20Q: Sensation and Perception - Learning and Adapting to the World Around Us

From the Desk of Ann Kummer

The term “sensation” is the physical feeling resulting from something that comes into contact with the body through our senses. It relates to the “neurobiological ‘avenues’ for obtaining information about the natural world,” as the author of this article will explain. The term “perception” refers to the person’s ability to interpret sensations. In this 20Q article, Dr. Richard Andreatta provides a very interesting overview of the neuroscience underlying sensation and perception. He then discusses the importance of the client’s ability to sense and perceive in order to achieve the desired functional outcomes from therapy and also how sensation and perception relate to the brain changes that occur during the learning process.

Here is a little information about Dr. Andreatta:

Richard (Richie) D. Andreatta, PhD, is a senior faculty member in both the Department of Communication Sciences & Disorders (CSD) and the Rehabilitation & Health Sciences Doctoral Program in the College of Health Sciences at the University of Kentucky (UK). Dr. Andreatta serves as the Director of Undergraduate Studies for the CSD department and is the Director of Undergraduate Research for the UK College of Health Sciences. Dr. Andreatta received his Ph.D. in Speech Physiology and Neural Science from Indiana University and conducted postdoctoral work in laryngeal neurophysiology at the National Institutes of Health. In 2019, Dr. Andreatta was elected as a Fellow of the American Speech-Language-Hearing Association (ASHA). At the University of Kentucky, Dr. Andreatta is the director of the Laryngeal & Speech Dynamics Lab and is currently active in two research areas encompassing vocal tract physiology and muscle biology in human participants and animal models, respectively. Other areas of scholarly interest include activity-dependent neuroplasticity, dynamic systems theory, and behavioral/cognitive neuroscience. Dr. Andreatta teaches undergraduate courses in anatomy & physiology, speech sciences, and communication neuroscience, and doctoral-level courses on topics ranging from basic neurobiology, sensorimotor integration, speech sensorimotor control, experience-dependent neuroplasticity, and dynamical systems theory.

Now…read on, learn, and enjoy!

Ann W. Kummer, PhD, CCC-SLP, FASHA, 2017 ASHA Honors
Contributing Editor 

Browse the complete collection of 20Q with Ann Kummer CEU articles at www.speechpathology.com/20Q

20Q: Sensation and Perception - Learning and Adapting to the World Around Us

Learning Outcomes

After this course, readers will be able to: 

• define sensation and perception
• describe how sensation and perception in the context of learning and treatment development are important
• describe the role of sensation and perception in relation to neuroplasticity 

Richard D. Andreatta

1. When I consider sensation and perception from an SLP perspective, I think of the brain.  Is that where we should start our discussion today?

I suggest we take a more unconventional approach to get us thinking about this topic. How do you know something is real? How do you know you’re sitting in your interview chair? How do you know that the color of things in this room or the objects themselves exist? If you were blind, would colors exist in your mind? If you had no sense of touch, would any physical object exist from your point of view? Imagine being able to see something resting on the skin of your hand, but not being able to feel it in any way; the moment you looked away from your hand, it would seem the object ceased to exist. How can something exist visually, but at the same instant, not physically (via touch)? And, lastly, the most mind-boggling question ever asked in the history of human existence, “If a tree falls in the woods and no one is around to hear it, does it make a sound?”

2.  These are definitely fun questions to ask, but why are they important to what clinicians do each day?

These fun philosophical questions are definitely big ideas and thought-provoking, but they are not trivial at all. In fact, they are very serious questions about the nature of how we come to know our world. Questions like these have driven our investigative curiosity to discover and appreciate the role of sensation and perception in human behavior. One of the most challenging concepts for students to appreciate is the idea that perception of our world is completely reliant on a nervous system’s ability to transduce, transmit, integrate, and cognitively process a rather limited range of sensory inputs.

3.  Can you explain exactly what you mean by this idea?

Think about what I just said in this way…everything learned about how we perceive and interact with nature—from the effects of gravity to the range of colors around us to the sounds of our language to the feeling of objects being held in our hands—is based solely and completely on our ability to detect energy from the natural environment, or what we call sensation. Then, sensation is transformed into a code that is understood and can be manipulated by the tissues of the nervous system, which is what we’ll call perception.

4.  This sounds fascinating, but why do SLPs and audiologists need to learn about sensation, perception, and how the brain learns? Is it really necessary for us to have this knowledge on a daily basis for our jobs?

