Which two techniques are commonly used by researchers to take pictures of individuals brains and compare their anatomy and activity?

lesion: An injury, area of disease, or surgical incision to body tissue. Much of what we know about the functions of brain structures or pathways comes from lesion mapping studies, where scientists observe the behavior of people with an injury to a distinct area of the brain or analyze the behavior of a laboratory animal resulting from a lesion made in the brain.

limbic system: A group of evolutionarily older brain structures that encircle the top of the brain stem. The limbic structures play complex roles in emotions, instincts, and appetitive behaviors.

long term potentiation (LTP): The persistent strengthening of a synapse with increased use, thought to underlie learning and memory.

Lou Gehrig’s disease: see amyotrophic lateral sclerosis (ALS)

M

machine learning: Also referred to as deep learning, machine learning is a type of artificial intelligence algorithm that can learn rules or identify diagnostic criteria from immense data sets of brain imaging or genetic information. These algorithms are becoming more prevalent in scientific research—and are also starting to be incorporated into translational neuroscience research and medical practice.

magnetic resonance imaging (MRI): A non-invasive imaging technology, often used for brain imaging. An MRI scanner includes intensely powerful magnets, typically 10,000 to 40,000 times as strong as the Earth’s magnetic field. These magnets, combined with coils that send electromagnetic pulses into the scanned tissue, induce radio-frequency signals from individual hydrogen atoms within the tissue. The scanner records and processes these signals to create an image of the scanned tissue. MRI scans can depict high resolution images of the entire brain, allowing clinicians to determine if the brain tissue visualized is normal, abnormal, or damaged due to a neurological disorder or trauma. MRI technology has also been adapted to measure brain activity with functional MRI methods.

manic-depressive disorder: See bipolar disorder.

medulla oblongata: The lower part of the brain stem, responsible for life-regulating functions like breathing and heart rate.

melatonin: A hormone that is secreted by the pineal gland in the brain in response to the daily light-dark cycle, influencing the body’s sleep-wake cycle.

memory: The encoding and storage of information, in a way that allows it to be retrieved later. In the brain, memory involves integrated systems of neurons in diverse brain areas, each of which handles individual memory-related tasks. Memory can be categorized into two distinct types, each with its own corresponding brain areas. Memory about people, places, and things that one has experienced directly or otherwise learned about is referred to as explicit or declarative memory and is highly dependent upon the hippocampus and temporal lobe. Memory about motor skills and perceptual strategies is known as implicit or procedural memory and involves the cerebellum, the amygdala, and specific pathways related to the particular skill (e.g., riding a bicycle would involve the motor cortex).

mental health: Referring to one’s psychological, emotional, and social well-being.

mesolimbic circuit: See reward/reinforcement brain network.

mesolimbic pathway: A specialized brain circuit implicated in the processing of risk and reward information.

metabolize: To break down or build up biochemical elements in the body, effecting a change in body tissue. For example, neurons and other brain cells metabolize glucose, a blood sugar, to derive energy for transmitting nerve impulses.

microbiota: The community of various microorganisms found in the digestive tract. Scientists are now learning that microbes found in the microbiota can influence brain development, mood, and behavior.

microglia: A small, specialized glial cell that operates as the first line of immune defense in the central nervous system.

midbrain: Also referred to as the mesencephalon, the midbrain is a small part of the brain stem that plays an important role in movement as well as auditory and visual processing.

mindfulness: The ability to be present and aware of the environment and our behavior within it.

minimally conscious: A state of altered consciousness, often caused by stroke, head injury, or loss of blood flow to the brain, in which an individual maintains partial conscious awareness, but may have great difficulty in communicating with, or understanding, other people.

molecular biology: The study of the structure and function of cells at the molecular level and how these molecules influence behavior and disease processes. Molecular biology emerged as a scientific discipline only in the 1970s, with advances in laboratory technologies for isolating and characterizing DNA, RNA, proteins, and other small biological entities.

mood: A state of mind or feeling. In neuroscience, depression and anxiety are considered mood disorders, for example.

motor cortex: The part of the brain’s cerebrum, just to the front of the central sulcus in the frontal lobe, that is involved in movement and muscle coordination. Scientists have identified specific spots in the motor cortex that control movement in specific parts of the body, the so-called “motor map.”

multiple sclerosis: A progressive neurodegenerative disease involving damage to the protective myelin sheaths of nerve cells in the brain and spinal cord. Symptoms include impaired movement, pain, and fatigue.

mutation: A permanent structural alteration to DNA that modifies its previous nucleotide sequence. In most cases, DNA changes either have no effect or cause harm, but occasionally a mutation improves an organism’s chance of surviving and procreating.

myelin: The fatty substance that encases most nerve cell axons, helping to insulate and protect the nerve fiber and effectively speeding up the transmission of nerve impulses.

