No. 1
Sensation: Understanding how we experience the world around us.
Feeling is a fundamental aspect of human experience. It refers to a specific sensation or effect experienced by the body or a specific thought that may arise without any specific cause. Simply put, sensation is the way we detect and respond to stimuli in our environment and within our bodies.
In psychology, sensation is defined as the ability to perceive things through the physical senses, such as touch, taste, sight, sound, and smell. It is the raw data that our sense organs receive before the brain processes and interprets it as perception.
What Is Sensation in Psychology? Definition, Examples, and Thresholds
Additional definitions of sense
Psychologists and researchers have expanded the definition of emotion in various ways:
One definition defines sensation as a mental process, such as hearing or smelling, that results from the immediate stimulation of an organ. This process is often considered separate from perception, which involves the brain's conscious interpretation of these sensory signals.
Another definition focuses on awareness, such as awareness of heat or pain, caused by direct stimulation of sense organs. For example, when you touch something hot, the burning sensation you feel is a burning sensation.
Sensation also includes the internal physical states that give rise to conscious awareness. An example of this is the feeling of hunger, which is caused by internal changes in the body that indicate the need for food.
Everyday examples of feeling.
Emotion is part of everyday life and can be experienced in a myriad of ways. Here are some examples that highlight how feelings arise in everyday scenarios:
- "I felt a tingling in my arm." It can be caused by an insect bite, injury, or allergic reaction.
- "He felt a burning sensation in his throat." This often happens after eating spicy food or during acid reflux.
- "She craved new experiences and sensations." This refers to the desire for new sensory input, such as traveling to new places or trying new foods.
- "He had a strange feeling that someone was watching him." It may reflect a psychological or emotional response rather than a physical response.
- "I couldn't quite shake the feeling that I had been betrayed." It represents a more complex interaction between emotion, memory, and sensory signals.
sense of action
Psychologists have long been fascinated by sensory processing, the way our bodies detect and respond to stimuli. A prominent contributor to this field is psychologist Eugene Galanter. He defined the concept of absolute threshold, which he defined as the smallest level of stimulus intensity that a person can detect 50 percent of the time.
This means that the stimulus must reach a certain minimum level before it becomes strong enough for us to feel it. For example, you may not notice a slight odor in the air until it becomes a little stronger. Once it exceeds your absolute limit, you will know it.
Absolute limit: Human sensitivity is limited
For more than a century, psychologists have conducted experiments to understand how sensitive our sensory systems are. These experiments include a range of psychological methods designed to determine the minimum number of stimuli that can be reliably detected.
The concept of absolute threshold allows scientists to measure this minimum point for all of our senses. These thresholds are surprisingly low, which shows how well the human body adapts to sensory input.
Here are some well-established absolute limits for the various senses, based on research in the field of sensory psychology. These limits represent the smallest amount of sensory input that the average human can detect under optimal conditions.
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- Vision: A candle flame can be seen from 30 miles away on a clear, dark night. This means that even the slightest glimmer of light, in the absence of competing brightness, can stimulate receptors in our eyes. Our eyes are very responsive to light, especially when our pupils are dilated in low-light environments.
- Hearing: The ticking of a clock or watch can be heard from up to 20 feet away in a completely quiet environment. This demonstrates the sensitivity of our auditory system, which is capable of picking up subtle vibrations in the air, especially when there is no background noise to interfere with the recognition of the sound.
- Taste: A teaspoon of sugar dissolved in two liters of water is enough for our taste buds to detect sweetness. This highlights how subtle our sense of taste is, especially in identifying the basic elements of taste such as sweet, salty, sour, and bitter, even in very dilute concentrations.
- Smell: A single drop of perfume can be detected as it diffuses and lingers in the air of a three-room apartment. The human olfactory system is exceptionally sensitive to airborne chemical compounds, allowing us to detect even the smallest amount of scent.
- Touch: A bee's wing gently falling on the cheek from a height of just 0.1 cm can be felt by human skin. This example emphasizes the incredible sensitivity of our sense of touch, especially in areas such as the face, which have a high concentration of sensory receptors.
These examples illustrate the extraordinary precision and responsiveness of our sensory system. They also show the minimum level of stimulus required for detection, known as the absolute threshold. Such sensitivity enables us to interact effectively with our environment, be alert to changes, and respond to both subtle and significant stimuli.
