The first gate of our memory: Let's learn about sensory memory.

Imagine that you are walking down the street and suddenly you smell a very nice smell, maybe it is the smell of fresh bread coming from that shop. Even after you have walked a few meters past that shop, the smell still lingers in your nose for a few seconds, right? Or even after someone touches your hand and then lets go, you can still feel the warmth of that touch for a while. That is what we call sensory memory, or ``Sensory Memory`` . This is the first and most amazing step in our memory system. Let's talk about this simply.

What exactly is sensory memory?

Simply put, sensory memory is a very short-term memory that collects information from our surroundings through our five senses (eyes, ears, nose, tongue, skin). This is also called the `(Sensory Register)`.

It's like taking a high-resolution photo instantly with a high-quality camera . Our sensory memory captures every little detail in our surroundings in less than a second. Then, from that pile of information, we select only the bits that we think are "wow.. this is important" and send them to our short-term memory.

We can't control how long this memory lasts. It usually fades within a few seconds. This short period of time is what allows us to continuously perceive changes and subtleties in our surroundings.

What are the main types of sensory memory?

There are 5 main types of sensory memory related to our five senses. You will understand this more easily if you look at a table.

Let's look at some examples from our lives?

These are not just words, but things we experience every day.

Iconic memory

Imagine the sky darkens and a lightning bolt suddenly strikes. After the light disappears, the image of that lightning bolt remains in front of your eyes for about a second, right? That's what is called `(Iconic memory)`. Another example is that when we spin a sparkler that we light at New Year's Eve, it appears to draw a circle. That happens because our `(Iconic memory)` remembers the places in the sky that were lit for a second.

Echoic memory

Even after you finish listening to your favorite song, the melody of that song keeps playing in your head for a few seconds, right? That's what happens with `(Echoic memory)`. Or when someone calls you, even if you don't pay attention to it, a second later you think, "Oh... who called me?" That's because the sound stays in your brain for a few seconds.

Haptic memory

After someone holds your hand tightly and then releases it, your hand still feels the touch, the pressure, for a while. Or even after you touch a rough cloth, your fingertips still feel the roughness. This is called `(Haptic memory)`.

Gustatory & Olfactory memories

These two often work together. The spiciness that lingers in the mouth after eating rice with a well-seasoned salt and pepper, or the sweetness that lingers on the tongue after eating a milk toffee are examples of `(Gustatory memory). Similarly, if the smell of bread when you walk past a bakery, or the smell of incense sticks when you walk past a temple, lingers in your nose even after you have passed that place, that is the work of `(Olfactory memory).`

How does this sensory memory work?

This process is very fast. It happens in a few steps:

1. Experiencing a sensation: First, you experience something through your five senses. For example, you see a beautiful flower.

2. The relevant part of the brain is activated: As soon as you see a flower, the part of the brain responsible for vision (sensory cortex) is activated instantly. It's like turning on a light bulb.

3. The brain selects what is important: Next, your brain decides in less than a second whether what you saw is important or not. "Oh... this flower is so beautiful, I need to remember this" or "This is just a random thing." The brain makes a choice.

4. Selection is sent to short-term memory: Only the information selected as important is sent to the next level of memory, short-term memory . The brain discards all other unnecessary information.

Let's also learn about the capacity and duration of sensory memory.

How much information can you remember? (Capacity)

The capacity of sensory memory is very large . This is because we use several of our senses at the same time.

Imagine a time when you were eating well.

• You see the color of the rice and the curry with your eyes .
• I smell each curry with my nose .
• The tongue detects tastes such as sour, bitter, sweet, and pungent.
• You can feel the texture of things like rice and fish through the skin (inside the mouth) .
• You can hear the "squeaking" sound that comes from eating a papadam with your ear .

Our sensory memory can hold all this information at once. That's what makes it so powerful.

How long is the information retained? (Duration)

Despite its large capacity, sensory memory retains information for a very short time . Typically, it is only 0.2 seconds to 2-4 seconds. This time varies depending on the sense. For example, iconic memory for vision lasts less than 1 second, while echoic memory for hearing can last for about 4 seconds.

The reason this is so short is to allow our brain to accommodate the new sensations that come to us every second.

What parts of the brain are involved in this?

This process, called sensory memory, involves different parts of the brain. Each sense has a separate pathway. For example, when you hear a sound, that sound is converted into an electrical signal that travels through the nerves to the brain. It first travels through the brainstem and then to the thalamus, a part of the brain that is located in the middle of the brain. The thalamus is the center that directs information to the right place. From there, the sound signal is sent to the part of the brain that is most relevant to hearing.

This relationship can be seen more clearly in the table below.

These areas, together with other parts of the brain, are precisely what carry out this amazing process called sensory memory.

Do you need to be careful about sensitive memory?

Sensory memory is a part of our body. Therefore, like any other physical part, it can be damaged or lose its function due to certain conditions. It can change due to aging, certain neurological conditions, or brain injuries.

If you have any concerns or questions about your memory, especially your ability to remember things, the best thing to do is to talk to your family doctor. He or she can examine you and refer you to a specialist for further treatment if necessary.

Sensory Memory, Memory, Brain, Five Senses, Iconic memory, Echoic memory, Haptic memory, memory types in Sinhala