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What is deep learning in AI?

Inspired by the human brain, deep learning is a powerful branch of artificial intelligence (AI) that is reshaping the future of how machines interact with the world. An advanced type of traditional machine learning, the deep learning model uses artificial neural networks to process and learn from large amounts of complex data.

The output of these deep artificial neural networks are the backbone of real-world deep learning applications, such as virtual assistants, speech recognition software, autonomous cars, cancer detection, and more. The emergence of deep learning is primarily due to its ability to automatically perform tasks that would otherwise require complex human analysis and/or a significant amount of time.

This article focuses on what deep learning is, how the layers in neural networks process and refine data, and how deep learning drives real-life applications and services.

Table of Contents:

What's the difference between deep learning, machine learning, and AI?

In addition to deep learning, you've likely heard the terms AI and machine learning in news reports, social media, and discussions with friends and family. However, they are quite different despite being closely related and often intertwined.

Think of AI, machine learning, and deep learning as layers in an onion. AI is the outer layer, covering everything from smart robot vacuums to your phone's voice assistant. The middle layer is machine learning, which teaches computers to learn from structured data. The innermost layer is deep learning, which teaches a computer how to learn from unorganized, unclassified, and unstructured data. Both machine learning and deep learning fit under the category of AI, but cover narrower and increasingly more specialized sets of applications.

Artificial intelligence

AI includes a variety of approaches and technologies. It's the broadest concept that refers to machines or systems being able to perform tasks that typically require human intelligence. These tasks include problem-solving, learning, planning, linguistic understanding, and perception. AI systems use a variety of algorithms, from simple rule-based algorithms to complex machine learning algorithms, to complete these tasks.

Deep learning is a branch of machine learning nested within AI.

Machine learning

A subset of AI, machine learning (ML) uses structured, labeled data to make predictions. ML engines can use unstructured data at the outset, but that data must always be preprocessed (structured) before entering the system. ML excels at spam detection, credit scoring, and recommendations.

Deep learning

Deep learning does not typically need human intervention for feature extraction and decision-making. Instead, a deep learning model processes unstructured data with a hierarchical neural network of more than three layers, automating feature extraction, pattern recognition, and decision-making. These layers also include hidden layers, which optimize predictions and improve accuracy of outputs.

How is deep learning similar to the human brain?

Both deep neural networks and the brain are composed of neurons and connections. In the brain, these are biological neurons and synapses, while in artificial neural networks, they are artificial neurons (mathematical functions) and weights (the strength of connections).

Layered processing: The brain has different regions and layers responsible for different types of processing, and deep learning systems have layered architectures where data is processed sequentially through these layers. In deep learning, the hidden layers do most of the heavy lifting.

Pattern recognition: Both are excellent at complex pattern recognition and classification tasks, such as learning to recognize and respond to patterns in the input they receive.

How is deep learning different from the brain?

The human brain is far more complex and efficient than any artificial neural network because it can handle various tasks with less energy and more adaptability.

Consciousness and cognition: The human brain possesses consciousness and cognitive abilities that artificial neural networks do not. The brain's understanding, reasoning, and emotional responses are far beyond the capabilities of current artificial systems.

Learning requirements: Humans only need a few examples to learn and generalize knowledge, whereas deep learning neural networks need a tremendous amount of data to learn.

Biological versus artificial: Neurons in the brain are biological cells operating through electrochemical processes, while artificial neurons in deep learning are mathematical functions computed digitally.

How artificial neural networks in deep learning models work

Let's look at the earlier illustration that showed the relationship between AI, machine learning, and deep learning. Adding data science at the top and neural networks at the bottom expands our perspective of how these pieces work together. See illustration below.

What is the role of algorithms in artificial deep neural networks?

The artificial neural network is the structure used in deep learning. It consists of layers of interconnected nodes (mimicking neurons in the brain) that process and transform input data. The algorithm used in deep learning refers to the entire process and set of rules the artificial neural network follows to learn from data. This includes how the network's weights are initialized, how data is fed into the network, how it adjusts its weights during training (the learning process), and how it makes predictions or decisions.

The most crucial part of the algorithm in deep learning often involves backpropagation and an optimization technique like gradient descent. These methods are used to train the artificial neural network by adjusting its weights based on the errors in its predictions.

Having outlined the structure of neural networks, we now proceed to a crucial aspect: training these deep learning models.

