Author: Dyna Rochmyaningsih
Institution: Laboratory of Zoology, Bogor Agricultural University, Indonesia
Working memory is the ability in the brain to temporarily hold and process acquired information. To perform memory task, human brain needs sufficient glucose pertaining to its energy demand. Thus, fasting, as a temporary condition of no glucose intake into the body, would logically give negative effect on memory performance. This assumption is supported by the finding of untreated patients of hypoglicemia (low blood glucose) that has syndrome of confusion and may have trouble of concentrating. Previous study also showed that overnight and morning fasts produced slower memory recall on schoolchildren in United States and Peru and also for the college students in United Kingdom. It was proposed that metabolic stress and the importance of glucose in the making of acetylcholin were the reasons of the effects. To the contrary, previous study in Indonesia showed that daily fast did not influence the memory of college students but improve the memory performance of teenagers. Thus, following these adverse conclusions, this study aims to find out whether or not fasting influence memory performance of adult human. In this experiment, blood glucose concentration of each subject was electrochemically measured using glucometer while their visual working memory was tested using sequential Delayed Matching to Sample (DMS) task. In this task, subjects were asked to match a number of visual stimuli and the order of its appearance corresponding to the level of the test. To hold the memory of the stimulus, 1500 ms delay period was given in each trial. After 60 trials, data of the reaction time and accomplished level were extracted from the test and would be further analyzed using regression analysis. This test was done in the fasting and the non-fasting conditions for each subject. Result showed that blood glucose level were high around 2.5 hours (110-120 mg/dl), decreased within 6 hours, and then remained constant until 24 hours (80-100 mg/dl). This homeostasis phenomenon was suggested to be the reason why the fasting duration did not influence memory performances both in reaction time and accomplished level. Fasting duration did not significantly influence reaction time with P-value 0.438 in the non-fasting condition and 0.966 in the fasting condition (P>0.05). It also did not significantly influence accomplished level with P-value of 0.432 in the non-fasting condition and 0.642 in the fasting condition (P>0.05). This experiment did not record hunger which was suspected to affect attentional memory processes. Moreover, learning effect and habituation are more considered to affect working memory performance.