Limits of variation: Detecting changes in perception
Another important concept in the study of perception is the threshold of difference. This is the minimum change in stimulus that must occur before a change is perceived.
For example, imagine a good cook tasting a dish and then adding a pinch of salt. The chef tastes the dish again to assess whether the taste has changed. The smallest amount of salt that produces a noticeable difference in taste is considered the threshold of difference.
This ability to detect change depends on the initial strength of the stimulus. When the original stimulus is weak, we can easily detect small differences, but when the stimulus becomes strong, it requires a very large change to notice any difference. This principle is essential to understanding how we adapt to stimuli and how our sensory systems adapt to changing situations.
The result
Sense plays an important role in how we experience and respond to the world. From the sting of a bee to the smell of fresh coffee, our sensory systems are constantly working, detecting and processing countless forms of input. Concepts such as absolute limits and differential limits help psychologists understand the limits and capabilities of these systems. Through careful study, we gain a deeper appreciation for the complexity of the human body and its remarkable ability to interact with the environment.
By exploring the science behind the senses, we not only gain insight into how we see the world, but we also become more aware of how accurate and powerful our sensory experiences are.
No. 2
The human eye, a marvel of biological engineering, allows us to navigate and appreciate the world in stunning detail and vibrant color. It's more than just an organ; it's a complex system that transforms light into the rich visual experiences we cherish. Have you ever wondered how light becomes sight or how our brains interpret the kaleidoscope of colors around us? Prepare to embark on an insightful exploration into the intricate structure of the eye, unraveling the mechanisms behind light perception, depth, and the fascinating phenomenon of color vision. From the tiny cells that capture photons to the neural pathways that transmit these signals to the brain, we will uncover the profound science of sight. Dive deep into this comprehensive guide to understand the very essence of how we see, and discover insights that will change your perception of vision forever. Continue reading to the end for a complete understanding.
Eye Senses and Vision: How the Human Eye Works, Sees Light, and Perceives Color.
The eye, of course, is only one part of the visual system.
Eye: The eyes are connected to each other by their sensory nerves.
The optic nerve extends along the diencephalon and travels along the occipital lobes of both hemispheres. The eyes receive stimuli that generate neural signals that return between the brain and the cortex and processes that enable patterns of grouping and organization of objects in the cortex.
The human eye is a visual recording device like a camera. Actually, it's a camera. The sensitive plate is the retina, which differs from the photographic plate in that the explorer recovers after each exposure to be ready for the next view.
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Discover how your brain begins the journey of perception by processing raw data through the senses. A must-read for psychology lovers!
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Structure of the human eye
The human eye is an organ that interacts with light and has many purposes, just like the sensory organs in the mammalian eye.
Rod cells and neurons in the retina allow conscious light perception and vision, including color discrimination and depth perception. The human eye can distinguish about 10 million colors.
As in the eyes of other mammals, the photosensitive ganglion cells of the human eye in the retina receive a light signal that affects pupil size.
Near the front of the eye, where light enters, is the raised colored iris with a hole in the middle we call the pupil.
The iris has small muscle fibers that regulate the shape of the purple eight-cross to the adjustable camera diaphragm. The front part of the eye consists of the curved, transparent cornea; a strong lens directly behind the pupil; and another lens whose curvature is adjusted by small ciliary muscles.
This muscle corresponds to the camera's focusing mechanism. Through it, the eye focuses on near or distant objects, and the transparent fluid allows light to reach the retina. The retina is a thin membrane.
It lines the back of the eyeball and contains sensory cells that connect neurons to the brain.
Visual receptors
Sensory cells in the retina are of two types: rods and cones. The incoming lights cause chemical and electrical changes in the rods and cones.
The cones have more developed cells than the rods in the fovea, which is a small depression in the retina directly below the pupil. There are only cones, and this is the center of clear vision. When we look directly at a small object in order to see it clearly, we turn our eyes so that the object's light falls on the fovea. Outside this small central area, rods and cones merge, with fewer cones farther into the retina. The farther you go, the less the difference in shape and color. From this fact we conclude that form and color vision are largely cone dependent.
