Chapter 2: Sensation and Perception Flashcards
Define sensation.
Aligns with transduction, which is the conversion of physical, electromagnetic, auditory, and other information from our internal and external environment to electrical signals in the nervous system
What performs sensation?
Performed by receptors in the PNS, which forward the stimuli to the CNS in the form of action potentials and neurotransmitters
What is the term that best defines a raw signal?
Sensation
Define perception.
Refers to the processing of information to make sense of its significance.
Define ganglia.
Collections of neuron cell bodies found outside the CNS
How do sensory receptors transmit information?
Receive stimulus, and transmit the data to the CNS through sensory ganglia
What happens once transduction occurs?
Electrochemical energy is sent along neural pathways to various projection areas in the brain, which further analyze sensory input
What do photoreceptors respond to?
Electromagnetic waves in the visible spectrum (sight)
What do hair cells respond to?
Movement of fluid in the inner ear structures (hearing, rotational and linear acceleration)
What do nociceptors respond to?
Painful or noxious stimuli (somatosensation)
What do thermoreceptors respond to?
Changes in temperature (somatosensation)
What do osmoreceptors respond to?
Osmolarity of blood (water homeostasis)
What do olfactory receptors respond to?
Volatile compounds (smell)
What do taste receptors respond to?
Dissolved compounds (taste)
Define threshold.
The minimum amount of a stimulus that renders a difference in perception
What are the three types of thresholds?
- Absolute threshold
- Threshold of conscious perception
- Difference threshold
Define the absolute threshold.
Minimum of stimulus energy that is needed to activate a sensory system (at which a stimulus will be transduced and converted into action potentials)
What kind of threshold is this? We’re talking about how bright, loud, or intense a stimulus must be before it is sensed.
Absolute threshold
Define the threshold of conscious perception. What is it also called?
- Stimulus below the threshold of conscious perception arrives at the CNS, but does not reach the higher-order brain regions that control attention and consciousness
- Subliminal perception
Define the difference threshold. What is it also called called?
- Minimum difference in magnitude between two stimuli before one can perceive this difference
- Just-noticeable difference
What does Weber’s law state?
- There is a constant ratio between the change in stimulus magnitude needed to produce a jnd and the magnitude of original stimulus.
- For higher-magnitude stimuli, the actual difference must be larger to produce a jnd
What does the signal detection theory state?
Focuses on the changes in our perception of the same stimuli depending on both internal (psychological) and external (environmental) context
Define response bias.
Refers to the tendency of subjects to systematically respond to a stimulus in a particular way due to nonsensory factors.
What are catch trials? What are noise trials?
Catch trials: signal is presented
Noise trials: signal is not present
What are the four possible outcomes for trials in basic signal detection experiments?
1) Hits: correctly perceives the signal
2) Misses: fails to perceive a given signal
3) False alarm: perceive a signal when none was given
4) Correct negatives: correctly identifies that no signal was given
What is the pathway for a stimulus to reach conscious perception?
Sensory receptor, afferent neuron, sensory ganglion, spinal cord, brain (projection areas)
How does sensory adaptation affect the difference threshold?
Adaptation generally raises the difference threshold for a sensory response; as one becomes used to small fluctuations in the stimulus, the difference in stimulus required to evoke a response must be larger
Which lobe is entirely devoted to vision?
Occipital lobe
What is the thick structural layer of the eye? What portion does it not cover?
- Sclera, or the white of the eye
- Does not cover the cornea
The eye is supplied with nutrients by two sets of blood vessels. What are they?
- Choroidal vessels: complex intermingling of blood vessels between the sclera and the retina
- Retinal vessels
What is the innermost layer of the eye? What does it contain?
- Retina
- Contains the photoreceptors that transduce light into electrical information the brain can process
What does the cornea do? Where is it located?
- Located in the front of the eye
- Gathers and focuses incoming light
Where does the anterior chamber lie? Where does the posterior chamber lie?
Anterior chamber: in front of the iris
Posterior chamber: between the iris and the lens
What is the colored part of the eye?
Iris
What are the two muscles in the iris? Which nervous systems are they associated with?
Dilator pupillae: sympathetic
Constrictor pupillae: parasympathetic
What produces the aqueous humor that bathes the front part of the eye? Where does it drain?
- Ciliary body
- Canal of Schlemm
Where does the lens lie? What does it do?
