Effects of asymmetric dopamine depletion on sensitivity to rewarding and aversive stimuli in Parkinson's disease

The left hemisphere learns what is right: Hemispatial reward learning depends on reinforcement learning processes in the contralateral hemisphere

“…However, transient modulations of fMRI signal across the mesolimbic DA system during reward processing has previously been demonstrated to be highly consistent with neural recordings in animals (D'Ardenne et al, 2008;Knutson et al, 2001b;Schultz et al, 1997;Tobler et al, 2005). Additionally, in line with studies using more direct measures of DA function, such as PET and DA neuron loss in Parkinson's disease patients (Maril et al, 2013), our recent fMRI data evidence a link between hemispheric differences in DA function and biases in approach and avoidance learning (Aberg et al, 2015). Note that, for ethical reasons, more invasive procedures, such as PET, are not easily available for studying healthy controls in many countries, making this fMRIbased approach an attractive alternative for estimating individual differences in DA function.…”

The “Creative Right Brain” Revisited: Individual Creativity and Associative Priming in the Right Hemisphere Relate to Hemispheric Asymmetries in Reward Brain Function

“…However, transient modulations of fMRI signal across the mesolimbic DA system during reward processing has previously been demonstrated to be highly consistent with neural recordings in animals (Schultz et al 1997;Knutson et al 2001aKnutson et al , 2001bTobler et al 2005;D'Ardenne et al 2008;Ferenczi et al 2016). Additionally, in line with studies using more direct measures of DA function, such as PET and DA neuron loss in PD patients (Maril et al 2013), we recently reported an association between hemispheric differences in striatal reward responses assessed by fMRI and biases in approach and avoidance learning (Aberg et al 2015) and spatial orienting biases (Aberg et al 2016). Thus, it is highly plausible that our measured reward asymmetry relates to hemispheric asymmetries in DA function.…”

“…Supporting this claim, the magnitude of phasic responses to reward in the mesolimbic system, including the ventral striatum, was found to correlate with the expression of stable personality traits, such as approach motivation and reward sensitivity (Simon et al 2010;Kennis et al 2013). Moreover, we recently demonstrated that hemispheric asymmetries in phasic Creativity and Hemispheric Functional Asymmetries Aberg et al | 9 at Université de Genève on November 14, 2016 http://cercor.oxfordjournals.org/ reward responses related to the expression of spatial orienting biases (Aberg et al 2016), and approach and avoidance behaviours (Aberg et al 2015), which both are well-documented personality features (Carlson and Glick 1989;Elliot and Thrash 2002;Elliot 2008;Tomer 2008) associated with a hemispheric imbalance in DA function (Maril et al 2013;Tomer et al , 2014Porat et al 2014). These observations converge to suggest that hemispheric asymmetries in DA function, including phasic reward responses, pertain to stable personality characteristics.…”

“…Supporting this notion, midbrain DA neuron loss in Parkinson's disease (PD) reduces neural responses to reward in the midbrain and in the ventral striatum (Schonberg et al 2010;van der Vegt et al 2013). Additionally, PD patients with larger loss of midbrain DA neurons in the right (vs. the left) hemisphere express more behavioural approach (vs. avoidance), while patients displaying larger DA neuron loss in the left (vs. the right) hemisphere show the reverse trend (i.e., increased avoidance vs. approach) (Maril et al 2013;Porat et al 2014). Similar biases in the expression of approach (vs. avoidance) behaviours have also been observed in healthy controls displaying asymmetric DA function in the striatum , including reward responses (Aberg et al 2015).…”

“…Thus, increased DA would prevent the coactivation of remotely related concepts (Kischka et al 1996;Angwin et al 2004;Roesch-Ely et al 2006). Critically, the level of DA activity may differ between hemispheres (Molochnikov and Cohen 2014), and this difference may shift the balance between behaviours subserved by each hemisphere (Maril et al 2013;Porat et al 2014;Tomer et al 2014;Aberg et al 2015Aberg et al , 2016. Importantly, interhemispheric difference in DA function, but not its absolute intrahemispheric level, predicts an individual's tendency to orient towards one specific side of space , or display increased approach (vs. avoidance) behaviours ).…”