PSY 426 Behavioral Neuroscience Exam 2 Study Guide

Comprehensive vocabulary flashcards covering sensory systems (vision, audition, vestibular sense, somatosensation, pain, gustation, and olfaction) and sleep/circadian neurobiology from PSY 426 Behavioral Neuroscience Exam 2.

Pupil

Opening in the center of the iris through which light enters the eye.

Retina

Rear surface of the eye lined with visual receptors (rods and cones), along with bipolar, ganglion, horizontal, and amacrine cells.

Fovea

Central area of the retina packed tightly with cones and nearly free of ganglion axons and blood vessels, specialized for acute, detailed vision where each cone connects to a single bipolar and midget ganglion cell.

Horizontal cells

Retinal cells that make inhibitory contact onto bipolar cells, mediating lateral inhibition.

Amacrine cells

Retinal cells that receive input from bipolar cells and send signals to other bipolar, ganglion, or amacrine cells to help ganglion cells respond to shapes and movement.

Blind spot

Area at the rear of the eye where the optic nerve exits and where no visual receptors are present.

Rods

Visual receptors abundant in the periphery ($\sim 120\text{ million}$ per retina) that respond to dim light, offer poor detail, do not distinguish color, and converge heavily onto ganglion cells.

Cones

Visual receptors concentrated in and around the fovea ($\sim 6\text{ million}$ per retina) that provide about $90\%$ of visual input to the brain and are essential for color vision, fine detail, and bright light.

Photopigments

Receptor chemicals composed of 11-cis-retinal bound to opsins; light converts 11-cis-retinal to all-trans-retinal, releasing energy that activates second messengers.

Parvocellular neurons

Visual ganglion cells located mostly in or near the fovea with smaller cell bodies and small receptive fields, highly sensitive to color and visual detail.

Magnocellular neurons

Visual ganglion cells distributed evenly throughout the retina with larger cell bodies and receptive fields, sensitive to large overall patterns and moving stimuli, but insensitive to color.

Koniocellular neurons

Visual ganglion cells with small cell bodies distributed throughout the retina that have several functions and project axons to many brain destinations.

V1 (primary visual cortex)

First stage of cortical visual processing located in the occipital lobe, receiving major input from the lateral geniculate nucleus (LGN) and organized in columns that process similar visual features.

Simple cells

Neurons in area V1 that feature fixed excitatory and inhibitory zones and respond best to bar- or edge-shaped stimuli in a particular orientation.

Complex cells

Visual cortex cells in V1 or V2 that respond to an oriented pattern regardless of exact location and respond most strongly to moving stimuli.

End-stopped (hypercomplex) cells

Visual cortex cells that respond strongly to a bar-shaped pattern of light anywhere within their receptive field, provided the stimulus does not extend beyond a certain point.

Blindsight

The ability of individuals with damage to visual cortex area V1 to respond to visual stimuli without reporting conscious awareness of seeing them.

V5 / MT (middle temporal cortex)

Cortical area receiving magnocellular input that responds to stimuli moving in a particular direction; damage results in motion blindness.

Trichromatic theory (Young-Helmholtz theory)

Theory stating that color perception results from the relative rates of response across three cone types sensitive to short (blue), medium (green), and long (red) wavelengths.

Opponent-process theory

Theory positing that color is perceived in paired opposites (red–green, yellow–blue) due to bipolar cells being excited by one set of wavelengths and inhibited by another, explaining visual afterimages.

Lateral inhibition

Reduction of activity in one neuron caused by activity in neighboring neurons, functioning to sharpen contrast and emphasize object borders.

Ventral stream

Cortical visual pathway traversing the temporal cortex known as the "what" path, responsible for identifying and recognizing objects.

Dorsal stream

Cortical visual pathway extending through the parietal cortex known as the "where" or "how" path, important for visually guided action and spatial localization.

Retinal disparity

The slight discrepancy between the visual images projected onto the left and right eyes, utilized by cortical neurons to determine stereoscopic depth and distance.

Strabismus

A childhood condition in which the eyes do not point in the same direction ("lazy eye"), causing stereoscopic depth perception to fail because cortical cells strengthen connections with only one eye.

Visual agnosia

Inability to recognize objects despite intact basic vision, typically resulting from damage to the ventral stream in the temporal cortex.

Prosopagnosia

Impairment in the ability to recognize faces caused by damage to the fusiform gyrus of the inferior temporal cortex.

Amplitude

Intensity of a sound wave, corresponding to perceived loudness.

Frequency

Number of compressions per second of a sound wave, measured in hertz ($\text{Hz}$), which determines perceived pitch.

