The human brain is perhaps the most complex machine that nature can make. An electrical maze with never-ending twists and turns, it’s truly a marvel at transmitting information efficiently, making humans the most intelligent creatures on the planet. Its only true rival is time. 

As we age, our brain naturally deteriorates as irreplaceable neurons degrade, with areas like the cerebral cortex becoming thinner. With the loss of volume, we also lose functionality as certain skills or knowledge diminish with the neurons. Although there is evidence of this physical change, the exact process is still a mystery. Professor Esther Khün, a neuroscientist at the Hertie Institute for Clinical Brain Research, and her team of researchers set out to solve this puzzle and uncovered a surprising result.

She focused her study on the primary somatosensory cortex, the area of the brain responsible for processing tactile senses. This area of the cortex is actually stacked with thin, individual layers that each correspond to unique functions to optimize information processing. The middle layer receives external signals, the upper layer is heavily involved in active processing and response to stimuli, and the deeper layer controls modulation. Modulation is the amplification or reduction of tactile signals, depending on how much attention the stimuli needs. MRI scans from men and women of varying ages showed that aging did not affect the layers equally. The deeper layers were noticeably thinner in older participants, while the middle and upper layers remained unaffected.

Form follows function and function follows form.

This finding can be explained by a common saying in the biology world: “Form follows function and function follows form.” Since the middle and upper layers are always processing external signals, they are always active, unlike the deeper layers that are only used depending on the context. The more active a region, the more likely the brain will prioritize its preservation, which is a feature of neuroplasticity, or the brain’s ability to change and adapt. Neuroplasticity is observed most frequently when the brain is young and establishing its neural networks, and it typically becomes less pronounced throughout adulthood, so it is remarkable that this phenomenon persists in older adults. 

While the adaptability of the brain is impressive, what is even more promising is the discovery that the brain has mechanisms to counteract the degradation of the deeper layers. In an adjacent study with mice, Prof. Khün found that myelin, the protective layer around neurons, in the deeper layers actually increased as the mice got older. Usually, the upper and middle layers have higher myelin content, which promotes faster and sharper nerve signals, so that we can quickly respond to our environment. It turned out that the density of PV neurons, which are heavily myelinated interneurons, increased within the deeper layers to compensate for cellular degeneration, but this mechanism wasn’t observed as the mice aged past 24 months. Although these counteracting mechanisms require further research, this opens a possibility to take advantage of these natural processes to improve and maintain brain function as we age, potentially impacting treatment for neurodegenerative conditions.

Until we can truly crack the scientific dilemma of degeneration, though, it’s clear that the simplest way to keep your brain sharp is by keeping it stimulated. The researchers found that once brain activity began to wane in old age, the mice lost myelinated PV neurons because they no longer used or needed those sensory processes. To prevent neuronal decay, we must continuously stimulate our senses with activities, hobbies, and the pursuit of knowledge that will keep us young even as we age. Time is a tough opponent, but don’t worry: your best weapons are, in fact, those crochet needles.