Lecture 5

Question 1

What is a feature detector?

Answer 1

Neurons that fire in response to specific features of a stimulus

Question 2

What are the 3 types of feature detectors?

Answer 2

Simple cortical cell
• Complex cortical cell
• End-stopped cortical cell

Question 3

What are orientation tuning curves?

Answer 3

plot the response of a simple cortical cell to line
stimuli of varying orientations

Question 4

Describe complex cortical cells

Answer 4

respond best to movement across the receptive field
of particularly oriented bar

Question 5

Describe Hubel and Wiesel study

Answer 5

dropped a slide into their slide projector, the image of
the edge of the slide moving down unexpectedly triggered activity in one of
these neurons

Question 6

Describe absolute threshold

Answer 6

smallest amount
of energy needed to detect a stimulus

Question 7

Describe the method of limits

Answer 7

Present stimuli of different intensities
in ascending and descending order
• Record whether the stimulus can be
perceived on each trial
• Average the cross-over point

Question 8

Describe selective adaptation

Answer 8

a phenomenon in which neurons tuned to specific stimuli
properties fatigue with prolonged exposure to stimuli containing those properties

• Fatigue or adaptation to stimulus causes a decrease in both:
  1. Baseline firing of those neurons
  2. The response of those neurons to repeated presentations of the stimuli they have been
  adapted to

Question 9

What stimuli are used for selective adaptation?

Answer 9

gratings and are
made of alternating light and dark bars

Question 10

Describe the selective adaptation experiment

Answer 10

1. Measure sensitivity to range of one stimulus property (e.g.
   orientation), which can be taken as your ‘baseline’ response
   • Determine contrast threshold by decreasing intensity of
   grating until person can just see it
   • Calculate the contrast sensitivity (sensitivity = 1/threshold)
2. Adapt neurons with extended exposures of stimuli that have
   the property being tested
3. Remeasure the sensitivity to range of that same stimulus
   property

Question 11

Describe selective rearing

Answer 11

raising animals in environments that contain only
certain types of stimuli (while depriving exposure to other kinds)

Question 12

Describe Blakemore and Cooper study

Answer 12

Blakemore and Cooper (1970) manipulated whether kittens were raised in

environments with (only) either horizontal or vertical lines
• Kittens raised in an environment of all vertical lines couldn’t perceive
horizontals, and vice versa

Question 13

Describe lesioning studies

Answer 13

An animal is trained to indicate perceptual capacities
2. A specific part of the brain is removed or destroyed
3. The animal is retrained to determine which perceptual abilities remain
4. The results reveal which portions of the brain are responsible for specific
behaviours

Question 14

Describe the object discrimination problem

Answer 14

Monkey is trained to look in the food well
under a specific object

Question 15

Describe landmark discrimination problem

Answer 15

Monkey is trained to look in the food
well next to a specific object

Question 16

Describe Ungerleider and Mishkin study

Answer 16

using ablation, part of the parietal
lobe was removed from half the monkeys and part of the
temporal lobe was removed from the other half
• Retesting the monkeys showed that:
• Removal of temporal lobe tissue resulted in problems
with the object discrimination task (implicating the
what pathway, or ventral stream), though not the LD
task
• Removal of parietal lobe tissue resulted in problems
with the landmark discrimination task (implicating the
where pathway, or dorsal stream), though not the OD
task

Question 17

What is a double dissociation?

Answer 17

two functions
that involve different mechanisms and operate
independently

Question 18

Describe commonalities between ventral and dorsal pathways

Answer 18

• Originate in the retina and continue
through two different types of ganglion
cells in the LGN (magnocellular and
parvocellular, parvocellular neurons
are more sensitive to colour and fine
detail)

• Have some interconnections

• Receive feedback from higher
brain areas