sensory processes Flashcards
an input about the physical world obtained by our sensory receptors
- activation of sense organs, stimulated by physical energy
sensation
the process by which the brain selects, organizes and interprets stimuli coming form the environment
perception
stimulus
any passing source of physical energy that produces a response in a sense organ
psychophysics
science studying the relationships between the physical world obtained by our sensory receptors
absolute threshold
the smallest intensity of the stimulus that is necessary for it to be detected
difference threshold
the smallest intensity change needed to detect a difference between 2 stimuli (JND)
JND
just noticeable difference
Weber’s fraction (k)
it’s a constant, the intensity by which the standard must be increased to be noticed (Ai) is proportional to the intensity of the standard (Ss)
- K = Ai / Ss
3 ways individuals are passive receivers
- evaluate and estimate the stimulus
- adapt their sensation to the environment
- decide to or not to report the difference detected
Steven’s law
had subjects do an estimate of magnitude: discovered the relationship between perceived magnitude and the intensity of stimulus is a power function
sensory adaptation
phenomenon in which the sensory capacity DECREASES with long exposure to the same stimulus
signal detection
considers the influence of a subject’s decision making on the presence of stimulus
- hit, miss, false alarm, correct rejection
image forming system consists of:
- cornea
- lens
- pupil
two types of photoreceptor cells in retina
- cones
- rods
cones
particularly in BRIGHT light situations light sensitive, responsible for detailed focus and colour
rods
thin and cylindrical
activated in LOW light, highly sensitive to light, colourless results
fovea
depression in the inner retinal surface (1.5 mm)
- photoreceptor layer is entirely cones and for maximum visual activity
role of the fovea
to see details in an object we move our eyes so that the object is projected by the fovea
- receptors are plentiful and closely packer = higher resolution
steps from eye to brain
- photoreceptor pick up visual signals because they detect light
- the bipolar cells receive info from receptors and send the info to the ganglion cells
- ganglion cells collect and synthesise info coming from bipolar cells
- info is sent from the back of the eye to the brain through ganglion axons, called optic nerve
blind spot
area where the optic nerve leaves the eye, so it has NO receptors
optic chiasm
point of conduction between 2 optic nerves, where they cross before making their way to the brain
primary visual area (BA 17)
located in occipital lobe in correspondence to the calcanne fissure
features extraction
in visual cortices there are specialized cells for the detection of lines oriented in a certain way (single cell recording)
ventral way (visual message to brain)
occipital lobe to temporal lobe
dedicated to the perception of attributes of an object, such as a shape, size and orientation (what is is)
dorsal way (visual message to brain)
analyses position of objects in space (where it is)
trichromatic theory
3 types of cones, each of which responds preferentially to a range of wavelength (blue/violet; green; yellow/red)
colour blindness
supports trichromatic theory: genetic disorder that determines inability to see RED or GREEN colour
opponent colour theory
receptors are linked in pairs and work in opposition to each other
- yellowish greens exist but reddish greens don’t
sound
movement air molecules caused by a source of vibration
from ear to brain steps
- enters from outer ear
- proceeds inside the auditory canal
- reaches the eardrum
- vibrations pass to the middle ear
- internal ear transforms sound into energy to send to brain
taut membrane that vibrates with passage of sound
eardrum
cochlea (inner ear)
spiral-shaped tube that contains fluid capable of vibrating in presence of sound
what happens to sound in internal ear
Sound waves are transduced into electrical impulses that the brain can interpret as individual frequencies of sound
basilar membrane
the main mechanical element of the inner ear
- crosses central part into the upper and lower cavity
hair cells
if moved by vibrations entering the cochlea, they send message to brain (sensory cells)
4 sound features
- frequency
- pitch
- amplitude
- loudness
resonance-place theory (sound)
different areas of the basilar membrane respond to different types of frequencies
temporal theory (sound)
the sound wave causes basilar membrane to vibrate and the rate of vibration determines the rate of impulses of nerve fibres in auditory nerve
semicircular canals
three tubes containing liquid that moves inside them when the head moves, signalling rotation or angular movement
otoliths
crystals that signal forward, backward, up and down movements along with the force of gravity
- register gravity and linear acceleration
olfaction
sense of smell
olfaction steps
- molecules of a substance enter the nasal canal
- molecules meet the olfactory cells
- through the fibres, the signal reaches the olfactory bulb located under the frontal lobes and connected with the olfactory cortex inside the temporal lobe (memory)
gustation
allows qualitative evaluation of a substance based on flavour
receptive cells in gustation
taste buds (10 000)
how many tactile receptors does the each cm of skin have?
130
3 types of somatic sensitivities (touch)
- meccanoceptive (pressure)
- thermal (temp)
- dolorific (pain)
has an evolutionary projection function
pain
phasic pain
sharp and brief
tonic pain
dull and long
“gate control” theory
specific receptors in spinal cord connected to parts of the brain
- when receptors are activated they open gate and the sensation of pain is experienced
how can the gate be closed (pain)
- competition between stimuli
- psychological factos
pain reduction: distraction method
tested on wounded soldiers with the use of virtual reality and worked
touch and vision
increased sensitivity when we see the part of the body affected (rubber hand theory)
vision and gustation
food appearance affects its palatability
vison and audition
mouth movements affect what we hear
- Mc Gurk effect
synesthesia
2 is green and 3 is red
- produces responses in more than one system
2 theories on synesthesia
- psycholinguistic theory
- neurogical theory
neurogical theory
synesthesia - activation effect of this ancestral perceptual system (poor inhibition between sensory areas)
psycholinguistic theory
activations of different sensory modalities evoke coherent emotional response