The critical role of layers in neural networks in deep learning models

As outlined above, neural networks are at the heart of deep learning and function through a series of layers. Each layer has a specific role in processing and interpreting data. Let's explore how these layers, which include input, hidden, and output layers, work together to enable a neural network to make predictions or decisions based on the information it receives.

Deep learning in neural networks.

Input layer: The process starts with the input layer, where the neural network receives its data in numerical form so it can communicate digitally.

Hidden layers: After the input layer, the data moves through three or more hidden layers. These layers are where the main calculations happen:

  • Weights and biases: Each neuron in these layers has weights and biases. Weights modify the importance of the input data, and biases shift the results up or down. The network adjusts weights and biases as it learns.
  • Activation functions: In each layer, activation functions act like gatekeepers. They decide how much information from each neuron should be passed on to the next layer. This decision is based on the strength of the signals the neurons receive.

Output layer: This is the final layer. For example, in a task where the network identifies objects in images, this layer shows the network's final decision.

How layers train the deep learning model

The most crucial parts of the deep learning algorithm often involve backpropagation and an optimization technique like gradient descent. These and other methods train the artificial neural network by adjusting weights based on errors and predictions.

Forward propagation: In training, the network takes in data and processes it through each layer. This is forward propagation, where every layer makes predictions based on its current weights, biases, and activation functions.

Backpropagation: After forward propagation, the network uses backpropagation. This is where the network looks at its errors and adjusts its weights and biases to improve. It uses a loss function to measure errors and an optimization algorithm to reduce these errors.

Iterative learning: The network repeats this process many times, improving with each cycle. Ideally, after many iterations, the network's weights and biases will reach values that allow it to make accurate predictions or decisions most of the time.

Gradient descent: In machine learning, gradient descent is used to improve a model by gradually adjusting its settings to reduce errors, similar to how you'd carefully adjust knobs to get the most precise picture on an old-fashioned TV.

Deep learning in real-world applications

Deep learning's ability to process and learn from large datasets makes it ideal for complex tasks that require pattern recognition, decision-making, and prediction. Below are some real-life applications of deep learning.

Computer vision, object detection, and facial recognition software

Deep learning techniques are pivotal in teaching computers to interpret visual data. They power applications like facial recognition systems in security, photo tagging in social media, and medical imaging for disease diagnosis.

Natural language processing (NLP) systems

In language processing, deep learning enables machines to understand human language. Deep learning methods are used for speech recognition, translation services, sentiment analysis, chatbots, and virtual assistants.

Autonomous vehicles

Self-driving cars use deep learning for object detection, collision avoidance, and navigation. They process vast amounts of data from sensors and cameras placed in various locations so they can understand their surroundings and make driving decisions.

Speech recognition applications

Applications like voice-to-text and voice-activated systems use deep learning to understand and process human speech. This technology is why virtual assistants and various speech recognition software are so effective.

Recommendation systems

Online streaming entertainment platforms use deep learning to analyze user behavior and preferences to offer personalized content recommendations.

Challenges in deep learning

While powerful, deep learning comes with its own challenges that can be daunting. Understanding these challenges is crucial for grasping the limitations and considerations necessary when working with deep learning models.


Grasping the intricacies of deep neural networks is complex. The way data moves through artificial neurons, layers, and the overall network requires a series of interconnected tasks.

Data requirements

Deep learning models thrive on massive amounts of data. However, having access to such vast datasets is only sometimes feasible. Moreover, even when data is available, not all machines are capable of processing it efficiently, which can be a significant hurdle.

Computational demands

The computing power required for deep learning is substantial. These models often rely on graphical processing units (GPUs), which are more powerful and have thousands of cores compared to the standard central processing units (CPUs). This makes deep learning resource-intensive and potentially expensive.

Training time

Training deep neural networks is a time-consuming process. It can take hours, days, or even months, depending on the dataset's size and the network's complexity.

Bias and privacy concerns

As deep learning models learn from data, there's a risk of inheriting biases present in the data, which can deliver an unfair or unethical output. Addressing fairness and privacy concerns are growing focus areas in the field.


At the heart of AI's evolution, deep learning is a testament to progress, offering groundbreaking solutions in pattern recognition and decision-making. However, it also brings to light critical considerations like data integrity, computational demands, and the ethical implications of machine learning, emphasizing the need for mindful advancement in the field.


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