Week 4: Sensory and Motor Function Flashcards
Perception
interpretation at the higher order; one sensation can produce multiple perceptions
Sensation
Early processing of energy
Similarity of sensory pathways
All 5 senses begin with a specialized organ and receptor cells, involve the PNS, synapse with the brain, interact with the thalamus (all except smell), and have dedicated cortical areas (primary and secondary)
Role of the thalamus
To direct AND modify sensory stimuli
Sense organs
Eyes = vision
Ears = hearing
Nose = olfaction/smell
Tongue = gustation/taste
Skin = touch
Rate adaptation
When exposed to prolonged stimulus, sensory neurons will adapt their firing rate (either increase or decrease)
Sensory Nerves
Cranial nerves = related to the face
Spinal/peripheral nerves = relate to touch/the body
All nerves stop in the thalamus before moving to cortex (except smell)
Sensory nerve - Smell
Nerve I - olfactory
Sensory nerve - Vision
Nerve II - optic nerve
Sensory nerve - Hearing
Nerve VIII - vestibulocochlear nerve; does two jobs of balance and hearing
Sensory nerve - Taste
Nerves 7, 9, 10 - Facial nerve, glossopharyngeal nerve, vagus nerve
Sensory nerve - Touch
Many peripheral nerves used to detect touch
Cortex for Smell
Primary = pyriform
Secondary = orbitofrontal
Cortex for Taste
Primary = insula
Secondary = orbitofrontal
Cortex for Hearing
Temporal (primary and secondary)
Cortex for Touch
Parietal (primary and secondary)
Cortex for Vision
Occipital (primary and secondary)
Sensory Cortexes
Follows hierarchical processing (always processed in the primary cortex before the secondary); has segregated representation; plastic and adaptable to change
Segregated representation
Different cells for different stimuli are organized together (ex: groups of cells for high and low frequencies); disproportionate compared to the body due to adaptive utility
Adaptive utility
When the representation of a sense is adapted to be bigger or smaller than the bodily representation based on amount of use
Smell/Olfaction
Uses: detection of threats (poison, smoke, etc.) and social behavior
Pathway: bipolar receptors -> glomerulus -> olfactory nerve -> primary Cortex (pyriform) -> secondary cortex (orbitofrontal); chemical sense that does NOT pass through the thalamus
Shape/docking theory of smell
Key-and-lock model. Suggests that specific odorants body with specific shaped sensory neurons/receptors
Anosmia
Loss of smell (usually due to other nervous system problems)
Taste/Gustation
Sweet, salty, sour, bitter, umami. Likely has an evolutionary basis in detecting nutrients we need
Pathway: taste cells -> bipolar neurons -> cranial nerves (7, 9, 10) -> Brainstem structures -> thalamus -> primary cortex (insula) -> secondary cortex
Taste map theory of the tongue
Specific areas of the tongue are specialized for specific tastes. Easily disproven, you can taste any flavor on any part of the tongue
Supertaster bud theory
Supertasters have more taste buds on their tongue. Currently in debate
Gustatory mapping
Cells are specified for different tastes, but receptors are distributed across the tongue rather than segmented
Intersectionality of taste
Experience and perception of taste can be affected by emotional state/mood, smell, vision, etc.
Spice/spicy
Can be considered it’s own sense, or as a subset of pain (interacts with pain receptors). Linked to capsaicinoids which activate TRPV1
Vision/Sight
Light waves (btw 700-400 nm) stimulate photoreceptors in the retina
Rods and cones in the retina process light. Cones are concentrated in the fovea. Cones have three sizes (long, medium, short). Colorblindness is caused by damage or malfunction in photoreceptors
Color perception is the most susceptible to change or differ from the real world
Pathway: photoreceptors -> Optic nerve -> Thalamus (lateral geniculate) -> Visual cortex
Trichromatic color theory/Young-Helmholtz Theory
All perceivable colors are a combination of red, blue, and green in some proportion
Opponent process theory
Colors are perceived/processed jointly and antagonistically; explains the existence of afterimages
Translateral visual pathway
The right field of view tracks onto the left hemisphere, and vis versa
Retinotopic mapping
Different parts of the field of view activate different areas in the cortex
Color constancy
The environment surrounding a color can make the same wavelength appear different or make two different wavelengths appear the same (ex: the perceived brightness of a color can be affected by a dim or bright surrounding environment)
Spectral Sensitivity Curve
Graph of the perceived brightness of the same wavelength color in two different lighting conditions
Hearing
Response of stereocilia to vibrations of various amplitudes (volume) and frequencies (pitch)
Follows topographic mapping
Humans are most sensitive to the frequencies they can general and/or are useful for survival (1000-10000 Hz)
Fundamental frequency
When given many pitches, you will perieve the largest frequency that divides into all other pitches; can cause illusory perceptions that were never in the sensation presented
Touch
Receptor cells all over the body transmit to the brain through the spinal cord travel system. Somatosensory cortex is topographically mapped
Spinal cord travel system
Highway for sensory info. Sensory goes up and into the brain, motor goes down and out to the body. Sensory tracts cross the midline which explains lateralization in the body/brain connection. Pain travels through a different system and has its own cortical areas
Gate control theory of pain
Tactile stimulation may block the gate for pain stimulation. Touch neurons travel faster due to more myelination, and thus reduce the strength of pain perception as less sensation can reach the brain.
Descending modulation of pain
Limits and manages amount of pain to aid survival but not debilitate us. Begins in the brain and moves down the spinal cord to affect signals travelling up. Involves the periaqueductal grey and the rostroventral medulla
Sensory intersections
Areas where senses interact and potentially influence each other. Ex: McGurk effect or synesthesia
Sensory mismatch
Adjustments don’t align with multiple competing inputs
Sensory competition
Senses can overload and inhibit each other
Motor system
Begins in the upper motor system and contains very large neuron tracts. Lower motor neurons communicate with muscles. Operates mostly from the frontal cortex
Prefrontal cortex in movement
Planning action
Premotor cortex in movement
Organizing action sequences
Primary motor cortex in movement
Contains the homunculus; involved in voluntary movement
Mirror neurons
Neurons that activate when performing OR watching others perform an action; allows us to immediately copy what we see. Only studied cellularly in animals
Movement theory
Representation is akin to movements over body parts; supported by stroke studies where diff strokes will cause the same issues due to similar brain structure across people
Lateral corticospinal pathway
external muscles (fingers, toes, etc)
Anterior corticospinal
Core muscles around the trunk of the body
Basal Ganglia
Group of structures that regulates movement. Focus being on the substantia nigra which gets its key input from dopamine
Cerebellum in movement
Core role of correcting error of movement. Ex: when throwing darts you can correct your movement and get better thanks to the cerebellum
