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)