Lecture 5 Flashcards
What is a feature detector?
Neurons that fire in response to specific features of a stimulus
What are the 3 types of feature detectors?
Simple cortical cell
• Complex cortical cell
• End-stopped cortical cell
What are orientation tuning curves?
plot the response of a simple cortical cell to line
stimuli of varying orientations
Describe complex cortical cells
respond best to movement across the receptive field
of particularly oriented bar
Describe Hubel and Wiesel study
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
Describe absolute threshold
smallest amount
of energy needed to detect a stimulus
Describe the method of limits
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
Describe selective adaptation
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
What stimuli are used for selective adaptation?
gratings and are
made of alternating light and dark bars
Describe the selective adaptation experiment
- 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) - Adapt neurons with extended exposures of stimuli that have
the property being tested - Remeasure the sensitivity to range of that same stimulus
property
Describe selective rearing
raising animals in environments that contain only
certain types of stimuli (while depriving exposure to other kinds)
Describe Blakemore and Cooper study
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
Describe lesioning studies
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
Describe the object discrimination problem
Monkey is trained to look in the food well
under a specific object
Describe landmark discrimination problem
Monkey is trained to look in the food
well next to a specific object
Describe Ungerleider and Mishkin study
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
What is a double dissociation?
two functions
that involve different mechanisms and operate
independently
Describe commonalities between ventral and dorsal pathways
• 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
