Perception Final ExamProf. David J. Heeger

Dec 18, 2006

Read these instructions: This exam is closed book, no notes, no index cards. Turn off your cell phone. Answer all questions. For multiple choice questions, mark your answers on the scantron card with a #2

pencil. For the short answer questions, mark your answers clearly on the answer sheet

provided at the end of this test booklet. Please make an effort to write legibly. Write your name on the answer sheet pages and on the scantron (1 point). Turn in the exam as well as the answer sheets.

Part I. Short Answer (4 points each). Write your name and your answers on the accompanying answer sheet. Be concise (one or two sentences will suffice). If your answer includes lots of extraneous facts then you will not receive full credit, even if the extraneous comments are true and even if the correct answer is buried somewhere in there.

1) We will show you an excerpt from Hubel and Wiesel's film of receptive fields. On the accompanying answer sheet, list all of the correct descriptors, but none of the incorrect descriptors (-1 point for each item that is listed incorrectly).

ON-center/OFF-surround receptive fieldOFF-center/ON-surround receptive fieldsimple cellcomplex cellhypercomplex celldirection selectiveorientation selective

2) Connect the name of the primary receiving area with its location (you may use locations more than once.)

Visual cortex Frontal lobeAuditory cortex Parietal lobeSomatosensory cortex Occipital lobe

Temporal lobe

3) We conduct a signal detection experiment on the same subject on two consecutive days. We find that the false alarm rate changes from day to day on the same well-practiced subject, even though the strengths of the signal and noise are fixed. What must also be happening to the hit rate and why? Draw a graph of an ROC curve to illustrate your answer.

4) Below are four pure tone sound waves and plots of the firing rates of two auditory nerve fibers in response to each sound wave. Explain how these data provide evidence for the temporal code theory of pitch perception.

5) Michael Posner, a famous cognitive neuroscientist, was once asked what is the main difference between human brains and other primate (e.g., chimps) brains that has allowed humans to be so much more successful. His answer was that human brains have special pathways for very fast neural processing. Which aspect of speech perception demands fast temporal processing? Explain why language learning disabilities are linked with deficits in fast processing.

6) When a patient has glaucoma, the usual flow within the aqueous and vitreous humors is disrupted, changing ocular pressure. How does this change in pressure disturb the eye, potentially leading to blindness?

7) During the second World War pilots wore red goggles while being briefed, immediately before, a night time mission. During the mission they wore no goggles. Using what you know about rod and cone wavelength sensitivity, explain (a) why the pilots wore goggles, and (b) why the goggles only passed long wavelength (650 nm) light, and not middle- or short-wavelength light.

8) List 2 of the 4 characteristic properties of parallel pathways in the visual and auditory systems? Use auditory sound localization as an example and explain how parallel pathways in the auditory system conform to these 2 characteristics.

9) How are visual cortical areas defined? List the 4 aspects of visual areas that differentiate one from another.

Part II. Multiple Choice (1.5 points each). Write your name and fill in the circles using a #2 pencil on the accompanying scantron card.

1) In the study of perceptual processes, the term “transduction” is defined to bea) temporal patterning of nerve impulses.b) neural processing.c) the conversion of environmental energy into electrical energy. d) electrical stimulation in the nervous system.

2) An experimenter inserts an electrode into the brain and records the electrical signals from a neuron. Which of the following will he not observe while recording from this neuron?a) action potentials that all have the same durationb) different firing rates for different types of stimulic) changes in the timing of action potentials with different types of stimulid) changes in the amplitude of action potentials with different types of stimuli

3) Which of the following is not an advantage of chemical synapse versus electrical ones?a) A chemical synapse can either excite or inhibit the postsynaptic neuron.b) A chemical synapse is faster than a direct electrical connection.c) The strength of a chemical synapse can be changed to enable learning.d) A chemical synapse can be either fast or slow.

4) The method of fMRI measures neural activity ______ as changes in ______.a) directly; electrical activityb) indirectly; electrical activityc) directly; blood flow & oxygenationd) indirectly; blood flow & oxygenation

5) Which of the following methods has the best temporal resolution?a) fMRIb) PETc) EEG

6) Two subjects’ thresholds on a visual detection task were measured using the method of constant stimuli. A stimulus was presented on each trial and the subjects reported whether they could see the target. Subject A detected 50% of the trials while subject B detected only 40% of the trials at that intensity. Which of the following interpretations can be made from this data?a) Subject A is better at the task than subject B.b) Subject A has a more liberal criterion than subject B.c) Subject B has a more liberal criterion than subject A.d) Subject B has more internal noise than subject A.e) None of the above conclusions can be made.

7) If the just noticeable difference for lifting a 200-gram weight is 10 grams, the just noticeable difference for lifting a 4,000-gram weight would be ______ grams.a) 10

b) 40c) 200d) 400

8) In response to a pure tone, each point along the basilar membrane moves up and downa) with the same frequency but different amplitudes.b) with the same frequency and the same amplitude.c) with different frequencies and different amplitudes.d) with different frequencies but the same amplitude.

