Levels of Neuroscience
Taken from the fourth edition of Neuroscience Exploring the Brain. [1]
History has clearly shown that understanding how the brain works is a big challenge. To reduce the complexity of the problem, neuroscientists break it into smaller pieces for systematic experimental analysis. This is called the reductionist approach. The size of the unit of study defines what is often called the level of analysis. In ascending order of complexity, these levels are molecular, cellular, systems, behavioral, and cognitive.
Molecular Neuroscience
The brain has been called the most complex piece of matter in the universe. Brain matter consists of a fantastic variety of molecules, many of which are unique to the nervous system. These different molecules play many different roles that are crucial for brain function: messengers that allow neurons to communicate with one another, sentries that control what materials can enter or leave neurons, conductors that orchestrate neuron growth, archivists of past experiences. The study of the brain at this most elementary level is called molecular neuroscience.
Cellular Neuroscience
The next level of analysis is cellular neuroscience, which focuses on studying how all those molecules work together to give neurons their special properties. Among the questions asked at this level are: How many different types of neurons are there, and how do they differ in function? How do neurons influence other neurons? How do neurons become “wired together” during fetal development? How do neurons perform computations?
The human brain has some 8.6 x 10^10 = eighty six billion neurons… [2]
Systems Neuroscience
Constellations of neurons form complex circuits that perform a common function, such as vision or voluntary movement. Thus, we can speak of the “visual system” and the “motor system,” each of which has its own distinct circuitry within the brain. At this level of analysis, called systems neuroscience, neuroscientists study how different neural circuits analyze sensory information, form perceptions of the external world, make decisions, and execute movements.
Behavioral Neuroscience
How do neural systems work together to produce integrated behaviors? For example, are different forms of memory accounted for by different systems? Where in the brain do “mind-altering” drugs act, and what is the normal contribution of these systems to the regulation of mood and behavior? What neural systems account for gender-specific behaviors? Where are dreams created and what do they reveal? These questions are studied in behavioral neuroscience.
Cognitive Neuroscience
Perhaps the greatest challenge of neuroscience is understanding the neural mechanisms responsible for the higher levels of human mental activity, such as self-awareness, imagination, and language. Research at this level, called cognitive neuroscience, studies how the activity of the brain creates the mind.
Sources
[1] Neuroscience Exploring the Brain — Bear, Mark F.
[2] The human brain has some 8.6 x 1010 (eighty six billion) neurons.
