    controlled trial. JAMA, 2004. 292(15): p. 1853-61.
  9. Shmuelof, L., J.W. Krakauer, and P. Mazzoni, How is a motor skill learned? Change and invariance at the levels
    of task success and trajectory control. J Neurophysiol, 2012. 108(2): p. 578-94.