PS2080A:  Conceptual Issues in Psychology
Term II,    FRIDAY   10 – 12 am    (Room 290 Yorkon)

Lecture 4:    Neuroscience I : Historical Concepts

Johannes M. Zanker, j.zanker@rhul.ac.uk, (Room 218)


Topics lecture 4


Neuroscience: a crucial part of psychology

Neuroscience deals with the brain (nervous system).
D. Hebb (1949) : ‘The problem of understanding behaviour is the problem of understanding the total action of the nervous system and vice versa

attributes of a scientific explanation: it should be testable, coherent (i.e., free of any internal contradiction), consistent with the empirical evidence that is available, and in the ideal case parsimonious (Occam’s razor: out of two equally strong explanations, prefer the simpler one)

so we have to keep to questions in mind:
-- is there only a superficial analogy between neural mechanisms and mental events or is there a causal  relationship
-- does a neuroscientific approach exclude other possibilities to explain thought processes ?


The beginnings: thinking and collecting knowledge about the brain

humans always were suspicious that the brain has a very special function for behaviour
(Edwin Smith Papyrus 2500 BC: hemiplegia; Hippocrates: lesions ~ seizures)

Trephanation:
ancient surgical procedure of operating on the human skull (eg Peru)
scraping, chiseling, or cutting bone

from Philip Schatz, http://schatz.sju.edu/neuro/nphistory/nphistory.html

on the other hand: Aristotle localised mental functions in the heart - so why do we now understand the mind in relation to the brain?

first step: the idea of central information processing - where does it come from ?
the origins and major historical steps of a neuroscientific approach


Albertus Magnus (1260) reviewed the brain as centre of mental activity, and localized sensation, rationality and memory in the three ventricles (cavities with cerebral fluid)

such views were recoveries of knowledge collected by writers of the antiquity (Galen, aka Claudius Galenus, 129-199) and Islamic scholars (Al-Haythem, 965-1039)

although mental function is incorporated in the body, the mind is still implicitly treated as immaterial ‘stuff’, in continuation of the Aristotelian tradition of mentalistic explanation (psyche generates behaviour)


The birth/return of anatomy: a new picture of the brain

from speculations to observational evidence: during the Renaissance we find a new interest in studying brain anatomy


Leonardo da Vinci (1506)
highly schematic sketches slowly leading to detailed anatomical studies (sometimes with mixed preparations: human-ox ventricle preparation)

Andreas Vesalius (1543)
very realistic descriptions within few decades, rapid development of anatomical techniques


very realistic descriptions within few decades, we witness a rapid development of anatomical techniques


Collecting evidence : size comparisons as modern example of looking at brain anatomy

what evidence supports the general claim that the brain is responsible for control of behaviour and the seat of reason (and emotion) ?
for instance, on a rather basic level, a comparative approach studies the relation between general brain anatomy and general mental capacities

    from Jerison 1976
brain size varies with body size: elephants and whales have larger (heavier) brains than humans, but these brains contribute to a smaller fraction of their overall body weight.
comparing different animal groups, it is obvious that relative brain size is larger, for instance, for primates than for other mammals, and much larger for mammals than for fish or reptiles.


Functional confirmation through studying brain pathology

a continuously growing body of evidence demonstrates that brain damage due to injuries or chronic/acute disease changes the intellectual capacities and personality of patients.
Philippe Pinel (1820s) and Jean Charot (1860s) started careful documentation of the behaviour of mentally ill patients in Paris asylums, which then was related to abnormalities of their nervous system found in autopsy – this started a new school of scientific endeavour : Neuropsychology
 

reconstruction of the brain of Phineas Gage (died 1861), who suffered from an accident which blasted an iron bar through his frontal cortex and changed his identity


Neurones as functional units: the beginnings

the initial concept of information transmission is part of a precise description of sensory control of the motor system
R. Descartes (1664) developed clear ideas about stimulus-response circuits: the fire signal (stimulus) is transmitted through the nerve to the brain, which the controls the retraction of the foot (response). Descartes suggested hydraulic transmission through nerves (see dualism, below)

