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Conceptual > Neuroscience: A historical perspective > Flashcards

Neuroscience: A historical perspective Flashcards

1
Q

What did Plato (~424 – 348 BC) say?

A

-“And first of all I considered questions like this: . . . if the element by means of which we think is the blood or the air or the fire or nothing of that but rather it is the brain (enkephalos) that conveys sensations like hearing, seeing and smelling, so that memory and opinion are produced and, once they had firmly settled [in our mind], knowledge is generated in such way”.

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2
Q

Who was the first to write about the brain? And what did they say about it?

A
  • Ancient Egyptians produced the earliest known written record referring to the brain on Edwin Smith Surgical Papyrus (1700 BC)
  • 48 cases of head and neck injuries: title, details of the examination, a diagnosis, and an indication of the treatment
  • Saw the importance of the brain in controlling behavior. But the heart was the seat of the soul.
  • At mummification: conservation of the heart but brain removed
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3
Q

What did Homer (~800 BC) say about the psyche?

A
  • Psyche: non-localized soul – a kind of “life-soul” or “breath-soul” that animates the body
  • representative of the individual life and identity.
  • NOT associated with any specific body part.
  • Silent during active life but appeared in dreams; abandoned the corpse at death
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4
Q

3 more different types of “body soul” located in the chest:

A
  • Thymos: emotions
  • Noos: reason
  • Menos: aggression
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5
Q

What did Natural philosophers ~500BC say about the mind?

A
  • Sought to explain the constitution of all matter in terms of specific basic substances
  • Rejected supernatural explanations
  • Addressed the problem of the nature of soul
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6
Q

Anaximenes (~ 560 BC):

A

the source of human thoughts was the air.

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7
Q

-Heraclitus (~550BC):

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identification of the rational soul with fire.

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8
Q

-Empedocles (495–435 BC):

A

blood localized all around the heart: function to produce thoughts

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9
Q

-Democritus (~ 460 BC):

A

two parts in human soul: a rational one localized to the chest or the brain, and an irrational one that was “spread over the whole body”.

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10
Q

What were the two main ways of thinking from the 5th century?

A

From 5th century BC: Two main theories of the origin of thinking activity: encephalocentrism and cardiocentrism

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11
Q

What is Encephalocentrism: ?

A

brain the seat of human consciousness, sensation and knowledge

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12
Q

What is -Cardiocentrism?

A

attributed all these faculties to the heart

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13
Q

What is poroi?

A

Alcmaeon of Croton, physician, early 5th century BC
-Recognized sensory and cognitive significance of brain: “All the senses are connected with the brain” through channel like structures called “poroi”.

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14
Q

First anatomical dissections on animal corpses found what?

A
  • Brain was the seat of consciousness and sensation: “all senses are compromised if the brain is moved and changes its place”
  • Distinguished between sensation and understanding: “Man differs from the other animals in that he alone has understanding, whereas, they have sensation but do not understand”.
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15
Q

Birth of Western Medicine - Hippocrates (460-370 BC). What did they say about animals and epilepsy?

A
  • Human brain similar to other animals
  • Lateralization of the effects of brain injury
  • Epilepsy not a “sacred” disease
  • The brain: “is our interpreter… The eyes and ears and tongue and hands and feet do whatsoever the brain determines… it is the brain that is the messenger to the understanding” “from the brain only arise our pleasures, joys, laughter and jests, as well as our sorrows, pains, griefs and tears… the brain is the most powerful organ in the human body.” (“De Morbo Sacro”)
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16
Q

What did Aristotle (384–322 BC) say about the heart?

A
  • Philosopher, biologist, anatomist
  • Cardiocentric: heart is seat of soul and intellect
  • Different soul faculties: Vegetative (plants & animals)/ Sensitive & Motor souls (animals)/Nous (humans, immaterial)
  • All soul faculties reside in the heart
  • Brain? - Secondary role since it is bloodless/no sensory properties
  • But made useful observations, e.g., distinction between cerebellum and cerebrum
  • Its function: To diminish the heat of the blood generated by heart; generator of sleep
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17
Q

Who was Galen of Pergamon (129-216 AD)?

