Basics of Artificial Neural Networks

Artificial Neural Networks (ANN) are an integral part of the field of deep learning. They are a computational model inspired by the human brain's structure and function, aiming to replicate the way neurons transmit information. ANN's potential lies in its ability to learn and make predictions by training on large amounts of data.

Structure of an Artificial Neural Network

An ANN consists of interconnected layers of nodes, commonly called neurons, arranged in a series of hidden layers between the input and output layers. Each neuron receives inputs, processes them, and forwards the result to the next layer until the final output is produced.

Input Layer

The input layer is the first layer of an ANN, taking the initial data as input. It has one neuron for each feature in the input data. The values from the input layer are then passed to the next layer.

Hidden Layers

Hidden layers are intermediaries between the input and output layers, performing complex computations. They consist of multiple neurons and can vary in number depending on the complexity of the problem. Each neuron takes inputs from the previous layer and applies a non-linear activation function to generate an output.

Output Layer

The output layer is the final layer of an ANN, producing the desired output based on the received inputs. It can have one or more neurons, depending on the nature of the problem. The activation function used in the output layer depends on the type of task: regression, binary classification, or multi-class classification.

Activation Functions

Activation functions introduce non-linearities to the ANN, enabling it to learn complex patterns in the data. Some common activation functions include:

  1. Sigmoid: Transforms the input into a range between 0 and 1, suitable for binary classification tasks as it models probabilities.
  2. ReLU (Rectified Linear Unit): Filters out negative values and keeps positive values intact, accelerating the learning process while being computationally efficient.
  3. Tanh: Similar to the sigmoid function, but the range is between -1 and 1, enabling better representation of negative inputs.
  4. Softmax: Applied in the output layer for multi-class classification problems, it converts the inputs into probability distributions, summing up to 1.

Learning in Artificial Neural Networks

Training an ANN involves iteratively adjusting the weights associated with each connection between neurons. This adjustment is made based on the error calculated by comparing the network's prediction with the actual output. The purpose of training is to minimize this error through a process called backpropagation.

Backpropagation calculates the gradient of the error with respect to each weight, enabling the network to update and improve its predictions. The optimization algorithm used, such as Stochastic Gradient Descent (SGD), adjusts the weights according to the calculated gradient, gradually reducing the error.


Artificial Neural Networks form the foundation of deep learning, allowing machines to learn from data just like the human brain. With their interconnected layers and diverse activation functions, ANNs enable complex computations and predictions. By iteratively adjusting the weights throughout the training process, ANNs continuously improve their accuracy and expand their capabilities. Understanding the basics of ANNs is crucial for anyone interested in embarking on the exciting journey of deep learning.

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