I would argue yes. I’ve heard some variation of this question during the many years I’ve taught communication neuroscience, and I’ve realized that it really is a very important question to be asking. The answer to this question goes directly to the heart and central purpose of treatment and its relation to the nature of the brain. Why do we need to learn about sensation and perception as communication sciences and disorders (CSD) professionals? I could spend hours trying to provide some lofty explanation as to the virtues of neuroscience training in CSD, but I prefer to answer this question by highlighting one inescapable truth that genuinely surprises most practitioners when they hear it for the first time. Whether you are treating a child for a misarticulated /s/ or /r/, a person who stutters, a patient who had a stroke and can no longer use language, or someone who is hearing impaired, the essence of all treatment and all clinical improvement is always about changing some aspect of the patient’s behavior, perception, or cognitive state.

The moment you invoke the idea of behavioral, perceptual, and/or cognitive adaptations, what we are really talking about are changes to the structure and operation of the nervous system itself. Absolutely everything we do as clinical speech-language pathologists and audiologists will have a direct impact on the nature, anatomy, and function of the client’s nervous system. In other words, behavioral changes are brain changes. I encourage students to let this idea sink in for a bit and then fully appreciate the magnitude of responsibility that rehab specialists assume when they decide to treat an individual. We are actively changing the brains and nervous systems of our clients through our clinical efforts. Changing the brain through controlled sensory experiences is, in fact, one of the key factors underlying the concept of neuroplasticity.

6. Neuroplasticity! Now that’s a term we understand as SLPs, but can you briefly explain what neuroplasticity is and how it relates to sensation and perception?

Neuroplasticity is a fundamental neurobiological process that allows us to behaviorally adapt and change during our lifetime. Our current appreciation of neuroplasticity is of a process that, in a general sense, acts as the default operating state of the brain. Neuroplasticity in its many forms is the biological process underlying the way animals learn and continuously adapt to changing environmental conditions or novel experiences. The term neuroplasticity comes from the idea that objects that are “plastic” are moldable and flexible in their form and shape. We have come to learn that our brains are exactly this - they are changeable in both structure and function. The adaptive changes that can be made to our brains are driven through use and experience. The link to what I was talking about earlier is that sensations form the key means through which neuroplastic adaptation is created. In a very general sense, sensation can be thought of analogously as being a “teacher”. Sensations (our “teachers”) help the brain discover important relationships about the world and help guide it to change its own responses to the conditions it encounters.

7.  From the perspective of a practicing professional in CSD, why is an understanding of sensation and perception even needed or relevant?

As I tell students in my university courses, rehab specialists across the spectrum are “practicing” clinical neuroscientists whether they realize it or not. It is important to put this information into context and appreciate that all forms of behavioral treatment rely on a client’s ability to sense and perceive the behavioral details of therapeutic activities being taught. Since sensation is so vital to developing neuroplastic changes in the brain, it directly follows that understanding the nature of sensation and perception allows you to more deeply appreciate how the brain adapts and learns new skills. Both of these factors, adaptation and learning, form the cornerstone of all effective treatments.

8.  Why are sensory systems such a point of emphasis for you? Shouldn’t we be focusing on motor (movement) systems instead?

While movement systems are very important for producing speech, movement is an outcome of what we observe a person doing during our treatments. Sensation, on the other hand, is the input that helps organize and give purpose to our movements through learning. Sensory systems are the only avenues through which our carefully crafted treatments can be appreciated and understood by a client. There is no other means to access the internal workings of the nervous system except through sensation. Even movement itself becomes a useless avenue for learning if we lack the means of detecting and appreciating (sensing) our own actions. Without sensation or perception of what is being taught and demonstrated by the speech-language pathologist or audiologist, the client will be unable to (a) internalize the specific details of a treatment task, (b) make behavioral changes in response to what is taught, and (c) appreciate the nature of those changes with regard to their own performance. Sensation and perception are simply that important!

9.  Can you explain the differences between sensation and perception further?

The senses that we learned about as a child—vision, touch, smell, hearing, and taste—represent the essential neurobiological “avenues” for obtaining information about the natural world. Our sense of touch, for instance, is born from the ability to detect mechanical energy from the environment (e.g., stretch, pressure, vibration) and convert that energy into electrochemical signals understood by the nervous system. Sensation is the process by which specialized neural structures, known as sensory receptors, located throughout the body, come to be activated by environmental and/or internal stimuli. Sensation is, at its simplest, a two-step process that transduces and transmits real-world stimulus energy of an event into and through the nervous system, respectively.