9) If an audiogram shows hearing loss that is approximately equal across the range of hearing, the problem is more likely to be due toa) ugly wax build-up in the ear canal.b) old age.c) tinnitus.d) macular degeneration.

10) Hair cells respond to auditory stimulia) with action potentials of constant amplitude.b) with graded potentials (smooth changes in voltage).

11) The characteristic frequency of a neurona) indicates the rate at which the neuron usually fires.b) is the only frequency to which the nerve fiber responds.c) changes with the frequency of the stimulus.d) is the frequency to which the neuron is most responsive.

12) A pure tone one octave above another tone has a frequency ______ of the lower tone.a) four times thatb) two times thatc) that varies with the amplitude

13) The tone complex depicted below will have the same perceived pitch as which of the following pure tone frequencies?a) 100 Hzb) 200 Hzc) 300 Hzd) 400 Hz

14) Which of the following is true about critical bands?a) The space that a critical band occupies on the basilar membrane is greater for

high center frequencies than low.b) The frequency width of a critical band is constant regardless of the center

frequency.c) When the bandwidth of a stimulus exceeds that of the critical band, the stimulus

sounds louder than a stimulus of equal energy but smaller bandwidth. d) When the bandwidth of a stimulus is less than that of the critical band, the stimulus

sounds louder than a stimulus of equal energy but smaller bandwidth.

15) Damage to which of these areas is likely to specifically effect speech perception, leaving patients with the ability to produce speech?a) Broca’s Areab) Wernicke’s areac) A1d) Cochlear nucleuse) White’s area

16) An infant born with perfect vision wears an eye patch over one eye for much of her first year of life. If given a vision test as an adult we will likely find thata) her vision is worse in the patched eye than the other eye.b) there is no vision problem because there has been more than enough time for a

complete recovery since she was an infant.c) she is stereo blind.d) a and c.

17) A patient complains of problems with her vision. A careful examination reveals that when she closes her right eye, there is a large scotoma in the lower right quarter of the left eye visual field. When she closes her left eye however, her vision is intact. What could be the problem?a) a puncture in the upper temporal part of retina of the left eye.b) right optic nerve damage.c) a lesion that has destroyed the left LGN.d) a lesion that has damaged part of V1 in the right hemisphere.

18) The optic disc is locateda) on the nasal (close to the nose) part of the retina in both eyes.

b) on the temporal (close to the temples) part of the retina in both eyes.c) on the nasal part of the retina in the right eye, but on the temporal part of the retina

in the left eye.d) on the temporal part of the retina in the right eye, but on the nasal part of the retina

in the left eye.

19) What happens when a photoreceptor absorbs light energy?a) the chemical structure of the photopigment molecule changesb) the electrons in the photopigment molecule jump to higher energy statesc) the photopigment molecule’s spontaneous firing rate increasesd) the entire photoreceptor isomerizes

20) What is the Purkinje shift and why does it happen? a) the shift in use of the rods to the use of the cones when light levels change from

low to highb) the shift in your Purkinje tree, which is stabilized on the retina causing it to be

invisible even when your eyes shiftc) the shift from seeing color to being essentially color blind when light levels change

from photopic to scotopic conditions because we utilize different photoreceptor systems

d) maximum spectral sensitivity shifts toward blue when light levels change from photopic to scotopic conditions because we utilize different photoreceptor systems

21) A spectrogram is a plot ofa) photoreceptor sensitivity vs. frequency.b) sound intensity vs. frequency.c) frequency vs. time.d) the wavelength composition of the light source.

22) The color usually perceived at 470nm is ______; the color usually perceived at 700nm is ______.a) red; blueb) blue; redc) green; blued) red; green

23) You have never seen a color that looks both green and red in your life. This can be explained by:a) trichromacy theoryb) color opponency theoryc) color constancy theoryd) dichromacy theory

24) Each layer of the LGN receives inputs froma) both midget (parvo) and parasol (magno) ganglion cells.b) either midget or parasol ganglion cells, but not both.

c) only one of the eyes.d) a and ce) b and c

25) What is an ocular dominance column?a) A group of neurons in the retina of a person’s dominant eye.b) A group of neurons in the visual cortex on the side of the brain opposite a person’s

dominant eye.c) A group of neurons in the visual cortex that preferentially respond to either right

eye or left-eye stimulation.d) A group of neurons in the visual cortex that preferentially respond to stimuli with a

particular orientation.

26) If we record from neurons along an electrode track that penetrates perpendicular to the surface of the primary visual cortex, we finda) neurons with largely overlapping receptive fields.b) neurons with receptive fields that are systematically displaced from each other, that

is, with adjacent locations in the visual field.

27) While fixating object A, another object B falls on your horopter. Youa) will perceive B as being positioned closer than A.b) will only be able to assess the distance to these objects if you change your

horopter.c) will retain the same horopter if you shift your point of fixation from A to B.d) can change the angle of disparity that each of the objects forms if your fixation

moves from A to B.

28) Most observers can see depth from binocular stereopsis without first extracting any delineated or recognizable objects.a) True.b) False.

