L4-Brain Function and Localization

Brain Functioning

• Research in brain function transitioned from phrenology to understanding where specific functions of the brain are located by studying patients with brain damage.
• Interest in electrophysiology and exploration of the link between the brain and behavior also emerged.
• Brain physiology evolved similarly to nerve function.
• In the 18th century, assumptions based on behavior and skull shape informed early understandings of the brain (phrenology).
• Clinical methods using humans with brain damage will reveal the brain/body link in terms of language and other behavior.
• Deliniating brain regions will become more accurate through electrophysiology experiments.

Franz Joseph Gall (1758 – 1828)

• As a child, Gall observed that classmates with larger, bulging eyes were able to memorize verbal material more easily.
• As an adult neuroanatomist, he sought to scientifically find modularity and localization of brain functions.
• Gall developed early ideas about phrenology, originally named Organology.
• He dissected animals and humans, taking a bottom-up approach.
• He found that the brain did not have a central processing unit, but rather proliferated outwards to regions of the cortex.
• Gall used cranioscopy to decipher the magnitude of one's faculties by examining the bumps and depressions on one's skull.

Cranioscopy

• The shape of a person's head was believed to reveal intelligence and emotional character.
• If a faculty was well developed, the brain region will grow and a bump will be noticeable on the skull.
• If a faculty was underdeveloped, it will cause an indent.
• Gall's atlas showed different plates (some overlapping, some far apart) of the skull.

Faculties of the Mind

• Gall proposed the brain was divided into 27 separate "organs," each corresponding to a discrete faculty.
• 19 of the organs were shared with other animal species, and eight were specific to humans.

Johann Gaspar Spurzheim (1776 – 1832)

• Spurzheim saw organology as an opportunity to advance his own career.
• In 1813, Spurzheim and Gall parted ways, and Spurzheim developed organology into phrenology.
• Spurzheim became a popular lecturer and writer.
• The public was interested in phrenology because of the mental muscle approach suggesting that if you were lacking in one area, you could work towards improving it.

Phrenology

• A phrenology chart suggested by Spurzheim in 1834 involved palpating the skull to see which faculties are dominant.
• Phrenology would move away from scientific evidence.

Phrenology: Side Show

• The psychograph, patented in 1905 by Henry Lavery, was a novelty device featured in department stores and theatre lobbies during the Great Depression.
• For a fee, The Psychograph Company operated from 1929 to 1937, describing a patient's personality by print-out in thirty-two categories in five minutes.

Phrenology in the USA

• Phrenology came to America in 1820, with a lecture to the Massachusetts Medical Society by John Collins Warren.
• The Fowlers brothers developed a successful business providing phrenological consultations, also selling phrenology busts for $1 each.

Pierre Flourens (1794 – 1867)

• In 1815, Flourens attempted to scientifically disprove phrenology.
• He used the method of ablation or extirpation, destroying part of the brain to note behavioural consequences and investigate localization of functions in the brain.
• His findings were contrary to phrenologists.

Ablation Studies: Experiments

• Experiments with pigeons and rabbits showed that ablation resulted in behavioural disturbances.
• Removal of the vestibular system in pigeons resulted in a loss of proprioception.
• Removal of the cerebellum in pigeons resulted in no muscular coordination.

Ablation Studies: Observations and Findings

• Destroying the medulla oblongata resulted in the death of the animal.
• Parts of the mid brain control visual and auditory reflexes.
• Flourens found that much of the brain worked as a single unit and that function lost to ablation was sometimes regained later.
• Flourens challenged Gall's view that personality could be attributed to the size or shape of the brain.
• Indents on the skull were hardly ever reflective of the state of the brain.