10.  What do you mean by “stimulus energy”?

Stimulus energy means the natural forces that are used by the brain to create a cognitive perception of an event happening to us in the world. Let's take sound as an example. Our cognitive appreciation of sound begins with energy in the form of very small changes in the way molecules of air gather together and move; what we call pressure waves of air. These tiny movements of air are the energy that hit the tympanic membrane and start the process of hearing. Let’s look at touch as another example. Touch perception requires what we call “mechanical” forces to be exerted on the skin. Mechanical forces are those experiences like stretching, vibration, pressing, or rubbing of the skin. These forces trigger the activity of a wide variety of sensors that allow our brain to use these mechanical inputs to appreciate things like texture, wetness, edges, and the weight of objects around us.

11.  Thanks for that quick explanation! You were saying that sensation is a 2-step process - can you elaborate?

The first step of sensation is called “transduction”, and this can be thought of as the “recording” or “sampling” phase of the process, whereby our specialized sensory receptors interact with real-word energy and forces to transform them into the electrochemical “language” of the nervous system. Think of this like what a language interpreter would do: Translate one language into another. Sensory receptors are the “interpreters” of our sensory systems. After transduction, the interpreted sensory inputs are transmitted through the nervous system in the form of action potentials along dedicated pathways to specialized regions of the brain that serve as initial processing stations for different classes or types of sensation.

12. Once we get sensation into the brain, is this when we start the process of perception?

Exactly right! If sensation is the recording and transmission of important stimulus features from the environment, then perception is the interpretation of these inputs once they reach the brain.

13. How do we learn to make these interpretations in the first place? Where does the ability to take sensations and make sense of them perceptually come from?

In a word, experience. Our lifelong experiences are the means through which we come to learn how to perceptually interpret sensations. Perception is at its essence a highly integrative process that is actively constructed by the brain and dependent on the memories of our past experiences. In short, perception is a cognitively and conceptually based event. Concepts such as sounds, smells, colors, and tactile feelings are all cognitively constructed ideas and exist only within the neural operations of the brain itself. On the other hand, the energies or forces underlying sound waves, heat, cold, and the physical properties of an object are the sensory input materials needed to construct these conceptual categories. To put this more simply, stimuli like air pressure variations, electromagnetic waves, chemical and organic molecules, strain, and stretch, are nothing but concrete forces that exist in nature. But when a nervous system with years of living experiences encounters these energies, they become transformed into our rich perceptions of sound, vision, smell, taste, and touch. So, let's return to that age-old question again: “If a tree falls in the woods and no one is around to hear it, does it make a sound?” The answer is “no,” it does not make a sound. The falling tree does create changes in air pressure, but not a “sound.” Why? Because sound is a perception that is cognitively constructed in our minds. Sound exists only if the right set of sensory receptors, along with a brain with sufficient experience with large falling objects, is present to detect and interpret the variations in air pressure the falling tree creates. Check off one deep-burning question of the universe as answered!

14. That’s fascinating. You’re saying that our own lifelong history of experiences in the real world is the very source of our ability to perceive and continue learning as we encounter different sensations each day.

Absolutely! The richness of our perceptions depends on the richness of our sensations and the experiences that produced them. This is why appreciating the concepts of sensation and perception matter to us as rehab specialists. As elegantly stated by Barlow (1998), therapy programs work to remodel patterns of behavior through graded and targeted training activities taught by an intervening therapist. At their essence, clinical interventions function to organize the sensory experiences of a patient by controlling the complexity, frequency, and form of various therapeutic tasks.

15. By controlling the form and timing of our treatments, we are giving the brains of our clients everything it needs to learn, is that right?

Not completely, because perception is more complicated than we think it is. The fact of the matter is that our nervous systems and the processes that create our perceptual abilities are far from ideal. Our nervous system measures and detects the environment using a surprisingly small set of sensors compared to the huge range of energy and forces that exist in nature. Think about this for a moment: We have only five (or maybe six, depending on who you reference) classes of sensory systems (tactile/proprioceptive, visual, olfactory, taste, hearing, and balance) available to us to form every possible experience we will ever encounter or be involved within our lifetime. Also, consider that a given sensory system is able to detect only a small and narrow range of the energies present in nature. A great example of this notion is our extremely limited capacity to sense visual energy. By many estimates, humans can detect less than 0.005% of the entire visible spectrum of light that exists naturally. Put another way, we are totally oblivious to 99.995% of the visual energy that exists around us!  But, with that 0.005% of the visual energy we can detect, we make the most of it to create our rich perception of a rainbow of colors.

16. Wait a moment! Our nervous systems are not able to record all the features of every sensation that exists in nature? Our experiences of the world are so rich and complex - how can that be? And what does this mean for our treatments?

