Photo of Michal Pietrzak

Michal Pietrzak

Resident Physician at the University Hospital in Linköping and PhD student at CSAN.

Ongoing research projects

  • ”Behavioral, affective and cognitive consequences of bariatric surgery”
  • ”Effects of the appetite-inducing hormone ghrelin on decision making in healthy volunteers”

Ghrelin, a hormone produced in the stomach, is the endogenous ligand for the growth hormone secretagogue receptor (GHSR), and promotes appetite through hypothalamic actions. GHS-R is also expressed in brain areas involved in motivation and decision-making, such as the mesolimbic dopamine (DA) pathway. Reduction of ghrelin levels is thought to be an important mechanism contributing to the weight loss following bariatric surgery. Findings also have shown that ghrelin influences drug- and food reward as well as novelty seeking. Finally, ghrelin also plays a role in integrating central circuitry involved in anxiety and responses to stress.
Decision making processes that involve reward and risk assessment subserve the solution of the tradeoff betweein exploiting available resources vs exploring the environment for novel resources. We hypothesize that these processes are modulated by signals that communicate the availability of food.



Michal Pietrzak, Adam Yngve, Paul Hamilton, Robin Kämpe, Rebecca Böhme, Anna Asratian, Emelie Gauffin, Andreas Löfberg, Sarah Gustavsson, Emil Persson, Andrea Johansson Capusan, Lorenzo Leggio, Irene Perini, Gustav Tinghög, Markus Heilig (2023) A randomized controlled experimental medicine study of ghrelin in value-based decision making Journal of Clinical Investigation, Vol. 133, Article e168260 Continue to DOI


Irene Perini, Robin Kämpe, Theodor Arlestig, Hanna Karlsson, Andreas Löfberg, Michal Pietrzak, Abraham Zangen, Markus Heilig (2019) Repetitive transcranial magnetic stimulation targeting the insular cortex for reduction of heavy drinking in treatment-seeking alcohol-dependent subjects: a randomized controlled trial Neuropsychopharmacology, Vol. 45, p. 842-850 Continue to DOI