N

narcotic: A synthetic chemical compound that mimics the action of the body’s natural endorphins—hormones secreted to counteract pain. Narcotic drugs have a valid and useful role in the management of pain but may lead to physical dependence in susceptible individuals if used for long periods.

nerve growth factor: Also referred to as a neurotrophic factor, this special protein helps regulate the growth and survival of nerve cells. One of the most well-known of these is brain-derived neurotrophic factor (BDNF).

nerve cell: See neuron.

nerve impulse: Also referred to as a nerve signal, the way that a neuron communicates with other cells by transmitting an electrochemical signal down the length of the axon.

nervous system: The system in the body that processes and transmits signals from the brain to the rest of the body to facilitate movement and behavior. It consists of two parts, the central nervous system, or the brain and spinal cord, and the peripheral nervous system, the nerves that branch off from the spinal cord extending throughout the rest of the body.

neural chimera: A research model where human stem cells are transplanted into an animal embryo to follow the genetic, molecular, and functional processes of brain cells as they grow.

neural implant (brain implant): A device that connects the brain and technological devices to record, translate, or modify brain activity.

neural induction: A developmental process where ectodermal cells “decide” to form the neural plate, the basis of what will eventually become the organism’s nervous system.

neural transplant: A research model where a few human cells are transplanted into the adult brains of animals to study how those cells respond to environmental stimuli.

neuroaesthetics: A field within cognitive neuroscience that examines the neural underpinnings of what humans find visually appealing or beautiful.

neurodiversity: The variations that exist in the human brain leading to differences in learning, mood, and emotion, as well as mental functions and social behaviors.

neuroeconomics: An interdisciplinary field of study that uses neuroscientific research to help explain human decision-making behavior.

neurodegenerative diseases: Diseases characterized by the progressive deterioration and death of nerve cells (neurodegeneration), typically originating in one area of the brain and spreading to other connected areas. Neurodegenerative diseases include amyotrophic lateral sclerosis (ALS), Huntington’s disease, Alzheimer’s disease, frontotemporal degeneration, and Parkinson’s disease.

neurodevelopmental disorder: Disorders or conditions arising from impairments during the development and maturation of the brain and/or nervous system. Neurodevelopmental disorders include schizophrenia and autism spectrum disorder.

neuroeducation: Sometimes referred to as educational neuroscience, this collaborative, interdisciplinary field of study uses findings in cognitive neuroscience to inform teaching and other educational practices.

neuroethics: An interdisciplinary field of study that addresses the ethical implications of our increased ability to understand and change the brain. Enhanced cognitive performance, life extension, the use of neuroscience in marketing, and many other issues are included in this ongoing social-scientific debate.

neurogenesis: The production of new, maturing neurons by neural stem and progenitor cells. Rapid and widespread neurogenesis obviously occurs in the fetal brain in humans and other animals, but neuroscientists long believed that neurogenesis essentially does not occur in the adult human brain. However, over the past two decades, research has shown that it does in fact occur in the dentate gyrus of the hippocampus and possibly other brain regions. This “adult neurogenesis” appears to be vital for normal learning and memory, and may help protect the brain against stress and depression.

neuroimaging: Different forms of medical imaging, including positron emission tomography (PET) and magnetic resonance imaging (MRI), that allow researchers to study the structure and function of the brain and nervous system.

neuroimmunology: A complex field in biomedical research, which focuses on the brain, the immune system, and their interactions. Neuroimmunology holds the potential for conquering ills as diverse as spinal cord injury, multiple sclerosis, and bodily reactions to bacteria or viruses, both naturally occurring and intentionally inflicted. In some circumstances, an abnormal neuroimmune response can damage brain tissue.

neurolaw: A field of study that applies neuroscientific findings to legal rules and standards.

neuromarketing: The measurement of physiological or neural information to gain insights into and influence consumer motivations and behavior.

neurophilosophy: An interdisciplinary field of study that investigates the relevance of neuroscientific discoveries to philosophical theories and questions.

neuroplasticity: Also referred to as brain plasticity or neural plasticity, this is the ability of the brain to change throughout the lifespan, forming new synapses and neural connections in response to the environment.

neurotypical: Often used to describe people who are not on the autism spectrum, this term is meant to characterize people whose brain functions, processing capabilities, and behaviors fall into a range that is common for the majority of humans.

neuron: A nerve cell. The basic unit of the central nervous system, the neuron is responsible for the transmission of nerve impulses. Unlike any other cell in the body, a neuron consists of a central cell body as well as several threadlike “arms” called axons and dendrites, which transmit nerve impulses. Scientists estimate that there are approximately 86 billion neurons in the human brain.

neuroscience: The study of the brain and nervous system, including their structure, function, and disorders. Neuroscience as an organized discipline gained great prominence in the latter part of the 20th century.

neurotransmitter: A chemical that acts as a messenger between neurons and is released into the synaptic cleft when a nerve impulse reaches the end of an axon. Several dozen neurotransmitters have been identified in the brain so far, each with specific, often complex roles in brain function and human behavior.

neurotrophic factor: See nerve growth factor.

non-maleficence: One of the three Belmont principles, the obligation of researchers to not harm patients or study participants. The phrase, “First, do no harm,” an oath spoken by doctors when they graduate from medical school, illustrates this principle.

nootropics: Drugs or supplements that are marketed as ways to improve cognitive functions like memory, attention, or creativity.

nucleotide: Sometimes referred to as a nucleic acid, these are the biological building blocks of DNA.

nucleotide sequence: A specific and ordered array of nucleotides that make up a specific genetic variant or allele.

nucleus accumbens: Part of the brain’s reward circuitry, or mesolimbic pathway, this small region in the midbrain releases dopamine in response to rewarding experiences.

nurture: A popular term for the influence of environmental factors on human development, such as the experiences one is exposed to in early life. The term is often used in the context of “nature versus nurture,” which relates to the interplay of “nature” (genetic or inherited, predetermined influences) and environmental, or experiential, forces.