Effects of Probiotics, Prebiotics and Synbiotic Supplementation on Cognitive Impairment: A Review

Learning and memory formation are the two essential terms widely used in the field of cognition. Learning can be defined as acquiring new information or skills. Memory is formed due to changes in the neuronal system as a result of continuous stimulus exposure. Both learning and memory are fundamental processes that occur in all living organisms. Memory is broadly categorized into two different categories such as short-term memory (STM) and long-term memory (LTM). Compared to STM, LTM plays an essential role in the day-to-day activities of different living organisms. LTM requires RNA and protein synthesis-dependent mechanisms for memory storage, which lasts up to their lifetime. LTM formation is initiated when the neurotransmitters are released from the presynaptic neuron; further released neurotransmitters bind with their respective receptors present in the postsynaptic neuron and initiate the calcium influx. Calcium influx results in the further activation of molecules involved in the neuronal signaling pathway and results in memory formation. Present review reports the outcome of recent studies which showed that probiotic supplement is responsible for the retrieval of memory in case of memory impairment and its uses in the treatment of neurodegenerative disorders like mild cognitive impairment (MCI), Alzheimer's disease (AD).  Recent research studies were shown that probiotic microorganisms may positively regulate neurotransmitter release and increase the calcium influx, brain derived neurotrophic factor (BDNF), and N-methyl-D-aspartate receptor (NMDAR) and plays a pivotal role in the LTM formation in gut-dysbiosed & memory-impaired animal models.