C2 - Sensation And Perception Flashcards
What is sensation
The taking of physical, electromagnetic, auditory, and other info from our internal and external environment to convert into electrical signals in the nervous system
What is perception
The process of processing information within the CNS in order to make sense of the informations significance
What is proximal and distal stimuli?
Proximal stimuli directly interacts with and affects the sensory receptors, this informs the observer about the presence of distal stimuli
What is psychophysics
The study of the relationships between the physical nature of stimuli and the sensation/perceptions they evoke
Ganglia
Collections of neurons cell bodies found outside of CNS
What are osmoreceptors?
Receptors that respond to changes in osmolarity of the blood (water homeostasis)
Sensory stimuli is transmitted where in the brain?
Projection areas, which further analyze the sensory input
All sensory information is sent to the CNS in the form of…
Action potentials
What is threshold
The minimum amount of stimuli that renders a difference in perception
What are the 3 main types of thresholds
-Absolute threshold
-Threshold of conscious perception
-Difference threshold
What is absolute threshold
The minimum intensity at which a stimulus must be to be transduced (converted into action potentials)
In other words it is about how bright, far, loud, or intense a stimulus must be before it is sensed
What does the stimulus never reach if it is below the absolute threshold
The central nervous system
What is the threshold of conscious perception
The level of intensity that a stimulus must pass in order to be consciously perceived by the brain
What is subliminal perception?
Information that is received by the CNS but does not cross the threshold of conscious perception
Main difference in being below absolute threshold vs below threshold of conscious perception
Below absolute threshold the stimulus will never be transduced and thus never reach the CNS
Below the threshold of conscious perception the stimulus arrives at the CNS but does not reach the higher-order brain regions that control attention and consciousness
What else is the difference threshold called?
The just noticeable difference (jnd)
What is the difference threshold?
The minimum change in magnitude required for an observer to perceive that two different stimulus are, in fact, different
If below the difference threshold, 2 possibly different stimuli will seem to the observer as…
The same
What happens in a common psychophysical discrimination testing experiment?
A participant is presented with a stimulus, it is then varied slightly until they report a change in stimuli, it is then recorded as the just noticeable difference
The just noticeable difference or difference threshold is usually reported or recorded as…
A fraction or percentage
Who was often credited with the observation that difference thresholds are proportional and must be computed as percentages?
Ernst Heinrich Weber
Often called the Webers Law
What does the signal detection theory study?
The effects of nonsensory factors such as experiences (memory), motives, and expectations on perception of stimuli
Both external and internal factors
Example in signal detection theory; how loud would someone have to tell your name in a crowd for you to notice? Well this comes down to what factors?
-Environmental factors
-Social factors
-Psychological factors
-Personality factors
A basic signal detection experiments consists of many trials, what is presented in these trials?
During each trial a stimulus may or may not be presented
Trials in which the signal is presented, and those without a signal are called…
-Noisy trials- are those with a presented signal
-Catch trials- are those without a presented signal
What are the 4 possible outcomes for each trial in a signal detection theory expirement?
A hit - a trial in which the signal is presented and the subject correctly perceives the signal
A miss - a trial in which the subject fails to perceive the presented signal
A false alarm - a trial in which the subject indicates perceiving the signal, even though the signal was not presented
A correct negative - a trial in which the subject correctly identifies that no signal was present
Our ability to detect a stimulus can change over time through repeated stimulation, if we start to block it out of our notice this is due to?
Sensory Adaption
Most of the exposed portion of the eye is covered by a thick structural layer known as…
The sclera
What is the colored part of the eye?
The iris
What is the white part of the eye?
The sclera
What covers the frontmost portion of the eye?
The cornea
The eye is supplied from nutrients by what 2 sets of blood vessels?
The choroidal vessels - a complex intermingling of blood vessels between the sclera and retina
Also the retinal vessels
What is the innermost layer of the eye?
The retina
What does the Retina contain?
Photoreceptors that transduce light into electrical information the brain can process
Photons of light to electrical signals
Cornea function
Gathers and focuses the light
What are the 2 chambers and there locations in the eye?
Anterior chamber - lies in front of the iris
Posterior chamber - between the iris and lens
The iris is composed of what 2 muscles?
Dilator pupillae - opens the pupil under sympathetic stimulation
Constrictor pupillae - constricts the pupil under parasympathetic stimulation
What 2 things is the iris continuous with?
The choroid, and the ciliary body
What is the choroid and it’s function?
It is a vascular layer of connective tissue that surrounds and provides nourishment to the retina
What is the ciliary body function?
Produce the aqueous humor that bathes the front part of the eye
Where does the aqueous humor drain into?
The canal of schlemm
Where is the lens and what is its function?
The lens is right behind the iris and helps control the refraction of the incoming light
What muscle is a component of the ciliary body, and what does it do?
The ciliary muscle, it is under parasympathetic control, when contracted, it pulls on the suspensory ligaments and changes the shape of the lens to focus on a image as the distance varies
A phenomenon called accommodation
What type of humor lies behind the lens?
The vitreous humor, a transparent gel that supports the retina
What is the retina considered a part of?
The CNS, as it’s a developed outgrowth of brain tissue
What is the duplicity or duplicity theory of vision?
It states that the retina contains 2 types of photoreceptors
-those specialized for light and dark detection
-those specialized for color detection
The retina is made up of approximately how many cones and rods?
6 million cones and 120 million rods
What are cones used for?
Color vision and to sense fine details, most effective in bright light
What forms do cones come in?
Cones come in 3 forms which are named for the wavelengths of light they best absorb
-Short (blue) wave
-Medium (green) wave
-Long (red) wave
When are rods most functional?
In reduced light because they are highly sensitive to photons
Only allow sensation of light and dark
All rods contain only a single pigment called
Rhodopsin
Why are rods less useful for detection of fine details?
Because rods are spread over a much larger area of the retina
What is the central location of the retina called?
The Macula
What does the macula contain?
A high concentration of cones
What is the center most region of the macula called? And what does it contain?
The Fovea, contains only cones
The further away you move from the fovea the more concentration of what?
Rods, and less of cones
Visual acuity is best at…
The Fovea
What leaves the eye?
The optic nerve
Region of the retina which is devoid of photoreceptors?
The optic disk, gives rise to a blind spot
Rods and cones do not connect directly to the optic nerve, instead what do they connect to? Describe them
Layers of neurons in between
First they synapse directly to bipolar cells, which highlight gradients between adjacent rods and cones
Then bipolar cells synapse with ganglion cells, axons of which group together to form the optic nerve
Bipolar and ganglion cells are located in front of rods and cones too, what does this mean?
That a photon must actually navigate past several layers of cells to reach the rods and cones at the back of the retina
As the number of receptors that converge through the bipolar neurons onto one ganglion cell increases, the resolution…
Decreases
multiple input signals are combined, resulting in a lower level of detail or resolution.
What do amacrine and horizontal cells do?
help enhance the contrast and highlight subtle variations in visual information by collecting input from multiple retinal cells within a specific region. This allows them to refine the signals before passing them on to ganglion cells, ultimately aiding in the perception of finer details and contrasts in the visual scene.
If an object is to your left than the photons from that object stimulate what side in each eye?
The right side of retina in each eye
An object in the nasal field of the right eye stimulates what fibers in the right eye?
The temporal retinal fibers
An object in the temporal field of the left eye would stimulate what fibers if the left eye?
The nasal retinal fibers