Eye movement:
The eyeball is rotated by 6 muscles in the socket, and the eyes are linked together at their motor nerve center to show almost perfect teamwork in their movement.
They make two coordinated movements, looking here and there around the landscape; their eyes are like a pair of parallel horseshoes. This is the conjugate movement of the eyes. But I change from a distant object to a background object. The eyes converge so that the foveae of both eyes receive light from the particular object being looked at.
Conjugate motion recorded by photography has been found to be of two types.
This is called the jump or saccade movement and the pursuit movement. A saccade movement moves the eye from one object to another, while a pursuit movement follows a moving object.
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Noor: What is it?
Light is a form of energy called electromagnetic radiation, which also includes radio waves and sound waves. Only a small fraction of this radiation can be seen. That is, our eyes can detect only a small fraction of this radiation. It is best to think of light as consisting of waves that have different frequencies and intensities.
The intensity of the light determines the brightness of the visual sensation. The light reflected from an apple lit by a candle will be of low intensity, so we see the red color of the apple as dim rather than bright. The frequency of the light wave largely determines the colors we see. That is, light waves of different wavelengths are perceived as different colors.
How do we see brightness?
The perception of brightness begins when light is absorbed by the receptor rods in the retina. These rods are highly sensitive to light intensity and are specifically designed to function under low-light conditions. When light strikes the rods, it triggers a series of chemical and electrical reactions, activating a chain of neurons that carry the visual signals through the optic nerve to the brain. The intensity of the light directly influences the level of activity generated in the retina. The greater the intensity, the stronger the stimulation of the rods and the more vigorous the neural activity transmitted to the brain. As a result, the sensation of brightness that we perceive becomes stronger. In simple terms, brighter light causes greater retinal and neural activation, leading to a more vivid experience of brightness in our visual perception.
How do we see colors?
Color vision is the ability of the human eye to distinguish between different wavelengths of light, independently of their intensity or brightness. This complex visual function allows us to perceive a wide range of colors and is primarily facilitated by specialized photoreceptor cells called cones, located in the retina. There are three types of cones in the human eye, each sensitive to a specific range of light wavelengths. Some cones respond best to blue light, others to green light, and some to red light. When light enters the eye, these cones are activated based on the wavelength they are most responsive to, and they send signals to the brain accordingly.
However, our perception of color is not determined by cone activity alone. The brain enhances this process through a mechanism known as opponent processing, which occurs in specialized neurons called opponent cells, particularly within the lateral geniculate nucleus (LGN) of the brain. These cells are designed to compare inputs from different cones. For example, certain opponent cells become excited when stimulated by red wavelengths and inhibited when exposed to green wavelengths, while others are excited by blue and inhibited by yellow. This balance of excitatory and inhibitory impulses enables the visual system to detect subtle contrasts and differences between colors.
Through this sophisticated processing system, the brain interprets the combined input from the cones and opponent cells, producing a full spectrum of color perception. Even when two light sources share similar brightness levels, the variation in wavelength allows us to distinguish between them as different colors. This neural interaction also contributes to color constancy, the phenomenon that allows us to recognize colors consistently even under different lighting conditions. The integration of cone responses and opponent cell activity ensures that humans experience a rich and accurate perception of the colorful world around them.
Color blindness.
Some people are colorblind. Color blindness is the partial or complete inability to distinguish colors. It is usually a sex-related disorder. Men develop this recessive trait more easily than women. There are different ways to develop color blindness. People with color blindness cannot distinguish between light colors such as pink or tan. Most people with color blindness have difficulty distinguishing between red and green, especially at poor saturation. There are rare ones that confuse yellow and blue. About one or two people in a thousand are the rarest, with no color visible at all. Color blindness is rare, and most people with color blindness are able to distinguish only a few colors. The most common form of color blindness, occurring in 10% of men and 1% of women, is red-green. People with red-green color blindness may see red and green as yellow-gray. They often confuse blue with yellow. Yellow blindness is rare and usually occurs only as a result of disease.
People who can see all colors are called trichromats. People with red-green or blue-yellow color deficiency are called dichromats (two colors), and people with color blindness are called monochromats (one color).
