Class 02 Historical Notes

Neuropsychology is a hybrid field of study which grew out of many different researchers from many different traditions of scientific research.

As mentioned in the first class, as far as we can tell or estimate, the brain is the single most complex entity or organ in the universe (except for the universe itself): 86 billion neurons, 85 billiion glial cells, 100 trillion synaptic connections and about 3,000 different types of neurons!

The level of complexity has meant that it has taken many centuries to understand how it functions. We are only vaguely aware of its functioning.

Consider this analogy: the European exploration of the Americas began in the period between 1000 and 1500 C.E., and developed particularly after 1492. What we know about the brain has been estimated by some researchers to be roughly equivalent to what Europe knew about the geography and natural history of the Americas in the either the late 1700s or early 1800s. That is, we are still possibly hundreds of years from understanding the brain completely.

[TBDLMD] = To be discussed later in the course in more detail

Prelude: The Ancient and Medieval World

1. Ancient Egypt

The oldest record about medicine and the brain comes from the Edwin Smith Surgical Papyrus discovered in the 19th century but written about the year 1600 BCE in Ancient Egypt. It contains records of 48 medical cases requiring some type of surgical intervention. Of these, 27 cases involve the head. These mostly seem to involve wounds or damage suffered to soldiers as a result of battle.

The author of the papyrus noted various qualities about the brain and what happens when it is injured:

An exposed brain pulses (as we know, this involves the flow of blood through the brain)

The surface of the brain contains both hills or bumps (i.e., gyri) and valleys or grooves (i.e., sulci)

A brain injury may result in a patient becoming unable to speak

Some patients with brain injuries shake uncontrollably (i.e., this is probably a description of seizure activity)

The Smith Papyrus is owned by the New York Academy of Medicine in NYC and is stored in its Rare Books collection

2. Ancient Greece and Rome

Alcmeon of Croton (ca. 480 BCE) acknowledged the brain as the site of the “governing facility”

Some Greek medical writers did carry out dissection of the parts of the brain (ca. 300 BCE) and 800 years later, Galen, the most famous doctor of the ancient world did so as well.

Among the most famous Greek thinkers, Aristotle (384-322 BCE) believed that human beings had both a physical body and a non-material spirit (a psyche). It was this psyche which is actually the origin of our thoughts, emotions, and peeptions, imagination, pleasure, pain, etc. But, he believed that the psyche worked through the heart in order to cause us to do things while the brain was there to cool down the person’s blood. The notion that the psyche (an actual word in Greek which was translated into English as "mind") is known as "mentalism."

Understanding the brain was limited by the acceptance of the theory of bodily humors, that is, four different kinds of fluids in the body which controlled various dispositions to act in particular ways or have a particular kind of personality. The relative balance among these four humors in each person determined what kind of person they were.

A. The Brain Hypothesis = The brain is the seat of the mind, i.e., the brain is responsible for all behavior

Are functions of the brain localized? Or are the functions spread throughout the brain?

Trepanning (“trepanation, trephination, trephining or making a burr hole”) is a surgical procedure in which a hole is drilled through the human skull (see above second image from the left).

The archeological evidence for the practice of trepanation goes back to at least 7,000-10,000 years ago. And, this evidence is found in skulls from all over the world including Europe, Asia, and the Americas.
The medical motivation for this procedure was to relieve pressure on the brain and drain away fluids that may have accumulated because of traumatic head injury. There is some evidence it may have been used to treat chronic headaches, epilepsy, and convulsions more generally.
There were also spiritual motivations for trepanation including the release of evil spirits
The archeological evidence suggests that the Incas of Peru were particularly adept at using trepanning to treat patients. The average long-time survival rate in the period from 1500-1500 CE is estimated at 75-83% (Marino & Gonzales-Portillo, 2000). This can be compared to the survival rate of cranial surgeries in the American Civil War 1861-1865 of approximately 46-56% (Chavez-Rivera & Sanchez, 2022).

Medieval Period in Europe (400-1600 CE): The brain was recognized as the "seat of the soul, the localization of motor and sensory activities, and the rete mirabile [i.e., the 'marvelous net' by which 'vital' spirit is transformed into 'animal' spirit -VWH]" (Clark et al., 1996). Borrowing from the Ancient Greeks, the ventricles of the brain and their fluid ("animal spirits") were held responsible for behavior. Even the French anatomist and philosopher, René Descartes (17th century; 1596-1650) adopted a hydraulic model of behavior with the ventricles causing movement.

Dualism: Like Aristotle, Descartes argued that there were two substances or aspects to a human being. We have a material body (called, in Latin, "res extensa" [the "thing extended into space']) which functioned like a machine (his "hydraulic" model) and a non-material spiritual mind (which he called "res cogitans" ["the thinking thing']) which was separate from the body. That "res cogitans" or mind controls what the material body does through the pineal body, that small structure or gland, which is at the top of the brainstem (see the 2nd image from the right above which displays what Descartes claimed).