Even if we only consider the ranges of energy that humans can detect, the sheer amount of sensory information flooding us at each moment in time is truly staggering. Our nervous systems are just not biologically capable of recording all environmental conditions and encoding the entire range of nature’s energy. We simply do not have enough brain tissue or the necessary sensory endings to transduce every bit of information or every variation of a sensory signal that we may ever encounter. Thus, what we are capable of sensing and perceiving is restricted by the limitations imposed by the anatomical and physiological features of the nervous system. To put this simply, if we don’t have a neural sensor for a type or range of energy that exists in nature, then from our point of view, that energy and sensation do not exist. Now, take this idea and apply it to a person who has had a stroke, experienced a traumatic brain injury, or has a congenital brain-based deficit. Their perception of the world will be very different from those who are healthy. These differences play a significant role in the clinical outcomes we will observe with treatment. Because perception requires sensations and brain systems to interpret those sensations, how we go about crafting our treatments requires us to be aware of these neural differences and adjust our treatment strategies accordingly. 

17. What factors should we be considering when we create a treatment that would play into what we know about sensation and perception?

For perception to be of functional use to us, we must have the ability to pick and choose or filter which parts of our sensory input are more important than others at any given moment. Factors such as attention, motivation, and emotional state all contribute significantly to this filtering process, by helping us to judge and select those pieces of information that are the most salient or relevant to our current behavior, our goals, and the environmental context. Many cognitive neuroscientists have argued that the ability to filter and select information important to our current state is key to our capacity to learn how to divide the world into meaningful and flexible perceptual categories of information. These perceptual categories are then used by the brain to help it predict and infer causality in nature. The brain can pick up on regularities that exist in the world even when you are not consciously aware of them. This is one of the brain’s “superpowers”, the ability to detect and extract patterns and regularities from streams of incoming sensory information. This ability is what is referred to as statistical learning; the general brain process that allows us to learn something complex from a small and relatively under-representative sampling of sensory inputs.

18. Can you explain more concretely what you mean by a perceptual category and why this is important to how we go about learning?

Perceptual categories can be thought of as classes of things or information that are created by determining the features that are in common among different sensory inputs acting upon us. For example, the perceptual category of "bottles" can be defined as objects that are hollow, can hold substances such as liquids, fit in your hand, and are made of glass or plastic. Perceptual categories are useful because they help us predict future events and interpret our novel experiences based on our past histories and memories with similar events. You can travel to any location on earth and know when you’ve encountered a bottle, even if you’ve never seen or experienced that exact type of bottle before. You’ve experienced enough examples of bottles in your lifetime to have learned the set of conditions that define this perceptual category (as the old saying goes, “if you’ve seen one, you’ve seen them all.”). While humans are not the only animals that can form perceptual categories from sensory experiences, we are by far the most creative and adaptable in this ability. In fact, our ability to inference and predict are ways of alleviating the need to remember every last scrap of information from a given experience. Inference and prediction allow us to rely on learned generalities from many sensory experiences to help us manage and (here’s the important point) create novel solutions to satisfy our current needs.

Here’s a thought experiment to help me illustrate this point. Let’s return to our bottle example - what other functional perceptual categories do the physical features of a bottle satisfy? In other words, in how many different ways can you “use” the features of a bottle so that it can satisfy different needs and goals? Obviously, bottles first and foremost operate as liquid containers. But what if you needed a vase to hold a flower? Bottles can be easily recategorized as vases. A bottle can also be used as a rolling pin to stretch out pizza dough, as a makeshift hammer to crush things, or even as a weapon to defend yourself. I’ve seen people use bottles as light diffusers, bug traps, and garden edging. A bottle can even be used as a simple musical instrument by blowing gently over the opening to produce a tone. Look at all the different perceptual categories I was able to place a bottle into in the span of a few moments. Our years of repeated and variant experiences with developing perceptual categories have given us the ability to (a) filter sensory information, (b) select salient information pertaining to an event, and (c) remember those choices. Through these practiced abilities, we develop and create the means by which we detect and appreciate the infinite novelty found within our world.

19. When I hear you say things like “filtering”, “selecting”, “creating”, the speech scientist in me can’t help but think that part of perception must be actively controlled or constructed by the brain in some way.

