Sleeping serves different functions. One of the functions is that it helps us remember the experiences that we had during the day.
REM sleep is considered to be very important for procedural memories (like riding a bike) and for the emotional memories (like the ones that involve fear). Slow-wave sleep, on the other hand, is considered to reflect the storing of the declarative memories, which are essentially the conscious record of your experiences and the things that you know for a fact (for an example, what you had for lunch).
These experiences are replayed in the brain while we are sleeping, and these experiences are much like movie segments that can be fast forwarded, rewound and paused. Replays occur in the hippocampus, which is the region of the brain that is important for the memories. This has been studied in rats when they are being tutored how to navigate a maze. After the exercise is finished, when the rat is resting, its brain will replay the path that the rat took through the maze. These replays will strengthen the connections between the brain cells, and that is why it is considered to be important for consolidating the memories.
But, you are probably wondering, why it is so important to remember what you had for lunch? It is not that important, and that is the main reason why the brain needs to be selective about which memories are important and which ones are not. Sleeping will allow the brain to go through these memories, discarding certain things, in order to remember the things that are important.
The ”synaptic homeostasis hypothesis” is a leading theory of sleep function, and it suggests that during the time that you are asleep, there is a widespread weakening of connections that are also known as synapses, all throughout your brain.
Scientists think that this counterbalances the strengthening of the connections that happen during the learning process when we are awake. By weakening these connections, sleeping essentially cleans the slate and frees “space” inside the brain so that we can learn more things the very next day. If the process of scaling down memories is corrupted, it can lead to much more intense and in some cases, unwanted memories.
The process of sleep can keep our brains optimally active, and it can be reflected in how the sleeping patterns change with our age. Babies and children spend more time sleeping than full-grown adults, and that is because their brains are learning much more stuff, as they are constantly exposed to situations in which they have never been before.
As we grow older, sleep begins to decline, and it becomes much more fragmented. This may lead to a reduced need for sleep or a breakdown in the sleep process. The bottom line is that there is much evidence that having healthy sleep patterns is the key to having a well-functioning and healthy brain.