No. 3
Introduction: A New Vision for Mental Health Diagnosis
The human retina is far more than just a gateway for visual information—it is a powerful extension of the brain itself. Recent research has revealed that the retina can offer valuable insights into brain health, particularly in relation to serious mental disorders like schizophrenia. Scientists have found that subtle changes in the thickness of the retina may reflect a person’s genetic risk for developing schizophrenia, even before any symptoms appear. This discovery opens exciting new possibilities for early detection, preventive strategies, and improved treatment approaches, all through simple, non-invasive eye scans. In this blog, we explore how the retina mirrors brain health and how technology like optical coherence tomography is transforming mental health diagnosis.
The Retina: A Mirror of Brain Health
The retina is not just a passive receiver of visual information—it is a vital extension of the central nervous system, closely tied to the brain both in structure and function. Formed from the same embryonic tissue as the brain, the retina carries a complex network of neurons, glial cells, and blood vessels that mirrors the brain’s intricate architecture. This deep biological connection means that subtle neurological changes within the brain may also manifest visibly in the retina. Recent large-scale studies have shown that individuals with a higher genetic risk for schizophrenia tend to have thinner retinal layers, even before any psychiatric symptoms become evident. These findings highlight the retina’s potential role as a non-invasive, early biomarker for mental health conditions. Thanks to advanced imaging technologies like optical coherence tomography, clinicians can now detect these minute retinal changes in a matter of minutes with remarkable precision. The ability to observe early signs of brain-related disorders through a simple eye examination offers a revolutionary pathway for early detection, preventive care, and improved treatment strategies. By focusing on the retina, researchers and clinicians are opening new doors in the quest to understand, predict, and ultimately prevent severe psychiatric illnesses like schizophrenia.
🔍 Explore Psychological Sensation:
Discover how your brain begins the journey of perception by processing raw data through the senses. A must-read for psychology lovers!
👉 Read: What Is Sensation in Psychology 🔗
To understand why the retina is such a good "mirror" for brain health, think of it as a small, accessible window into the central nervous system. Both the retina and the brain develop from the same embryonic tissue, meaning they share a very similar biological blueprint. This shared origin results in a close structural and functional connection. When there are changes happening in the brain, especially those related to neurological or psychiatric conditions, these changes can often be seen reflected in the delicate layers of the retina. This makes eye exams incredibly valuable, not just for checking your vision, but also for potentially spotting early signs of brain-related issues without needing more invasive or expensive procedures like brain scans. It's a simple, quick, and comfortable way to gain insights into a person's overall neurological well-being.
Optical Coherence Tomography: Revolutionizing Schizophrenia Research
Optical coherence tomography (OCT) is transforming how scientists study mental health. Similar to an ultrasound for the eye, OCT uses light waves to create detailed images of the retina within minutes. Unlike traditional brain imaging techniques, which can be expensive and time-consuming, OCT is quick, non-invasive, and cost-effective. This makes it an ideal tool for large-scale screenings and early diagnosis efforts. Thanks to the precision of OCT, researchers can now measure retinal thickness with incredible accuracy, potentially identifying subtle neurological changes associated with schizophrenia years before the disorder fully develops.
Imagine shining a tiny, harmless light into your eye. That's essentially what OCT does. This light bounces off the different layers of your retina, and a special camera captures how it reflects. From these reflections, a computer builds a super-detailed, cross-sectional picture of your retina. Think of it like slicing through a cake to see all its layers, but without actually cutting anything. This allows doctors to see if any of the retinal layers are thinner or thicker than they should be, which can be a clue to what's happening in the brain. For conditions like schizophrenia, these "minute retinal changes" are incredibly subtle, but OCT's precision is so high that it can pick them up. This is a huge step forward because it means we might be able to catch signs of the disorder much earlier, even before someone starts showing clear symptoms. This early detection opens the door to starting treatments sooner, which can make a big difference in how the illness progresses and how well a person can manage it.
Genetic Risk and Retinal Changes: Connecting the Dots
Using extensive data from the UK Biobank—a massive resource containing genetic and health information from over half a million individuals—scientists calculated polygenic risk scores for schizophrenia. Their analysis revealed a direct association between higher genetic susceptibility and thinner retinal tissue. Although the individual effects are small, the large sample size made it possible to confirm the link statistically. This finding provides a crucial piece of evidence that the biological roots of schizophrenia may be detectable in the eye long before behavioral symptoms emerge.
