Introduction
„Quality of life is closely correlated with being satisfied with life – namely the way in which a person positions himself towards life as a whole”, says Raina Şaguna, integrative psychotherapist and clinical psychologist(1). The satisfaction is measured by looking at indicators regarding certain aspects of life, for example: work, family life, financial status, free time or health status. According to D. Katz, in this universe we can identify three distinct aspects which help bring it into effect. Firstly, our own body, the reactions of which we cannot control, unless we are aware of its limits and capabilities.
Then comes, secondly, the surrounding space, which implies a proximity orientation, where unmediated sensory information dominates and, thirdly, a long distance one, where the individual is directed towards unknown and distant landmarks, which cannot be directly perceived(2). This behavioural process, through which the body has the capacity to correctly pinpoint, in time and space, its own systems and those of its surroundings is a complicated one, achieved through the so-called senses (some of them being actual organs). In order to be able to „get along” in everyday life, functional and harmonic integration is necessary, not only of some components that we hold from birth, but also many others that we obtain along the way. Developmentally, hearing begins first – more than three months before birth. The newborns and babies require touch to develop properly (it is thought to be the first sense that humans develop)(3). In the first weeks after birth, the sense of olfaction is dominant. In three months, sight develops from black and white to multicolour. Up until the age of three years old, the space of the child is an affectional “living space”, devoid of shapes and sizes, a “topological” space, according to Jean Piaget, characterized by vicinity, separation, order and continuity(4). Between 3 and 7 years old, the child reaches a “Euclidian space”, that is more homogenous, in which it recognizes geometric shapes.
Aristotle described the five senses: sight, hearing, touch, smell and taste, but research in several fields describes a number of additional senses that include nociception (the sense of pain), the sense of time, equilibrioception (the sense of balance), proprioception (the sense of where your body is in space), kinaesthesia (the sense of joint and muscle motion and acceleration), thermoception (the sense of temperature differences), and magnetoception (the sense of direction), as well as the interoceptive senses (the internal senses of respiration, heartbeat, hunger, and the need for digestive elimination), among others.
Every ultraspecialized component offers multiple information to the central nervous system, which after processing each one, also performs an analytical synthetic correlation, allowing us to respond to changes in our environment.
The properties and functions of the senses and sensory systems emanate from a variety of disciplinary perspectives, including neuroscience, cognitive psychology, philosophy of perception, critical theory, literature, performance, architecture, and the visual arts.
SIGHT. The sense of vision seems to be the most important one. Some authors consider that we experience nearly 80% of all our impressions through our vision. That is why it is thought that the human eyes are more complicated than that of any other creature. The retina is covered with two types of light sensitive cells – up to 120 million rods, which cannot detect colour, but they are more sensitive than about 7 million cones which can. Humans have three types of cones which perceive the presence of red, green and blue. These combine in different levels to create the full range of colours we see. The cones allow us to have a central vision with details, and the rods perceive light better at night, also helping us in our peripheral vision and in our perception of motion. Our eyes aren’t just performing a task, they are the portal through which our brain can tell us about our world, learn new things, and make wonderful memories. We live in a visually dominant culture, but that does not necessarily mean that what you visually perceive is the real world.
HEARING. Hearing is very important, as it is one of the main senses we use to vocally communicate to other humans. But what is very important to emphasise is that we can simultaneously hear 360 degrees of our physical environment, around corners, through walls and, more importantly, we can hear weight and density, whereas vision only provides surface information. It was proven that subjects react faster to sonically encoded messages than to visual displays, and discriminated a wider range of messages. Likewise, the ear is in a constant state of standby, through which, during sleep, even with our eyes closed, we remain in contact with the outside world. Sound expresses deeper emotions, neuropsychic states and integrates more with proprioception, balance and fine motor control. If it is compensating for the loss of another sense, then it always becomes the most important sense, however this can happen spontaneously as well.
TOUCH. The sense of touch is spread through the whole body. Classically, there are four kinds of touch sensations that can be identified: cold, heat, contact and pain. It consists of several distinct sensations communicated to the brain through specialized neurons in the skin, especially in case of small spaces. Pressure (500,000 sensory receptors), temperature (around 16,000 warm and about 150,000 cold thermoreceptors), light touch, vibration, pain (4 million receptors) and other sensations are all part of the sense of touch and are all linked to different receptors in the skin. The fingertips have a greater concentration of nerve endings. Hair on the skin increases the sensitivity and can act as an early warning system for the body.
