Brain Regions Activated by Episodic, Working, and Semantic Memory Tasks

Selected regions of the prefrontal cortex (PFC) have been shown to be activated by many diverse, complex cognitive operations by use of functional brain imaging with positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) (Nyberg, 2003). Semantic memory, episodic memory, verbal and spatial working memory, conceptual priming, written word recognition, smell perception, and sustained attention are all cognitive functions which lead to these activations found in the prefrontal cortex. Different regions of the PFC are activated depending on the memory task. Frontopolar activation is associated with semantic memory tasks, working memory, and episodic memory.

Nyberg conducted two PET experiments on episodic, working, and semantic memory to look for a similarity in particular activations connected with different memory systems.
He tested 29 healthy males with negative medical histories and similar university educations. PET scan images were compared to determine brain region activations after assigned tasks were completed.

Four regions of the prefrontal cortex (P < 0.05) were found related to the three areas of memory: left frontopolar cortex, left mid-ventrolateral PFC, left mid-dorsolateral PFC, and dorsal anterior cingulate cortex. The central executive in the working memory is thought to have involved the four regions of the brain in accomplishing different memory tasks. Active encoding and retrieval of information was found in the mid-ventrolateral PFC. Paying attention to information which involved all the memory tasks depended heavily on the dorsolateral PFC.

This study showed that although similarities in brain activity were elicited across different memory tasks, specific different areas were activated. The human brain has multiple processing components that are activated depending on the task, but it does show that the memory systems are related (Nyberg, 2003). This study is important because complex brain processes common to many different memory tests have not been well-studied.

As a teacher this study causes me to reflect on how complex the brain and memory systems are. How little we understand and how much we need to learn.

Reference:

Nyberg, L., Marklund, P., Persson, J., Cabeza, R., Forkstam, C., Petersson, K.M., & Ingvar, M. (2003). Common prefrontal activations during working memory, episodic memory, and semantic memory. Neuropsychologia. 41, 371-377.