How Does the Human Brain Work?
Start here: Explore the primary parts of the brain and how it works at the cellular level.
How Do We Study the Brain?
Neuroscience is the study of the brain and the nervous system. Learn about the varied organisms, tools, and technologies scientists and engineers use to answer questions about the brain.
How Do Neurons Work and Change Over Time?
The human brain contains approximately 86 billion neurons with trillions of connections among them. Find out how they work together to shape learning, memory, and behavior.
Where Do Feelings and Emotions Come From?
As conscious humans, we label and define many of the emotions we are aware of experiencing. But emotions also operate on a subconscious level. Learn how neuroscientists approach the study of emotions in a video featuring Caltech researchers.
Where Does Consciousness Come From?
Neuroscientists and philosophers alike continue to work toward a more comprehensive understanding of how the brain gives rise to our subjective experiences. Explore the open question of how consciousness and the brain are connected.
How Can AI Advance Understanding of the Brain?
The fields of artificial intelligence (AI) and neuroscience are closely intertwined. AI was inspired by the human brain, and, in turn, AI can help us better understand the brain's complex inner workings.
Ask a Caltech Expert
Dive deeper into questions of neuroscience. How do brain–machine interfaces work? What happens in the brain while we sleep? Find answers from Caltech researchers.
Terms to Know
The amygdala is a small almond-shaped structure located deep within the temporal lobes of the brain. (Its name comes from the Greek word for almond.) The amygdala is involved in many aspects of emotional processing and regulation, particularly fear and anxiety. It receives input from sensory systems, such as those that control vision and hearing, and sends output to various regions of the brain to coordinate reactions to danger and other emotional triggers.
An axon is a long, thin fiber that extends from a nerve cell, or neuron, and carries electrical signals away from the cell to other neurons, muscles, or glands.
The basal ganglia are a group of structures deep within the brain that are involved in movement and also play a role in procedural learning, habit formation, reward processing, and emotional processing. Neurological and psychiatric disorders such as Parkinson's disease, Huntington's disease, Tourette's syndrome, obsessive-compulsive disorder, and addiction have been associated with problems in the basal ganglia. The study of these structures is an active area of neuroscience research.
Brain mapping is the process of creating a detailed map or model of the structure and function of the brain, and is often used to understand, identify, and treat neurological disorders. Structural methods focus on the brain's anatomy and use imaging techniques such as magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI). Functional methods seek to understand areas of the brain involved in functions such as speech or sight. These use techniques such as functional magnetic resonance imaging (fMRI), positron emission tomography (PET), and electroencephalography (EEG) to identify parts of the brain that are activated during specific tasks.
The central nervous system is made up of the brain and spinal cord.
The cerebral cortex is the outermost layer of the brain and is made up of gray matter. It is divided into two hemispheres, left and right, which are connected by a thick bundle of nerves called the corpus callosum. The cerebral cortex is involved in a wide range of processes—including sensation, attention, memory, thought, and language—with different regions, or lobes, specializing in different functions. Problems in the cerebral cortex have been linked to disorders such as Alzheimer's disease and schizophrenia.
A connectome is a map, or diagram, of all the connections among nerve cells in the brain. The term is inspired by the word "genome," which describes an organism's complete genetic information.
Dendrites are branch-like projections that extend from nerve cells, or neurons. They receive input from other neurons and transmit it to the cell body.
An EEG, or electroencephalogram, is a test that measures the brain's electrical activity using sensors attached to the scalp. EEGs can be used to diagnose and monitor disorders such as epilepsy.
Functional magnetic resonance imaging (fMRI) is an imaging technique that indicates brain activity, in part by measuring and comparing blood flow in different areas. fMRI is used to understand how the brain works as well as in preparing for brain surgeries.
The hippocampus is a small seahorse-shaped structure in the brain's temporal lobe that plays a major role in memory, receiving input from sensory systems and other brain regions, and sending output to the cerebral cortex to coordinate memory formation and retrieval. The hippocampus is also involved in processes including spatial navigation, decision-making, and learning. Problems with the hippocampus are linked to disorders including Alzheimer's disease, epilepsy, and depression.
Lateralization describes how each side, or hemisphere, of the brain tends to dominate or specialize when it comes to different functions, such as speech and language (left hemisphere for most humans).
Magnetic resonance imaging, or MRI, is a technique that creates detailed images of organs and tissues inside the body using powerful magnets and radio waves.
Myelin is a fatty substance that covers the axons of nerve cells. This myelin sheath acts as an insulator and allows for faster and more efficient transmission of electrical signals along the axon. In people with multiple sclerosis (MS), the immune system attacks the myelin sheath causing loss and damage, or demyelination, which results in impaired nerve function and symptoms such as weakness, numbness, and cognitive difficulties.
Neurons, or nerve cells, are the fundamental units of the nervous system. While neurons vary in size and shape, they include three main parts: branch-like dendrites, which receive signals from other cells; a soma, or cell body, which integrates those signals; and an axon, which transmits signals. Scientists estimate there are 86 billion neurons in the human brain.
Neuroplasticity refers to the brain's ability to change and adapt in response to new experiences and other stimuli. It is an important process that shapes learning, memory, and behavior.
Neurotransmitters are chemicals that nerve cells use to send signals across a synapse to other nerve cells, muscles, and glands. They convey messages that control breathing, digestion, sensation, emotions, learning, and much more. Serotonin, for example is a neurotransmitter with a role in mood.
The peripheral nervous system includes the network of nerves that runs throughout the body, carrying information to and from the brain and spinal cord (which make up the central nervous system).
Synapses are tiny gaps between nerve cells, where nerve cells communicate with one another via neurotransmitters. Information is sent across synapses to other nerve cells or to muscles or glands.