Paul Broca (1824 – 1880)

• Broca observed someone with a brain disorder in a clinical setting.
• The clinical method involves posthumous examination of brain structures to detect damaged areas assumed to be responsible for behavioral conditions that existed before death.
• Broca treated a man only capable of saying the word "Tan" because he could not say any other word, though could comprehend speech, named Louis Victor Leborgne.
• In 1861, Broca dissected Leborgne's brain and found a lesion in the left hemisphere's frontal lobe caused by neurosyphilis, which, he concluded, had been responsible for Leborgne's loss of speech.

Broca's Area (1861)

• This region, the left, lateral portion of the frontal lobe, appeared to be responsible for speech production was called Broca's area.
• Broca's aphasia involves an impairment in language.
• Broca also engaged in craniometry to determine the relationship between brain size and intelligence and concluded that a larger brain meant the person was more intelligent; suggesting that men are smarter than women.

Broca's Aphasia

• Someone with Broca's aphasia understands the questions but often has trouble formulating the words they want to use.

Wernicke's Area

• Approximately 10 years later, Carl Wernicke identified a similar type of problem as Broca, but patients were able to speak but not able to actually comprehend language.
• Lesions were revealed at a junction of the parietal, temporal, and occipital lobes in the brains of patients suffering from this language problem.
• Wernicke's area is associated with the understanding of spoken and written language.

Wernicke's Aphasia

• Someone with Wernicke's aphasia can produce speech but their responses do not make any sense.

Phineas Gage (1848)

• There was much more research in neuroscience which further shows the effects of brain damage on localized brain regions causing a change in behaviour.
• In 1848, Phineas Gage was a foreman working on a railroad and was using a tamping iron when the powder detonated prematurely.
• The tamping iron drove through Gage's left cheek, into his brain and exited through his skull.

Frontal Lobe Damage

• Gage survived the accident but began acting very differently.
• He became irritable, used profanity, and had a difficult time making and following through with plans.
• He was unable to maintain a job or a relationship.
• Gage would become the exemplar of what the frontal lobe is responsible for, specifically executive functioning (planning, emotional regulation, delaying gratification).

Electrophysiology

• During the Danish-Prussian war of 1863, Eduard Hitzig was able to work with soldiers wounded in battle with exposed brains.
• He applied wires from a battery to the cortex and then observed involuntary reactions, twitching and/or screaming.

Gustav Fritsch and Eduard Hitzig (1870)

• In 1870, Hitzig joined another physician, Gustav Theodor Fritsch, to test the hypothesis that the motor area is in the cortex.
• They restrained live dogs and removed parts of their skulls to expose the cortex.
• With a current from a battery, they stimulated different regions noticing the cortex was not insensitive.
• If a region on the right hemisphere was stimulated, the left leg moved, discovering both the motor cortex and contra-laterality.

David Ferrier (1843 – 1928)

• In 1876, Ferrier used similar methodology as Fritsch and Hitzig, but using non-human primates.
• He was able to fine tune regions that would provoke the movement of one finger or even the twitch of an eyelid.

Nerve Physiology

• In the 17th-19th century, bodies were believed to function like machines.
• Descartes suggested that animals and human bodies functioned as a machine.
• Descartes believed that nerves were hollow tubes with thin threads; when animal spirits were released, the fibers allowed for reflex.
• Nerves are not hollow, there is directionality and specificity.

David Hartley (1705 – 1757)

• David Hartley became known as the father of associationism due to his physiological perspective of this process.
• He was influenced by Newton and Locke.
• Hartley contended that a physiological response was required to engage the physical mind, synthesizing Newton's conception of nerve transmission with empiricism.
• Newton contended that nerves were solid.
• Newton believed that when a vibration in the nerves had started, the law of inertia maintained it.

Vibrations and Vibratiuncles

• Hartley suggested that whenever there is an interaction with the world, there begins a vibration in the nerves which carries the vibration to the brain.
• The vibration in the brain causes sensations.
• Vibrations in the brain are sustained via inertia, even after the impression is gone.
• This lingering vibration forms an idea.
• Ideas are vibratiuncles (formed from sensations) that are less intense vibrations.
• Ideas may become associated through contiguity.
• Similar to Locke, Hartley postulated simple and complex ideas.
• Simple ideas become associated to form complex ideas when vibratiuncles come together through contiguity or simultaneous association.