A
  • Greek physician (working in Rome) Brain “receives all sensations, produces images and understands thoughts”. Rigorous anatomical methodology to provide “apodeictic proofs”
  • Brain and spinal cord were the only sources of the nerves
  • Spinal cord originated from the brain and they were composed of the same substance (nervous tissue).
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18
Q

Galen’s experiments and the Ventricular Hypothesis Using pigs

A
  • Experiment: a pig stopped squealing, but kept breathing, after he severed nerves in the throat -> the voice came from the brain and not from the heart
  • Soul communicated with rest of the body through animal spirits, produced and stored in three ventricles (brain cavities).
  • The spirits (or ‘psychic neuma’) were controlled by the soul, which was located in the solid parts of the brain.
  • Travelled between the brain and the organs via the nerves (hollow tubes).
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19
Q

What happened in the renaissance period?

A
  • Controversy between encephalocentrists and cardiocentrists continued into Renaissance period and beyond…
  • E.g., Galenist physician Jean Fernel (1497–1558): cardioncentrism is an unbelievable delirium (“deliratio incredibilis”).
  • 16th Century: Mystical physiologist M. Servetus reasserted the primacy of the heart and claimed that the blood was the seat of human soul.
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20
Q

The Brain and Mind: Related but still separate (13th Century)

A
  • Albertus Magnus (1260): brain was centre of mental activity; identified sensation, rationality and memory with the three ventricles
  • Some realised that mental and brain function were inextricably linked (but how?)
  • Although mental function incorporated in the body, the mind still immaterial
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21
Q

The Rebirth of Neuroanatomy: 15th Century

-Leonardo Da Vinci (1452-1519)

A
  • Da Vinci followed medieval tradition in relating the structure of the brain to mental function
  • Attention to anatomical detail
  • Produced first wax cast of ventricles
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22
Q

What did Da Vinci say about ventricles?

A
  • Ventricles of the brain responsible for its major functions.
  • Soul resides in the brain, but because the soul is incorporeal, it resides in the cavities (ventricles) rather than the surrounding brain tissue.
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23
Q

Vesalius: Non-Ventricularist? (16th Century)

A
  • De Humani Corporis Fabrica”
  • Rejected theory of ventricular localization of the soul/intellect
  • Evidence: All mammals: same anatomical organization as humans but not equivalent intellect.
  • BUT… Ventricles: storage of ‘animal spirits’ that followed the nerves to reach the muscles or sense organs.
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24
Q

What did René Descartes (1596-1650): say about fluid dynamics?

A
  • Brain-behaviour relationships were mediated by fluid dynamics
  • Used prevailing technology as a metaphor
  • ‘Balloonist’ Theory: Brain controlled the body mechanically by sending fluids from the ventricles to the peripheral nerves
  • Located the mind in the pineal gland, but still separated mind and body (‘Cartesian Dualism’).
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25
Q

What is Cartesian dualism and gap?

A
  • Cartesian Dualism: Interaction between immaterial mind and material body within the pineal gland
  • BUT: ‘The Cartesian Gap’: How can an immaterial mind cause anything in a material body, and vice versa?
  • Modern science has abandoned such dualist approaches
26
Q

Where is the pineal gland located?

A
  • Why the pineal gland? Located between the two hemispheres of the brain and not bifurcated
  • Descartes made key contribution of opening up all animal activity to mechanical analysis
27
Q

What is the pineal gland?

A

-The pineal gland is a small endocrine gland in the brain: produces melatonin (modulates wake/sleep patterns).

28
Q

The cortex as seat of psychological functions

A
  • Post-mortem examinations of patients with neurological problems
  • Said human psychological attributes are functionally dependent on the cortex
  • Still Cartesian (i.e. dualist): an immaterial soul/mind that interacts with the body.
  • But key difference: the point of contact and causal interaction between the mind and the body is in the cortex not the pineal gland
29
Q

What is the problem with the cartesian gap?

