62 Biological Psychology
Luria, who died in 1977. Luria approached detection and
evaluation of damage to higher regions of the human brain
both as a clinician with extraordinary expertise in neurology
and as a scientist interested in higher functions of the nervous
system (e.g., his book Language and Cognition,1981).
Yet another origin of cognitive neuroscience is recording
the activity of the human brain, initially using the EEG.
Donald Lindsley was a pioneer in this work. Lindsley did
his graduate work at Iowa and worked with L. E. Travis,
himself an important figure in psychophysiological record-
ing. Lindsley then took a three-year postdoctoral at Har-
vard Medical School (1933–1935). The neurophysiologist
Alexander Forbes was at Harvard doing pioneering studies
on brain-evoked potentials and EEG in animals. The first
human EEG recording laboratory was set up at Harvard, and
Lindsley and other pioneering figures such as Hallowell Davis
did the first EEG recording in America (Lindsley, 1936).
More recently, the method of averaging evoked potentials
recorded from the human scalp made it possible to detect
brain signals relevant to behavioral phenomena that could not
be detected with individual trial recording. Donald Lindsley
was a pioneer in this field as well, doing early studies on
evoked potential correlates of attention. E. Roy John and oth-
ers developed complex, comprehensive methods of quantita-
tive analysis of EEG and evoked potential recordings.
But the techniques that have revolutionized the study of
normal human brain organization and functions are of course
the methods of imaging. The first such method was X-ray-
computed tomography, developed in the early 1970s. The
major innovation beyond simple X rays was complex mathe-
matical and computer techniques to reconstruct the images.
Somewhat later, positron emission tomography (PET) was
developed. It is actually based on a long used method in
animal neuroanatomy—autoradiography. In this technique, a
radioactive substance that binds to a particular type of mole-
cule or brain region is infused and brain sections are prepared
and exposed to X-ray film. For humans PET involves inject-
ing radioactive substances, for example, radiolabeled oxygen
(^15 O), in water. Increased neuronal activity in particular re-
gions of the brain causes a rapid increase in blood flow to the
regions, as shown years earlier in work by Seymore Kety and
others. Consequently, the radioactive water in the blood be-
comes more concentrated in active brain areas and is de-
tectable by radioactivity detectors.
The most widely used method at present is magnetic reso-
nance imaging (MRI). This is based on the fact that changes
in blood flow cause changes in the blood’s magnetic proper-
ties, which can be detected as changes in a strong imposed
magnetic field. This method was first used in 1990 (Ogawa,
Lee, Kay, & Tank). The current procedure is termed
functional MRI (f MRI), involving very fast acquisition of
images. A landmark publication in human brain imaging is
the elegant book by two pioneers in the field, Michael Posner
and Marcus Raichle, Images of Mind(1994). The f MRI pro-
cedures have several advantages, such as the fact that they
are noninvasive—no radioactive substance is injected—and
provide better spatial resolution than does PET imaging.
Functional magnetic resonance imaging exploits variations
in magnetic susceptibility that arise from molecular binding
of oxygen to hemoglobin, which can be used to detect blood
flow changes associated with neuronal activity. At the present
time, these neuronal activity-related signals can be derived
from areas of the brain with a spatial resolution of 1 to 2 mm.
Moreover, the temporal resolution of this functional imaging
technique is compatible with the time course needed to carry
out most perceptual and cognitive operations. An important
and promising strategy for the use of fMRI is its use in con-
junction with other kinds of neurobiological techniques, in-
cluding neurophysiology and anatomical and behavioral
analyses. Thus, fMRI provides an extraordinary new window
through which one can probe the neural machinery of cogni-
tion (Albright, 2000).CONCLUSIONPhysiological psychology, the field concerned with biologi-
cal substrates of behavior and experience (mind), has to be
the most important discipline in psychology and the life sci-
ences. The two great questions in science are the nature of the
universe and the nature of the mind. Over the past century,
the field of physiological psychology has spun off a number
of areas that are now separate fields in their own right: vision,
audition, psychophysiology, behavioral genetics, behavioral
neuroscience, and cognitive neuroscience. It seems that in
this sense physiological psychology is destined to self-
destruct. But to participate in the process is surely among the
most exciting intellectual endeavors of our time.REFERENCESAckernecht, E. H., & Vallois, H. V. (1956). Franz Joseph Gall, in-
ventor of phrenology and his collection(C. St. Leon. Trans.).
Madison, WI: Medical School, Department of History.
Adrian, E. D. (1940). Double representation of the feet in the sen-
sory cortex of the cat. Journal of Physiology, 98,16.
Albright, T. D. (2000). Functional magnetic resonance imaging of
the brain in nonhuman primates: A prospectus for research on
aging. In P. C. Stern & L. L. Cartensen (Eds.), The aging mind.
Washington, DC: National Academy Press.