Sensation, Perception & Consciousness – Lecture 4

A vocabulary set covering key imaging methods, sensory systems, signal processing concepts, and consciousness topics from the lecture.

Spatial Resolution

Ability of a brain-imaging method to pinpoint the exact location of neural activity.

Temporal Resolution

Ability of a brain-imaging method to track rapid changes in neural activity over time.

Electroencephalography (EEG)

Technique that records scalp electrical activity; excellent temporal but poor spatial resolution.

Event-Related Potential (ERP)

Averaged EEG response time-locked to a specific stimulus or event.

Positron Emission Tomography (PET)

Imaging that detects radioactive tracers to map metabolism or molecule distribution.

Fluorodeoxyglucose (FDG)

Common PET tracer that follows glucose uptake, indicating neuronal activity.

Magnetic Resonance Imaging (MRI)

Imaging that uses strong magnetic fields to create high-resolution structural brain images.

Functional MRI (fMRI)

Adapted MRI that measures brain activity via blood-oxygen changes (BOLD signal).

BOLD Signal

Blood-Oxygen-Level Dependent contrast underlying fMRI functional images.

Neurovascular Coupling

Link between neuronal activity and subsequent local blood-flow changes.

Lesion Study

Examination of behavioral deficits after brain damage to infer region function.

Patient HM

Bilateral hippocampal removal patient with severe anterograde amnesia.

Phineas Gage

Railroad worker whose frontal-lobe injury caused personality and impulse changes.

Sensation

Initial reception and amplification of environmental energy by sensory organs.

Perception

Organization and interpretation of sensory information into meaningful experience.

Müller-Lyer Illusion

Visual illusion showing misperception of line length due to arrowheads.

Sensory Receptor Cell

Specialized cell that transduces environmental energy into neural signals.

Photoreceptor

Light-sensitive retinal cell (rod or cone).

Rod

Retinal photoreceptor active in dim light; concentrated in periphery.

Cone

Retinal photoreceptor active in bright light; enables color; dense in fovea.

Fovea

Central retinal region with highest cone density and visual acuity.

Optic Nerve

Axon bundle carrying retinal signals to the thalamus.

Lateral Geniculate Nucleus (LGN)

Thalamic relay nucleus for visual information.

Primary Visual Cortex (V1)

Occipital-lobe area that first processes cortical visual input.

Trichromatic Theory

Young-Helmholtz idea that color arises from three cone types.

Opponent-Process Theory

Color vision model with antagonistic pairs (Red-Green, Blue-Yellow, Black-White).

Mach Bands

Illusory brightness bands caused by lateral inhibition at edges.

Sound Amplitude

Magnitude of air-pressure change; perceived as loudness.

Sound Frequency

Cycles per second (Hz) of pressure change; perceived as pitch.

Cochlea

Fluid-filled inner-ear organ where hair cells transduce sound.

Hair Cell

Mechanoreceptor in cochlea that converts vibration into neural signals.

Vestibular System

Inner-ear canals and otolith organs that sense balance and head movement.

Proprioception

Sense of body position and effort from muscles, joints, and skin.

Somatosensory Cortex

Postcentral gyrus region mapping touch and body sensations.

Absolute Threshold

Lowest stimulus intensity detected >50% of the time.

Subliminal Stimulus

Input presented below conscious detection threshold.

Signal Detection Theory

Framework separating sensory sensitivity from decision bias in detection tasks.

Hit

Correctly reporting a present stimulus.

False Alarm

Reporting a stimulus when none is present.

Miss

Failing to report a present stimulus.

Correct Rejection

Correctly stating no stimulus when absent.

Just Noticeable Difference (JND)

Minimal change in stimulus intensity that is reliably discriminable.

Weber-Fechner Law

Proportional relation ΔI / I = K describing JND growth with intensity.

Consciousness

Subjective awareness of self and environment.

NREM Stage 1

Lightest sleep; theta waves appear.

NREM Stage 2

Sleep stage with spindles and K-complexes.

NREM Stage 3/4

Deep slow-wave sleep dominated by delta activity.

REM Sleep

Rapid-eye-movement stage with vivid dreams and muscle atonia.

Chronotype

Individual preference for timing of sleep-wake cycle (morningness/eveningness).

Early Bird

Morning chronotype; linked to better academics and mental health.

