Our brain must have a constant supply of glucose and must cross the blood-brain barrier into brain. When too little or too much glucose cross the barrier into the hippocampus where memory processes take place, as a result false messages are given to the brain. The neurotransmitters send confused messages that effect short term memory, attention span and ability to concentrate. If a memory can't become embedded in short-term memory, it is not there to be transferred to long term memory.
To avoid these disorders we must keep blood sugar levels as constant as possible which help the brain stay supplied with the correct amount of glucose to regulate the messages from neurotransmitters.