You are exactly right! We are capable of remarkable control and regulation of our own appreciation of an experience through changes in attentional state and engagement. When learning a new skill, such as driving a car for the first time, our attentional system actively suppresses vast quantities of sensory information from all sources to help keep our hands steady on the wheel, the car going straight, and our eyes firmly on the road ahead. This type of attentional control occurs frequently during our daily lives. For example, if I tell you to start paying attention to the glasses you are wearing or any jewelry you might have on right now, suddenly what was once perceptually unnoticed instantly becomes noticeable. Before I suggested this example to you, you were likely unaware of your glasses sitting on your face or your jewelry on your fingers or neck. Yet, tactile sensory receptors were still firing and centrally transmitting information about these items as you move your body about, even when you were not aware of them. Before I said anything, these inputs were not salient or important to you until you were made aware of them. By focusing your attention on your glasses and jewelry, you altered your perceptual system yourself to raise the already present tactile inputs coming from your skin to a higher level of conscious awareness. As you can imagine, the ability to alter your perceptions based on your level of attention has major implications for exactly how and what we learn from our experiences in the world. Therapeutically, intent and attention become critical factors to manipulate directly during the course of treatment. If you consider that many treatment tasks are multimodal (made up of many different types of sensory information) in nature, helping a client to actively attend to specific features or characteristics of a therapeutic task may allow the person to change their perceptual systems in specific ways to better achieve an intended treatment outcome. During treatment, a clinician needs to stay alert to the ebb and flow of a patient’s engagement and adjust the treatment form and intensity accordingly to optimize learning.

20. This has been such a fascinating discussion on the nature of sensation and perception and its role in how the brain adapts and learns about the world around us. Any closing remarks?

First, thanks for having me here and letting me talk about a topic that I love discussing. Secondly, let me say that if people want to know more about this topic, I’ve included several suggested readings for them to follow up with, including a reference to my neuroscience textbook specifically written to help CSD students and clinicians understand the broad details and complexities of the nervous system during behavior. Lastly, let me re-emphasize the major point I’ve made that understanding the nature of sensation and perception goes directly to the heart of ensuring that our treatments are effective in accomplishing the outcomes we want to see in our patients. If treatment is about teaching and getting our clients to learn new skills and ways of behaving, then it follows that sensation and perception are critical inputs that help accomplish these outcomes. When you couple this idea with the understanding that our nervous systems are highly malleable and adaptable, you realize that sensation and perception are the keys to driving the brain’s adaptability. With this idea, you now have the insight needed to craft interventions that directly control and push the nervous system of a patient to respond in ways that will allow them to improve their functional interactions with the world.

Acknowledgments

Excerpts used for this article were adapted from selections from the text, Neuroscience Fundamentals for Communication Sciences & Disorders (Andreatta, 2019), with permission from Plural Publishing, Inc.

References and Suggested Readings

Amaral, D. G. (2013). The functional organization of perception and movement. In E. R. Kandel, J. H. Schwartz, T. M. Jessell, S. A. Siegelbaum, & A. J. Hudspeth (Eds.), Principles of Neural Science (5th ed., pp. 356–369). New York, NY: McGraw-Hill.

Andreatta, R. D. (2008). Sensorimotor elements of the orofacial system: Reviewing the basics. Perspectives on Speech Science and Orofacial Disorders, 18, 51-61.

Andreatta, R. D. (2019). Neuroscience Fundamentals for Communication Sciences and Disorders. San Diego, CA: Plural Publishing.

Barlow, S. M. (1998). Real-time modulation of speech-orofacial motor performance by means of motion sense. Journal of Communication Disorders, 31(6), 511-533.

Baars, B. J., & Gage, N. M. (2010). Cognition, Brain, and Consciousness: Introduction to Cognitive Neuroscience (2nd ed.). Oxford, UK: Elsevier.

Danzl, M.M., Etter, N.M., Andreatta, R.D., & Kitzman, P.H. (2012). Facilitating neurorehabilitation through principles of engagement. Journal of Allied Health, 41(1), 35-41.

Gardner, E. P., & Johnson, K. O. (2013). Sensory coding. In E. R. Kandel, J. H. Schwartz, T. M. Jessell, S. A. Siegelbaum, & A. J. Hudspeth (Eds.), Principles of Neural Science (5th ed., pp. 449–474). New York, NY: McGraw-Hill.

Kleim, J. A., & Jones, T. A. (2008). Principles of experience-dependent neural plasticity: Implications for rehabilitation after brain damage. Journal of Speech-Language-Hearing Research, 51(1), S225–S239.

Kuhl, P. K. (2010). Brain mechanisms in early language acquisition. Neuron, 67(5), 713–727.

Thelen, E., & Smith, L. B. (1996). A Dynamic Systems Approach to the Development of Cognition and Action. Cambridge MA: MIT Press.