What Is Sensation? What Is Perception? Explain How the Human Being Processes an Environmental Stimulus That Passes Through the Nose and Tongue. What Are the Main Forms of Hearing Disorders and State How They Are Generally Treated.

WHAT IS SENSATION? WHAT IS PERCEPTION? EXPLAIN HOW THE HUMAN BEING PROCESSES AN ENVIRONMENTAL STIMULUS THAT PASSES THROUGH THE NOSE AND TONGUE. WHAT ARE THE MAIN FORMS OF HEARING DISORDERS AND STATE HOW THEY ARE GENERALLY TREATED.

Sensation refers to the process of obtaining sensory information through the stimulation of body parts or to the conscious feelings or sense impressions themselves. The latter definition is akin to that of perception. Sensations are classified as exteroceptive, interoceptive, and proprioceptive. Exteroceptive sensations provide information about the external environment and include the sensations of sight, hearing, taste, smell, temperature, pain, pressure, and touch. The exteroceptive sense organs are located on the exterior of the body and include the eyes, ears, tongue, nose, and the temperature, pain, pressure, and tough receptors of the skin. Interoceptive sensations provide information about the internal environment and include such sensations as pain, hunger, thirst, nausea, fatigue, and suffocation. The sense organs involved, called interoceptors, are located mainly in the visceral organs. Proprioception sensations provide information about body position and movement. The sense organs for proprioception are located in the muscles, tendons, joints, and the organs of balance in the ear.

A great deal of peripheral processing of sensory information usually occurs before transmission of the electrical impulses along the nerve fibers projecting toward the central nervous system. The strength of a stimulus is most often transformed to a frequency of electrical potentials in these fibers. The information is transmitted to the brain where after further processing and analysis, conscious sensations results. Sensations may be artificially generated by the direct electrical stimulation of the sensory nerves and, in some cases, by the electrical stimulation of the brain itself. Specific conscious sensations depend on the functioning of certain brain regions. Damage to particular brain region because of stroke, injury, infection, or tumor my result in the selective loss of sensory abilities. The perception of even such ordinary objects as tables and chairs probably depends on a complex interplay of heredity and early childhood experience, although the relative importance of these two factors is not known.

More research has been devoted to the visual and auditory than to any other because they are the major sources of information about the external environment. Interest in the other senses however, has increased in recent years. For example, researchers are attempting to learn whether olfactory stimulation is based on chemical energy, radiant energy, or the shapes of molecules. Also, skin sensations have been found to be important for the maintenance of health. For example, if animals are prevented from licking their young, the young frequently die of gastrointestinal or genitourinary failure. Evidently, in the absence of the skin stimulation, the autonomic nervous system fails to maintain proper motor activity in the organs of these systems. Similarly, the skin stimulation that accompanies breast-feeding appears to have physiological benefits for infants

Understanding Sensation

In order to fully understand sensation one must understand the relationship between stimulation and sensory experience. Psychologist who study sensation consider three (3) broad issues:-

Lowest limit of sensory capabilities

What is the minimal amount of stimuli one can respond to and the minimal change in stimuli that one can detect.

Describing the psychological relation between particular types of physical stimuli and sensory experience.

For example, changes in wave length of light to translate into experience of different colours.

Separation of sensation from psychological factors to show how past ...

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Understanding Sensation

In order to fully understand sensation one must understand the relationship between stimulation and sensory experience. Psychologist who study sensation consider three (3) broad issues:-

Lowest limit of sensory capabilities

What is the minimal amount of stimuli one can respond to and the minimal change in stimuli that one can detect.

Describing the psychological relation between particular types of physical stimuli and sensory experience.

For example, changes in wave length of light to translate into experience of different colours.

Separation of sensation from psychological factors to show how past experience influence sensory processes.

Our sensory receptors are somewhat limited in the types of information which can be received, and the amount of stimulation needed to generate a noticeable sensation. To be noticed, a stimuli must be compatible with a sensory receptor and the intense enough to stimulate that receptor. The level of such intensity is called sensory threshold. There are two sensory thresholds:-

Absolute Threshold

This represents the weakest or minimum sense-organ stimulation that can produce a sensation. Anything below or absolute pass undetected/unnoticed.

Example: A spot of light appearing in a dark room must reach some measurable intensity before it can be distinguished from darkness, and sound emitted in a soundproof room must reach a certain intensity before it can be heard.

Difference Threshold

This represents the smallest change in intensity of a stimulus that can be detected and distinguished from another.

Example: Two reds must differ in wave length by some finite amount before they can be discriminated from each other, and two tones must differ in a measurable amount before one is heard higher than the other. Thresholds are therefore identified at the transition between no experience and some experience (the absolute).

In addition to the two thresholds, there is what is called a just noticeable difference (JND). This represents the change in intensity of the same magnitude as the difference threshold (e.g. we say the stimulus is brighter or heavier).

Sensory Adaptation

The fluctuations in sensory threshold are illustrated by way of sensory adaptation. This is the reduced sensitivity (raised threshold) after prolonged exposure to a stimulus. It is familiar within vision, smell and temperature, though not entirely limited to these senses. Sensory adaptation serves a useful function in allowing us to focus on important changes in the environment. This is crucial to our survival. As with most things, there are advantages and disadvantages.

