The brain begins to age very early, and as soon as we reach 25 years of age, the number of neurological connections begins to decrease. From the age of 50 onwards, the weight of the brain decreases on average by 2% every ten years. This natural development has its consequences, and this reduction in neurons will gradually slow down our mental and motor functions (in our movements and our reflexes).
This slowdown is also directly related, besides the decrease in neurons, to a drop in impulse speed, the actual transmission of information between neurons. This is why the more we age, the more time we need to process information. A global slowdown then takes place, which impacts on cognitive and intellectual function, and particularly memory. Indeed, the drop in processing speed can lead to the disappearance of information, before it can even be processed, which can in large part explain forgetfulness.
Furthermore, aging sensory organs (hearing, sight, smell…) provide poorer sensory perception, and get in the way of proper information capture, thereby diminishing our ability to memorize it properly. Very many senior citizens complain about their declining memory. These complaints often betray a fear of the most famous and most publicized disease linked to memory loss: Alzheimer’s. Yet despite what is often believed, it is wrong to assume that decreasing intellectual and memory performance is necessarily linked to a pathology like Alzheimer’s.
It is indeed perfectly normal for intellectual capabilities to decrease with age, simply because the brain ages, just like the rest of the body. Certain cognitive functions (intellectual functions: language, memory, attention, abstract thought, spatial representation, judgment, reasoning…), will be more susceptible than others to aging. This is the case in particular of attention and memory.