What Is a Neural Network? A Simple Explanation

Neural networks are computational models inspired by the human brain's structure and functioning. They consist of layers of interconnected nodes, known as neurons. These networks are used in various machine learning tasks like image recognition, natural language processing, and game playing. 

Machine learning (ML) and artificial intelligence (AI) are closely related to neural networks, as neural networks are a core technology used within many ML and AI systems. 

The rise of AI and ML has introduced a range of new concepts and technologies, with neural networks being a key element of ML programming. In fact, neural networks are often considered the foundation of how machine learning models are designed to "think" and learn from data. But before diving into the intricacies of neural networks, it’s important to first understand the distinction between AI and ML at a high level and how they differ.

What is AI and Gen AI?

Artificial Intelligence (AI) is technology that enables computers and machines to simulate human learning, comprehension, problem solving, decision making, creativity, and autonomy. AI can make recommendations to users and experts based on seeing or identifying objects and responding to human language.

Nowadays, most AI experts deal with “Generative AI” or “Gen AI”. This refers to the ability of AI to create original text, images, videos, or other content from scratch. Gen AI is the focus of most AI news items today due to its impressive outputs based on human language inputs. 

For example, Gen AI image generators such as DALL·E and MidJourney allow users to describe an image and see it come to life; you can type “Cute German Shepherd puppies” and these tools will generate an original picture of German Shepherd puppies. This process uses Gen AI but has been trained to do so using machine learning.

What is Machine Learning?

Machine Learning (ML) sits directly underneath AI. It creates “models” by training an algorithm to make predictions or decisions based on data it has received or processed. A “model” is a program that has been trained on a set of data to recognize patterns or make certain decisions without further human intervention. 

For example, ML can be used to develop a model that predicts future tire prices based on historical trends and external factors. One of the most widely used and powerful types of ML algorithms is the neural network, which mimics the way the human brain processes information.

Now that we understand the role of AI and ML as they relate to neural networks, let’s explore neural networks: their components and functionality.

Structure of a neural network

A neural network consists of several layers:

• Input Layer: Receives data or features, which refer to the individual measurable properties or characteristics of the data used as input. These features are the elements that the neural network uses to learn patterns, make predictions, or classify information. For example, in an image recognition task, the features might include aspects like pixel values, edges, or shapes; in a financial model, features could be variables such as income, expenses, or stock prices

• Hidden Layers: Perform computations and transformations on the input data. A network can have one or more hidden layers, with each layer composed of neurons. This process transforms the data, allowing the network to capture non-linear relationships and deeper patterns that are not immediately obvious in the raw input.

• Output Layer: Produces the final result or prediction, based on the data processed through the previous layers. It directly interacts with the hidden layers and uses their processed information to generate an output that matches the task the network is designed to perform.

Each neuron in a layer is connected to neurons in the subsequent layer, and each connection has a weight that determines the strength of the connection. These weights are adjusted as the network learns. Here is an example of a basic architecture:

How neural networks learn

Neural networks learn through a process called “training”, which involves:

• Forward Propagation: Input data is passed through the network, layer by layer, to generate an output prediction.

• Loss Function: A comparison is made between the network’s prediction and the actual target value (in supervised learning). The difference is called error or loss, calculated using a loss function.

• Backpropagation: To minimize the error, the network adjusts the weights using a technique called backpropagation. In this process, the network computes the gradient (derivative) of the loss function with respect to each weight and updates the weights to reduce the error.

• Optimization: An optimization algorithm like Stochastic Gradient Descent (SGD) is used to adjust the weights iteratively until the network learns to make accurate predictions.

You can see a few of these examples in this diagram:

Types of neural networks

Neural networks come in various forms depending on the problem they’re designed to solve. Some common types of neural networks include:

Feedforward Neural Networks (FNN) 

In FNNs (also known as Artificial Neural Networks (ANN)), information flows only in one direction—from input to output. This is used for tasks like image classification.

Convolutional Neural Networks (CNN)

Primarily used for image and video analysis. They use convolutional layers to detect features like edges and patterns.

Recurrent Neural Networks (RNN)

Designed for sequential data, such as time series or language. They have loops that allow information to persist, making them suitable for tasks like language modeling or speech recognition.

You can see below for more details about each of these:

Neural Networks in AI and ML

Neural networks are a foundational element of AI and machine learning, playing a vital role in enabling machines to learn from data. They are the key drivers behind many intelligent systems. Below are the three main types of learning where neural networks are applied:

Supervised learning

In supervised learning, neural networks map inputs to known outputs (labels). For instance, in image classification, a network learns to identify images by detecting patterns within labeled datasets, such as distinguishing between pictures of cats and dogs.

Unsupervised learning

Neural networks can also learn from unlabeled data. In unsupervised learning, autoencoders, a type of unsupervised neural network, are used for tasks like data compression or anomaly detection, where the system finds patterns and structures in the data independently.

Reinforcement learning

Neural networks are also employed in reinforcement learning, where systems learn by receiving rewards or penalties based on the actions they take in a specific environment, such as training AI to play games or control robots.

In summary, neural networks play a versatile role in machine learning, offering powerful tools to analyze and learn from both labeled and unlabeled data. Their ability to learn from interactions within environments further extends their applicability in areas requiring continuous improvement.

Applications of neural networks

Neural networks have revolutionized a wide range of industries, bringing significant advancements in various fields through their ability to process complex data. Here are some key real-world applications of neural networks:

Image recognition

CNNs can identify objects within images. From facial recognition in security systems to medical imaging in healthcare, CNNs are essential in modern image analysis.

Natural Language Processing (NLP)

Neural networks, particularly transformers, power AI systems that understand and generate human language. These models are used in chatbots, language translation, and sentiment analysis.

Autonomous vehicles

Neural networks help vehicles perceive their environment and make driving decisions, enhancing safety and navigation.

Game playing

AI systems that use neural networks can master complex games like chess or Go by learning strategies through reinforcement learning, showcasing how machines can excel at tasks previously dominated by human intelligence.

Conclusion

In summary, neural networks work by learning patterns from data, adjusting internal parameters, and making predictions. They are key to the functioning of AI systems, enabling machine learning models to achieve high levels of performance in tasks that require pattern recognition, decision-making, and prediction. As we embark on another technological advancement, there is truly no ceiling to the possibilities that neural networks can achieve.