Sensation And Perception Flashcards
Sensation
Aligns with transduction - conversion of external and internal signals into electrical signals in the nervous system - raw information
Perception
Processing of the electrical signals to make sense of them and make them significant
Neurons that respond to stimuli and trigger electrical signals
Sensory receptors
Ganglia
Collections of neuron cell bodies found outside the CNS
Provide examples of sensory receptors
Photoreceptors, hair cells, nocireceptors, thermoreceptors, osmoreceptors, olfactory receptors, taste receptors
Threshold
Minimum amount of stimulus that renders a difference in perception - different for everyone !!!
Absolute threshold
Minimum stimulus energy that is needed to activate a sensory neuron ( to be transduced into action potential)- sensation not perception
Threshold of conscious perception
Signal reaches the CNS but does not reach the higher order brain regions that control attention and consciousness
Aka subliminal perception
Minimal difference in magnitude between two stimuli before once can perceive this difference
Difference threshold or just noticeable difference (jnd)
Webers law
There is a constant ratio between change in stimulus magnitude needed to produce a jnd and the magnitude of the original stimulus
For higher magnitude stimuli the actual difference must be large to produce a jnd
When does Weber’s law not apply
At the extremely high and low end of each range
Signal detection theory
Changes in our perception of the same stimuli depending on internal (psychological ) and external (environmental) context
Tendency of subjects to systematically respond to a stimulus in a particular way due to non sensory factors
Response bias
Trial in which the signal is presented
Catch trial
Trial in which the signal is not presented
Noise trial
Subject correctly perceives the signal
Hit
Subject fails to perceive a given signal
Misses
Subject seems to perceive a a signal when none was given
False alarm
Subject correctly identifies no signal was given
Correct negative
Adaptation
Our detection of a stimulus can change over time
Sclera
White of the eye -thick structural later that surrounds eye except cornea
Choroidal vessels
Blood vessel between sclera and retina
Retinal vessels is a second set of vessels found in the eye
Retina
Innermost layer of the eye which contains photoreceptors that transducer light into electrical information
Cornea
Clear dome like window in the front of the eye which gathers and focuses incoming light
Anterior chamber
Lies in front of iris
Posterior chamber
Between iris and lens
Coloured part of eye
Iris
Which muscles causes the pupil to open
Dilator pupillae- under sympathetic stimulation
Which muscle constricts pupil
Constrictor pupillae - under parasympathetic control
Produces the aqueous humour
Ciliary body
Where does aqueous humour drain
Canal of schlemm
Lens
Lies behind iris and helps control the refraction of incoming light
Accommodation
Ciliary muscle which is under parasympathetic control contracts and pulls on the sensory ligaments and changes the shape of the lens
Transparent gel that supports the retina
Vitreous
Which body system does the retina belong to?
Belongs to the CNS - is an outgrowth of brain tissue
Duplexity
Retina contains 2 types of photoreceptors - one for light and dark and one for colour detection
Used for colour vision and to sense fine details
Cones (are most effective in bright light )
What are the three types of cones and how do they differ?
Named for the weave length of light they best absorb
S - BLUE
M- Green
L -Red
Allow for the sensation of light and dark and permits night vision
Rods - they pigment is callled rhodopsin
Macula
Central section of eye that has high conc of cones
Centre most point of macula that contains only cones
Fovea
Where in the eye do we have the best visual acuity
The fovea - also the most sensitive to daylight
Blind spot
Where the optic nerve leaves the eye - no photoreceptors here
Bipolar cells
Highlight difference between rods and cones - synapse with ganglionic cells which then group together to form the optic nerve
As the number of receptors that converge through _____ cells onto ganglion cells resolution ________
Bipolar cells, decreases
______ vision has greater sensitivity to fine detail because _____?
Colour vision, because less cones converging onto a ganglion
What are amacrine and horizontal cells important for?
Important for edge protection as they increase perception of contrasts
Physical connection between eyes and brain and flow of visual information
Visual pathways
Right visual field projects on the ____ of each eyes retina and the left visual field projects on the _____
Right projects on left and left projects on right
Optic chiasm
Fibres from the nasal half of each each eyes retina crosses paths - they carry the temporal (towards side of head) field of view
Temporal fibres which carry the nasal field of view do not cross thee chiasm
All fibres corresponding to the left visual field from both eyes projects to the right side of the brain and the fibres corresponding to the right visual field from both eyes projects on the left side of brain
Reorganized paths leaving the optic chiasm
Optic tracts
From the optic chiasm the info goes to
Lateral geniculate nucleus (LGN) of thalamus through radiations in the temporal and parietal lobe to the visual cortex in the occipital lobe
Parallel processsing
Ability to simultaneously analyze and combine information regarding colour shape and motion compared to our memories to determine what is being viewed
Shape is detected by ______ cells which have high _______ and low ________
Parvocelllular - high spatial resolution but low temporal resolution
Motion is detected by _______ cells because they high ______ and low ______
Magnocellular cells — high temporal resolution and low spatial resolution
Provide blurry but moving image of object
Auditory pathway
Vestibulocochlear nerve to brain stem where is ascend to the medial geniculate nucleus (MGN) of the thalamus to the auditory cortex in the temporal lobe
Some sound is also sent to the superior olive which localized sound and inferior colliculus which is involved in the startle reflex
What are the 5 basic tastes
Sweet, sour, bitter, salty, umami (savoury )
Somatosensation
Touch - has four modalities : Pressure Vibration Pain Temperature
Responds to deep pressure and vibration
Pacinian corpuscle
Responds to light touch
Meissner corpuscle
Responds to deep pressure and texture
Merckle discs
Responds to stretch
Ruffini endings
Responds to pain and temperature
Free nerve endings
Two point threshold
Minimum distance necessary between two points of stimulation on the skin such that the points will be felt as two distinct stimuli
Depends on density of nerves
Physiological zero
Temperature is judged relative to normal skin temp b/w 86 and 97 F feels cold below feels warm above
Can turn pain signals off affecting whether or not we receive pain - spinal cord is able to preferentially forward signals from other touch modalities reducing pain sensation
Gate theory of pain
Ability to tells where ones body is in space
Kinaesthetic sense or propioception
Bottom up (data driven) processing
Object recognition by parallel processing and feature detection
Brain takes individual sensory stimuli and combines them together to create a cohesive image before determining what the object is
Top down (conceptually driven) processing
Memories and expectations allow brain to recognize while object and then the components based on these expectations
Perceptual organization
Ability to use data and concept in tandem to create a complete picture or idea
Gestalt principles
Ways for the brain to infer missing parts of a picture when it is incomplete
Law of proximity
Elements close to one another tend to be perceived as a unit
Law of similarity
Objects that are similar tend to be grouped together
Law of good continuation
Elements that appear to follow the same pathway are grouped together - tendency to perceive continuous patterns rather than abrupt stops
Subjective contours
Perceiving contours and therefore shapes in the stimulus that are not actually present
Law of closure
When a space is enclosed by a contour it tends to be perceived as a complete figure - perceived to be more closed than they actually are
Law of pragnanz
Perceptual organization will always be as regular, simple and symmetric as possible - this governs all of gestalt principles