Descartes' interpretation of nerves (in particular exchange of fluids), while being based on surprisingly modern anatomical knowledge, is no longer supported by current knowledge of nerve function (electrochemical transmission). As such it is reflecting the lead technology of its time (hydraulics) but it is an early clear and explicit attribution of information transmission to peripheral nerves


Early microscopy & physiology: discovering microstructure and function

two important discoveries that revolutionised the views of the nervous system

the development of the light microscope allowed Anton van Leeuwenhoek to study the microstructure of nerves and describe nerve fibres (1718)

the end of the ‘vital-fluid’ concept was final when Luigi Galvani demonstrated that muscle contractions could be elicited by electrical stimulation of the nerve (frog nerve-muscle preparation)

note: systematic observation & experimentation is used to replace pure speculation based on traditional knowledge !!

Histology: discovering the neurone

the development of new histological techniques (the fixation & staining of biological tissue, such as the nervous system) allowed to study the microscopic structure of the nervous system in so far unknown detail, leading to a rapid explosion of knowledge.  

Purkinje, 1837:
retinal neurones

Otto Deiters, 1865:
single neurones with long axons in spinal chord

importanat steps in discovering and identifying the neurone as basic element of the nervous system:


Single cell physiology: establishing the neurone

the development of single-cell physiology firmed the general acceptance of the neurone doctrine and provoked new versions of this concept (see later)
the electrophysiological properties of individual neurones reflect specific features, or feature combinations of the outside world, such as orientation or motion direction in a very simple case 

(after Hubel & Wiesel, 1977)

this general way of interpreting nervous activity (neurones are encoding and processing information as fundamental basis of sensory experience, behavioural control and other mental events) has outstanding explanatory power on all levels of human mental activity ...


Charting and mapping: A Renaissance obsession

one of the major steps towards a modern, scientific culture is the detailed and systematic description of the physical and biological environment : maps are an essential concept in this attempt to create order and relate things to each other

an example from astronomy demonstrates far-reaching consequences meaning of developing veridical maps

this 'scientific revolution' had immense intellectual, social, nad political consequences (and was heavily opposed by the church establishment...)

with all the achievements of 20th century science, would it be possible to map the mind ?


Projecting and representing : the initial concept of maps in the brain

Descartes (1596-1650) attempted to explain how the nonmaterial mind interacts with the material body (dualism) to generate behaviour - thus breaking with the Aristotelian view of a immaterial psyche generating behaviour (mentalism)

this includes a mechanism of dispatching information from the outside world through the physical body (optical projection – hydraulic transmission) to the non-material mind that resides in the pineal body: formation of maps (neighbouring points in the environment are represented in neighbouring points in the brain)


Early ideas of functional compartments

on a large scale the outside world represented in functional compartments: brain regions that ar specialised fro particular tasks. this concept can be found through the whole history of neuroscience: the localisation of specific functions in particular brain regions !
G. Reisch (1503), after Galenus
 
Leonard da Vinci (1504)

the localisation of functions in the brain ventricles from the antique tradition was copied in the early anatomical studies of the Renaissance genius Leonardo !


Phrenology

in the early 19th century, this rather speculative way of attributing functions to brain regions led to the ‘science’ of phrenology: studying the relationship between a person’s character and the morphology of the skull. (why was it called a 'science' 150 years ago? why do we no longer accept this view today?)

<<<
brain is the home of all mental activity, providing an opportunity of ‘anatomic characterology’
Franz Joseph Gall (1758-1828)

>>>
such a Phrenometer was still in use in 1907

the basic concept: the brain is composed of many particular organs, which are reflected by the shape of the skull: bumps (extensive measurements) can be interpreted as predominant development of particular ‘faculties’, such ideas dominated popular science in the 19th centuru and were still influential in the 20th century.


