Chapter 2: Sensation & Perception Flashcards
Sensation
“Sensation more appropriately 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.”
Perception
The processing of sensory information to make sense of its significance.
Sensory Receptors
Nerves that respond to stimuli and trigger electrical signals.
Sensory Ganglia
Collections of cell bodies outside the central nervous system. Sensory ganglia help transmit data to the CNS.
Common Types of Sensory Receptors
Photoreceptors (sight), hair cells (hearing), nociceptors (pain), thermoreceptors, osmoreceptors (osmolarity of the blood), olfactory (smell) receptors, and taste receptors.
Absolute Threshold
The minimum of stimulus energy that is needed to activate a sensory system.
Threshold of Conscious Perception
The minimum of stimulus energy that will create a signal large enough in size and long enough in duration to be brought into awareness.
Difference threshold or Just-Noticeable Difference (JND)
Minimum difference in magnitude between two stimuli before one can perceive this difference.
What is the difference between Absolute threshold and Conscious Perception threshold?
A stimulus below the absolute threshold will not be transduced, and thus never reaches the central nervous system. A stimulus below the threshold of conscious perception arrives at the central nervous system, but does not reach the higher-order brain regions that control attention and consciousness.
Weber’s Law
States that the jnd for a stimulus is proportional to the magnitude of the stimulus, and that this proportion is constant over most of the range of possible stimuli.
Thus, for higher magnitude stimuli, the actual difference must be larger to produce a jnd.
Extremely high and low ends of each range must have larger differences.
Signal detection theory
Refers to the effects of nonsensory factors, such as experiences, motives, and expectations, on perception of stimuli.
What does signal detection experiments allow us to look at?
Response bias. In a signal detection experiment, a stimulus may or may not be given, and the subject is asked to state whether or not the stimulus was given.
There are four possible outcomes: hits, misses, false alarms, or correct negatives.
What are trials in which a signal is presented? Without a signal?
With signal = Catch trial.
Without signal = Noise trial.
Possible Outcomes from a Signal Detection Experiment Trial
Hits, in which the subject correctly perceives the signal.
Misses, in which the subject fails to perceive a given signal.
False alarms, in which the subject seems to perceive a signal when none was given.
Correct negatives, in which the subject correctly identifies that no signal was given.
A significant proportion of misses or false alarms gives an indication of response bias in the subject.
Adaptation
Refers to a decrease in response to a stimulus over time.
Cornea
Gathers and filters incoming light.
Iris
The iris is the colored part of the eye. The iris contains the dilator pupillae, which opens the pupil under sympathetic stimulation; and the constrictor pupillae, which constricts the pupil under parasympathetic stimulation.
Ciliary muscle
Contraction of the ciliary muscle, a component of the ciliary body, is under parasympathetic control. As the muscle contracts, it pulls on the suspensory ligaments and changes the shape of the lens, a phenomenon known as accommodation.
Retina
Retina is in the back of the eye and is like a screen consisting of neural elements and blood vessels. Its function is to convert incoming photons of light to electrical signals.
Duplexity or Duplicity Theory of Vision
States that the retina contains two kinds of photoreceptors: those specialized for light-and-dark detection, and those specialized for color detection.
Rods vs. Cones
Cones = Color vision and fine details.
Rods = Permits night vision and works best in low light.
What is the center most point of the retina called?
Fovea. The fovea, contains only cones. As one moves further away from the fovea, the concentration of rods increases while the concentration of cones decreases. Therefore, visual acuity is best at the fovea, and the fovea is most sensitive in normal daylight vision.
Note, there are many more rods than cones in the human eye.
What is the visual pathway of the eye?
Starts from the eye, and travels through the optic nerves, optic chiasm, optic tracts, lateral geniculate nucleus (LGN) of the thalamus, and visual radiations to get to the visual cortex.
Parvocellular Cells
Detects shape and high color resolution.
Mangocellular cells
Detects motion. But the moving object is seen blurry.
Outer Ear
The outer ear consists of the pinna (sound waves reaches this part of the ear first), external auditory canal, and tympanic membrane(aka eardrum; vibrates in phase with incoming sound waves).
Middle Ear
The middle ear consists of the ossicles: malleus (hammer), incus (anvil), and stapes (stirrup).
The middle ear is connected to the nasal cavity by the Eustachian tube.
What is the actual apparatus that allows us to hear?
The Organ of Corti. Which is apart of the cochlea.
Inner Ear
Consists of the cochlea, which detects sound; utricle and saccule (detect linear acceleration) and semicircular canals (detect rotational acceleration).
What does the hair cells in the organ of Corti do?
These hair cells convert the physical stimulus into an electrical signal. They also amplify incoming sound.
Auditory Pathway
The auditory pathway starts from the cochlea and travels through the vestibulocochlear nerve and medial geniculate nucleus (MGN) of the thalamus to get to the auditory cortex in the temporal lobe.
What are the receptors for taste called?
Taste buds. Taste comes in five modalities: sweet, sour, salty, bitter, and umami (savory).
Inferior Colliculus
Involved in the startle reflex and helps keep the eyes fixed on a point while the head is turned.
Superior Olive
Localizes sound.
Two-Point Threshold
The minimum distance necessary between two points of stimulation on the skin such that the points will be felt as two distinct stimuli.
Physiological Zero
The normal temperature of the skin, to which objects are compared to determine if they feel “warm” or “cold”.
Nociceptors
Are responsible for pain perception. The gate theory of pain states that pain sensation is reduced when other somatosensory signals are present.
Kinesthetic sense (proprioception)
Refers to the ability to tell where one’s body is in three-dimensional space.
Bottom-up (data-driven) processing
Refers to recognition of objects by parallel processing and feature detection. It is slower, but less prone to mistakes.
Top-down (conceptually driven) processing
Refers to recognition of an object by memories and expectations, with little attention to detail. It is faster, but more prone to mistakes.
Gestalt principles
Ways that the brain can infer missing parts of a picture when a picture is incomplete.
Law of Proximity
Elements close to one another tend to be perceived as a unit.
Law of Similarity
Objects that are similar appear to be grouped together.
Law of Good Continuation
Elements that appear to follow the same pathway tend to be grouped together.
Subjective Contours
Refers to the perception of nonexistent edges in figures, based on surrounding visual cues.
Law of Closure
When a space is enclosed by a group of lines, it is perceived as a complete or closed line.
Law of Prägnanz
Perceptual organization will always be as regular, simple, and symmetric as possible.