29) What range of depth is binocular disparity most useful for?a) beyond the horopter onlyb) the range in which binocular rivalry occurs

c) only for objects you are currently fixating d) within arms length

30) Odysseus decides to trick his friend Polyphemus, a one-eyed giant, into thinking that Odysseus is now his size. He beaches his ship on a long, featureless stretch of sand, and positions himself a few hundred meters inland from the ship, holding out his hand. When the giant comes down to the beach for his morning bath, he stops and stares at Odysseus and the ship. The image of the ship at Polyphemus' retina is five times smaller than the image of Odysseus and appears to be resting in Odysseus' outstretched hand. Odysseus' prank succeeds because _____.a) binocular vision is always necessary for depth perception.b) monocular cues always provide sufficient information for an unambiguous

interpretation of size and depth.c) Odysseus and the ship are perceived to be at the same distance.d) the images of Odysseus and the ship project to different areas of the retina.

31) Motion aftereffects, such as the waterfall illusion, are most likely caused bya) the autokinetic effect.b) akinetopsia.c) strabismus.d) adaptation.

32) If you are moving straight ahead, the vectors (arrows) in your optical flow field ______ the object you are heading towards.a) point away fromb) point perpendicular toc) point towardd) curve away from

33) A monkey is trained to perform a motion discrimination judgment on a field of dots that have no coherent motion, i.e. the movement of the dots is random and uncorrelated. On one trial, the experimenter records from a neuron in MT that is selective for upward motion. On the next trial, the experimenter stimulates that same upward-selective MT neuron. How would the monkey's behavior change from the trial where the experimenter records from the MT neuron to the trial where the experimenter stimulates the MT neuron?a) The monkey would be more likely to respond that the dots are moving upward.b) The monkey would be more likely to respond that the dots are moving downward.c) There would be no difference in the monkey's response during the two trials.

34) Which of the following is not a difference smooth pursuit and saccadic eye movements?a) saccades are ballistic and cannot be stopped once launched while smooth pursuit

eye movements are under constant control of the viewerb) saccades are faster than smooth pursuit eye movements

c) saccades can be made in the dark while smooth pursuit eye movements require a visual stimulus to follow

d) saccades are a biomechanical reflex programmed to keep fixation on a fixed object in the world whereas smooth pursuit is a reflex programmed to keep fixation on a moving object

35) Patient A has damage to the parietal lobes. Patient B has damage to the temporal lobes. Which description is more likely to characterize the deficits shown by these patients?a) Patient A has difficulty recognizing objects and is unaware of his deficit. Patient B

has difficulty with spatial orientation and localization and is aware of his deficit.b) Patient A has difficulty with spatial orientation and localization and is unaware of

his deficit. Patient B has difficulty recognizing objects, and is aware of his deficit.c) Patient A has difficulty recognizing objects and is aware of his deficit. Patient B has

difficulty with spatial orientation and localization and is unaware aware of his deficit.d) Patient A has difficulty with spatial orientation and localization and is aware of his

deficit. Patient B has difficulty recognizing objects and is unaware of his deficit.

36) Do any cells in the brain respond to illusory contours?a) yes, in V1 b) yes, in V2c) no, neurons only respond to physically real stimuli

37) Blindsighta) refers to the fact that damage to the cortex causes blindness.b) occurs when a person who is blind claims that he or she can see.c) occurs when a person can point to the location of a visual stimulus when forced to

guess, even though they have brain damage such that they are effectively blind.d) is a scientific hoax.

38) Although there have been many demonstrations that attention can affect the firing rates of neurons in secondary cortical visual areas (like V4 and MT), cognitive factors and task demands have no influence on activity in V1.a) Trueb) False

39) Subjects are given the following two visual search tasks. Which one will they be able to do with shorter exposure to the stimulus?a) Find a red X among green Xs, blue Os, yellow +s, and orange Ls.b) Find a blue X among green Xs and blue Os.

40) In an experiment, subjects are asked to respond to a target stimulus as quickly as possible by pressing a button. On some trials, the target stimulus is presented in the right visual field and on the other trials the target stimulus is presented in the left visual field. Before each stimulus is presented, the subjects are provided with a cue specifying where the subject should focus their attention. Some of the cues are valid, pointing to where the target will be presented. Some are invalid, pointing away from where the target will be presented, and some are neutral, not specifying any location.

You would expect that reaction times would be fastest for the _____________ trials, followed by the ______________, and then the _______________ trials.a) invalid, neutral, validb) valid, neutral, invalidc) neutral, valid, invalidd) valid, invalid, neutral

41) Which of the following is considered to be valid evidence against the hypothesis that face recognition is functionally specialized? a) After training, people are faster at recognizing upright relative to inverted greebles

(a novel class of object shapes). b) Neurons in monkey inferior temporal cortex show selective responses to pictures of

monkey faces. c) Studies have discovered a neuron in the temporal lobe of a human subjects’ brain

that responds only to pictures of Bill Clinton. d) Imaging studies have revealed regions of the human brain that respond more for

pictures of faces compared to houses and other non-face objects.

42) The infereotemporal (IT) cortex in the visual system has been suggested to be functionally specialized for a) color perception.b) object perception.c) motion perception.d) depth perception.

Perception Final Exam Answer Sheet Dec 18, 2006

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