Sensory input and what can go wrong

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Sensory inputs and what can go wrong

Our senses are the foundations of learning and behaviour, our brain and our body work together to develop our sensory pathways.

The five senses

The senses are the ways that humans and other animals perceive the world around them. There are five main senses: vision, hearing, smell, taste, and touch. Each sense has a specific organ or system that detects and processes sensory information, such as light, sound, chemicals, or pressure. The sensory information is then sent to the brain, where it is interpreted and integrated with other information to form a coherent perception of reality (Goldstein, 2019).

Vision is the sense of sight, which allows us to see colours, shapes, distances, and movements. Vision is mediated by the eyes, which contain photoreceptors that convert light into electrical signals. The signals are then transmitted to the visual cortex in the brain, where they are processed and analysed to form visual images (Wolfe et al., 2018).

Hearing is the sense of sound, which allows us to hear noises, voices, music, and speech. Hearing is mediated by the ears, which contain hair cells that vibrate in response to sound waves. The vibrations are then converted into electrical signals and sent to the auditory cortex in the brain, where they are processed and decoded to form auditory sensations (Moore, 2012).

Smell is the sense of odour, which allows us to detect and identify different scents. Smell is mediated by the nose, which contains olfactory receptors that bind to odour molecules. The receptors then generate electrical signals and send them to the olfactory bulb in the brain, where they are processed and recognized as specific smells (Doty, 2017).

Taste is the sense of flavour, which allows us to enjoy and distinguish different foods and drinks. Taste is mediated by the tongue, which contains taste buds that contain taste cells. The taste cells have receptors that interact with chemicals in food and saliva. The receptors then generate electrical signals and send them to the gustatory cortex in the brain, where they are processed and categorized as basic tastes: sweet, sour, salty, bitter, and umami (Spector & Glendinning, 2009).

Touch is the sense of tactile sensation, which allows us to feel textures, temperatures, pain, and pressure. Touch is mediated by the skin, which contains various types of touch receptors that respond to different stimuli. The receptors then generate electrical signals and send them to the somatosensory cortex in the brain, where they are processed and localized as touch sensations (Johnson & Hsiao, 1992).

The senses are essential for survival, communication, learning, and enjoyment. They provide us with information about our environment and ourselves. They also interact and influence each other in complex ways. For example, vision can affect hearing (the McGurk effect), smell can affect taste (the flavour), and touch can affect pain (the gate control theory) (Goldstein et al., 2020). Understanding how the senses work can help us improve our sensory abilities and enhance our quality of life.

Body awareness, head position/movement and gut awareness

The senses of body awareness, head position/movement, and gut awareness are related to the proprioceptive and vestibular systems, which are part of the eight sensory systems that humans have (STAR Institute, n.d.). The proprioceptive system provides information about the position and movement of body parts in relation to muscles and joints, while the vestibular system provides information about the orientation and balance of the head in space (Healthline, 2020). These systems help us to recognize where our body is in space, how to move it, and how much force we need to use (Berkshire Healthcare, n.d.).

Body awareness is the conscious and connected feeling of one’s own body. It involves being able to identify and meet one’s needs, such as hunger, thirst, tiredness, or emotional distress. It also involves being able to sense and control one’s movements, posture, and balance. Body awareness can be improved by physical exercises, meditation, mindfulness, and therapy (Healthline, 2020).

Head position/movement is the ability to keep the head stable and aligned with the rest of the body. It involves the vestibular system, which is composed of organs in the inner ear that detect changes in gravity, motion, and acceleration. The vestibular system helps us to maintain our equilibrium, coordinate our eye movements, and orient ourselves in space. Head position/movement can be affected by disorders such as vertigo, dizziness, or motion sickness. It can be enhanced by exercises that stimulate the vestibular system, such as spinning, swinging, or tilting (STAR Institute, n.d.).

Gut awareness is the sensation of one’s internal organs and their functions. It involves the interoceptive system, which is the most recently discussed set of sensations related to the body. The interoceptive system helps us to monitor our physiological states, such as heart rate, blood pressure, temperature, digestion, and emotions. Gut awareness can influence our mood, behaviour, and decision-making. It can be cultivated by practices that increase our attention to our bodily signals, such as breathing exercises, yoga, or biofeedback (STAR Institute, n.d.).

Proprioception

Proprioception is the sense of self-movement, force, and body position that is mediated by sensory receptors in the muscles, tendons, and joints (Proprioception – Wikipedia, n.d.). Proprioception is essential for coordination, balance, and posture, especially during locomotion. Proprioception can be affected by injuries, medical conditions, age-related changes, or alcohol use that impair the sensory feedback loop between the body and the brain (Healthline, 2020). Proprioception can be assessed by various tests, such as touching the nose with the eyes closed or standing on one foot. Proprioception can be improved by physical therapy, occupational therapy, and exercises that challenge the sensory system and enhance motor control (WebMD, 2020).

