2: Neurocognition Flashcards

Question

What is sensation?

Answer 1

Reception of stimulation from the environment and the encoding of it into the nervous system Initial encoding into the nervous system

Answer 2

Process of interpreting sensory information

Answer 3

-- Rods/cones: the back layer of neurons stimulated by light, beginning the process of vision. The periphery (20+ degrees) are composed of mainly rods (so no colour vision) 120 M rods, 7 M cones -- Bipolar cells: Patterns of neural firing from rods/cones are passed on to a second layer, the bipolar cells, which collect the messages and move them along to a third layer, the ganglion cells -- Ganglion cells: Receive messages from the bipolar cells- the axons of the ganglion cells converge at the rear of the eye, forming the bundle of fibers that makes up the optic nerve -- Optic Nerve: Projects neural messages to visual cortex in occipital lobe

Answer 4

-- The highly sensitive area of the retina responsible for precise, focused vision >> Covers about 1 to 2 degrees of visual field -- Most cones are in the fovea

Answer 5

- - Only fraction of light waves reach retina - - One cone synapses with one bipolar cell. In contrast, in peripheral vision, tens to hundreds of rods converge on a single bipolar cell (120M rods reduced down to about only 1M ganglion cells) - - Such convergence results in a loss of information because a bipolar cell cannot “know” which of its many rods triggered it

Answer 6

- - contralaterality principle: each eye transmits to both hemispheres, however each half of the retina gathers information from the contralateral visual field - - The left half of the retina in each eye receives images from the right visual field and the right half of each retina receives images from the left visual field - - Thus, the right visual field projects to the left half of the retina in both eyes, and this is then transmitted to the left hemisphere. Similarly, stimuli in the left visual field project to the right half of both retinas, and are then sent to the right hemisphere.

Answer 7

- - Movement of the eyes from one fixation point to another - - Jerky & variable: 25ms – 175 ms - - Nothing “seen” during a saccade

Answer 8

- - Eyes pause to foveate and gather visual information - - For the most part we take in visual information only during a fixation. It is almost as if we are blind during the actual saccade (if the eye did encode information during the saccade, we’d see a smear)

Answer 9

- - allows the sensation of a visual pattern, sound, or touch to linger for a brief moment after the sensory stimulation is over - - the information that is being held within our Sensory Memory appears to be unprocessed (not making any sense of it. It has to be processed for it to move to short term memory)

Answer 10

- - Information accumulates over time (50ms) | - - Not “all-or-none”

Answer 11

-- The apparent persistence of a visual stimulus beyond its physical duration

Answer 12

-- superimposed dot patterns -- delay varied: 0 to 500 ms @ 0 ms delay > 1 pattern, see letters (VOH) @ ~ 75 ms > 2 patterns, but perceive letters @ > 250 ms > 2 patterns, no letters -- Visual SM lasts for a short period of time: about between 250ms – 500ms

Answer 13

- - participants had to report all items in the display - - Only able to report ~ 3 of 9 items - - Problem with whole report technique; working short-term memory rather than sensory-memory because maybe all the items got into sensory memory but because it fades away so quickly you don’t get the chance to report them all

Answer 14

- -Subjects saw three rows of letters flashed on a screen for just 1/20 of a second. A tone following the exposure signalled which row of letters the subject should report to the experimenter. - - If interval short between the tone and presentation, then close to 100% accurate however their accuracy steadily declined as the delay of the tone increased to one second. Why? Because the memory trace in the visual sensory store decays in about 1/4 (250ms) of a second - - Conclude: capacity of visual SM is very large

Answer 15

-- Can select items from display based on: > Location > Colour > Even angles/line versus circles -- However, cannot select based on higher-level features > e.g., not able to select based on letters vs. digits (meaning sensory memory deals with primitive features so cannot categorize based on letters or numbers) -- Conclude: Information in SM is pre-categorical, not semantic

Answer 16

- - Originally thought that information in SM simply decayed over time - - But, turns out that information can be erased from SM through interference; forgetting caused by the effects of intervening stimulation or mental processing - - this is called masking; the partial or complete obscuring of one stimulus (the target) by another (the masker) - - Masking occurs because we can’t keep different sensory information to integrate cause all this sensory information will overlap and blur out everything

Answer 17

- - presented a display of two rows of letters, eight letters per row, for 50 ms. A blank white postexposure field, varying in duration, followed the display and was itself followed by a partial report cue - - The bar marker was just above (or below) the position of the to-be-reported letter, and the circle marker surrounded the position where the to-be-reported letter had just been - - With the bar marker, the results that were similar to those obtained by Sperling, such as higher performance with short delays of the cues - - With the circle marker, accuracy was lower than with the bar marker, especially when the target letter resembled the circle marker (for instance, when the letter c had been shown at that position). - - These results suggest that the circle had in some way disrupted the memory trace for the letter in that position - - Thus, a later visual stimulus interfered with the memory for the prior stimulus at that location (called backwards masking)

Answer 18

- - Backward Masking: when Target followed by Mask - - Forward Masking: when Mask before the Target - - Energy; such as a flash of light; affect peripheral (early) - - Pattern ; has features (information) and is central & interrupts processing of features - - Masking is strongest with energy masks when it happens at the same time as the stimulus

Answer 19

Monocular: target & mask to one eye Binocular: target & mask to both eyes Dichoptic: target to one eye, mask to other eye

Answer 20

-- Occurs with mono & binocular, not with dichoptic

Answer 21

Is effective with all, even dichoptic

Answer 22

- - Shows that features coded in SM (not just energy) - - Processing in SM is NOT passive, but dynamic - - Masking arases information to allow for next event to be cleanly encoded into SM