6A: Sensing the environment Flashcards
What is a threshold?
The minimum amount of stimulus required to cause an action potential
What is the absolute threshold?
The minimum intensity of a stimulus that one can detect
What is the difference threshold?
The minimum difference in intensity between two stimuli that one can detect; also known as the just noticeable difference
What does Webers Law indicate?
There is a constant ratio between the change in stimulus to produce a difference threshold and the magnitude of the original stimulus;
What is Weber’s constant/fraction?
1/5 or 2%
What is Signal Detection Theory?
It states that nonsensory factors can influence thresholds; it focuses on changes in our perception of the same stimuli depending on psychological and environmental context;
The ability to discern between stimuli and noise
What are the parts of a signal detection experiment?
Consists of catch trials (where stimuli is present) and noise trials (where stimuli are absent)
What are the outcomes of a signal detection experiment?
HIT = signal present and detected
MISS = signal present and not detected
FALSE ALARM = single absent and detected
CORRECT NEGATIVE/REJECTION = single absent and not detected
What is sensory adaptation?
It is the ability of our bodies to become accustomed to a stimulus after repeated application of the stimulus; both the physiological and psychological component get decreased
What does sensory adaptation allow us to do?
It allows us to differentiate meaningful information from the background; unable to feel clothing after getting dressed
What do sensory receptors do?
They respond to stimuli and trigger electrical signals
What are sensory pathways?
Sensory pathways are nerve endings or sensory cells that receive stimuli and carry the information through sensory ganglia and arrive at the CNS
What are Ganglia?
Ganglia are found outside of the CNS and they are group of neuron cell bodies
What are Projection Areas?
Projection areas are portions of the brain that analyze the sensory input
What are the major sensory receptors?
Hair cells, Photoreceptors, Thermoreceptors, Mechanoreceptors, Osmoreceptors, Nocireceptors, Olfactory receptors, Chemoreceptors
What do Hair cells detect?
Movement of fluid in the inner ear
What are simple receptors?
Neurons with free nerve endings
What are complex neural receptors?
Nerve endings that are enclosed in connective tissue capsules
What are special senses receptors
These are neurons that release neurotransmitter onto sensory neurons that initiate action potentials
Which lobe of the brain is devoted to vision?
Occipital lobe
How does the eye receive nutrients?
Choroidal and retinal vessels
What is the duplicity theory of vision?
This theory posits that the retina contains two kinds of photoreceptors which are specialized for light and dark detection
What is the function of Rods? What kind of pigment(s) do they contain?
It functions in reduced illumination and allow for sensation of light and dark; they have a low sensitivity to detail; pigment = rhodopsin
What is the function of Cones? What kind of pigment(s) do they contain? How does the Fovea relate to cones?
It functions in color detection and sensing of fine detail; contain S, M and L pigments; Fovea only has cones so its important in visual acuity and sensitivity to daylight vision
What is the function of amacrine & horizontal cells?
They receive input from many of the retinal cells before it is passed onto the ganglion cells; they focus the slight differences between the visual information in each cell increases the perception of stimuli
What are the two muscles of the iris and what do they do?
Dilator pupillae = opens the pupil under sympathetic stimulation
Constrictor pupillae = constricts pupil under parasympathetic stimulation
What is the Choroid and what is its function?
It is a continuous structure of the iris along with the ciliary body; it produces aqueous humor and washes the anterior chamber of the eye
Where is the lens of the eye located and what is its function?
It’s located behind the iris and controls the refraction of entering light
What is the function of the ciliary muscle (part of the ciliary body)?
It contracts under parasympathetic stimulation to change the shape of the lens (known as accommodation)
What is the function of vitreous humor?
It’s a transparent gel that supports the retina behind the lens
What is the function of the Macula and where is it located?
It’s responsible for detailed central vision, it is located in the central section of the retina
What is the pathway for visual information?
Optic nerve -> optic chiasm -> optic tracts -> lateral geniculate nucleus -> visual radiations -> visual cortex (occipital lobe)
Where does the right visual field project?
Onto the left half of the retina and the left side of the brain
Where does the left visual field project?
Onto the right half of the retina and the right side of the brain
What is parallel processing?
The ability to simultaneously analyze and combine information; includes color, shape, depth and motion - correlated with feature detection;
Features are compared to memories to determine what is being viewed
What processes color, shape and motion?
Cones, Parvocellular Cells and Magnocellular cells
What are the parts of the outer ear?
