Reference no: EM133452241

Questions

1. In the retina, the chromophore that signals absorption of a photon

A) is a large molecule derived from vitamin B+.
B) is manufactured entirely by horizontal cells that then insert it into the receptors.
C) moves gradually to the receptor's outer membrane to open ion channels.
D) changes its configuration very rapidly.

2. Cortical magnification in the occipital lobe of the cortex (area V1) refers to the

A) functional blocks of neurons first described by Hubel and Wiesel.
B) enlarged area of V1 devoted to the area of the visual field close to the fixation point.
C) relatively small numbers of K-cells that project to an enlarged area devoted to peripheral visual field.
D) assumption that the eye's optics project a distorted map of the visual field onto the retina.

3. At the transition of a brighter to a dimmer area of a retinal image

A) the transition is enhanced by neurons whose receptive fields are only partially covered by the image.
B) the transition is enhanced only by edges of an image that is moving across the receptive field.
C) any variation in appearance of that boundary is termed a Helmholtz Band.
D) the transition is enhanced because the light from the brighter area is increased.

4. The finest detail that can be seen (i.e., acuity limit) is set by

A) the angle subtended by each receptor at the central (i.e., nodal point) part of the eye's optics.
B) the cones located in the retina's para-fovea.
C) the diameters of the smallest receptive fields of retinal ganglion cells.
D) parallel processing of the retinal image by neurons in V1.

5. Measures of an individual's psychophysical thresholds

A) vary due to variations in neuronal responses due to noisy spontaneous firing rates.
B) have frequency plots that are negatively skewed.
C) vary due to tester's response bias when using forced-choice methods.
D) None of the above.

6. Fechner's Law states that sensation is proportional to the logarithm of stimulus intensity. This means that

A) it contradicts Weber's Law.
B) it results in a positively accelerated sensory function.
C) just-noticeable sensory steps increase as stimulus intensity is increased.
D) magnitude of sensation equals the square-root of the JNDs.

7. In humans, objects whose images are focused on the far periphery of the retina can be seen

A) as colored.
B) appear to have sharp boundaries.
C) only when the eye is dark-adapted.
D) only when the eye is stationary.

8. Bi-polar cells in the vertebrate retina

A) all respond only with hyperpolarization when the retina is stimulated.
B) are the first neuronal stage with receptive fields with opposed excitatory and inhibitory regions.
C) do not exist in the "midget" cell lines.
D) are the only retinal neurons that respond to differences in wavelengths of stimuli.

9. Astigmatism is a defect of the eye's optical properties.

A) It can only be corrected by surgery to weaken some of the extra-ocular muscles.
B) It can be corrected by wearing external cylindrical lenses.
C) It occurs in hyperopes but not in myopes.
D) Is a mythical concept.

10. Form agnosia is one of the possible results of damage to the infero-temporal lobe. It means that such persons

A) can still draw a picture of an object placed in front of them.
B) have no memories of different objects.
C) can draw, based on memory, a picture of an object when they are told what it is.
D) cannot draw any sort of images of real objects.

11. Myopia is a form of optical defect of the eye

A) that occurs mostly in young children.
B) that cannot be corrected with external optical items.
C) that is associated with spending more time looking at distant objects.
D) that usually increases with age.

12. Forced-choice psychophysical methods can only be used

A) when comparing simultaneous side-by-side stimulus displays.
B) with subjects capable of understanding verbal instructions about the task.
C) to measure increases in stimulus intensity for a given viewing situation.
D) none of the above.

13. Light adaptation is essentially over by the time retinal signals reach the retinal ganglion cells.

A) Single rods do not exhibit any adaptation across most of the range of light intensities.
B) Only the amacrine cells control the level of light adaptation.
C) The process can only be studied by recording from individual neurons.
D) Massed potentials, such as the ERG, cannot clarify the process of light adaptation.

14. Complex cells in the visual cortex respond to

A) images of inverted faces.
B) a specific pattern anywhere across most of the visual field.
C) objects moving rapidly towards the observer.
D) images that continually flicker on and off.

15. Lightness of an object is determined

A) only by the absolute amount of light it reflects
B) by the contrast between its reflectance and the reflectance of its surrounds.
C) by the type of edge separating one part of the image from another.
D) only be the albedo of the background to the object.

16. When presented with a new object, or entering a new environment, we use eye movements to explore the object or the space. What are the movements and how are they organized?

A) We explore with a series of saccades to and from items that attract our attention.
B) For faces, we keep returning to brief fixations on eyes, mouth, hairline.
C) For interiors of a building, we saccade to the major objects or surfaces.
D) All of the above.

17. Comparing responses of cells in parvocellular layers of LGN with cells in the magnocellular layers.

A) Parvo cells are non-linear, but their responses grow slowly with increasing stimulus intensity.
B) Magno cells are non-linear - their response functions are negatively accelerated.
C) Magno cells are the only ones that interact with K-cells.
D) Parvo cells' responses grow until they exceed responses of magno cells.

18. A brief, bright light flash creates a retinal after-image. Although the image seems to fade quickly, it still affects sensations/percepts of stimuli whose images are superimposed on it.

A) After-image's influences fade at usual rate of dark-adaptation.
B) Stimuli superimposed on after-image sometimes appear brighter than usual.
C) Stimuli superimposed on a fading after-image can never be detected.
D) None of the above.

19. Visibility of objects farther away than a myope's "far-point."

A) Such objects can be seen clearly provided the ciliary muscle is slightly weaker than normal.
B) With age more distant objects are clearly visible because the far-point moves farther away.
C) Always appear blurred, unless corrective lenses are worn.
D) Straining to see such objects shift the near-point closer to the observer.

20. Under good photopic light levels, the acuity limit is affected only by

A) the angular subtense of rods in the center of the fovea.
B) the angular subtense of close-packed cones in central fovea.
C) the packing density of cones immediately surrounding the fovea.
D) how many millions of cones can be found in the central fovea.

21. The sensitivity of the scotopic visual system at the short wavelengths of the visible spectrum is lower than the sensitivity of rhodopsin. This is because

A) a pigment in the eye's lens absorbs wavelengths shorter than about 380 nm.
B) the spectral sensitivity of rhodopsin molecules is augmented as wavelengths shorten.
C) rhodopsin absorption is very much better to ultra-violet wavelengths than to the usual range of visible wavelengths.
D) of the compensatory mechanism that makes rhodopsin very sensitive to infra-red.

22. A photopigment's "chromophore"

A) is normally in the all-trans configuration.
B) is normally in the 11-cis retinal configuration.
C) is the same as a photoreceptor's photopigment.
D) remains attached to a receptor's opsin in both 11-cis and all-trans configurations.

23. In the retina of a newly born human

A) the fovea is already fully formed.
B) the periphery of the retina is still abnormally thin.
C) fovea is very immature.
D) the fovea still has too many cones; some must be "weeded-out."

24. The foveal pit exists because

A) there are no ganglion cells associated with receptors in this region.
B) cells in the inner nuclear and ganglion cell layers are pulled to the side.
C) this makes it easier to re-combine bleached photopigment molecules.
D) the final layer in the human retina consists of cells containing a highly reflective pigment.

25. The retinal distribution of rods and cones is such that

A) only rods exist across the entire retina.
B) there are many more rods than cones.
C) there are no cones in the peripheral retina.
D) packing density of rods is much lower just outside the fovea.

26. A photon

A) is emitted by any object with a temperature above absolute zero.
B) vibrates at a fixed frequency.
C) travels in a straight line at the speed of light.
D) All of the above are true.