19th Century: the era of the great physiologists

Pierre Flourens: (d. 1867) Using ablation methods on animals (see below) was able to establish localization of various functions, e.g., sensation & movement in cortex, coordination of movement in cerebellum.
There were others, e.g., von Helmholtz, Muller, Bois-Reymond, et al., who contributed widely to our knowledge of the body and brain

20th Century: Rise of biological & neuropsychology

Karl Lashley (1929) Brain Mechanisms & Intelligence

Mass Action: the detrimental effects of lesions are proportional to the amount, not the location of the damage to tissue
Equipotentiality: notion that brain tissue has ability to assume the functions of other brain tissue

Donald O. Hebb (1948): Model of localized cell assemblies; theory of long-term memories established by repeated neural firing ("Neurons that fire together wire together")

Alexander Luria (1950s-1960s) Hierarchical structure and functional neural systems [TBDLMD]

Ablation Research: Study of behavioral impairment following the surgical removal of tissue. Done on animals.
Lesion Research: Study of behavioral impairment following damage to the brain by disease or trauma

B. The Neuron Hypothesis = the nervous system is composed of separate, autonomous units (neurons) that interact but are not physically connected. The neuron is the basis of the nervous system.

Santiago Ramón y Cajal (d. 1934): great Spanish anatomist & microscopist. Established that the neurons were independent of each other; they were connected but not continuous.
Charles Sherrington (c. 1952): British neuroanatomist. Established the concept of the "synapse" (the gap between neurons) and synaptic functions.
The implication of the "Neuron Hypothesis" is that the fundamental processes of cognition and brain activity are solely the result of what neurons do.

This pure form of the hypothesis has been under challenge for the last decade by growing evidence of other major influences, in particular, the roles of (a) glial cells in regulating neurons, (b) the emerging understanding of the functional networks of the brain, and (c) the microorganisms making up the "microbiome" {W} in our intestinal system (they have been related to issues in depression, anxiety, autism, et al.). [TBDLMD]

C. Further 20th Century Advances related to Neuropsychology

Neurosurgery

Wilder Penfield: Montreal neurosurgeon; localization of language, memories. Creation of the "homunculus" -- the diagram of the sensory and motor cortices as they relate to sensation and movement of specific body part.
Patient H.M. (Henry Molaison): As the results of his neurosurgery were charted in +40 years of research by neuropsychologists, many of the fundamental understandings of the nature of memory emerged, e.g., the distinction between short- and long-term memories.

Psychometrics & Statistical Evaluation: the development of psychological tests and the statistical tools by which to analyze the significance of the results.

Sir Francis Galton (late 19th century): pioneered the use of statistics to evaluate human behavioral performances
Alfred Binet (early 20th century): Earliest intelligence testing of children
David Wechsler (mid 20th century): Intelligence testing of adults.
Using the normal distribution (bell-shaped curve) to establish what is normal, abnormal, and how much so...

Advances in brain imaging & measurement technology [TBDLMD]

includes CT (computerized tomography), magnetic resonance imaging (MRI), diffusion MRI, functional MRI, magnetoencephalography (MEG), positron emission tomography (PET), transcranial magnetic stimulation (TMS), optogenetics, Brainbow, and others

Clinical testing: 1930s-late 20th century [TBDLMD]

Ward Halstead (1930s-1940s; Northwestern University): Developed a batter of tests to measure aspects of intelligence which were "organic" (compared to those which were the results of learning (akin to Raymond Cattell's fluid vs. crystallized intelligence)
Ralph Reitan (1950s-1990s): Used Halstead's tests in a larger clinical battery in order to assess the presence and nature of brain impairment.
Arthur Benton (1950s-1990s): Development of individual neuropsychological tests to evaluate numerous higher cognitive functions, e.g., visual-spatial analysis, face recognition, auditory perception, etc.
The "Boston" Approach: Edith Kaplan & Harold Goodglass (Boston University, 1950s-present): Combined quantitative evaluation of tests with qualitative analysis of errors and how the testee responds ("process" analysis); tests of aphasia, memory.

Behavioral Neurology [TBDLMD]

Kurt Goldstein (1920s-1970s): synthetic or holistic approach to brain function; the "abstract" attitude; higher executive or command functions; "cognitive set" ; complexity in functioning

Norman Geschwind (1950s-1980s; +1985): sequential model of language comprehension and functioning (resurrected Broca, Wernicke from 19th century)

References

Chavez-Rivera, A. D., & Sanchez, T. R. (2022). Trepanation reveals the success of the Incas. American College of Surgeons, 107(11). https://www.facs.org/for-medical-professionals/news-publications/news-and-articles/bulletin/2022/november-december-2022-volume-107-issue-11/from-the-archives/

Clark, E., Dewhurst, K., & Aminoff, M. J. (1996). An illustrated history of brain function: Imaging the brain from antiquity to the present. San Francisco, CA: Norman Publishing.

Kolb, B, & Whishaw, I. Q. (2015). Fundamentals of human neuropsychology (7th ed.). New York: Worth Publishers.

Marino, R., & Gonzales-Portillo, M. (2000) Preconquest Peruvian neurosurgeons: A study of Inca and Pre-Columbian trephination and the art of medicine in ancient Peru. Neurosurgery, 47(4), 940-950.

	PSY 448 Clinical Neuropsychology	Last Revised August 26, 2025
Introduction