Vestibular system – what is it and what difficulties can it cause?

The vestibular system is a part of the inner ear that helps to maintain balance and spatial orientation. It consists of three semicircular canals, the utricle, and the saccule, which detect rotational and linear movements of the head, respectively. The vestibular system sends signals to the brain stem and the cerebellum, which coordinate eye movements and posture to keep a stable visual field and prevent falls (WebMD, 2023).

Vestibular dysfunction occurs when there is a problem with the vestibular system or its connections to the brain. It can cause symptoms such as dizziness, vertigo, imbalance, nausea, vomiting, hearing loss, tinnitus, and vision problems. Vestibular dysfunction can have various causes, such as infections, injuries, tumours, autoimmune diseases, genetic disorders, medications, or ageing (Vestibular Disorders Association, n.d.).

Some common vestibular disorders are:

• Benign paroxysmal positional vertigo (BPPV): This is caused by tiny calcium crystals that dislodge from the utricle and enter the semicircular canals, where they interfere with the fluid movement that senses head rotation. This causes brief episodes of intense vertigo triggered by changes in head position. BPPV can be treated with specific head manoeuvres that reposition the crystals back to the utricle (WebMD, 2023).
• Labyrinthitis: This is an inflammation of the labyrinth, the structure that contains the vestibular system and the cochlea (the hearing organ). It can be caused by bacterial or viral infections, allergies, or autoimmune reactions. It can cause vertigo, nausea, vomiting, ear pain, hearing loss, and fever. Treatment may include antibiotics, steroids, or anti-emetics (WebMD, 2023).
• Vestibular neuritis: This is an inflammation of the vestibular nerve, which carries signals from the inner ear to the brain. It can be caused by viral infections that spread from other parts of the body. It can cause sudden onset of severe vertigo, nausea, vomiting, and difficulty walking. Treatment may include antiviral drugs or vestibular rehabilitation exercises (WebMD, 2023).
• Meniere’s disease: This is a disorder of the inner ear fluid balance that causes episodes of vertigo, fluctuating hearing loss, tinnitus, and ear fullness. The exact cause is unknown, but it may be related to excess fluid accumulation in the inner ear due to a virus, allergy, or autoimmune reaction. Treatment may include dietary modifications, diuretics, or surgery in severe cases (WebMD, 2023).
• Peri lymphatic fistula (PLF): This is a tear or defect in the membrane that separates the middle ear from the inner ear. It can allow perilymph (the fluid in the inner ear) to leak into the middle ear and cause changes in pressure and hearing. It can be caused by trauma, surgery, infection, or congenital defects. It can cause vertigo, nausea, hearing loss, and tinnitus. Treatment may include bed rest, pressure-equalizing tubes, or surgery (WebMD, 2023).

Interoception

Interoception is the collection of senses that provide information to the organism about the internal state of the body, such as hunger, thirst, temperature, pain, and emotions (Wikipedia, n.d.). Interoception can be both conscious and subconscious, and it involves the integration of signals from various physiological systems in the brain (Cambridge Dictionary, n.d.). Interoception is important for maintaining homeostasis, self-awareness, and mental wellbeing (Autism.org.uk, n.d.).

Interoception dysfunction can cause problems in recognizing and regulating one’s own bodily and emotional states, which can lead to difficulties in coping with stress, anxiety, depression, and other mental health issues. Interoception dysfunction can also affect social cognition and empathy, as well as decision-making and impulse control. Some conditions that have been associated with interoception dysfunction include autism spectrum disorder, anorexia nervosa, bulimia nervosa, post-traumatic stress disorder, obsessive compulsive disorder, and somatic symptom disorder (Wikipedia, n.d.).

Sensory overload

Sensory overload is a phenomenon that occurs when the sensory inputs from the environment exceed the capacity of the nervous system to process them (APA Dictionary of Psychology, n.d.). Sensory overload can result from both physical stimuli, such as noise, light, or temperature, and symbolic stimuli, such as information, messages, or tasks (Lipowski, 1975). Sensory overload can have various behavioural effects, such as anxiety, stress, confusion, irritability, or withdrawal (Scheydt et al., 2017). Sensory overload can also be related to some psychopathological conditions, such as schizophrenia, autism, or post-traumatic stress disorder (Ludwig & Stark, 1973). Sensory overload can be influenced by individual factors, such as personality, motivation, or coping skills, and situational factors, such as duration, intensity, or complexity of the stimuli (Kitamura et al., 1971). Sensory overload is a complex concept that requires further research and theoretical development to understand its causes and consequences.

