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To investigate neural processes underlying temporal credit assignment in the striatum, we recorded neuronal activity in the dorsomedial and dorsolateral striatum (DMS and DLS, respectively) of rats performing a dynamic foraging task in which a choice has to be remembered until its outcome is revealed for correct credit assignment. Choice signals appeared sequentially, initially in the DMS and then in the DLS, and they were combined with action value and reward signals in the DLS when choice outcome was revealed. Unlike in conventional dynamic foraging tasks, neural signals for chosen value were elevated in neither brain structure. These results suggest that dynamics of striatal neural signals related to evaluating choice outcome might differ drastically depending on the requirement for temporal credit assignment. In a behavioral context requiring temporal credit assignment, the DLS, but not the DMS, might be in charge of updating the value of chosen action by integrating choice, action value, and reward signals together.

Inhibitory interneurons are thought to play crucial roles in diverse brain functions. However, roles of different inhibitory interneuron subtypes in working memory remain unclear. We found distinct activity patterns and stimulation effects of two major interneuron subtypes, parvalbumin (PV)- and somatostatin (SOM)-expressing interneurons, in the medial prefrontal cortex of mice performing a spatial working memory task. PV interneurons showed weak target-dependent delay-period activity and were strongly inhibited by reward. By contrast, SOM interneurons showed strong target-dependent delay-period activity, and only a subtype of them was inhibited by reward. Furthermore, optogenetic stimulation of PV and SOM interneurons preferentially suppressed discharges of putative pyramidal cells and interneurons, respectively. These results indicate different contributions of PV and SOM interneurons to prefrontal cortical circuit dynamics underlying working memory.

This study was conducted to provide basic data for development of a dietary education textbook and guidebook by investigating and analyzing eating behavior, nutrition knowledge and educational needs in elementary school students. Most of the subjects were eating three meals a day (71.5%) and breakfast (75.3%). The percentage of students who consumed proper amount of meals (49.2%) was low. The percentage of students consuming salty food and fatty foods was 28.6% and 42.1%, respectively. The consumption of meat, fish, egg, bean and tofu was high, while the consumption of vegetables, fruits and seaweed was low. The percentage of students consuming processed food was high, but the percentage reading nutrition labels (34.9%) and hazard analysis critical control point (HACCP) mark (26.9%) when buying processed foods was very low. Total scores of eating behavior and nutrition knowledge were significantly higher in female students than in male students (p < 0.05-p < 0.001). The desirable frequency of the education was once a week (60.5%). The most preferred educational method was ‘experiment and cooking practice’ (40.1%). The students wanted dietary information as ‘cooking’ (39.0%). As a result of this study, many problems were found in the eating behavior of students and nutritional knowledge was observed to be low as well. On the other hand, the demand for dietary education was very high. The findings of this study suggested the need for developing dietary education programs in order to encourage proper eating habits of students. (Korean J Community Nutr 18(1) : 11~24, 2013)