Timbre

Tone quality or tone complexity of a sound wave, determined by its harmonics.

Pinna

Flesh and cartilage outer ear structure that alters the reflection of sound waves into the ear canal to assist in locating sound sources.

Ossicles

Three tiny middle-ear bones (malleus/hammer, incus/anvil, stapes/stirrup) that amplify vibrations from the tympanic membrane and transmit them to the oval window.

Hair cells

Auditory sensory receptors positioned between the basilar and tectorial membranes in the cochlea whose mechanical bending triggers action potentials in the auditory nerve.

Volley principle

Auditory coding principle wherein groups of auditory nerve axons take turns firing to produce volleys of impulses for sounds up to $\sim 4000\text{ per second}$.

Sound shadow

Loudness disparity between ears created when high-frequency sounds ($\sim 2000\text{--}3000\,\text{Hz}$) are blocked by the head, used as a cue to localize high-frequency sounds.

Conductive (middle-ear) deafness

Hearing impairment occurring when middle-ear bones fail to transmit vibrations to the cochlea, leaving the inner ear intact such that patients hear their own voice clearly.

Nerve (inner-ear) deafness

Hearing impairment caused by damage to the cochlea, hair cells, or auditory nerve, often restricted to specific frequencies and commonly accompanied by tinnitus.

Semicircular canals

Jellylike fluid-filled structures within the vestibular organ lined with hair cells that activate during head movements to guide compensatory eye movements and balance.

Merkel disks

Touch receptors composed of modified dendrites that detect light touch and fine spatial details, such as the distances between grooves.

Pacinian corpuscles

Skin receptors that detect sudden displacement or high-frequency vibrations while resisting gradual or constant pressure.

Gate control theory

Theory stating that spinal cord areas receiving pain inputs also receive touch signals and descending brain inputs that can "close the gates" to decrease pain perception by releasing endorphins.

Endorphins

Endogenous chemicals that bind to morphine-sensitive opioid receptors in the spinal cord and midbrain periaqueductal gray to relieve pain.

Labeled-line principle

Sensory coding principle where each receptor responds to a limited range of stimuli and sends a direct, dedicated pathway to the brain.

Across-fiber pattern principle

Sensory coding principle where individual receptors respond to a wide range of stimuli, with perception determined by the distributed pattern across many neurons.

Umami

A primary taste category detected by glutamate receptors, exemplified by monosodium glutamate and characterized by a flavor resembling unsalted chicken broth.

Oleogustus

A proposed sixth primary taste category referring to the ability to taste fats.

Nucleus of the tractus solitarius (NTS)

Medullary nucleus that is the first central brain structure to receive taste inputs from cranial nerves.

Flavor

The unified sensory combination of taste and smell, whose respective neural pathways converge in the endopiriform cortex.

Endogenous circadian rhythms

Internal biological pacemakers that operate on an approximately $24\text{-hour}$ cycle to govern sleep, temperature, hormone secretion, and other physiological processes.

Zeitgeber

German term for "time giver"; an external environmental stimulus—primarily sunlight—that resets and synchronizes an endogenous circadian rhythm.

Suprachiasmatic nucleus (SCN)

Hypothalamic nucleus located above the optic chiasm that acts as the primary master control center for generating unlearned circadian rhythms of sleep and temperature.

Retinohypothalamic path

Small axonal branch of the optic nerve traveling directly from retinal ganglion cells to the SCN to reset circadian rhythms in response to light.

Melanopsin

Distinct photopigment found within a specialized subpopulation of retinal ganglion cells that respond directly to light without requiring input from rods or cones.

Pineal gland

Endocrine structure located posterior to the thalamus that is regulated by the SCN to secrete the sleep-inducing hormone melatonin.

Sleep spindles

Bursts of $12\text{--}14\,\text{Hz}$ EEG brain waves lasting at least half a second that characterize Stage 2 sleep.

K-complexes

Sharp EEG waveforms seen during Stage 2 sleep associated with temporary inhibition of neuronal firing.

Slow-wave sleep (SWS)

Stages 3 and 4 of sleep characterized by slow, large-amplitude EEG waves, marked physiological deceleration, and highly synchronized neuronal firing.

REM (paradoxical) sleep

Sleep stage characterized by fast, irregular, low-voltage EEG patterns, high brain activity, rapid eye movements, dreaming, and profound postural muscle relaxation mediated by the pons.

PGO waves

High-amplitude electrical spikes associated with REM sleep that initiate in the pons, propagate to the lateral geniculate nucleus, and terminate in the occipital cortex.