1. Ψ
Sensation
&
Perception

2. Psychophysical Methods Electrophysiological MethodsΨ
-Discussion Section-
Session 2 – Methods
Psychophysical Methods
Electrophysiological Methods

3. Presentation 1: Human orientation discrimination tested with long stimuli (1984) presented by Michelle Arroyo
Presentation 2: Oblique effect: A neural basis in the vsiual cortex (2003) presented by Hillary Schiff

4. BACKGROUND

5. The concept of the receptive field
A receptive field is that part of the visual field that a neuron responds to by changing it’s firing rate if a stimulus is in it.
It’s part of the external world but a property of a neuron.

6. Model: RF Overlap Convergence Eccentricity World PR in retina
Neuronal layer 1
Neuronal layer 2

7. The receptive field map
Size scales with
Eccentricity
Cortical hierarchy
1 degree of visual angle = roughly 1.5 * the area of the thumbnail at arm’s length

8. Both papers today deal with V1
V1 in the monkey = Area 17 in Cats/People
=Striate cortex (Cytoarchitectonically)
=Primary visual cortex (Functionally)
RF sizes small. Generally smaller than 1 degree. Foveally smaller than ¼ degree.
Tuned (Differentially Sensitive) for 6 qualities in the receptive field, including Spatial Frequency and Orientation.

9. Spatial Frequency in cycles per degree of visual angle
High Contrast Low
Low Spatial Frequency High

10. Orientation
0, 180
45, 225
90, 270
135, 315

11. (Orientation) Tuning curves
Firing rate in Hz
Orientation in degrees
Tuning width in degrees
Watkins & Berkley (1974)

12. Length summation in V1 RF

13. Perception and Memory…
Introducing memory
Out of the pan into the fire…
On the next slide, memorize one of the cards but keep it a secret.

16. Now for the real thing…