Have you ever noticed that there are certain times of the day when your brain feels exceptionally sharp, while at other times, even reading a few pages of a book becomes a challenge? Many people assume that this is due to laziness or a lack of discipline. In reality, these changes are largely influenced by the biological clock (circadian rhythm), which regulates hormone secretion, alertness, and patterns of brain activity [1].

The human biological clock is primarily synchronised by sunlight. When morning light enters the eyes, signals are sent to the suprachiasmatic nucleus (SCN) in the hypothalamus, the body's master biological clock. The SCN then regulates the secretion of hormones such as cortisol and melatonin, thereby influencing the physiological state of the brain [2].

Early in the morning, cortisol levels increase while melatonin levels decrease. This helps the brain enter beta mode, a state that is well suited for concentrating, making decisions, and solving problems. It is therefore not surprising that many people feel more productive in the morning.

As midday approaches and fatigue begins to set in, the brain shifts into alpha mode. Although it appears to be less active, the brain is actually filtering out unnecessary stimuli, allowing us to maintain our focus on relevant information. This is why taking a short break after working or studying can help improve mental performance [3].

As evening approaches and light levels decrease, melatonin production begins to increase. The brain gradually shifts into theta mode, a state that is important for creativity, imagination, and memory organisation. During deep sleep, delta mode becomes dominant. This is when the glymphatic system clears metabolic waste from the brain while strengthening neuronal connections and supporting the brain's recovery process [4].

In addition, there is also gamma mode, which is often associated with complex information processing and the coordination of communication between different regions of the brain. This mode helps integrate information from the senses, experiences, and memories into meaningful understanding [5].

In reality, no single mode is better than the others. Each plays an important role according to the body's needs at different times of the day. However, modern lifestyles often force us to remain alert and focused throughout the day, even when our biological clock is signalling that the brain needs rest.

Perhaps from now on, before blaming yourself for having difficulty concentrating or feeling mentally exhausted, take a look at the clock. The problem may not be that your brain is weak, but that you are asking it to work at a time that is not aligned with its natural biology.

References:

1. Joseph S. Takahashi. (2017). Transcriptional architecture of the mammalian circadian clock. Nature Reviews Genetics, 18(3), 164–179.
2. George C. Brainard, Hanifin JP, Greeson JM, et al. (2001). Action spectrum for melatonin regulation in humans: evidence for a novel circadian photoreceptor. Journal of Neuroscience, 21(16), 6405–6412.
3. Wolfgang Klimesch. (2012). Alpha-band oscillations, attention, and controlled access to stored information. Trends in Cognitive Sciences, 16(12), 606–617.
4. Maiken Nedergaard, Xie L., Kang H., Xu Q., et al. (2013). Sleep drives metabolite clearance from the adult brain. Science, 342(6156), 373–377.
5. Pascal Fries. (2015). Rhythms for Cognition: Communication through Coherence. Neuron, 88(1), 220–235.

Prepared By:

Dr. Siti Nor Ani Azaman

Biology Unit

Date of Input: 24/07/2026 | Updated: 24/07/2026 | hasniah