A
  • Still problem of Cartesian gap

- BUT… Impact: Diverted attention from the ventricles for the first time in over 1000 years to the cortex

30
Q

Function of cortex

A

-Little progress in the understanding of the function of the cortex for nearly 200 years between the death of Thomas Willis in 1675 and the experiments of Fritsch and Hitzig about 1870

31
Q

Understanding the Nervous System (19th Century)

A

-Advances in microscopy -> advanced the
understanding of the organization of the nervous system  -Improved histological methods -> nerve cells could be examined in increasing detail
-Reticularists vs. Cell Theorists: Most of the 19th century: on-going debate about the organization of the nervous system.

32
Q

What is a cell made up of?

A
  • Cell body: contains metabolic machinery that maintains the neuron.
  • Dendrites: large tree-like branches that receive inputs from other neurons via synapses
  • Axons extend away from the cell body, represent the output side of the neuron, down which signals can travel to synapses
33
Q

Reticularists vs. Cell Theorists

A
  • Reticularists: nervous system comprises a large network of tissue, or reticulum, formed by the fused processes of nerve cells.
  • Cell Theorists: the nervous system consists of distinct nerve cells.
  • Both groups: same methods to study nerve cells, but came to different conclusions about the fine structure of the nervous system
  • Limit: low magnification and poor resolution of the available microscopes
34
Q

What is the Reticular theory?

A
  • The whole brain is a syncytium or a continuous mass of tissue that shares a common cytoplasm
  • (Syncytium: a large cell-like structure)
  • “the finest divisions of the protoplasmic processes ultimately take part in the formation of the fine nerve fibre network which I consider to be an essential constituent of the grey matter of the spinal cord..” Joseph von Gerlach (1820-1896):
35
Q

What is Cell Theory?

A
  • The body is composed of elementary units, cells, but the idea that the nervous system is also made up of such discrete cells was controversial
  • First cell theory (Theorie der Zellen): 1830s, by Schwann (see also Schleiden): “In general we should attribute autonomous life to cells”.
  • Rudolf Virchow (1821–1902): In 1855, uttered his famous sentence: “omnis cellula e cellula” : “cells can only multiply from themselves”
36
Q

What are Purkinje Cells?

A
  • 1820: Achromatic lenses provided clearest images yet of tissue samples.
  • Johannes Evangelista Purkinje (1787-1869, anatomist, Bohemia, i.e. Czech Republic): First to use a microtome to prepare nervous tissue for examination under the microscope.
  • Purkinje is most famous for discovering the cerebellar cells (“Purkinje cells”): among the largest in the vertebrate brain
  • His student, Valentin, published first microscopic image of a nerve cell (1836)
37
Q

What is Golgi staining?

A
  • 1873: Invented the silver nitrate method of tissue staining. (“la reazione nera”; “the black reaction”)
  • Golgi thought that his observations confirmed the hypothesis that the nervous system consisted of a continuous network (i.e. reticulum).
38
Q

What is Rete Nervosa Diffusa (Golgi)?

A
  • Nervous tissue: continuous network (reticulum), not discrete units
  • “One single nerve fibre may have connections with an infinite number of nerve cells, as well as with completely different parts of nerve centres which may be a long way from each other.” (Golgi, 1906)
  • Holistic approach: nervous system as a reticulum, opposing the theory of localization of cerebral function (see Broca).
39
Q

What led to the work of the neuron docterine?

A
  • Santiago Ramón y Cajal (1852-1934, neuroanatomist, Spain)
  • His work eventually led to the acceptance of the Neuron Doctrine:
  • The neuron as the anatomical and functional unit of the nervous system
  • “the relationship between nerve cells was not one of continuity, but rather of contiguity”
40
Q

Staining: New and improved

A
  • 1887: New staining method: Cajal pioneered an improved method: immersing tissues in fixative and silver nitrate a second time, staining the tissues more deeply
  • 1888: Cajal observed that the endings of the axons in a section of chick cerebellum were consistent with the location of dendrites.
41
Q

Did investigators like the reticular theory?

