Illustrated structure of CLOCK circadian regulator

Source: Atika Atikawa/Wikimedia Commons

Given that my last post, “Why Age Accelerates Time,” attracted an enormous audience of readers, I feel obliged to push the content further. My colleagues, posting enlightening pieces about time, all have terrific senses of what time is and how we can use that understanding to our benefit.

Time in this century is not the same as time in the past. So the dead philosophers who wrote tomes on the subject had some things right and others wrong. For Plato, time is our experience with daylight. For Kant, time is adopted through a-priory knowledge, a phenomenon that comes with being a human awakened by cognitive sense endowments that follow life’s experiences. He’s not far off. William James believed that time is intricately tied to space; one cannot be thought of without the other. And the French philosopher Henri Bergson wrote that “time is an imprint in the mind initiated by imagination, a continuum of ideas, one after another, a rhythm of human consciousness.”

What are the sensory organs for time perception?

But by 2023 standards, time is far more publicly precise and demanding, and certainly more biophysically plastic. In that respect, time has become more confusing because of its social rigidity on the one hand and its body chemistry flexibility on the other.

So, how does that work? Let’s consider one of the many Psychology Today blog posts that hit on time’s rigidity as well as its elasticity. Marc Wittmann’s “The Mystery of Subjective Time: A Case for Embodiment” fittingly tells us that “we, with our bodies, are time.” Wittmann means that we have the state of our bodies—the moods, physical feelings, sharpness of attention, and other body conditions—in a feedback loop with time.

Wittmann tells us, “There is no sensory organ for time perception similar to the receptors for the other senses,” and then tells us that the insular cortex contributes to sensing the passage of time.

That is true. It is a discovery furthering our understanding that the mind and body have a built-in time system, a microbiological clock that harmonizingly performs critical life-supporting tasks. To extend Wittmann’s insular cortex experiments, though, I would add some points about a wondrously specialized nucleus in the hippocampus that sits relatively distant from the insular cortex.

The suprachiasmatic nucleus in the hippocampus is a circadian oscillator that synchronizes specific cell groups and clock genes working together to spend the day turning protein production on and off, depending on the time. It is a pacemaker synchronized to the circadian rhythm system.

The body’s rhythms of life-sustaining biochemical mechanisms

Circadian rhythm control structures do not act as a sensory system to give a person the feeling of the passage of time. Rather, they work by reminding clock genes when to start transcriptions for critical life-sustaining biochemical mechanisms under a 24-hour feedback loop. In the late evening, cells go to work to build stable and unstable protein molecules in the cytoplasm until they reach a threshold (at roughly midnight) when they begin to turn protein building off completely. In the morning, proteins decay. After several hours, they expire to begin the approximately 24-hour cycle over again.

The frequency of daily hour-to-hour oscillation of the body machine is controlled by the rate at which proteins accumulate in the cytoplasm, the rate at which the entire threshold group of proteins moves from the cytoplasm to the nucleus, and the rate at which proteins break down once in the nucleus. That’s the clock we are talking about.

The biochemical and genetic structures shape time by way of cell-to-cell endogenous-controlled feedback loops in sync with intracellular geophysical cycles to bring about behaviors of the entire organism. The healthy human body has many feedback mechanisms that signal functional information, from when to stop eating to when to rest.

Eat too much, and the energy-regulating hormone leptin is produced to trigger a bloated feeling. Cells absorb nutrients by day and shut down at night. During the body’s life, cells die and are replaced. We can see that sequence happening with skin abrasions. Small rips of tissue are replaced with regrown cells. The same happens with cells well within the interior of the body and organs, where the cycle of breakdown and replacement follows the rhythm of sleep and wake times.

That is my simple version of the body’s clock rhythm. It’s not about time precision but rather about how the organs biochemically cooperate to keep basic life processes functioning. So, the question remains: Does that rhythm, which ticks and beats through chemical changes in millions of cells of the body, instill some feeling of time passing? I have no answer but do know more after reading Wittmann’s riveting blog.

Yes, our bodies know time.