Sensation and Percetion (2)

Sensation

is the conversion, or transduction, of physical, electromagnetic, auditory, and other information from the internal and external environment into electrical signals in the nervous system.

Perception

is the processing of sensory information to make sense of its significance.

Sensory receptors

are nerves that respond to stimuli and trigger electrical signals.

Sensory neurons

are associated with sensory ganglia.

Sensory ganglia

collections of cell bodies outside the central nervous system.

Projection areas

Sensory stimuli are transmitted to here in the brain, which further analyze the sensory input.

Common sensory receptors

include photoreceptors, hair cells, nociceptors, thermoreceptors, osmoreceptors, olfactory receptors, and taste receptors.

Threshold

is the minimum stimulus that causes a change in signal transduction.

Absolute threshold

is the minimum of stimulus energy that is needed to activate a sensory system.

Threshold of conscious perception

is the minimum of stimulus energy that will create a signal large enough in size and long enough in duration to be brought into awareness.

Difference threshold or just-noticeable difference (jnd)

is the minimum difference in magnitude between two stimuli before one can perceive this difference.

Weber’s law

states that the jnd for a stimulus is proportional to the magnitude of the stimulus, and that this proportion is constant over most of the range of possible stimuli.

Signal detection theory

refers to the effects of nonsensory factors, such as experiences, motives, and expectations, on perception of stimuli.

Response bias

Signal detection experiments allow us to look at this. In a signal detection experiment, a stimulus may or may not be given, and the subject is asked to state whether or not the stimulus was given. There are four possible outcomes: hits, misses, false alarms, or correct negatives.

Adaptation

refers to a decrease in response to a stimulus over time.

Eye

is an organ specialized to detect light in the form of photons.

Cornea

gathers and filters incoming light.

Iris

divides the front of the eye into the anterior and posterior chambers. It contains two muscles, the dilator and constrictor pupillae, which open and close the pupil.

Lens

refracts incoming light to focus it on the retina and is held in place by suspensory ligaments connected to the ciliary muscle.

Ciliary body

produces aqueous humor, which drains through the canal of Schlemm.

Retina

contains rods and cones.

Rods

detect light and dark.

Cones

come in three forms (short-, medium-, and long-wavelength) to detect colors.

Macula

The retina contains mostly cones in this, which corresponds to the central visual field.

Fovea

The center of the macula is this, which contains only cones.

Bipolar; ganglion

Rods and cones synapse on ______ cells, which synapse on _______ cells.

Horizontal; amacrine

Integration of the signals from ganglion cells and edge-sharpening is performed by _________ and ________ cells.

Vitreous; sclera; choroid

The bulk of the eye is supported by the ________ on the inside and the _______ and ________ on the outside.

Eye, optic nerves, optic chiasm, optic tracts, lateral geniculate nucleus (LGN) of the thalamus, visual radiations, visual cortex (occipital lobe)

The visual pathway

Optic chiasm

contains fibers crossing from the nasal side of the retina (temporal visual fields) of both eyes.

Visual radiations

run through the temporal and parietal lobes.

Parallel processing

the ability to simultaneously analyze and combine information regarding color, form, motion, and depth. Vision and all senses is processed through this.

Color

is detected by cones.

Parvocellular cells

Form is detected by this, with high spatial resolution and low temporal resolution.

High; low

Parvocellular cells detect form with ______ spatial resolution and _____ temporal resolution.

Magnocellular cells

Motion is detected by this, with low spatial resolution and high temporal resolution.

Low; high

Magnocelular cells detect motion with _____ spatial resolution and _____ temporal resolution.

Binocular neurons

Depth is detected by this.

Outer; middle; inner

The ear is divided into the ______, ______, and ______ ear.

Outer ear

consists of the pinna (auricle), external auditory canal, and tympanic membrane.

Middle ear

consists of the ossicles: malleus (hammer), incus (anvil), and stapes (stirrup). The footplate of the stapes rests on the oval window of the cochlea. This is connected to the nasal cavity by the Eustachian tube.

Ossicles

consists of the malleus (hammer), incus (anvil), and stapes (stirrup).

Malleus

hammer

Incus

anvil

Stapes

stirrup

Cochlea

The footplate of the stapes rests on the oval window of this.

Eustachian tube

connects the middle ear to the nasal cavity.

Inner ear

contains the bony labyrinth, within which is the membranous labyrinth.

Perilymph

The bony labyrinth is filled with this

Endolymph

The membranous labyrinth is filled with this.

Membranous labyrinth

consists of the cochlea, which detects sound; utricle and saccule, which detect linear acceleration; and semicircular canals, which detect rotational acceleration.

Cochlea

detects sound

Utricle and saccule

detect linear acceleration

Semicircular canals

detect rotational acceleration

Cochlea, vestibulocochlear nerve, medial geniculate nucleus (MGN) of the thalamus, auditory cortex (temporal lobe)

The auditory pathway

Superior olive

Sound information projects to this, which localizes the sound.

Inferior Colliculis

Sound information projects to this which is involved in the startle reflex.

Smell

the detection of volatile or aerosolized chemicals by the olfactory chemoreceptors (olfactory nerves) in the olfactory epithelium.

Olfactory nerves, olfactory bulb, olfactory tract, higher order brain areas (Limbic system)

The olfactory pathway

Pheromones

chemicals given off by animals that have an effect on social, foraging, and sexual behavior in other members of that species.

Taste

the detection of dissolved compounds by taste buds in papillae. It comes in five modalities: sweet, sour, salty, bitter, and umami (savory).

Somatosensation

refers to the four touch modalities: pressure, vibration, pain, and temperature.

Two-point threshold

the minimum distance necessary between two points of stimulation on the skin such that the points will be felt as two distinct stimuli.

Physiological zero

the normal temperature of the skin to which objects are compared to determine if they feel "warm" or "cold."

Nociceptors

are responsible for pain perception.

Gate theory of pain

states that pain sensation is reduced when other somatosensory signals are
present.

Kinesthetic sense (proprioception)

refers to the ability to tell where one's body is in three-dimensional space.

Bottom-up (data-driven) processing

refers to recognition of objects by parallel processing and feature detection. It is slower, but less prone to mistakes.

Top-down (conceptually driven) processing

refers to recognition of an object by memories and expectations, with little attention to detail. It is faster, but more prone to mistakes.

Perceptual organization

refers to our synthesis of stimuli to make sense of the world, including integration of depth, form, motion, and constancy.

Gestalt principles

are ways that the brain can infer missing parts of a picture when a picture is incomplete.

Law or proximity

says that elements close to one another tend to be perceived as a unit.

Law of similarity

says that objects that are similar appear to be grouped together.

Law of good continuation

says that elements that appear to follow the same pathway tend to be grouped together.

Subjective contours

refer to the perception of nonexistent edges in figures, based on surrounding visual cues.

Law of closure

says that when a space is enclosed by a group of lines, it is perceived as a complete or closed line.

Law of pragnanz

says that perceptual organization will always be as regular, simple, and symmetric as possible.