Limbic system

The limbic system is a complex network of brain structures that includes the cingulate gyrus, the hippocampus, the amygdala, and other subcortical nuclei. The limbic system is involved in various functions such as emotion, memory, motivation, and behaviour regulation (Bubb, Metzler-Baddeley, & Aggleton, 2018). Dysfunction of the limbic system can lead to various psychiatric and neurological disorders, depending on which part of the system is affected. For example, temporal lobe lesions can cause personality changes, hallucinations, and schizophreniform symptoms (Trimble, 1984), while frontal lobe lesions can cause apathy, lack of initiative, and impaired executive functions (Acosta-Cabronero & Nestor, 2012). Midbrain and tegmental lesions can also produce diverse behavioural syndromes, such as confabulation, impulsivity, and abnormal dreaming (Solms & Panksepp, 2012). Therefore, understanding the anatomy, function, and dysfunction of the limbic system is essential for diagnosing and treating various mental and neurological conditions.

amygdala

The amygdala is a small, almond-shaped structure located in the medial temporal lobe of the brain. It is part of the limbic system, which is involved in emotion, motivation, memory, and learning. The amygdala plays a key role in processing emotional stimuli, especially those related to fear, threat, and reward. It also modulates the consolidation and retrieval of emotional memories (Whalen & Phelps, 2009).

The dysfunction of the amygdala can cause various psychological and neurological problems, such as anxiety disorders, depression, schizophrenia, autism, Alzheimer’s disease, amnesia, and epilepsy. These disorders may result from abnormal development, damage, or degeneration of the amygdala or its connections with other brain regions. For example, patients with amygdala lesions show impaired recognition of facial expressions of emotion, reduced fear conditioning and extinction, and impaired social behaviour (Aggleton, 1992). Patients with Alzheimer’s disease show reduced amygdala volume and activity, which may contribute to their cognitive decline and emotional disturbances (Whalen & Phelps, 2009). Patients with epilepsy involving the temporal lobe may experience seizures that originate from or spread to the amygdala, causing intense emotional experiences such as fear, anger, or euphoria (Aggleton, 1992).

The amygdala is also involved in the memory of reward, which is essential for learning and motivation. The amygdala receives inputs from various sensory modalities and projects to the ventral striatum, which mediates reward-related behaviour. The amygdala encodes the value and salience of rewarding stimuli and modulates their reinforcement effects. It also influences the formation and retrieval of reward-associated memories in other brain regions, such as the hippocampus and the prefrontal cortex (Gaffan, 1992).

Thalamus

The thalamus is a complex structure in the brain that acts as a relay station for sensory and motor information. It receives inputs from various sources, such as the eyes, ears, skin, and spinal cord, and sends them to the appropriate areas of the cerebral cortex for further processing. The thalamus also receives feedback from the cortex and modulates the transmission of sensory and motor signals. The thalamus plays a critical role in perceptual processing, attention, memory, emotion, and arousal (Sherman & Guillery, 2006).

The thalamus consists of several nuclei that have different functions and connections. Some of these nuclei are classified as first-order relays, which receive inputs from ascending pathways that carry information from the periphery to the brain. For example, the lateral geniculate nucleus receives visual inputs from the retina and sends them to the primary visual cortex. Other nuclei are classified as higher-order relays, which receive inputs from cortical areas and send them to other cortical areas. For example, the pulvinar nucleus receives inputs from the parietal and temporal cortices and sends them to the frontal cortex (Sherman & Guillery, 2006).

The thalamus is involved in many functions and disorders of the brain. Dysfunction or damage to the thalamus can cause various symptoms, depending on the location and extent of the lesion. Some of these symptoms include:

• Sensory loss or impairment: Damage to the sensory relay nuclei can cause loss or impairment of sensation in the opposite side of the body. For example, damage to the ventral posterior nucleus can cause loss of touch, pain, temperature, and vibration sensation (Cleveland Clinic, n.d.).
• Visual impairment: Damage to the visual relay nuclei can cause visual field defects or blindness in the opposite side of the visual field. For example, damage to the lateral geniculate nucleus can cause homonymous hemianopia (Cleveland Clinic, n.d.).
• Movement disorders: Damage to the motor relay nuclei can cause abnormal movements or postures in the opposite side of the body. For example, damage to the ventral lateral nucleus can cause hemiballismus, which is a disorder characterized by involuntary flinging movements of the limbs (Cleveland Clinic, n.d.).
• cognitive impairment: Damage to the higher-order relay nuclei can cause impairments in attention, memory, language, executive functions, or spatial awareness. For example, damage to the pulvinar nucleus can cause neglect syndrome, which is a disorder characterized by reduced awareness of stimuli in the opposite side of space (Sherman & Guillery, 2006).
• Emotional impairment: Damage to the limbic relay nuclei can cause impairments in emotion regulation, motivation, or social behavior. For example, damage to the medial dorsal nucleus can cause apathy, depression, or psychosis (Taber et al., 2004).

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