chapter 3 Flashcards
perception
understanding what is going on outside of the brain to know how to act to achieve goals
the inverse problem
know how to determine the distal stimulus (world) from the proximal stimulus (sound, sight, touch)
sources of information
genes, past experience, internal state, environmental context, proximal stimulus
sensory receptors
cells to transduce (convert) external phenomena (light, sound, pressure etc) into neural signals
neural pathway
from sensory receptors via thalamic nuclei to cerebral cortex
hierarchy of stimulus
attempt to construct useful representation of distal stimulus
photoreceptors
1 type of rod, 3 types of cones
rods
more sensitive, work well in dark places
cones
3 types, work well in lit areas, each cone has different sensitivity of light. S-cones (short, blue), M cones (medium, green), L cones (long, red/yellow)
large concentration at fovea
primary visual field
partial crossover at optic chiasm, info from left visual field gets sent to the right side of brain
sound
changes in air pressure
ear drum
tympanum: converts changes in air pressure into mechanical vibrations
sound vibration travel
vibrations travel through bones of middle ear to oval window of cochlea. hair cells in cochlea detect vibrations
basilar membrane
location of maximal excitation along basilar membrane depends of sound frequency
proprioception
mechanical forces on muscles, tendons and joints
nocioception
harmful chemical, mechanical or thermal stimuli
thermoception
hot and cold
mechanoreception
pressure, vibration and distortion
4 types of mechanoreceptors
some closer to surface (touch : messier corpuscle, merkel disc receptor), some deeper in dermis (weight : ruffini ending and pacinian corpuscle)
webers law
just noticeable difference
delta I/I = K
receptive field
are of sensory surface to which a neutron response, higher order neutrons have larger receptive field and response to more complex sensory stimuli
receptor size
receptive field close to fovea are small, become larger in size on outer areas. receptor more likely to fire if photoreceptors in centre are stimulated, stimuli on surround makes receptor fire less (inhibited)
auditory receptive field
frequency of sound
somatosensory receptive field
area on skin. size and accuracy vary with location on body
topography
spatial organization of sensory surface is generally preserved in primary sensory cortex
cortical magnification
area of cortex is proportional to density of sensory receptors
plasticity
changes in neural organization
bottom-up
stimulus driven, feedforward connections
top-down
driven by goals and expectations, feedback connections, depends on past experiences, environmental context
