The two sensations that are picked up through free nerve endings are thermoception, which detects temperature, and nociception, which detects pain sensation. These sensations all go to the somatosensory cortex in the parietal lobe, which is responsible for the interpretation of these senses. Pain has both psychological and physical components. Some pain can be inflammatory, which comes from some type of tissue damage. Other pain is neuropathic, which comes directly from damage to a nerve. Because there are psychological components to pain, interventions such as relaxation techniques can be employed to treat pain. Pain medications and deep brain stimulation are also used to treat pain. Another sense is referred to as vestibular sense. This is directly picked up by the semicircular canals of the inner ear. There are hair cells in these canals that respond to head movement and to gravity. It is something people don t often think about unless they have vertigo, which is a kind of spinning dizziness that can come from problems with the inner ear. It is this same vestibular system that helps to detect things like proprioception and kinesthesia. Proprioception helps to perceive the body s position in space and kinesthesia helps to determine how the body is moving. Kinesthesia and proprioception are also responsive to the receptors in the joints, skin, muscles, and tendons that detect tension and stretch.
GESTALT PRINCIPLES OF SENSATION It was more than a hundred years ago that it was first observed that rapidly flickering images were able to be detected as movement. This led to many things, including the development of Gestalt psychology. It is based on the premise that the whole perception is more than the sum of the sensory parts that are perceived. There are relatively predictable ways that a person organizes his or her sensory information. Figure 20 shows the figure ground relationship, which is a perception puzzle used in Gestalt psychology:
104
