MCAT 6A

Thalamus (Forebrain)

relay station for sensory information except for smell which is sent to the olfactory cortex

Parietal Lobe

associated with somatosensation (touch, pressure, pain, temp.) and spatial processing

Occipital lobe

associated with vision

Sensory receptors are

Part of sensory nerves that respond to stimuli

Sensory ganglia

enlargements along peripheral nerves that transmit signals to the CNS

Projection areas

areas in the four lobes (frontal, parietal, temporal, occipital) of the brain where sensory processing occurs

Absolute Threshold

the minimum stimulus energy that will activate a sensory system

Threshold of conscious perception

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

Difference threshold

The minimum difference in magnitude between two stimuli before one can perceive the difference

Weber's Law

states that the just noticeable difference for a stimulus is proportional to the magnitude of the stimulus

Signal detection theory explains

how humans make decisions in the presence of uncertainty/noise

Sensory Adaptation

describes how receptors can increase or decrease their sensitivity to a stimulus

Cornea

gathers and filters incoming light

Iris

controls the size of the pupil

Lens

refracts incoming light to focus it on the retina

Aqueous humor is the

clear, watery fluid that fills the space between the cornea and lens of the eye. It provides pressure to maintain the shape of the eyeball

Retina

sensory membrane that lines the back of the eye

Rods

photoreceptors in the retina that detect light/dark

Cones

photoreceptors in the retina that detect color

Retinal disparity

a visual binocular cue that facilitates depth perception

Horizontal and amacrine cells

integrate signals from photoreceptors and perform edge-sharpening

Magnocellular

cells that process motion (where pathway, depth and motion)

Parvocellular

cells that process shape (what pathway, form, and color)

Parallel processing

idea that our eyes process color, form, and motion at the same time

visual pathway

eye -> optic nerves -> optic chiasm -> optic tracts -> lateral geniculate nucleus (LGN) -> visual radiations -> visual cortex

3 main divisions of the ear are

Outer, middle, and Inner ear

outer ear includes

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

middle ear includes

malleus (hammer), incus (anvil), stapes (stirrup)

malleus is one of the three ossicles in the middle ear and

is also called the hammer

incus is one of the three ossicles in the middle ear and

is also called the anvil

stapes is one of the three ossicles in the middle ear and

is also called the stirrup

inner ear includes

cochlea, otolithic organs, and the semicircular canals

Pinna (auricle)

acts as a kind of funnel which assists in directing sound further into the ear

External auditory canal

transmits sound from the pinna to the eardrum

Tympanic membrane

thin flap of skin that is stretched tight like a drum and vibrates when sound hits it

Cochlea transduces

sound into nerve impulses to be sent to the brain

vestibular system

a sensory system that is responsible for providing our brain with information about motion, head position, and spatial orientation. It also involves motor functions that allows us to keep our balance.

Semicircular canals are responsible for

balance

superior olive

is located in the brain stem and its function is to localize sound

Vestibulo-ocular reflex

Keeps the eyes fixed on a single point as the head rotates.

Inferior colliculus

responsible for the startle reflex and vestibulo-ocular reflex.

Auditory pathway after the oval window

Cochlea —> vestibulocochlear nerve —> superior olive —> inferior colliculus —> medial geniculate nucleus —> auditory cortex

Smell is the

Detection of volatile or aerosolized chemicals by the olfactory chemoreceptors

Pheromones

Chemicals given off by animals that have an effect on social foraging and sexual behavior.

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

A temperature that is felt by the skin as neither warm nor cold

Nociceptors

sense pain

Gate control theory

Theory of pain asserting that non-painful input closes the nerve "gates" to painful input, which prevents pain sensation from traveling to the central nervous system.

Proprioception

The sense that tells you information about your body's position.

Top-down processing

The recognition of an object by memories and expectations

Top-down processing uses background

knowledge which influences perception and is driven by theory rather than data

Top-down processing uses

deductive reasoning

Bottom-up processing

one will process details first, then the whole object

The Continuity Principle

Tendency to perceive lines in the smoothest path possible

Gestalt principles

Principles that try to explain how we perceive things the way we do.

Gestalt principle of proximity

Objects that are placed close together are perceived as being more related than those spaced farther apart.

Gestalt principle of similarity

We tend to perceive things that physically resemble one another as part of the same object.

Gestalt principle of closure

We tend to see complete figures even when part of the information is missing.

