Chapter 1: Introduction to Neuropsychology
Introduction to Neuropsychology
The 10% Myth
- Claim that humans only use 10% of their brain was tested by Marie-Jean-Pierre Flourens and
Karl Lashley who both performed experiments that involved damaging or removing large
portions of brain of animals.
- Following these procedures, the animals were observed, and often the animals could still
perform basic functions –even when they had sustained injury to as much as 90% of their
What is Neuropsychology?
- Psychology is the study of behaviour. It is an attempt to describe, explain, and predict
- Neuropsychology is also the study of behaviour; neuropsychologists attempt to describe,
explain, predict, and change behaviour. However, neuropsychology is the study of the relation
between behaviour and the activity of the brain
- Two main types of neuropsychology:
Clinical neuropsychology: the branch of neuropsychology concerned with psychological
assessment, management, and rehabilitation of neurological disease and injury
Experimental neuropsychology (a.k.a. cognitive neuropsychology or cognitive
neuroscience): focuses on how human behaviour arises from brain activity, which
includes explaining how patterns of behavioural impairments can be explained in terms
of disruptions to the damaged neural components
Heart, Mind, and Brain: The Early History of Neuropsychology
- Cardiac or cardiocentric hypothesis: a belief that the heart was the source of human
behaviours, and was introduced by Empedocles (known for his position that all matter was
composed of 4 elements fire, air, water, and earth) – 495-435 B.C.
Remnants of the cardiac hypothesis that live on in popular culture include Valentine’s
day and hearts, a broken heart, “makes my blood boil” etc.
- Aristotle came to the same conclusions due to the heart normally being very active and
warm, concluding that the heart was the source of thought and sensation – 384-322 B.C.
- Cephalocentric hypothesis (brain hypothesis): the brain is responsible for
behaviour/functions argued by Hippocrates (430-350 B.C.) and Galen (A.D. 129-199).
- Trephination: damaging the brain resulting in death or disabling of an individual, but
presumably for its therapeutic value (7000 years ago)
- Writings from ancient Egypt dating back 5000 years that document the symptoms of brain
damage Chapter 1: Introduction to Neuropsychology
The Mind-Body Problem
- What is the relationship between the inner “mental life” that we experience and the body?
Does the mind or soul have physical form? If not, how can it interact with the body?
- Rene Descartes presented a “reflexive” theory of the control of behaviour in which he
described the flow of “animal spirits” through “valvules” within nervous tissue filaments. This
theory accounted for reflexive behaviours by describing how external stimuli would move the
skin, in turn moving the filaments, releasing the animal spirits and innervating the muscles
(accounts for some involuntary behaviour but not voluntary ones)
Descartes believed that voluntary behaviours depended on the interface of the
mechanistic body with a rational, decision-making soul. The location of this interaction
was the Pineal Gland, due to its unitary nature, and surrounded by cerebrospinal fluid
(thought to be reservoirs for the animal spirits necessary for action.
Dualism: Descartes proposed that the mind and body are separate but interacting
Monism: posits that the mind and body are unitary (“There is no ghost in the machine”
– Gilbert Ryle)
The Recent History of Neuropsychology
- The year 1990 began with the declaration that the 1990’s would be the decade of the brain
Cataloguing the Effects of Lesions
- Lesioning: destroying tissue
Legallois was a French physiologist who discovered that lesioning the medulla resulted
in the immediate cessation of breathing
The discovery of the respiratory center within the medulla was the first widely accepted
function to be localized within the brain
- Bell and Magendie studied the nerves that exited the spinal cord. They observed that the
dorsal roots (the nerves that leave the spinal cord on the back of the spinal cord) had sensory
functions, whereas the ventral roots (the nerves that leave the spinal cord on the front) were
responsible for motor functions.
This view of functional segregation of the spinal cord set the stage for others to examine
whether or not the brain was also organized into separate sensory and motor
In 1811, Bell suggested that the entire nervous system should be investigated for
functional and anatomical segregation
- Gall and his colleague Johann Spurzheim undertook that challenge, suggesting that the cortex
was functionally localized (stated that there were 27 distinct cognitive abilities (faculties) that
could be localized on the cortex of the human brain (non-humans had only 19) Chapter 1: Introduction to Neuropsychology
- Gall also believed that the cortex behaved like a muscle, in that increased size of an area was
associated with increased function. The increase in size of the cortical area would result in a
deformation of the skill, or a bump, which then could be empirically , measured by using a
technique called cranioscopy.
Phrenology: measurements of the skull and pronouncements on personality, and
popular in the 19 century
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