Advantages

Without the process of sensory adaptation, we would constantly be distracted by the stream of sensations which we experience daily. For instance, we would not adapt to our clothes rubbing against our skin, or bodily feelings, as our blinking eyes, or the feel of our tongue in our mouth.

Disadvantages

Our sensitivity to most odor drops by 70%, hence in a situation where smoke or harmful chemicals are present, sensory adaptation may reduce our sensitivity to existing danger.

PERCEPTION

Perception is a more active, complex, even creative process. It is the process of selecting, organizing and making sense of sensory information. It is a more cognitive and central process than sensation. In other words we sense the presence of a stimulus be we perceive what it is. In understanding perception, it has three levels of complexity.

Detection which refers to whether people can sense that they are being stimulated by some form of energy. For example, a light may be so dim they can barely detect its presence.
Recognition. This means being able to identify as well as detect a particular pattern of stimulation.
Discrimination means being able to perceive patters of stimulation as different. For example, a person may hear slight differences between too similar music tones.

There are a number of general principles that helps us to understand the process of perception. One of the most important is the principle of closure. It tells us that we have the general tendency to perceive things as complete and unified. We tend to “fill in” parts that are missing, or parts that conform to an overall impression. The opposite of the principle of constancy is also important. Sometimes an object or pattern of stimulation will remain constant but the perceived effect will vary. Another important principle relates to perceptual context. The perception of an object or event depends in part on the context (surrounding conditions).

Perceptions are selective. We do not react equally to all the stimuli impinging upon us. We focus on a few called attention, through which we keep in focus, selected stimuli and resit distracting stimuli. Preparatory set is one condition for perception. There is some selectivity in perception before the stimulus appears. We can prepare ourselves to perceive and to act upon stimuli that we expect to appear. Such preparation goes by the name set, carrying the same meaning as in the situation of a runner who gets set to run at the sound of the gun. His set includes the readiness to hear the gun, and the readiness to run. In essence, what a person perceives depend in part upon what he is ready for, and this is the meaning of preparatory set as it affects perceiving.

SMELL

The senses of smell and taste are often referred to as the lower senses, as well as chemical senses. It is ironic that so little is understood of processes of the sense of smell, although of all the senses smell has a more direct route to the brain.

Olfaction refers to the sense of smell, which is dependent on odor molecules in the air entering the nasal cavity. These molecules are dissolved in the moist nasal tissues and brought in contact with millions of hair-like receptors called cilia, which are located in the olfactory mucosa inside the top of the nose. Odor molecules reach the olfactory receptors by two ways – inhalation and exhalation. When we inhale, our receptors are stimulated by air entering our nostrils, and when we exhale, our receptors are again stimulated by air leaving the nose. Most food flavour, stem from the olfactory receptors as we exhale and gives food its flavourful “taste”. Evidence that food flavouring is more smell than taste is seen in the experiment that follows:-

An apple and a raw potato are bitten with the nose held tightly. The taste is indistinguishable.

TASTE

The loss of the sense of smell has profound effects not only on smell but its companion taste. Taste is defined as the sensory experience resulting from stimulation of taste bud receptors. These receptors are located mainly on the surface of the tongue, and also on other areas inside the mouth – the soft palate, the pharynx, and the larynx.

It was formerly supposed that the cortical area of taste was closely associated with the area of smell, but it appears that taste is more closely related to the sensivity of the skin in the face. Like smell, taste receptors are carried on the same nerve fibers that control facial expression. This is supported by an infant’s facial expression in response to taste. (Patton & Ruch 1946)

The taste cells generate neural impulse when stimulated through a pore at the top of the taste bud. Once a taste neuron has been triggered, it sends impulse to the medulla at the base of the brain, and then to the parietal cortex for interpretation.

Taste receptors adapt quickly to the presence of the same stimulus e.g. potato chips – each succeeding chip taste less salty as they are eaten. This adaptation ro stimuli is a general sensory characteristic. The primary function of each sense is to provide new information to the brain.

HEARING DISORDERS

Hearing disorders: Many people have hearing problems. Three such problems have been studied extensively:-

Conduction Deafness: This refers to problems associated with conducting or transmitting sounds through the outer and middle ear. In addition to excessive exposure to loud noises, common causes of conduction deafness are excessive wax or damage to the hammer, anvil or stirrup.

Sensorineural Deafness: This is deafness caused by damage to the inner ear, especially the hair cells.

Central Deafness: This is caused by disease and tumors in the auditory pathways and auditory cortex of the brain. Although sensorineural and central deafness can be inherited, they can also develop from exposure to measles and other contagious diseases before birth, inadequate oxygen supply during birth and childhood diseases as meningitis.

Conduction can be treated, hearing aids are often used to offset hearing loss due to damage to the bones of the middle ear. Sensorineural and central deafness are treatable only with cochlear implants – an electrode implanted in the cochlea which serves to stimulate the auditory nerve – or surgery directly on the auditory portion of the central nervous system.