Pinna/Auricle and Tympanic Membrane
What are the parts of the middle ear?
Malleus, incus and stapes
What are the parts of the inner ear?
Cochlea, Vestibule, Semicircular Canals
What is the function of the Eustachian Tube?
It equalizes pressure between the middle ear and the environment
What happens to sound when it enters the cochlea?
It passes through the oval window and causes vibrations which allow the hair cells to move and turn the physical stimuli into electrical signals
What is the function of the vestibule?
It’s sensitive to linear acceleration and it’s used as a part of balancing apparatus and determining 3D orientation
What is the function of the semicircular canals?
It’s sensitive to rotational acceleration and they contain hair cells in their canals which bend to interpret change
What is the auditory pathway?
Vestibulocochlear nerve -> brainstem -> medial geniculate nucleus (thalamas) -> auditory cortex (temporal lobe) & inferior colliculus
Location, characteristics of Hair Cells
Located within the organ of corti in the cochlea, they are epithelial cells with stereocilia on their surface and they rest on the basal lamina
Functionality of Hair Cells
Vibrations reach the basilar membrane -> hair cells move which opens ion channels that produce action potential and the brain identifies the pitch of the sound
4 modalities of somatosensation
Pressure, Vibration, Pain and Temperature
Pacinian Corpuscles
Respond to Deep Pressure and Vibration
Meissner Corpuscles
Respond to Light Touch
Merkle Discs
Respond to Deep Pressure & Texture
Ruffini Endings
Respond to Stretch
Free Nerve Endings
Respond to Pain & Temperature
What is the Two-Point Threshold?
The minimum distance necessary between two points of stimulation on the skin to be felt as two distinct stimuli
What is Physiological Zero?
The point to which temperature is judged, below PZero = cold, above PZero = warm
What is the Gate Theory of Pain?
There is a special mechanism that can turn pain signals on or off and affect whether or not we receive pain
What does the gate theory of pain involve?
The spinal cord forwarding stimuli from the various modalities; if non-painful stimuli is detected, the gate closes.
What are the five basic tastes?
Sweet, Sour, Salty, Bitter & Umami
How are tastes detected?
By chemoreceptors (they’re sensitive to dissolved compounds)
How is taste information processed?
Taste buds -> brain stem -> thalamus taste center -> other parts of the brain
What is olfaction?
Response to volatile or aerosolized compounds
What are pheromones?
Compounds that carry interpersonal information; play a bigger role in animals than humans
What is the olfactory pathway?
Olfactory Receptors -> Olfactory Bulb -> Olfactory Tract -> Brain (limbic system)
What is proprioception (kinesthetic sense)?
Sensing the body’s position in space; involves hand-eye coordination, balance and mobility
Where are proprioceptors located?
Muscles, Ligaments and Joints; contain stretch receptors
What are the two types of object recognition?
Bottom-Up and Top-Down Processing
What is Bottom Up Processing?
It is a data driven process; it occurs via parallel processing and feature detection;
The brain first combines individual sensory stimuli into a cohesive image -> emotional response -> brain cognition -> action occurs
Features are processed before comprehension is achieved
What is Top Down Processing?
It is a conceptually driven process; occurs via object recognition by memories and expectations; quick recognition of an object occurs first and then analysis of detail occurs
What is Perceptual Organization?
It is the process of forming a complete picture by applying all sensory ideas about an object through top-down and bottom-up processing; it applies information about depth, form, motion and constancy helps to complete the picture
Depth Organization
Involves seeing objects in 3D in a 2D space; Binocular cues depend on both eyes
Monocular cues depends on one eye
Form Organization
Organization of the visual field into objects that make it stand out from the background
Motion Organization
Seeing the object in motion
Constancy Organization
Recognizing objects by size, shape and color from different angles
What are Gestalt Principles?
The way the brain acts to infer the missing parts of a picture when a picture is incomplete
GP: Proximity
Elements close to one another tend to be perceived as a unit
GP: Similarity
Objects that are similar tend to be grouped together
GP: Good Continuation
Elements that appear to follow in the same pathway tend to be grouped together; tendency to perceive continuous patterns in stimuli rather than abrupt changes
GP: Subjective Contours
Perceiving shapes that are not actually present in the stimulus
GP: Closure
When a space is enclosed by a contour it tends to be perceived as a complete figure; certain tend to be perceived as more complete than they really are
Law of Prägnanz
States that perceptual organization will always be as regular, simple and symmetric as possible
