Stimulation and Detection - AP Psychology

Action potentials are caused when different ions cross the neuron's membrane. The inside of the neuron becomes more positive due to the rush of sodium into the cell during depolarization. This raises the membrane potential from resting (roughly ) to the threshold level of about , which triggers the action potential and raises the membrane potential to roughly .

Following the action potential, potassium exits the neuron to reduce the membrane potential before the sodium-potassium pump restores the resting potential.

EEG (electroencephalogram) involves the placement of electrodes on a person's scalp to detect brain waves, specifically when the subject is asleep.

Rods (which detect black and white) and cones (which detect colors) are both located in the retina, which lines the back of the eye. After the rods and cones detect visual stimuli the information is relayed to the brain via the optic nerve, which exits the eye via the optic disc. There are no photoreceptors on the optic disc, resulting in our blind spot.

An echoic memory is a momentary, sensory memory of auditory stimuli that lasts for only a couple of seconds. This form of sensory memory may be forgotten or sent to our long-term memory for further encoding.

The just-noticeable difference is the minimal change that can occur in a stimulus to just barely be detected by the observer. In this case, the stimulus is the brightness of light.

As for the other answer choices, the absolute threshold is the minimal intensity at which a stimulus can just barely be detected. This concept is similar to the just-noticeable difference but has to do with detection of existence, rather than detection of change. Sensory adaptation refers to how an observer becomes less sensitive to a stimulus over time. Signal detection states that an observer's response to a stimulus depends on both their sensitivity and their decision criterion. Transduction is the process of physical signals being converted to neural signals.

Neurons are specialized cells that transmit nerve signals. These cells make up the nervous system, and consist of an axon (sends nerve impulses to other neurons), dendrites (receive nerve impulses from other neurons), and soma ( the cell body of the neuron).

Glial cells are considered part of the nervous system as well, but do not represent the fundamental functional unit. Instead, glial cells supply support and nourishment to neurons.

Top-down processing uses larger context to assume smaller bits of missing information. Bottom-up processing is the opposite - using small bits of information to understand a bigger picture. Signal detection theory is the ability to choose between and identify stimuli. Perceptual constancy refers to the tendency in humans to see familiar things as having similar shapes, colors, and sizes, in spite of changes that may have occurred in that object.

Autokinetic illusion is when a single unmoving light in a dark room appears to move when stared at for several seconds. It is not a monocular depth clue.

Interposition refers to the monocular depth clue indicating an objects relative closeness by seeing whether that object is stacked on top of an object, or whether an object is stacked on it.

Relative size refers to objects farther away appearing smaller.

Shadow (or shading) refers to closer objects reflecting more light, and thus appearing less dark, than objects further away.

Absolute threshold refers to the minimum amount of a given stimulus (light, odor, sound, pressure, or taste) that can be detected at least 50% of the time.

Rods and cones are the light-sensitive receptor cells that are responsible for transducing light waves into neural impulses.

The primary function of the ear canal is to facilitate the travel of auditory information into the ear, and to the parts of the ear used to process this information. While the ear canal, in helping the sensitive organs of the inner ear be less exposed to damage, may be said to protect these structures it is not the ear canal's primary purpose.

Olfactory neurons come in direct contact with the stimuli. They also are directly in the brain. Other sensory receptors transmit information to a separate neuron that relays the information to the brain.

Glutamate is found in protein rich foods and the artificial flavoring MSG (Monosodium Glutamate). It triggers the taste sensation umami. Umami is the most recently defined taste-sensation, it is best described as a meaty taste. The other four basic taste sensations are: salty, bitter, sweet, and sour.

Sensation can be described as the process of how our nervous system and sensory receptors receive and translate stimuli from our environment. Perception is the process by which our brains organize and interpret sensory stimuli, which allows us to recognize significant events and objects. Sensation functions as a bottom-up process because it starts at a smaller level and works its way up (i.e. from sensory receptors to processing centers). Perception functions as a top-down process because it starts at a larger level and gets smaller as it continues (i.e. from the sensory input down to our expectations and experiences).

The signal detection theory predicts when we will detect weak signals (stimuli). This theory negates the idea of absolute thresholds because the purpose is to ascertain why individuals react to the same stimulus differently. Additionally, it seeks to understand why one individual may perceive a stimulus differently based on circumstances. For instance, an exhausted parent may jump at the slightest whimper of a sleeping baby but fail to recognize a louder noise (i.e. the dryer buzzer indicating dry clothes). The absolute threshold is defined as the minimum stimulus required for detection 50 percent of the time; therefore, it is an incorrect choice. Conversely, a stimulus may be considered subliminal when it is below one's conscious awareness: not detected 50 percent of the time. This is also incorrect. Transduction would be incorrect because it is the process by which stimuli are translated from sensation to perception. Last, priming is also incorrect because it is defined as the process of predisposing one's memory, perception, or response by making unconscious associations. This is usually exercised in experiments using flashing images and masking stimuli.

The difference threshold is the noticeable difference a person can detect between any two stimuli 50 percent of the time. The concept of difference threshold is often associated with Weber's law. This law states that in order for an individual to perceive a difference between to stimuli then the stimuli must be a certain percent different and not a given amount. This becomes an issue of proportion versus static amount.

Ewald Hering created the opponent-process theory. While he saw truth in the Young-Helmholtz trichromatic theory, he felt that it left many questions of color vision unanswered. For example, how is it that people that cannot see red or green see yellow? Hering came to an understanding using “afterimages.” For instance, if you stare at a green square for long enough and then stare at a white sheet of paper, you will see a red square. Red in this case is green's opponent color. The same works for yellow and blue and black and white. You may be familiar with figures in text books having an image of a flag that's normally red, blue, and white be colored in green, yellow and black. with a blank white space next to it. This is an example of the afterimage effect, staring at the discolored flag for an ample period of time and then immediately staring at a blank white space will yield the creation of an image of the flag in its normal colors. A century later, researchers supported Hering’s theory. There are three sets of opponent retinal receptors: green-red, blue-yellow, and black-white. This theory complements the Young-Helmholtz theory.

The periphery of the retina contains many more rods than cones. Rods allow people to easily detect changes in light, and cones allow us to see in color and are located in the center—fovea—of the retina where visual acuity is best. Rods might not help us with seeing things super accurately, but they do help us with detecting motion because of the changes in light. The blind spot is where the bundle of nerves at the rear of the eye chamber block incoming light to hit the retina; thus, creating a "hole" in our vision. Nearsightedness has to do with visual acuity based on distance from the object, not peripheral vision.

Sensory adaptation is a gradual decline in sensitivity to prolonged stimulation. Senses—in this case taste—will automatically adapt to decline their sensitivity to stimulation over time. Habituation is a closely related concept that involves less sensitivity over time; however, habituation has to do more with physiological, cognitive, and perceptual processes rather than basic sensory processes. Taste bud cell death does not occur after prolonged stimulation.