Brain as Controller: Sensory Processing Flashcards
chain of sensory system
sensory systems –> brain & CNS –> motor systems –> environment –> (restart)
exteroreceptors
external environments
1. Classical senses
- eyes (vision), cochlea (hearing), vestibular apparatus (balance, gravity…), olfactory epithelium (smell)
2. cutaneous senses
- touch receptors, temp sensors, pressure receptors, nociceptors (pain), skin stretch receptors
- (these are all to do with skin feelings)
interoceptors
chemical and physical state of the rest of the body
- chemosensors (O2, CO2…)
- pH sensors
nociceptors (pain, damage)
- muscle length and tension sensors
- proprioceptors
- temp sensors
types of sensory receptors
- rods or cones - vision
- hair cells - hearing, rotational acceleration, linear acceleration
- olfactory neurons - smell
- taste receptor cells - taste
- nerve endings - heat, touch, cold, pain, proprioception, muscle length/tension
properties of sensory receptors
- each have a sensory modality
- will respond to stimuli above a certain threshold
- will transduce signals into action potentials
perception vs sensation
perception is what the brain perceives from the sensation, whereas sensation is what the sensor actually feels or experiences
encoding identity of sensation
- distinguished by neural pathways it travels through
- action potentials along distinct neural pathways have the ‘label’ of that modality
encoding intensity of sensation
intensity of stimulus is encoded by population and frequency
1. population coding - excites CNS interneurons by spatial summation
2. frequency coding - excites downstream CNS interneurons by temporal summation
–> intense stimuli: excite more neurons more often
sense coverage
dense coverage (palm of hand) vs sparse distribution
measuring sensation - human psychophysic
- sensory threshold is a central idea
1. absolute threshold - sensitivity
- smallest amount of stimulus required to produce a sensation
2. difference threshold - resolving power
- amount of change in stimulus to produce a JND (just noticeable difference)
receptive field
areas of the body surface or sensory organ that will excite a particular sensory neuron
Weber-Fechner Law
law relating sensation to stimulus intensity
adaptation
decrease in sensation upon continued stimulation - allows sensory signals to encode position, velocity and acceleration
classification of mechanoreceptive afferents
depth
I - closer to skin surface
II - deeper beneath skin surface
rate of adaptation
rapidly adapting - phasic
slowly adapting - tonic
sensing modality
Mechanoreceptors: frequency response and rate of adaptation
- Merkel (SA I)
- form and texture perception
- low frequency vibrations
disk shape, near border between epidermis and dermis, stimulus = pressure, frequencies 0.3-3Hz - Ruffini (SA II)
- static and dynamic skin deformation
- skin stretch
many fibers inside cylindrical capsule, dermis, 15-400Hz, stimulus = stretching of skin - Meissner (RA I)
- motion, slip/grip
- dynamic skin deformation
stack of flattened cells with nerve fiber winding through, in dermis just below epidermis, 3-40 Hz, stimulus = taps on skin - Pacinian corpuscle (PC / RA II)
- high frequency vibrations
- gross pressure changes
layered capsule surrounding nerve fiber, deep in skin, 10- >500 Hz, stimulus = rapid vibration
