Sensation is the ability to receive and process stimuli received through the sensory organs. External stimuli are visual, auditory, olfactory, gustatory, and tactile. Internal stimuli are processed through kinesthetic (body position awareness) and visceral (large organ stimuli) systems. Perception is the ability to experience, recognize, organize, and interpret sensory stimuli. Cognition is the intellectual ability to think, including memory, judgment, and orientation. Sensory, perceptual, and cognitive alterations can be temporary or progressive and can result from disease or trauma.

The central nervous system (CNS) and peripheral nervous system (PNS) work together to collect stimuli, transport the stimuli to the brain, and respond to stimuli. The components of the sensory system are the afferent nerve pathways, which transmit impulses to the brain; the efferent nerve pathways, which send sensory impulses from the brain; the spinal cord; the brainstem; and the higher cortex (cerebrum).

The components of cognition are consciousness (including arousal and awareness), memory, affect, judgment, perception, and language. Consciousness affects both intellectual and emotional functions and depends upon the reticular activating system (RAS) in the brainstem, the control for sleep and wakefulness. Orientation is the ability to be aroused, to perceive the environment accurately, and to recognize patterns. Clients with altered speech have either expressive aphasia, the ability to understand communication but not to speak clearly, or receptive aphasia, the ability to speak well but the inability to understand the message that is spoken.

The factors affecting sensation, perception, and cognition are age, environment lifestyle, stress, illness, and medications. The infant or small child has an immature nervous system and is still learning cognitively. Cognitive ability is nourished and maintained by a stimulating environment and does not decline in older age. Memory impairments occur in the aged as a result of pathology, but not due to age. The environment, the person’s lifestyle, and stress levels can be stimulating but are also demanding. Likewise, illnesses and medications can lead to sensory, perceptual, and cognitive problems.

Sensory, perceptual, and cognitive alterations include sensory deficits, deprivation, and overload. Disorientation is a mentally confused state in which the person’s awareness of time, place, self, and/or situation is impaired (“Disoriented x4”). Disorientation can be caused by sensory over-stimulation or sensory under-stimulation.

A sensory deficit is a change in the perception of sensory stimuli, such as visual and hearing losses. People with a sensory deficit are more likely to experience sensory deprivation or sensory overload. Sensory deprivation is a state of reduced sensory input from the internal or external environment. It is manifested by alterations in sensory perception, as a result of illness, trauma, isolation, or medications that depress the CNS, such as narcotics or sedatives. Sensory overload is a state of excessive and sustained multi-sensory stimulation manifested by behavior change (anxiety, irritability, and similar problems) and perceptual distortion. Sensory overload is caused by increased internal stimuli, such as pain or disease; invasive treatments; excessive noise; the presence of strangers; and medications that stimulate the CNS.

Assessment of sensation, perception, and cognition includes a health history, physical examination (including cranial nerves), mental status assessment (including LOC), assessment of functional abilities, and an environmental assessment. The mental status and level of consciousness assessment includes (1) noting general appearance, speech content, memory, logic, judgment, and speech patterns displayed; (2) performing a Glasgow Coma Scale; and (3) using a brief mental status screening test, such as the Mini-Mental Status Examination. Sensation is tested by assessing pain, light touch, and vibration in the hands and feet. The cranial nerves are assessed to determine visual or hearing problems, taste, smell, and motor activity of the face. Cerebellar function is assessed by observing the client’s gait and motor ability. Reflexes are assessed to test the nervous system.

The nursing diagnoses related to sensation, perception, and cognition are Disturbed Sensory Perception (Visual, Auditory, Kinesthetic, Gustatory, Tactile, or Olfactory), Disturbed Thought Processes, Social Isolation and Risk for Injury. Goals for clients with these nursing diagnoses are related to safety, meaningful stimulation, orientation, intact functioning of senses, and ability to perform activities of daily living.

Implementation includes managing sensory deficits (tactile, auditory, visual), managing sensory deprivation, managing sensory overload (assisting for the confused), caring for the unconscious client, using restraints, and complementary and alternative therapies (herbals, aromatherapy). Evaluating care requires reviewing whether expected outcomes were reached.