Law of Pragnanz

States that people will perceive and interpret ambiguous or complex images as the simplest form(s) possible.

Rhodopsin

Biological pigment found in the rods of the retina

Convergence

The simultaneous inward movement of both eyes toward each other. This action stretches the extraocular muscles, and the amount of stretch is measured and used by the brain to determine the depth of an object.

Monocular cues

Cues that provide depth information when viewing a scene with one eye.

Motion parallax

A monocular depth cue that refers to the fact that objects moving at a constant speed across the frame will appear to move a greater amount if they are closer to an observer.

Subliminal stimuli

Stimuli that fall below a person's threshold for perception

if you move your head quickly and then stop suddenly

The endolymph continues to move in the semicircular canals and this gives you a false sense of moving (dizziness).

Liberal strategy (Signal Detection Theory)

A strategy in signal detection theory in which the observer always says "yes" whenever there may be a signal (which might cause some false alarms).

Gestalt principle of symmetry

States that elements that are symmetrical to each other tend to be perceived as a unified group.

Object constancy

The tendency of animals and humans to see familiar objects as having a standard shape, size, color, or location regardless of changes in the angle of perspective, distance, or lighting.

Conservative strategy (Signal Detection Theory)

A strategy in signal detection theory in which the observer says "yes" only when the signal is almost certain (which might cause some misses).

Gestalt law of common fate

States that humans perceive visual elements that move at the same speed and/or direction as parts of a single stimulus

Gestalt law of past experiences

States that elements tend to be perceived according to an observer's past experience and culture

Conjunctiva

The thin transparent layer of tissue that lines the inner surface of the eyelid and covers the white part of the eye.

Anterior chamber (AC)

The aqueous humor-filled space inside the eye between the iris and the cornea's innermost surface (the endothelium).

Ciliary body

Part of the eye that includes the ciliary muscle (which controls the shape of the lens) and the ciliary epithelium (which produces the aqueous humor). Suspensory ligaments are attached to the ciliary muscle.

Posterior chamber

A narrow space behind the peripheral part of the iris, and in front of the suspensory ligament of the lens and the ciliary processes; it is filled with aqueous humor.

Vitreous chamber

The largest of the three eye chambers, located behind the lens and in front of the optic nerve.

Macula

An oval-shaped, pigmented area in the retina that contains a very high concentration of cones and very few rods.

Fovea

A tiny pit located at the center of the macula that is completely covered in cones and provides the clearest vision of all.

Choroid

The vascular layer of the eye containing connective tissues, lying between the retina and the sclera. Its function is to provide nourishment to the outer layers of the retina through blood vessels.

Sclera

Also known as the "white" of the eye, this is the opaque, fibrous, protective outer layer of the human eye containing mainly collagen and some elastic fiber (lined with the conjunctiva).

Visual phototransduction

The process by which light is converted into electrical signals in the rods, cones, and photosensitive ganglion cells of the retina of the eye.

Photopic system

System of vision associated with cones that occurs at high levels of light

Scotopic vision

System of vision associated with rods that occurs at very low levels of light.

Opsins

Proteins made light-sensitive via retinal, found in photoreceptor cells of the retina.

Mesopic vision

System of vision associated with both rods and cones occurring at moderately low levels of light.

Photopsin

A biological pigment found in the cones of the retina.

In human eye

There are more rods than cones

Rods are

1000x more sensitive to light than cones.

Rods are

found in the periphery, while cones are concentrated in the fovea.

Blind spot

An area where the optic nerve connects to the retina containing no rods or cones.

Optic chiasm

An X-shaped structure formed by the crossing of the optic nerves in the brain.

Visual field processing

Right visual field input goes to the left brain; left visual field input goes to the right brain.

Trichromatic theory

Theory that three cone types detect different wavelengths (red=60%, green=30%, blue=10%).

Opponent-process theory

Theory stating cone photoreceptors form three opposing color pairs: blue/yellow, red/green, black/white.

It is impossible for human to see certain color combinations such as

reddish-green or yellowish-blue and is explained by opponent-process theory of color vision

Organ of Corti is the sensitive element in

the inner ear that transduces mechanical sound vibrations into nerve impulses.

Organ of corti includes the

Basilar membrane and the tectorial membrane

Place theory

Posits that one is able to hear different pitches because different sound waves trigger activity at different places along the cochlea’s basilar membrane. High= apex, Low=base

Humans can hear sounds

at frequencies between 20 Hz and 20,000 Hz