Psychology Sensation, Perception, Movement, and Circadian Rhythms

What causes vision?

Light stimulates receptors in the retina, which send signals to the brain.

Law of specific nerve energies

The brain interprets activity in a sensory nerve according to the sense it represents.

Fovea

The central retinal area with the highest visual acuity and many cones.

Rods vs. cones

Rods are sensitive to dim light; cones support color vision and fine detail.

Blind spot

The point where the optic nerve exits the eye, with no photoreceptors.

Trichromatic theory

Color vision begins with three cone types responding to different wavelengths.

Opponent-process theory

Color processing uses opposing pairs: red-green, yellow-blue, and white-black.

Lateral inhibition

Active neurons suppress neighboring responses, enhancing contrast at edges.

Receptive field

The area of the visual field that influences a neuron's activity.

Parallel processing

The brain processes color, form, depth, and movement simultaneously.

Ventral visual stream

Processes object identity and recognition — the "what" pathway.

Dorsal visual stream

Processes spatial information and visual guidance of movement — the "where/how" pathway.

Prosopagnosia

Difficulty recognizing faces despite relatively intact vision in other respects.

Motion blindness

Difficulty perceiving movement, associated with damage to MT/MST regions.

Optic chiasm

The point where some optic nerve fibers cross to the opposite side of the brain.

Primary visual cortex (V1)

The cortical area that initially processes visual information.

Auditory transduction

Converting sound vibrations into neural signals in the inner ear.

Basilar membrane

Vibrates in response to sound; different locations respond best to different frequencies.

Place theory

Pitch depends on where the basilar membrane vibrates most strongly.

Frequency theory

Pitch is coded by the timing or frequency of neural impulses.

Primary auditory cortex

A cortical region that processes sound information, including frequency.

Conductive deafness

Hearing loss caused by problems transmitting sound through the outer or middle ear.

Sensorineural deafness

Hearing loss caused by damage to the inner ear's receptors or auditory nerve.

Vestibular system

Detects head position and acceleration; helps coordinate posture and eye movements.

Somatosensory system

Processes touch and other sensations from the skin and internal tissues.

Proprioceptor

A receptor that detects body-part position and movement.

Dermatome

An area of skin whose sensory input travels through a particular spinal nerve.

Pain receptors (nociceptors)

Bare nerve endings activated by potentially damaging stimuli.

Gate theory of pain

Other sensory input can reduce pain transmission through spinal cord pathways.

Endorphins

Activate opioid receptors and decrease pain-neuron activity.

Placebo effect on pain

Expectations can engage top-down control from the prefrontal cortex, reducing pain.

Five basic taste qualities

Sweet, sour, salty, bitter, and umami; fat may also be a taste.

Taste buds

Structures containing modified sensory cells that respond to chemicals in food.

Bitter taste

Helps detect potentially harmful substances.

Olfaction

The sense of smell, based on receptors responding to airborne chemicals.

Olfactory receptors

Respond to particular chemicals and combinations of chemicals.

Pheromone

A chemical signal that influences communication or behavior within a species.

Synesthesia

Stimulation of one sense produces an additional experience in another sensory modality.

Sensory adaptation

Reduced responsiveness to a stimulus that remains constant over time.

Three types of muscle

Skeletal, smooth, and cardiac muscle.

Acetylcholine

The neurotransmitter used at all nerve-muscle junctions.

Proprioceptors in movement

Provide feedback about body position and movement.

Muscle spindles

Proprioceptors that detect muscle length and changes in stretch.

Golgi tendon organs

Proprioceptors that detect tension in tendons.

Central pattern generator

A neural circuit that produces a rhythmic sequence of movements.

Primary motor cortex

Sends commands that help control voluntary movement.

Basal ganglia

Help select, initiate, and regulate movements.

Cerebellum

Coordinates timing, accuracy, balance, and learned movement.

Parkinson's disease

Caused by degeneration of dopamine-producing neurons in the substantia nigra.

Symptoms of Parkinson's disease

Slowness, difficulty initiating movement, tremor, rigidity, and possible cognitive changes.

L-dopa

A medication precursor that enters the brain and is converted into dopamine.

MPTP

A toxin that can damage substantia nigra neurons and produce Parkinsonian symptoms.

Huntington's disease

An inherited disorder caused by a mutation involving repeated CAG sequences in the huntingtin gene.

Symptoms of Huntington's disease

Impaired motor control, apathy, depression, memory problems, and other cognitive changes.

Huntington's disease inheritance

It is autosomal dominant; an affected parent has a 50% chance of passing it on.

Circadian rhythm

An internal biological rhythm that cycles approximately every 24 hours.

Suprachiasmatic nucleus (SCN)

A hypothalamic structure that coordinates circadian rhythms.

Light and the SCN

Special retinal ganglion cells send light information that helps reset the biological clock.

Zeitgeber

An environmental cue, especially light, that synchronizes a biological rhythm.

Melatonin

A hormone released by the pineal gland that promotes sleepiness and helps regulate timing.

Jet lag

A temporary mismatch between the body's circadian rhythm and the local time.

Why is traveling east harder on sleep rhythms?

It usually requires advancing the internal clock, which is harder than delaying it.