October 2021 - Think Science India

1. Why Do We Dream?

Much remains unknown about the process and purpose of dreams. Although it is a part of our everyday lives, we rarely think about it once we are awake. Sleep itself is a complex series of events that leaves us fresh and energised day after day. These different stages of sleep also occasionally lead us to creative and incredible solutions to problems that normally seem unsolvable.

Many research projects about dreams have been undertaken to understand the science behind them. The current view is that the same specific areas of brain that control activities we dream about when awake are activated while dreaming. Our memories, managed by the hippocampus, also play a major role in the process of dreaming.

Why do dreams contain fragments of our memories?

Hippocampus, in simple terms, helps form memories. It also uses memories to create scenarios. This could be a reason that fragments of our memories are a part of our dreams which then get simple or strange to downright bizarre, fantastic overlays that define dreams.

Some of the proposed purposes of dreaming include the following

Processing, analysing and consolidating past experiences and memories.
Cognitive simulation of events and experiences gathered when awake.
Understanding and reflecting on niggling subconscious issues.

5 stages of sleep have been described

Stage 1: 4-5% of the sleep time. This is the period of light sleep with slow eye movements when muscle activity reduces.
Stage 2: Around 50% of sleep happens in this stage. The eye movements now stop and brain waves become slower. There are sporadic bursts of rapid waves called sleep spindles.
Stage 3: Slow brain waves called delta waves start appearing in this stage. This is a short phase comprising of around 4-6% of the sleep time.
Stage 4: Stage 3 and 4 are the periods of deep sleep when there are no eye movements or muscle action. If woken from this stage, a person can experience disoriented for a few minutes to adjust to wakefulness. The brain produces delta waves. 12-15% of total sleep occurs in this stage.
Stage 5: This comprises of 20-25% of sleep time. It is also called the REM or Rapid Eye Movement stage. As the name suggest, the eyes seem to move jerkily and quickly along with other features such as rapid, irregular breathing, rise in heart rate and blood pressure.

While it was thought that dreaming was restricted to this REM phase, a new study from scientists at the Wisconsin Institute of Sleep and Consciousness, however, has shared findings which indicate that dreams can occur during both REM and non-REM sleep equally.

Dreams are not always remembered. However, when remembered, they include vivid visual and emotional content. Many studies have been undertaken to pinpoint the regions of the brain activated during dreaming to help decipher their purpose.