- Lies right behind the iris
- Helps control the refraction of the incoming light
Contraction of the ciliary muscle, a component of the ciliary body, is under the control of which nervous system?
Parasympathetic
As the ciliary muscle contracts, it pulls on what? What does that do? What is this phenomenon?
- Pulls on suspensory ligaments
- Changes the shape of the lens
- Accommodation
What lies behind the lens and supports the retina?
Vitreous
Where does the retina lie? What is its main function?
- In the back of the eye; screen that consists of neural elements and blood vessels
- Convert incoming photons of light to electrical signals
What does the duplexity or duplicity theory of vision state?
The retina contains two kinds of photoreceptors:
- Those specialized for light-and-dark detection
- Those specialized for colour detection
What are cones? When are they most effective? How are their three forms differentiated?
- Used for colour vision and to sense fine details
- Most effective in bright light
- Forms are named for the wavelengths of light they best absorb (S, M, L)
What are rods? Why are they more functional in reduced illumination? What do they permit?
- Only allow sensation of light and dark because they all contain a single pigment called rhodopsin
- Permit night vision
What is the central section of the retina called? It has a high concentration of what? What is its center-point called? What is special about it?
- Macula
- Cones
- Fovea, contains only cones
Which region is most sensitive in normal daylight vision? Where is visual acuity best?
- Fovea
- Fovea
Rods and cones connect with what? Which highlight what?
- Connect with bipolar cells
- Highlight gradients between adjacent rods or cones
Bipolar cells synapse with what? Which group together to form what?
Ganglion cells, which group together to form the optic nerve
Does color vision or black-and-white vision have a greater sensitivity to fine detail? Why?
- Color vision
- Since the number of cones converging onto an individual ganglion cell is SMALLER than for rods
Integration of the signals from ganglion cells and edge-sharpening is performed by what? What do they do?
- Horizontal and amacrine cells
- Increase our perception of contrasts
Define visual pathways.
Refer to both the physical anatomical connections between the eyes and the brain and the flow of visual information along these connections
What is parallel processing? What does it also call on?
- The ability to simultaneously analyze color, shape, and motion of an object and to integrate this information to create a cohesive image of the world.
- Also calls on memory systems to compare a visual stimulus to past experiences to help determine the object’s identity
List the structures in the visual pathway, from where light enters the cornea to the visual projection areas in the brain.
Cornea, pupil, lens, vitreous, retina (rods and cones, bipolar cells, ganglion cells), optic nerve, optic chiasm, optic tract, lateral geniculate nucleus (LGN) of thalamus, radiations through parietal and temporal lobes, visual cortex (occipital lobe)
What is shape detected by? They have very high what? Which permits what?
- Parvocellular cells
- Very high colour spatial resolution
- Permit us to see very fine detail
Why can parvocellular cells only work with stationary or slow-moving objects?
Since they have very low temporal resolution
What is motion detected by? They have very high what? They have low what?
- Magnocellular cells
- High temporal resolution
- Low spatial resolution, rich detail is not seen when object is moving
What is the cartilaginous outside part of the ear called?
Pinna or auricle
What is the main function of the pinna?
To channel sound waves into the external auditory canal
What does the external auditory canal do?
Directs sound waves to the tympanic membrane (eardrum)
What determines the rate at which the tympanic membrane vibrates?
The frequency of the sound wave (high rate = high frequency)
Louder sounds have greater intensity, which corresponds to an increased ______ of this vibration.
amplitude
The middle ear houses the three smallest bones in the body. What are they called? What is their role?
- Ossicles
- Help transmit and amplify the vibrations from the tympanic membrane to the inner ear
What is affixed to the tympanic membrane? What does it act on? What does that act on?
- Malleus (hammer) is affixed
- Malleus acts on the incus (anvil)
- Incus acts on the stapes (stirrup)
What is the entrance to the inner ear?
Cochlea
How is the middle ear connected to the nasal cavity? What is its role?
- Eustachian tube
- Helps equalize pressure between the middle ear and the environment
The inner ear sits within what? What does it contain? (3) What do these structures form?
- Sits within a bony labyrinth
- Contains the cochlea, vestibule, and semicircular canals
- Membranous labyrinth
What is the membranous labyrinth filled with? It is suspended within the bony labyrinth by a thin layer of another fluid called ______. What is its function?
- Potassium rich fluid called endolymph
- Perilymph
- Transmits vibrations from the outside world and cushions the inner ear structures
The cochlea is divided into how many parts? What are these called?