SMELL. Our sense of smell is capable of identifying seven types of sensations. These can be categorized as follows: camphor, musk, flower, mint, ether, acrid, or putrid. Humans have 400 smelling receptors. It was once believed that humans could take in only 10,000 different smells, but a recent publication suggested that humans can discriminate between 1 trillion different odours(5). The nose also cleans the air we breathe and impacts the sound of our voice, conferring it the so-called timbre.
Smell is an aid in the ability to taste (expiratory olfaction). Poor olfactive ability in people may be a symptom of a medical condition (schizophrenia and depression) or aging (75 percent of people over the age of 80 years old may have major olfactory impairment)(6).
There’s a saying among common folk according to which aging is the progressive death of the sensory organs. Smells are sent to the mouth in a process called olfactory referral.
TASTE. Adults have a minimum of 2,000 to 4,000 taste buds (sometimes this number can reach 10,000, but several of them disappear due to aging). Most of them are on the tongue, but they also line the back of the throat, the epiglottis, the nasal cavity and the esophagus. The tongue is able to taste more than just four separate flavors (salty, sweet, sour, bitter), because there is also a fifth taste, defined as umami or savory(7). About half of the sensory cells in taste buds react to several of the five basic tastes. The other half of the sensory cells are specialized to react to only one taste. Spicy is not a taste. It is actually a pain signal, according to the National Library of Medicine (USA). The tongue also picks up texture and temperature in our food, like creamy, crunchy, hot or dry.
THE VESTIBULAR SENSE (sense of equilibrium). Often referred to as our „sixth sense”, balance relies on input from several areas of the body. It has several sensory inputs from the balance organs located in the inner ears, visual inputs and inputs from the muscles and joints in our legs and spine. This is the reason why it is considered a real system. These perceptions contribute to our state of physical balance and keep us safe from falling. It has major emotional implications through the 25th area in the vicinity of the vestibular center, which is responsible for psychosomatic conditions. The vestibular and kinesthetic senses work hand-in-hand through the proprioceptive feedback mechanisms.
PROPRIOCEPTION. Proprioception offers the ability to sense the position, location, orientation and movement of the body and its parts, through:
Once supersonic speeds and weightlessness have been achieved, new and important observations regarding equilibrium and implicitly orientation have been made. These extreme conditions open new doors for scientific research and certainly for a radical reconsideration in the practical value of different senses.
EQUILIBRIUM, defined as the ability of a person to maintain the upright position and to perform body movement tasks without oscillating or falling, is a complex network with several input mandatory for normal functioning – proprioception/somatosensory, visual and vestibular cues. In healthy persons, this mechanism is functioning at a subconscious level without a permanent attention.
In lesions of the aforementioned sensorial systems, equilibrium is altered, transitory or permanent, and an intense and conscious effort is needed to overcome the dizziness and imbalance sensations.
Together with stance and balanced movements, spatial cognition plays an important role in daily activities, movement independence and spatial orientation. Vestibular lesions, as well as aging impede upon this skill by affecting the cortical vestibular function, and spatial cognition decreases, in the sense of direction and spatial anxiety. Elderly people will limit their social activities and will prefer isolation.
These various “new” senses work together and may involve the coordinated use of the sense organs. Furthermore, the latest components identified which contribute to quality of life are:
Dizziness, one of the most frequently met problem in general population (incidence of 23% and higher in elderlies), significantly impairs health-related quality of life(8) and has a strong contribution to disability(9).
Many dizzy patients experience anxiety, depression(10) and an overall reduced quality of life(11).
Dizziness and imbalance can be secondary to lesions in any of the four sensorial systems mentioned:
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visual impairments – astigmatism, uncorrected impaired visual acuity or other pathology in the visual system
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proprioceptive disfunction – neck disorders, which affect the mechanoreceptors from joints, ligaments and deep cervical neck-muscles
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sensorial impairment – such as peripheral neuropathy due to diabetes
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vestibular peripheral or central lesions.