Night Owl

Evening chronotype; associated with higher cognitive ability and sensation seeking.

Dream Protection Theory

Freudian idea that dreams transform unacceptable wishes into symbolic content.

Activation-Synthesis Theory

Hobson & McCarley model: dreams interpret random brainstem activity.

Evolutionary Dream Theory

Hypothesis that dreams simulate threats to aid survival planning.

Overfitted Brain Hypothesis

Proposal that dreams combat overfitting of neural networks during learning.

Hypnosis

Induced trance-like state with heightened suggestibility and focused attention.

Dissociative Theory (Hypnosis)

View that hypnosis splits consciousness into separate streams.

Socio-Cognitive Theory (Hypnosis)

Explanation emphasizing social role-playing and expectation in hypnotic behavior.

Near-Death Experience (NDE)

Profound experience reported during life-threatening events; studied with Greyson scale.

Greyson NDE Scale

Questionnaire quantifying intensity of near-death experiences.

Meditation

Practice of training attention or altering consciousness, e.g., mindfulness.

Mindfulness Meditation

Non-judgmental awareness of present moment; used for anxiety and pain therapy.

Hallucination

Perception without external stimulus; may arise from drugs or illness.

Déjà Vu

Illusory feeling of having already experienced a current situation.

Five Basic Tastes

Sweet, salty, sour, bitter, and umami.

Umami

Savory taste linked to glutamate signaling protein-rich foods.

Taste Pathway

Taste cells → cranial nerves VII, IX, X → brainstem → thalamus (VPM) → insula.

Supertaster

Individual with heightened taste sensitivity due to denser taste buds.

Olfaction

Sense of smell important for survival and social interaction.

Olfactory Bulb

First brain relay for smell; contains glomeruli for odor mapping.

Primary Olfactory Cortex

Pyriform area receiving direct olfactory bulb input; bypasses thalamus.

Orbitofrontal Cortex (OFC)

Frontal region integrating smell and taste; important for flavor perception.

McGurk Effect

Perceptual illusion where vision alters heard speech sounds.

Synesthesia

Condition where stimulation of one sense involuntarily triggers another.

Sensory Competition

Phenomenon where simultaneous inputs vie for neural processing resources.

Absolute Refractory Period (EEG context)

Brief time after neural firing when another action potential cannot occur.

Beta Waves

13 Hz EEG activity linked to alert wakefulness.

Alpha Waves

7–13 Hz EEG rhythm present during relaxed wakefulness.

Theta Waves

4–7 Hz EEG activity seen in light sleep.

Delta Waves

1–4 Hz EEG activity characteristic of deep NREM sleep.

Sleep Latency

Time required to transition from wakefulness to sleep.

Sleep Spindles

Brief 12–15 Hz bursts in NREM2 linked to memory consolidation.

K-Complex

High-amplitude NREM2 waveform responding to internal or external stimuli.

Glymphatic System

Brain waste-clearance pathway enhanced during sleep.

Pain

Subjective experience signaling potential tissue damage; involves ACC, insula, PFC.

Anterior Cingulate Cortex (ACC)

Limbic structure involved in pain and emotion processing.

Insula

Brain region integrating interoception, taste, and pain experiences.

Hairy Skin Receptor

Mechanoreceptor detecting light touch on hairy skin surfaces.

Meissner Corpuscle

Fast-adapting mechanoreceptor for fine touch in glabrous skin.

Weber Fraction (K)

Constant ratio of JND to baseline stimulus intensity.

Bias (Signal Detection)

Tendency to favor ‘yes’ or ‘no’ responses independent of sensitivity.

Epworth Sleepiness Scale

Self-report tool measuring daytime sleepiness.

Sensory Illusion

Misinterpretation of real sensory information, e.g., Necker cube.

Speech Segmentation

Ability to perceive word boundaries in continuous speech.

Artificial Intelligence Challenge (Perception)

Difficulty for AI in performing human-easy perceptual tasks.

Gamma Rays

Shortest-wavelength electromagnetic radiation; not visible to humans.

Visible Spectrum

Approximately 400–700 nm wavelengths detectable as light.

Magnetic Field Strength (Tesla)

Measurement of MRI magnet intensity; higher T improves image resolution.

Radiofrequency Pulse (MRI)

Energy burst that disturbs proton alignment, producing measurable signals.