- Three parts called scalae
Which scala in the cochlea houses the hearing apparatus? What is it called? What does it rest on?
- The middle
- Organ of Corti
- Rests on a thin, flexible membrane called the basilar membrane
What is the organ of Corti composed of? What is it bathed in?
- Thousands of hair cells
- Bathed in endolymph
What is the relatively immobile membrane that rests on top of the organ of Corti?
Tectorial membrane
The other two scalae that surround the hearing apparatus are filled with what?
Perilymph
What permits the perilymph to move within the cochlea?
The round window, a membrane-covered hole in the cochlea
What structures are used to detect linear acceleration? What is their function?
- Utricle and saccule (vestibule)
- Balancing apparatus
What structures are used to detect rotational acceleration?
Semicircular canals
List the structures in the auditory pathway, from where sound enters the pinna to the auditory projection areas in the brain.
Pinna, external auditory canal, tympanic membrane, malleus, incus, stapes, oval window, perilymph in cochlea, basilar membrane, hair cells, vestibulocochlear nerve, brainstem, medial geniculate nucleus (MGN) of thalamus, auditory cortex (temporal lobe)
How does the organization of the cochlea indicate the pitch of an incoming sound?
The basilar membrane is tonotopically organized: high-pitched sounds cause vibrations at the base of the cochlea, whereas low-pitched sounds cause vibrations at the apex of the cochlea
What converts the physical stimulus into an electrical signal in hearing?
Hair cells in the organ of Corti
Which is used for light and which is used for music: LGN and MGN.
LGN: light
MGN: music
Where are olfactory chemoreceptors located? What must happen to cause a signal?
- In the olfactory epithelium in the upper part of the nasal cavity
- Chemical stimuli must bind to their respective chemoreceptors to cause a signal
What is the olfactory pathway?
Nostril, nasal cavity, olfactory chemoreceptors on olfactory epithelium, olfactory bulb, olfactory tract, higher-order brain regions including limbic system
Where are taste buds found?
In little bumps on the tongue called papillae
What is the taste pathway?
Taste buds, brainstems, ascend to taste center in the thalamus, travels to higher-order brain regions
What are the four modalities of somatosensation?
Pressure, vibration, pain, and temperature
What do Pacinian corpuscles respond to?
Deep pressure and vibration
What do Meissner corpuscles respond to?
Light touch
What do Merkle discs respond to?
Deep pressure and texture
What do Ruffini endings respond to?
Stretch
What do free nerve endings respond to?
Pain and temperature
Where does information from somatosensation receptors travel to?
Somatosensory cortex in the parietal lobe
Define two-point threshold.
Refers to the minimum distance necessary between two points of stimulation on the skin such that the points will be felt as two distinct stimuli
The temperature is judged relative to what? What temperature is that?
- Physiological zero, normal temperature of the skin
- Between 86 and 97 oF
Nociceptors send signals that respond to what?
Pain
What does the gate theory of pain suggest?
There is a special “gating” mechanism that can turn pain signals on or off, affecting whether or not we perceive pain (explains why rubbing an injury seems to reduce the pain)
What is kinesthetic sense also called? What does it refer to?
- Proprioception
- Refers to the ability to tell where one’s body is in space
How is sensory information integrated in bottom-up processing?
Requires each component of an object to be interpreted through parallel processing, and then integrated into one cohesive whole
How is sensory information integrated in top-down processing?
Starts with the whole object and, through memory, creates expectations for the components of the object
In terms of Gestalt Principles, describe proximity.
Components close to one another tend to be perceived as a unit
In terms of Gestalt Principles, describe similarity.
Components that are similar (in color, shape, size) tend to be grouped together
In terms of Gestalt Principles, describe good continuation.
Components that appear to follow in the same pathway tend to be grouped together; abrupt changes in form are less likely than continuation of the same pattern
In terms of Gestalt Principles, describe subjective contours.
Edges or shapes that are not actually present can be implied by the surrounding objects (especially if good continuation is present)
In terms of Gestalt Principles, describe closure.
A space enclosed by a contour tends to be perceived as a complete figure; such figures tend to be perceived as more complete (or closed) than they really are
In terms of Gestalt Principles, describe Pragnanz.
Perceptual organization will always be as regular, simple, and symmetric as possible
Define perceptual organizations.
Refers to the ability to use both bottom-up and top-down processes, in tandem with all of the other sensory clues about an object, to create a complete picture or idea
