Learning in Hierarchical Architectures: from Neuroscience to Derived Kernels

author: Tomaso A. Poggio, McGovern Institute for Brain Research, Massachusetts Institute of Technology, MIT
published: July 30, 2009,   recorded: June 2009,   views: 820
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Slides
0:00 Learning in Hierarchical Architectures: from Neuroscience to Derived Kernels
0:56 Message of today (1)
1:07 Message of today (2)
1:27 Learning in Hierarchical Architectures: from Neuroscience to Derived Kernels
1:28 Today’s supervised learning algorithms: sample complexity problem and shallow architectures
1:43 Supervised learning
3:00 Classical learning theory and Kernel Machines (Regularization in RKHS) (1)
4:52 Classical learning theory and Kernel Machines (Regularization in RKHS) (2)
6:05 Present learning algorithms: “high” sample complexity and shallow architectures
8:04 Visual Cortex: hierarchical architecture, from neuroscience to a class of models
8:34 The Ventral Stream (1)
10:52 The Ventral Stream (2)
11:22 The Ventral Stream (3)
12:10 The Ventral Stream (4)
15:11 The Ventral Stream (6)
16:20 - Missing examples of Freedforward connections only
17:23 The Ventral Stream (7)
18:11 Model of Visual Recognition (millions of units) based on neuroscience of cortex (1)
21:57 Model of Visual Recognition (millions of units) based on neuroscience of cortex (2)
24:43 Two operations, one circuit? (1)
26:14 Instead of Gaussian, normalized dot product
27:03 Two operations, one circuit? (2)
27:09 Learning: supervised and unsupervised (1)
29:16 Learning: supervised and unsupervised (2)
30:57 Physiology, psychophysics, computer vision
31:18 Hierarchical feedforward models of the ventral stream (1)
31:23 Hierarchical feedforward models of the ventral stream (2)
33:20 Rapid Categorization
34:03 Hierarchical feedforward models of the ventral stream (3)
34:46 Hierarchical feedforward models of the ventral stream (4)
35:06 Hierarchical feedforward models of the ventral stream (5)
35:58 Models suggest new architectures for learning
36:04 Hierarchical feedforward models of visual cortex may be wrong
37:40 Derived Kernels
38:09 Plan
38:15 The goal
39:02 The visual cortex model
40:20 An Architecture of Patches
40:53 Images as Functions
41:54 Transformations
42:45 Templates
43:22 Recursive Definition (1)
43:30 Recursive Definition (2)
48:55 Plan
49:00 Invariance
49:33 Examples: Discrimination Results for 1-D strings
50:16 Hierarchy can reduce sample complexity: empirical support
50:55 Invariance
51:12 Examples: Discrimination Results for 1-D strings
51:22 Hierarchy can reduce sample complexity: empirical support
51:39 Summary
54:11 Extensions (video+attention) and limitations of feedforward hierarchical models
54:13 Extension to motion: model of the dorsal stream
56:21 From neuroscience to models: extension to attention (1)
56:31 From neuroscience to models: extension to attention (2)
57:03 From neuroscience to models: extension to attention (3)
57:54 From neuroscience to models: extension to attention (4)
58:24 Limitations of present feedforward hierarchical models
60:46 Collaborators in recent work

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Description

Understanding the processing of information in our cortex is a significant part of understanding how the brain works, arguably one of the greatest problems in science today. In particular, our visual abilities are computationally amazing: computer science is still far from being able to create a vision engine that imitates them. Thus, visual cortex and the problem of the computations it performs may well be a good proxy for the rest of the cortex and for intelligence itself. I will briefly review our work on developing a hierarchical feedforward architecture for object recognition based on the anatomy and the physiology of the primate visual cortex. These architectures compete with state-of-the-art computer vision systems; they mimic human performance on a specific but difficult natural image recognition task. I will sketch current work aimed at extending the model to the recognition of behaviors in time sequences of images and to accounting for attentional effects inhuman vision. I will then describe a new attempt (with S. Smale, L. Rosasco and J. Bouvrie) to develop a mathematics for hierarchical kernel machines centered around the notion of a recursively defined "derived kernel" and directly suggested by the model and the underlying neuroscience of the visual cortex.

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