Let's break down what "polygenic risk scores" mean. It's like adding up many small genetic clues. We all have thousands of genes, and some of them might slightly increase or decrease our risk for certain conditions. A polygenic risk score is a way of calculating a person's overall genetic likelihood of developing a disease, based on many genes working together. So, when scientists found that people with a higher genetic risk for schizophrenia also tended to have thinner retinal layers, it was a very important discovery. It suggests that the same genetic factors that make someone more likely to develop schizophrenia also affect the development or health of their retina. This connection means that a simple eye scan could one day help identify individuals who are genetically more vulnerable to schizophrenia. For families with a history of the disorder, this could be life-changing, offering the chance for early monitoring, support, and perhaps even preventive measures long before any noticeable symptoms appear. It shifts the focus from reacting to the illness to proactively understanding and managing risk.
The Inflammatory Hypothesis: A New Direction for Treatment
Another significant outcome of the study supports the inflammatory hypothesis of schizophrenia. Genetic variations that promote inflammation seem to impact both brain and retinal structures. This strengthens the idea that inflammatory processes may play a major role in the development or worsening of schizophrenia. If this hypothesis continues to gain support, it could revolutionize treatment strategies. By targeting inflammation early with specific medications, it might become possible to delay or even prevent the onset of schizophrenia in at-risk individuals, offering new hope for millions worldwide.
Inflammation is your body's natural response to injury or infection, like when you get a cut and it swells. But sometimes, inflammation can become chronic, meaning it stays around for a long time, even without an obvious injury. This long-term inflammation can harm different parts of the body, including the brain. The inflammatory hypothesis of schizophrenia suggests that this kind of ongoing inflammation in the brain might contribute to the development or worsening of the disorder. The new research showing a link between genetic factors that cause inflammation and changes in both the brain and retina gives strong support to this idea. This is exciting because if inflammation is a key player, then we might be able to develop new ways to treat or even prevent schizophrenia. Imagine if a simple medication that reduces inflammation could help protect the brain and retina, potentially delaying or stopping the illness from taking hold. This opens up a whole new avenue for research and treatment, moving us closer to a future where we can intervene much earlier and more effectively for those at risk.
A Future of Preventive Mental Health Care
The ability to detect early signs of schizophrenia through a simple eye scan could transform mental health care. Imagine a future where routine eye exams also serve as early warning systems for serious mental disorders. While larger and longer-term studies are still needed to validate these findings fully, the path forward is clear. By combining genetic information, advanced imaging technologies like OCT, and an understanding of inflammation's role in brain health, the possibility of preventing schizophrenia before it takes hold is becoming more realistic. As research continues, the retina could very well be the key to unlocking a new era of preventive psychiatry.
The close connection between the retina and the brain provides a revolutionary opportunity to detect early signs of neurological and psychiatric disorders. Studies have confirmed that individuals with a higher genetic risk for schizophrenia often exhibit noticeable thinning of the retinal layers long before clinical symptoms emerge. With the use of fast and non-invasive imaging technologies like optical coherence tomography, it becomes possible to monitor these subtle changes quickly and affordably. As research continues to grow, the retina may soon become a standard tool in early detection, offering hope for timely interventions and better treatment outcomes for those at risk of schizophrenia. Understanding the retina’s role in brain health could change the future of mental healthcare forever.
This vision of preventive mental health care is truly groundbreaking. Instead of waiting for severe symptoms to appear, which can often be a painful and challenging experience for individuals and their families, we could potentially identify risks much earlier. This would allow doctors to offer support, lifestyle changes, or even early treatments that could lessen the impact of the illness, or perhaps even prevent it from fully developing. It would involve a team effort, with eye doctors, brain specialists, and genetic experts working together to provide comprehensive care. The benefits of such early intervention are enormous: better quality of life for individuals, reduced burden on healthcare systems, and a more hopeful outlook for those who might otherwise face a difficult journey. The retina, a small part of our eye, holds immense promise as a powerful tool in this new era of proactive mental health. As scientists continue to uncover its secrets, we move closer to a future where mental health challenges can be addressed with unprecedented foresight and effectiveness.
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