Thesis defense Heiko Bergmann (Donders Series 136)

18 February 2014

Promotors: Prof.dr. R.P.C. Kessels, Prof.dr. G. Fernández

Two is not always better than one: on the functional and neural (in)dependence of working memory and long-term memory

In everyday language as well as in the scientific literature we often distinguish between two memory systems: short-term memory (STM; sometimes also called and used interchangeably “working memory”) and long-term memory (LTM). Simply put, the former contains the memory for the past 30 to 120 seconds, while the latter consists of all memories beyond this time. In addition, it has been proposed that STM and LTM are subserved by different underlying brain areas, with particularly frontal brain regions supporting STM and a small brain structure deep in the brain, called the hippocampus, being crucial for the formation and storing long-term memories. However, there have always been some doubts among the scientific community if a distinction between memory systems can truly be based on the time interval between study and test phase. Rather, according to this alternative account, memory systems should be distinguished as a function of the processing modes, that is, what kind of and how information is cognitively processed and how exactly a memory test is solved. Finally, it has been argued that largely the same brain areas appear to be activated during the execution of a STM and LTM task if the processing modes of the two tasks are being held constant. The thesis investigates in more detail the functional and neural commonalities and differences between STM and LTM, using behavioural and neuroimaging techniques.