Dizziness Handicap Inventory (DHI) is a useful tool for evaluating the impact of dizziness and disequilibrium on daily activities and quality of life(12), because is a self-report questionnaire addressed to multiple aspects of life – physical, functional and emotional. It is used in evaluating dizziness’ impact and also for monitoring the treatment’s efficacy.
COMPENSATION AND REEDUCATION. Through the existing connections between these receptors, there are numerous possibilities for substitutive interactions, in order to be able to adapt to the situation at hand. Certain humans can have such good hearing, that they can read their environment almost like bats (similar to echolocation). Those who are visually impaired develop a sensitivity towards certain stimulations, like air moving through a large space, or sometimes they can perceive with their face (which almost always is uncovered) or the back of their hands differences in air currents or the direction of light rays (or the sun). Functional restructuring through establishing a tactile, motory or auditory-motory dominance gives a specific note to spatial orientation, based on a series of factors, which do not hold particular significance for those with healthy eyesight. The connection between them is assured by the system of reflexes which encompass the vestibulo-ocular reflex, the acustico-visual reflex, the vestibulo-spinal reflex, and the vestibulo-cortical reflex. Besides experience, the mental development of the individual also plays an important role in temporo-spatial and social orientation. It is not clear, though, whether spatial memory functions automatically or if it requires the conscious control of the brain, or whether it can switch from one mode to another, alternating its navigation based on circumstances.
Each and every sense has value, that is to say, all of them together provide a unique equilibrium that one cannot fully embrace without every sense. Advancements in science have enhanced the quality of life for many people with sensory disabilities by providing alternative methods of communication, increased mobility, additional educational tools, and technology designed for sensory enhancement, such as artificial lens, cochlear implants etc. These also include: Braille, bells at railway crossings, audible, vibrating and tactile pedestrian signals, other hearing aids, guide dogs, talking clocks, walking canes etc. There are multiple possibilities for recovery and important possibilities of reorganising mechanisms, although these functional adaptations can never match the normal.
Unfortunately, the large majority of studied patients have extremely limited knowledge about the use of this arsenal of sensory organs. There is a clear inadvertence between groups with different levels of education. Every individual predominantly relies on the first two senses, sight and hearing, while ignoring the maximal exploitation and the extraordinary value of the other senses, on which many don’t even know elementary facts. This is why we consider it absolutely necessary to involve the ENT specialist in informing and educating the population, in order to raise awareness about the role and the value of the sensory organs in the qualitative unreeling of life. When spatial orientation involves the motory component, the sensory component, the cognitive component and the motivational-affective component, activities regarding these components must therefore be projected in such a way that their specific objectives will eventually lead to the realisation of the general purpose of attaining autonomy in movement, a fundamental aspect of later socio-professional independence.
When discussing the level of expertise of some people that are based on a sensory organ (the absolute hearing of a musician, the refined sense of taste of a sommelier, the sense of smell of the perfumer, or the perfect balance of a tightrope walker), then things take a turn. These levels of discovery, knowledge and understanding of the surroundings can only be obtained through perfecting these receptors, as the classic saying goes: “the key to success is 5% talent and 95% work”. We are again faced with information, education and professionalism.
We cannot come to an end without stating the idea that the more we perceive about the surrounding world, the better we will get at identifying and separating evil from good, and we will be able to avoid unpleasant things and choose positive aspects, in order to achieve a better quality of life.
Aristotle said that there is no unique recipe to achieve happiness and that there is no unique manifestation of happiness, because its significance depends on each individual.
In conclusion, testing and maintaining functionality, respectively the therapeutic approach of these components which assure survival in the best possible conditions, deserve our increased attention, especially in the case of therapeutic decisions, whether they be radical or conservative, from the field of related specialties.
Authors contributions
Gheorghe Mühlfay conceived the article, data analysis, and writing of manuscript. Radu Neagoe: interdisciplinary coordination, patient investigation and critically revised the manuscript. Karin Ursula Horváth: interdisciplinary coordination, patient investigation and drafting the manuscript. Mădălina Georgescu: data analysis and final approval of the manuscript.
All authors read and approved the final manuscript.
Acknowledgments
This paper was published under the frame of the University of Medicine, Pharmacy, Sciences and Technology of Târgu Mureş, Romania, in an International Research Grant supported by MED-EL Wien, Austria (Financing Agreement no. FN48608h/1036/22.01.2016).
Conflict of interests: The authors declare no conflict of interests.