Mapping : the neuronal substrate

a scientific approach has to replace the incidental observation by systematic analysis of causal relationships - the function of neurons is a good starting point for such an endaveaour. mapping of the environment on the brain requires extended networks of neurones, which are most obvious in the visual system: retinotopic maps are generated in the cortex from a parallel network of functionally identical units covering the visual field with small receptive fields - histology (the microscopic study of living tissues) can open the view on the architecture (and thus, design!) of the brain !

          Wässle et al. 1981, anatomical and physiological pixellation in the retina

        Cajal 1911, columnar structure in cerebellar cortex: could be the basis of a map!


Lesion studies inform histology

Tan, a famous patient presented by Paul Broca (1824-1880) at the Paris anthropology meeting in 1861, had longstanding language difficulties (‘tan’ was the only word he could speek) - extensive frontal lobe damage was revealed in autopsy.

several similar cases were used as motivation to suggest the principle of discrete localisation of psychological function, which was sometimes regarded as independent vindication of Gall’s phrenology (but a direct connection between these two areas of inquiry were not established). they provide indirect functional evidence for localisation and mapping in the human cortex.


warfare as instrument of ‘scientific progress’: ‘improvement’ of guns (Franco-Prussian 1871, Russo-Japanese 1904, WW I, …)
>> smaller brain lesions from gunshot wounds, leading to neurological conditions
>> well circumscribed anatomical cortex regions can be elated to specific behavioural & perceptual effects … (Poppelreuter 1917)

“The hardship and ferocity of the last war led me to publish these observations. The awfulness and horror of the experience, of which those who did not take part cannot have the slightest appreciation, at the same time raised the hope in me and in all other physicians that in the future war may be prevented”     T. Inouye (1909)

results from an extensive histological and cyto-architectonic analysis (e.g. J. Flechsig)
was the basis of a systematic charting of the brain: K. Brodmann (1909)

this combination of cyto-architecture & functional anatomy prsents a picture of the cortex that today is still used as reference!


The establishment of cortical maps

the systematic combination of anatomical, physiological, and computational techniques confirmed the concept of mapping during the second half of the 20th century

in the visual system, maps can be found in successive stages of information processing (different brain regions): retina > LGN > V1 > V2 > V3 > V4/V5
furthermore, various features are superimposed in these maps, like eye of origin, preferrend orientation, motion direction, spatial frequency, etc.


deoxyglucose staining marks the regions of activity in histological preparations: eye of origin, for instance, is organised in stripes (demonstrated by monocular stimulation): ‘ocular dominance maps’ (here compared in size & structure with fingerprint, from Hubel & Wiesel 1977) 

evidence from activity staining of neral tissue: location in the visual field is organised in 'retinotopic maps’ (from Tootel, 1983?) 


the most recent, and perhaps most immediate, evidence for cortical maps is functional imaging: observing the brain in action (see neuroscience II lecture)
 
similar organisation in the somatosensory system : homunculus represents body surface on somatosensory cortex (mapping touch from body surface)


A synoptic view of the brain

the tradition of functional localisation is a key theme of modern neuroscience, with a huge variety of novel methods contributing to a comprehensive view of brain structure and function

anatomy, electrophysiology & lesion studies  supports the view of 32 distinct areas in the visual cortex, communicating with each other in a dense network of reciprocal connections

<<<
a travel guide to the biological information highway, from van Essen et al. 1992


Neuroscience : philosophical implications

is the mind ultimately depending on (or embodied in) the brain? is the brain the machinery of the mind? are they one and the same thing? are they separate?
-- a modern version of the classical body-mind problem in philosophy

the prevailing view is a structure and function relationship:  neuroscience describes the physical embodiment of psychological functions in terms of neural structures
growing anatomical, histological and physiological knowledge led to the formulation of the ‘neurone doctrine’, which was stated repeatedly in various versions:


Summary: historical concepts of neuroscience


key reading:


some study questions


last update 16-04-2005
Johannes M. Zanker