Issue #2: Shift Invariance. Backprop cannot handle shift invariance (it cannot generalize from 0011, 0110 to 1100) But the cup is on the table whether you see it right in the center or from the corner of your eyes (i.e. in different areas of the retina map)
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memory of a situation
There are two different types of learning
Schafer collateral pathway
1 sec. stimuli
At 100 hz
The activity-dependent tuning of the developing nervous system, as well as post-natal learning and development, do well by following Hebb’s rule.
Explicit Memory in mammals appears to involve LTP in the Hippocampus.
Many computational systems for modeling incorporate versions of Hebb’s rule.
LTP and one-shot memory
Twin requirements of LTP induction:
F = B/N
the point is, with a fan-out of1000,
if we allow 2 intermediate layers,
we can almost always find a path
P = (1-F) **B**K
P = Probability of NO link between X and Y
N = Number of units in a “layer”
B = Number of randomly outgoing units per unit
F = B/N , the branching factor
K = Number of Intermediate layers, 2 in the example
106 107 108
# Paths = (1-Pk-1)*(N/F) = (1-Pk-1)*B
Finding a Connection in Random Networks
For Networks with N nodes and branching factor,
there is a high probability of finding good links.
Recruiting a Connection in Random Networks
Cognition and Language
Neural Net and learning
Tinbergen’s Four Questions
How does it work?
How does it improve fitness?
How does it develop and adapt?
How did it evolve?
~ 4 connections
Artist’s rendition of a typical cell membrane
Gaits of the cat: an informal computational model
O = output layer
What are the drawbacks of each representation?
What happens if you want to represent a group?
How many persons can you represent with n bits? 2^n
What happens if one neuron dies?
How many persons can you represent with n bits? n
On Vo Co
Adapted from Gary Dell, “Producing words from pictures or from other words”
adds additional somatosensory information to
the movement to be imitated
provides an early
description of the action
Parietal mirror neurons (PF)
(inferior parietal lobule)
Frontal mirror neurons (F5) (BA 44)
copies of the motor plans necessary to imitate actions for monitoring purposes
codes the goal of the
action to be imitated
Somatotopy of Action Observation
Buccino et al. Eur J Neurosci 2001
English has 11 basic color terms