RESEARCH METHODS

Introduction

In experimental research everything depends upon the method; for it is the method that produces the results. A new method to precise results; a vague method has always led only to confused results. (Flourens, 1842/1987, p. 15)

Behavioral Neuroscience Is a Life Science

Visualizing the Human Brain

Computerized Tomography:

Magnetic Resonance Imaging:

Positron Emission Tomography:

Microscopic Approaches to Brain Anatomy

Recording Brain Electrical Activity

The Electroencephalogram:

Magnetic Recording:

Event-Related Potentials:

Microelectrode Recording:

Patch Clamps:

Brain Stimulation

Human Brain Stimulation:

Magnetic Stimulation:

Neurochemical Approaches

Chemical Stimulation:

Microiontophoresis:

Microdialysis:

Brain Lesion Analysis

Summary:

The study of the biological basis of behavior depends critically upon the integrity of the experimental methods by which theoretical ideas are tested. Fortunately, the physical, chemical, and engineering sciences over the past several decades have provided increasingly powerful and precise tools for the study of the nervous system and its functions.

Perhaps the most spectacular of these new methods are the brain-imaging technologies. Computerized tomography utilizes multipass X-ray data to construct images of horizontal slices though the human brain. Magnetic resonance imaging, a more recent development, provides images with higher resolution, in any arbitrary plane, without the use of ionizing radiation. Positron emission tomography permits the imaging of the functional and chemical activity of the nervous system in addition to providing data about brain structure. Microscopic methods and histological procedures clarify the structure and functions of the nervous system at the cellular level. Staining methods are now routinely available to visualize many specific properties of individual neurons, including their metabolic demands and chemical properties.

Recording the electrical activity of the brain and its cells also has contributed greatly to understanding nervous system functions, since neurons process information by altering their electrical potential. The electroencephalogram recorded from the scalp has been particularly useful in the study of sleep and certain neurological disorders, such as epilepsy. Magnetoencephalography may provide a way of obtaining more information concerning the sources of EEG signals. Brain responses to specific sensory stimuli may be extracted from the ongoing EEG by event-related signal averaging. Recording may also be performed to study the electrical activity of single nerve cells by using microelectrodes or even portions of a cell by using patch clamp methods.

Yet another approach to analyzing brain functions is to study the behavioral effects of either brain stimulation or brain damage. Electrical or chemical methods may be employed to stimulate the brain. Similarly, a variety of procedures are useful in producing restricted brain lesions. In either case, careful behavioral analysis is required to understand the precise effects of the experimental treatment.