Chapter 7: The Network Approach Flashcards
What is the Artificial Neural Network (ANN)?
A computer simulation of how populations of real neurons might perform some task
What is the Input Layer?
The first layer of the three-layer network that receives stimulus input and where stimulus is represented
What is the Output Layer?
The third layer of a three-layer network. It generates a representation of a response based on inputs from hidden layer.
What is the Hidden Layer?
A second layer of a three-layer network. This is where the input layer sends its signals. It performs intermediary processing.
What problems are ANNs good at?
- Problems of Classification (pattern recognition, concept formation)
- Control Problems (programming of robot movements)
- Problems of Constraint Satisfaction (for ill-defined problems)
What are Serial Processors?
Processors that perform one computation at a time. The result of a particular computing unit can then serve as the input to a second computation. (e.g.: traditional PCs)
What is Parallel Distributed Processing?
E.g. brain or ANNs. Large numbers of computing units perform their calculations in parallel.
What is the Knowledge-Based Approach to problem-solving?
Conceptualizing the problem and its solution in terms of symbolic representations and transformations of these symbolic representations.
What is the Behaviour-Based Approach to problem-solving?
Leaving the computational details up to the network itself and not paying much attention to symbolic representations or rules
What is a Distributed Representation?
Mental representations as patterns of activation among the network’s elements.
What is a Local Representation?
Representing concepts via activity of a single node
What do nodes represent?
Neurons or basic computing units
What do links represent?
Connections between nodes
When does a node fire?
When the input is greater than or equal to the threshold value.
What do weights specify?
They specify the strength of the links between the nodes
What is the Basis function?
It specifies the amount of stimulation a given node receives. It sums up all of the inputs the node receives multiplied by the weights associated with the connection between processing units
What is the Activation function?
It maps the strength of the inputs a node receives onto its output.
What did McCullosh and Walter Pitts propose?
They were the first researchers to propose how biological networks might function. They assumed that each neuron had a binary output (sends out a signal or not) and whether or not a neuron would fire was determined by a threshold value.
What is a Cell Assembly?
A small group of neurons that repeatedly stimulate each other.
What is a Phase Sequence?
A group of connected cell assemblies that fire synchronously or nearly synchronously
What are Perceptrons created by Rosenblatt on 1958?
Perceptrons are neural nets designed to detect and recognize, store and use patterned information. They can learn from experience.
What is the Error signal?
The difference between the actual and desired output.
Describe the Generalized Delta Rule learning model (also known as back-propagation)
The network uses the error signal to modify the weights of the links. The modified weights allow the network to generate a response that is closer to the desired one. After repeated presentations of the stimulus in the presence of feedback, the network is able to produce the target response.
What are three basic types of Network Dynamics?
Wh1. Convergent (a significant amount of activity at first which then slows down)
- Oscillatory (The weighs fluctuate periodically)
- Chaotic (The network’s activity varies in a chaotic fashion)