A

-Cajal found no evidence of a reticulum
-Instead: “Each nerve cell is a totally autonomous physiological canton.”
-Other investigators began to abandon their belief in the reticular theory.

42
Q
  • Waldeyer stated in 1891 about neurons…
A

-“The nervous system is constituted by numerous nervous units (neurons) without anatomical or genetic connection. Each nervous unit comprises three parts: the nerve cell, the nerve fibre and the terminal arborizations.”

43
Q

How did the synapse emerge?

A
  • Cajal began to indicate the direction of nervous conduction
  • Cajal (1891): This diagram shows for the first time the famous arrows that “indicate the direction of the nervous impulse”
  • Influenced Sir Charles Sherringto
44
Q

What did the development of electron microscopy techniques show?

A
  • Mid-1950s: Development of electron microscopy techniques (De Robertis & Bennett, 1955; Palay & Palade, 1954)
  • Reaffirming Cajal’s (1933) proposal : “physical contact—of the nerve endings—may attain great intimacy, but in any case there always exists between the two surfaces of the synapse a separating frontier”
45
Q

The Neuron Doctrine (four main tenets)

A
  1. The fundamental structural and functional unit of the nervous system is the neuron
  2. Neurons are discrete cells that are not continuous with other cells
  3. The neuron is composed of 3 parts - the dendrites, cell body and axon
  4. Information flows along the neuron in one direction (from the dendrites to the axon, via the cell body).
46
Q

The Neuron Doctrine (Three reasons for delay)

A
  1. Technical: the methods of histological preparation and the optical quality of microscopes had to be improved
  2. The area of study itself: nerve cells have an extraordinary complex and variable structure
  3. Theoretical: belief that cell continuity was necessary for cells to interact
47
Q

Early observations on the effects of brain damage (patient unable to speak)

A
  • 1585 German physician von Grafenberg; “Observationes medicae de capite humano” (‘‘Medical observations on the human head’’)
  • Key observation: “I have observed in many cases of…major diseases of the brain that, although the tongue was not paralyzed the patient could not speak”
  • Explanation: “…because, the faculty of memory being abolished, the words were not produced”.
48
Q

Localization of brain functions (19th century)

A
  • Brain equipotentiality theory: The brain functions as a whole with all parts having an equal significance Main Proponents: Flourens and later K. Lashley
  • Localization theory: High degree of specialization in the brain Main proponents: Gall & Spurzheim
  • Both theories had enthusiastic advocates in the 20th (and perhaps 21st) century
49
Q

What is phrenology?

A
  • Franz Joseph Gall (1758-1828) & Spurzheim (1776 – 1832)
  • Main principles:
  • Brain composed of many organs, each dedicated to a particular skill
  • The size of an organ is a measure of its power.
  • The shape of the brain is determined by the development of the various organs.
50
Q

Examples of phrenology

A

(1) instinct of reproduction,
(2) love of offspring,
(3) self-defense and courage
(4) cleverness,
(5) pride and arrogance,
(6) caution and forethought,
(7) memory of words,
(8) sense of language and speech,
(9) kindness, morality, and compassion, and
(10) religion… etc….
- Spurzheim added more…

51
Q

What does phrenology do?

A
  • As the skull takes its shape from the brain, ‘reading’ its surface provided an accurate index of psychological aptitudes
  • Greater use of a faculty = the brain area associated with it increased
  • Careful analysis of the skull would give insight about the person’s personality: ‘anatomical personology’
52
Q

What is a phrenometer (1907):?

