Sleep, Sensation & Perception

Electroencephalogram (EEG)

-Measures electrical activity in brain (brain waves, frequency/amplitude)

-Through electrodes that measure electrical impulses generated by large groups of cortical neurons

Non-REM sleep

-3 stages (N1, N2, and N3)

-quiet sleep, low frequency, high amplitude; synchronized activity

REM sleep

-active sleep, high frequency, low amplitude

-paradoxical sleep – active brain and physiological arousal, but major muscles nearly paralyzed

-very difficult to arouse

N1

-alpha waves (awake/relaxed, drowsy) → theta

-falling asleep

-if someone awakes during N1, may deny they were sleeping

N2

-theta waves continue

-are interrupted by sleep spindles (sudden bursts of fast waves) + K-complexes (large, slow waves)

-relaxed muscles, slowed breathing, reduced HR

-body temperature drops

N3

(Deep, Delta)

-aka slow-wave sleep, Deepest level of sleep

-theta → Delta waves (slower/low frequency compared to theta; high amplitude)

-difficult to awaken during N3

REM/Stage R

-BETA waves (characteristic of awake and alert state) + THETA waves

-(paradoxical) temporary muscle paralysis + active sleep

-very difficult to arouse

NREM/REM cycling in normal adults

-REM stages get longer throughout the night

-N3 gets shorter

Sleep in newborn infants

-more time in REM (active sleep)

-start in REM/active → non-REM/quiet

-sleep longer (14-16 hrs)

Sleep in older adults

-more trouble falling asleep, wake up more often

-evenly distributed REM sleep over the night (instead of increasingly longer REM)

-shorter deep sleep (shorter N3)

-Advanced sleep phase (aka circadian phase advance) – go to sleep earlier, wake up earlier

Cones

-Color

-Visual acuity (sharpness, precise detail)

-Best in bright light

Rods

-Responsible for dim light vision (more light-sensitive); don’t perceive color

-Peripheral vision

Trichromatic theory

-3 cones (color receptors) in retina – RBG

-applies to initial processing in retina

Opponent-process theory

-3 types of opponent-process cells (R-G, B-Y, W-B)

-processing beyond the retina

-explains R/G and B/Y colorblindness, phenomenon of negative afterimages

Red-green colorblindness (cause)

-mostly d/t genetic mutation

-genetics = recessive gene on X chromosome

-more common in men (XY), only need 1 mutated gene from mom (X)

-women (XX) need 2 mutated genes, from mom and dad

-can also be from injury/disease (e.g., diabetes, multiple sclerosis)

Blue-yellow colorblindness (cause)

-autosomal (any of 22 non-sex chromosome pairs) dominant gene

-so, affects M/F equally

Depth perception comes from…

Binocular and monocular cues

Binocular cues

-rely on both eyes, for close objects (bc disparity is greater for close objects)

retinal disparity

-binocular cue, for closer objects

-closeby visual stimuli have more disparity between L/R eye views

convergence

-binocular cue

-coordination of eyes turning inward

Monocular cues

-rely on just 1 eye, for further objects

e.g., relative size of object, linear perspective

e.g., interposition (overlap) of objects

motion parallax

relative motion of objects

Nociceptors (what, where)

-Pain receptors, located in skin, muscles, internal organs, joints

-Detect stimuli (mechanical, thermal, chemical) that are damaging/threatening damage

Two types of nerve fibers in spinal cord

-small unmyelinated fibers – transmit pain signals to brain

-large myelinated fibers – other sensory signals (sensory, motor)

Gate Control Theory

-"gate" in spinal cord regulates transmission of pain signals to brain, opens for pain signals

-gate can be closed by large fibers sending non-pain signals (e.g., applying heat/cold)

-gate can be closed by transmission of info from the brain (e.g., distraction, guided imagery)

Grapheme-color synesthesia

-number/letter stimuli trigger associated sensations (color)

-d/t increased cross-activation/cross-connectivity between brain’s sensory areas

-seems to have a genetic component

-most common synesthesia

Psychophysics

-study of rship between physical stimulus ←→ strength of sensation (psychological phenomenon)

Weber’s law

-predicts the just noticeable difference (JND) for a type of stimulus (weight) occur at a constant proportion

-stimulus needs to increase by a constant proportion → for sensation to register it

e.g., JND of 2% for weight: 100 → 102

Fechner’s law (aka Fechner-Weber law)

-sensation of a stimulus increases logarithmically with stimulus magnitude

(meaning, JND changes/increases as stimulus increases)

-more accurate for extreme intensities; only applies to some stimuli (like Weber’s)

Stevens’s Power Law

-more accurate than Weber and Fechner’s laws

-exponential rship btwn sensation and stimulus magnitude

-exponent is different for different stimuli

Signal Detection Theory

-proposes signal detection = sensory + decision-making process, that’s shaped by noise, uncertainty

e.g., environmental distractions

e.g., level of motivation and fatigue

e.g., random neural activity in the perceptual system

Sensitivity and decision criterion (in signal detection theory)

sensitivity (d’)– ability to distinguish signal from noise

decision criterion – aka decision bias, response bias; tendency to make a positive (signal is present) in ambiguous situations

-people can have same sensitivity, but differing deciison

Receiver operating characteristic (ROC) curve

-measures how often hits (true +) and false alarms (false +) change as a decision criterion and sensitivity shifts