brian disorders

Development of Physiological Influences

• The brain

• Nerve function

• Visual perception

• Brain localization

• Psychophysics

A. The Brain

• Australopithecus africanus

• Trephining

Egyptians

• Threw away brain when mummifying

Greek Doctors: Are There Animal Spirits in There?

• dissected brains and optic nerves; brain is organ of thought

• the soul is in the fourth ventricle and the "animal spirits" (intellectual, motor system) are in the brain itself (cerebrum)

Galen’s Cell Doctrine

• Galen localized the mind to the ventricular system of the brain

• First cell: imaginativa (imagination) and "fantasia" (fantasy)

• Second cell: "aestimativa" (judgment), "cognitativa" (thought) and "ratio" (reason)

• Third cell: "memorativa" (memory)

Pre-Renaissance

• “Animal Spirits”

Renaissance - da Vinci

• da Vinci’s system

• Anterior ventricle: 'intelletto' (intellect) and 'imprensiva’

• Middle ventricle: 'volonta' (will) and 'senso comune’

• Posterior ventricle: 'memoria' (memory)

Renaissance - Descartes

• Agreed with Galen about ventricles

• Nerves are tubes with valves connected at one end to the ventricles (animal spirits) to muscles at the other end (hydraulic theory)

B. Nerve function (electricity view)

Whytt's (b. 1714) Reflex

• Reflexive contraction of pupil to light

• Reflexes were involuntary and depended on spinal cord

• Nervous tissue contained a sentient principle

Galvani-Volta Debate

• Luigi Galvani (b. 1737) claimed that he discovered animal electricity (electrical body fluid)

• Count Alessandro Volta (b. 1745) said that all that happened was that the frog conducted static electricity

• "Galvanic skin response" – GSR

• Volta….. Volts, Voltage

• Giovanni Aldini provided basis for a novel written by a famous writer………...

du Bois-Reymond (b. 1818)

• Discovered the action potential

• He or Galvani the "Father of Electrophysiology“?

Sir Charles Bell (b. 1774)

• Experiments with rabbits

• Francois Magendie – experiments with puppies

Bell-Magendie Law

• dorsal roots of spinal nerves bring in sensory information

• ventral roots carry motor fibers down to the muscles

Johannes Muller (b. 1801)

• Directly aware only of the activity in our nerves, not external reality

• Doctrine of specific nerve energies - same stimulus applied to different sensory nerves results in different sensations

C. Research on Visual Perception

Hermann von Helmholtz (b. 1821)

• Medicine, physics, math, psychology, music, philosophy

• "On the conservation of force“• Metabolism• Determined wavelength of ultraviolet light• Optics• Theory of velocity of air in open tubes

(acoustics)• Thermodynamics (Law of conservation of

energy)

Contributions to Psychology

• Measuring the speed of the nerve impulse (REACTION TIME)

• Young-Helmholtz trichromatic color theory

• Place theory of pitch perception

Ewald Hering (b. 1834)

• Opponent-process theory of color perception

Hering Illusions

Hering bow

Jan Purkinje (b. 1787)

• Shift from cone to rod vision in twilight

• Purkinje effect in stars - red source will cease to be visible before the yellow or white source

D. Brain Localization

Phrenology

Franz Gall (b. 1758); his pupil Spurzheim

• The mysterious “Miss Leisler”

• "Neither sin nor friends will ever leave me."

Gall’s Work on Nervous System

• Nervous system is like a tree

• Distinction between gray matter (neurons) and white matter (axons)

• CNS fibers terminate in the cortex, not the medulla

• Identified origins of cranial nerves I-VIII

• Pyramidal tracts crossing brain hemispheres

Gall’s Claim:

• Mental activities localized in the cortex

• Wanted to develop a functional anatomy and physiology of the brain, as well as a revised psychology of personality

• Led to theories concerning localization and cranioscopy

The System of Organology

• Brain is organ of the mind

• Brain is a collection of organs representing various propensities, sentiments, faculties

• Size of each organ indicates its power

• Skull conforms to brain's shape

• Mind's functions located in different places in the brain

How Many Faculties of Mind?

• Gall sez 27• Spurzheim sez 37

Napoleon’s & Descartes’ Heads

Phrenology taken over by Quacks

• Employment• Marriage prospects• Children's prospects• 1920's - “The

Psychograph”

Problems with Phrenology

• Arbitrary choice of faculties

• Observations not fitting in explained away

Contributions of Phrenology

• Established brain as the source of mind

• Mental functions localized in the brain

Pierre Flourens (b. 1794)

• "An Examination of Phrenology" 1824

• Ablation technique- removal of one of six separate areas of brain

6 Different Brain Functions

• Cerebral hemispheres - willing, judging, memory, seeing, hearing

• Cerebellum - motor coordination• Medulla oblongata - mediation of sensory/motor

functions• Corpora quadrigemina (inferior/superior colliculi)

- vision• Spinal cord - conduction• Nerves - excitation

Flourens vs. Gall

• Flourens’ approach reflected localization, but he stressed the common action of the various parts

• Emphasis on the common unity of the entire system

“Recovery of Function”

• Also observed recovery of mental function over time - forerunner of "neural plasticity"

Brain Localization: The Story of Phineas Gage

• Sept. 13, 1848 - Vermont - a deadly day for Phineas

• Iron rod entered under left cheek, exited through top of head, landed 30 yards away.

• Dr. John Harlow

• MRI analysis by Damasio shows damage in ventromedial region on left side of brain

http://www.offoffoff.com/theater/2002/phineasgage.php3

Language Localization in Brain

Paul Broca (b. 1824)

• Patient named Leborgne

• Autopsy showed lesion to 3rd convolution of left frontal lobe

• Concluded this area important for speech articulation

Broca’s Brain!

Karl Wernicke (b. 1848)

• Damage in top left temporal lobe causes poor language comprehension (Receptive aphasia)

Psychophysics – the Beginning of Psychology?

Ernst Weber (b. 1795)

• Investigated 2-point thresholds for touch

• Jnd's investigated for various stimuli

• Jnd's vary by a constant ratio called “Weber Fraction”

• First to quantitatively measure the mind?

Gustav Fechner (b. 1801)

• "Elements of Psychophysics" 1860

• The term “Psychophysics” coined - science of studying the relation between the physical and the mental (stimulus and sensation)

• Fechner's Law• Devleoped: method of limits, method of

constant stimuli, method of average error (adjustment)