A
  • Designed to measure “bumps” on the skull
    Phrenology
    -The functional specializations of phrenology were not empirically derived and were not constrained by theories of cognition
    -Skull shape has nothing to do with cognitive function!
    -But Gall & Spurzheim made important observations, e.g., the brain is folded to conserve space
53
Q

Early arguments against Gall & localization

A
  • Flourens studied animals and discovered that brain lesions in particular brain areas did not cause particular behavioural deficits.
  • Developed the notion that the whole brain participated in behaviour, a view known as “aggregate field”.
  • “All sensations, all perceptions and all volitions occupy the same seat in these (cerebral) organs. The faculty of sensation, percept and volition is then essentially one faculty” (Flourens, 1824)
54
Q

Brain Mapping with Lesions

A
  • First evidence for cortical specialisation in 1861 for the uniquely human capacity for speech
  • Patient who lost the ability to speak 20 years previously.
  • Brain examined post-mortem - Lesion identified in left inferior frontal cortex
  • Early association between a specific area (‘Broca’s area’) and a specific dysfunction (Broca’s aphasia)
55
Q

Wernicke’s aphasia: language understanding

A
  • 1874: German physician Karl Wernicke language problems could also occur after damage to the posterior part of the left hemisphere.
  • These problems, however, had nothing to do with speaking, but rather with the understanding of language.
56
Q

What did exposing cortex of dogs stimulated with an electric current at different sites show?

A
  • Areas on the surface of the cortex gave muscular contractions involving the face and neck on the opposite side of the dog to the stimulated hemisphere.
  • Unilateral ablation of forepaw area did not affect sensation but the dog showed impaired motor activity
  • Generalisation: other functions also linked to specific areas “certainly some psychological functions, and perhaps all of them, in order to enter matter or originate from it, need circumscribed centres of the cortex”.
57
Q

The first brain map? - Fritsch and Hitzig (1870)

A
  • Exposed cortex of dogs stimulated with an electric current at different sites
  • Areas on the surface of the cortex gave muscular contractions involving the face and neck on the opposite side of the dog to the stimulated hemisphere.
  • Unilateral ablation of forepaw area did not affect sensation but the dog showed impaired motor activity
  • Generalisation: other functions also linked to specific areas “certainly some psychological functions, and perhaps all of them, in order to enter matter or originate from it, need circumscribed centres of the cortex”.
58
Q

Motor cortex in humans - epilepsy

A
  • Epilepsy: ‘”in very many cases of epilepsy, the convulsions are limited to one side of the body; […] the cause is obvious organic disease on the side of the brain, opposite to the side of the body convulsed, frequently on the surface of the hemisphere” (1863)
  • Speculation: the motor cortex must be organised somatotopically: the hand, face and foot, which possess the greatest capacity for specialised movement, receive the largest representation in the motor cortex.
59
Q

Effects of electrical stimulation of the human brain (Penfield & Roberts, 1959)

A
  • Post-central gyrus:
    1: tingling right thumb and slight movement;
    19: sensation in lower lip outside;
    17: sensation right upper lip inside;
    16: tingling in right side of tongue at the tip;
    14: sensation in the “joint of the jaw and in the lower lip inside”.
    Pre-central gyrus:
    11: feeling in my throat which stopped my speech;
    12: quivering of jaw in a “sidewise manner”;
    13: pulling of jaw to right.
60
Q

Brain Mapping with Anatomy - Brodmann (1909)

A
  • Systematic investigation of variation in cellular properties of the cortex in primate brains
  • Somatosensory map: Neurons are organised so that adjacent areas of the body surface are represented in adjacent areas of cortex
  • Motor map: Neurons are organised so that adjacent musculature is represented in adjacent parts of the motor cortex
  • Identification of ~50 cortical areas
61
Q

How has mapping contributed to the science of ‘mind’?

A
  • Empirical approach to explaining sensory experience and behaviour in mechanistic terms.
  • Shift from dualism to materialism.
  • ‘Reductionism’: the brain as a whole can be explained in terms of the working of its parts.
  • But does brain mapping necessarily inform the understanding of the mind/cognitive models? Can/should brain and mind still be studied separately?

Conceptual (10 decks)

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