PSY102 - Unit 4 (Sensation and Perception)

Detection of physical energy by sense organs, which then send information to the brain.

The brain's interpretation of raw sensory inputs.

The process of converting an external energy or substance into neural activity.

Specifalized cell responsible for converting external stimuli into neural activity for a specific sensory system.

Lowest level of a stimulus needed for the nervous system to detect a change 50 percent of the time.

The smallest change in the intensity of a stimulus that we can detect.

The process by which we perceive stimuli consistently across varied conditions.

Process of selecting one sensory channel and ignoring or minimixing others.

Intensity of reflected light that reaches our eyes.

Colour of light.

Part of the eye containing transparent cells that focus light on the retina.

Part of the eye that changes curvature to keep images in focus.

Changing the shape of the lens to focus on objects near or far.

Membrane at the back of the eye responsible for converting light into neural activity.

Central portion of the retina.

Sharpness of vision.

Receptor cells in the retina allowing us to see in low levels of light.

Receptor cells in the retina allowing us to see in colour.

Part of the visual field we can't see because of an absence of rods and cones.

Idea that colour vision is based on our sensitivity to three different colours.

Inability to see some or all colours.

Ability to judge distance and three-dimensional relations.

Stimuli that enable us to judge depth using only one eye.

Stimuli that enable us to judge depth using both eyes.

Failure to perceive an event when our attention is directed elsewhere.

Our sense of hearing.

Complexity or quality of sound that makes musical instruments, human voices, or other sources sound unique.

Bony, spiral-shaped sense organ used for hearing.

Tissue containing the hair cells necessary for hearing.

Membrane supporting the organ of Corti and hair cells in the cochlea.

Our sense of smell.

Our sense of taste.

Sense receptors in the tongue that respond to sweet, salty, sour, bitter, umami, and perhaps fat.

Odourless chemicals that serve as social signals to members of one's species.

Our sense of touch, temperature, and pain.

Our sense of body position.

Our sense of equilibrium or balance.

Pain or discomfort felt in an amputated limb.

Three fluid-filled canals in the inner ear responsible for our sense of balance.

Transduction is the process of converting an external energy, such as light or sound vibration, into activity in the nervous system. The doctrine of specific nerve energies refers to how each of the sensory modalities vision, hearing, touch, and so on) is handled by specific regions of the brain, especially specific regions of the cerebral cortex (visual cortex, auditory cortex, and so on). Evidence suggests that even though most connections in the brain are faithful to one sense modality, brain regions often respond to information from a different sense. For example what we see affects what we hear when watching video with sound.

Information travels from primary sensory to secondary sensory cortex and then on to association cortex. Along the way, perception becomes increasingly complex. We also process many different inputs simultaneously, a phenomenon called parallel processing. All the processing comes together to generate an integrated perception experience referred to as binding.

The lens in the eye accommodates to focus on images both near and far by changing from "fat" to "flat." The lens optimally focuses light on the retina, which lies at the rear of the eye. The retina contains rods and cones filled with pigments. Additional cells in the retina transmit information about light to the ganglion cells, and the axons of these cells form the optic nerve.

Our visual system is sensitive to shape, colour, and motion. We use different parts of the visual cortex to process these different aspects of visual perception. Cells in the primary visual cortex, called V1, are sensitive to lines of a particular orientation, like a horizontal line or a vertical line. Colour perception involves comparing the reflectance from an object with the reflectance of surrounding elements in the scene. Our visual system detects motion by comparing individual "still frames" of visual content.

Blindness is a worldwide problem in underdeveloped countries. Curable causes of blindness, like cataracts and glaucoma, often go untreated. Other forms of blindness such as diabetic retinopathy are incurable. There are several types of colour blindness: red-green colour blindness is the most common type and it affects mostly males.

Sound waves created by vibration of air molecules are funnelled into the outer ear. These vibrations perturb the eardrum, causing the three small bones in the middle ear to vibrate. This process creates pressure in the cochlea contraining the basilar membrane and organ of Corti, in which hair cells are embedded. The hair cells then bend, thereby exciting them. The message is relayed through the auditory nerve.

We accomplish pitch perception in three ways. Place theory is pitch perception based on where along the basilar membrane hair cells were maximally excited. Frequency theory is based on the hair cells reproducing the frequency of the pitch in their firing rates. In Volley theory, groups of neurons stagger their responses to follow a pitch. We also perceive where a sound is coming from, a phenomenon called "sound localization."

Gustation (taste) and olfaction (smell) are chemical senses because our sense receptors interact with molecules containing flavour and odour. The tongue contains taste receptors for sweet, sour, salty, imami (a "meaty" or "savoury" flavour), and perhaps fat. Our ability to taste different food also relies largely on smell. Olfactory receptors in our noses are sensitive to hundreds of differnt airborne molecules. We use our senses of taste and smell to sample our food. We react to extremely sour tastes, which may be due to food spoilage, with digust. We also appear sensitive to pheromones, odourless molecules that can affect sexual response.

We process information about touch to the skin, muscle activity, and acceleration. These are called "somatosensory" for body sensation, "proprioception" for muscle position sense, and "vestibular sense" for the sense of balance and equilibrium. The somatosensory system responds to light touch, deep pressure, hot and cold temperature, and tissue damage. Our muscles contain sense receptors that detect stretch and others that detect force. We calculate where our bodies are located from this information. We're typically unaware of our sense of equilibrium.

The perception of pain differs from the perception of touch because there's a large emotional component to pain not present with touch. This is because pain information activates parts of the limbic system addition to the somatosensory cortex. There's evidence that pain perception can be reduced by a "stoic" mind-set as well as cultural and genetic factors. Disorders of pain perception called pain insensitivities, are associated with an increased risk of injury. As unpleasant as pain may be, it's essential to our survival.