1. Psychophysical and Physiological Evidence for Viewer-centered Object Representations in the Primate
N.K. Logothetis and J. Pauls
Cerebral Cortex (1995)

2. Background Theories of object representations Face selective cells
Input representation
Image
Match ?
Transformations
Recognition
Stored memory representations
Theories of object representations
3D models (Marr, Biederman)
View dependent 2D templates (Basri & Ullman, Poggio)
Face selective cells
Found in STS
Mostly view dependent

3. Methods
Trained three juvenile rhesus macaques on an object recognition task
Performed psychophysical tests after training
Recorded from the upper bank of the anterior medial temporal sulcus (AMTS)
Stimuli:
Computer generated ‘wire like’ and ‘amoeboid’ objects

4. Training
Began with training monkeys to recognize a single view of an object presented sequentially among distractor objects
Slowly increased rotations up to + or – 90o before training with a new object
Feedback with juice reward

5. Testing

6. Recordings
Recorded from 773 neurons in AMTS

7. Findings—psychophysical
Recognition performance fell off sharply when object rotated more than 30-40o beyond training view
Both for wire and amoeboid objects

8. Findings—psychophysical
Interpolation with wire objects
Monkeys could interpolate between two training views up to 120o apart
Three to five views allowed monkey to generalize to entire ‘great circle’

9. Findings—psychophysical
‘Pseudo-mirror symmetrical’ wire objects
Some of the wire objects have mirror symmetrical 0o and 180o views due to lack of self-occlusion

10. Findings—psychophysical
Viewpoint invariance for ‘basic’ objects among different class distractors

11. Findings—physiological
View specific, object specific cells (71 of 773)
Cell responses to distractor views
Cell responses to target views

12. Findings—physiological
View invariant, object specific cells (8 of 773)

13. Findings—physiological

14. Findings—physiological
Multiple cells tuned to different views of the same object

15. Author’s conclusions:
Object recognition depends on training view
A small number of stored views can be used to achieve invariance with wire like objects
Neurons in IT found that respond selectively to learned objects, mostly to specific views
Problems:
Highly unnatural stimuli
View selective neurons used for recognition or after recognition?
Interpolation with self occluded (solid) objects?