Involuntary to Voluntary Behavior

• Nerve vibration was also responsible for the experience of pleasure and pain, suggesting a hedonist perspective of motivation.
• Mild to moderate vibration produced pleasure and excessive nerve vibration produced pain.
• Through experience, people associate certain behaviors with pleasure or pain, and as such will either continue a behavior or not.

Luigi Galvani

• Luigi Galvani studied the electrical nature of nerve impulses.
• His research culminated in De vibus electricitatis in motu musculari commentarius.
• Electricity could generate a muscular contraction.
• This discovery occurred serendipitously when his assistant was using a scalpel on a nerve in a frog's leg, when a spark from a nearby generator caused the leg to twitch.

Reflex Experiments

• Galvani sought to replicate the finding that electricity could generate a muscular contraction with frog legs hanging on a copper wire during a thunderstorm.
• He believed that the animal tissue contained an “animal electricity”.
• Alessandro Volta proved that the electricity did not emerge from the animal tissue itself, but from the effect produced by the contact of two different metals.

Giovanni Aldini

• Giovanni Aldini travelled around Europe, drawing up big crowds to watch him apply an electrical stimulation to dead animals.
• In London, 1802, he electrically stimulated the heads of cows making their eye lids twitch, or their jaws begin to move.

Reanimating Corpses

• Aldini “Galvanized” the corpse of George Forster, who had just been executed for murdering his wife and child, in 1803.
• Aldini electroshocked the face (twitching the eyes and mouth) and inserted an electrified rod into the corpse's rectum (causing the body to spring up and animate, terrifying the onlookers).
• Mary Shelley was inspired by Galvani and Aldini's work to write Frankenstein.

Bell-Magendie Law

• Charles Bell and Francois Magendie demonstrated that sensory nerves enter the dorsal roots of the spinal cord and motor nerves emerge from the ventral roots.
• Bell and Magendie shared the acclaim for nerve specificity and proved that nerve physiology could be divided into sensory and motor function.

Developments in Early Physiology

• In 1811, Charles Bell suggested that there were two different types of nerve fibers: motor and sensory.
• In 1822 Francois Magendie used live puppies, stimulating anterior spinal cord portions resulted in movement (motor neurons) with no sign of pain.
• Stimulating posterior spinal cord portions resulted in pain (sensory neurons) without the ability to pull away.

From Hollow Tubes to Nerve Specificity

• Sensory nerves carried impulses from sensory receptors to the brain, whereas motor nerves carried impulses from the brain to muscles and glands.
• Nerves are no longer thought of as general conveyers of vibrations or spirits.

Doctrine of Specific Nerve Energies

• Müller demonstrated each sensory nerve contains specific energy that, when stimulated, will create a sensation.

Johannes Müller (1801 – 1858)

• Johannes Müller researched and wrote extensively about the human and animal visual system.

Expanding the Bell-Magendie Law

• Müller replicated the findings of Bell and Magendie, in terms of motor and sensory nerves.
• He located motor and sensory nerves of the frog, and found that, by cutting the motor nerve, the frog could still sense the stimulus but was unable to move.

Doctrine of Specific Nerve Energies

• Müller expanded on Bell and Magendie's findings by demonstrating even more specificity to sensory nerves.
• Each of the five types of sensory nerves has its own energy and results in a characteristic sensation.
• Each nerve responds in its own characteristic way, regardless of the stimulation that activated it.

Adequate Stimulation

• Each sensory system is maximally sensitive to a specific type of stimulation (specific irritability)
• Adequate stimulation refers to light waves for the visual system, sound waves for the auditory system, temperature/texture for touch, and chemicals for taste/smell.

Experiencing the World

• Correspondence between the physical world and our experience depends on our senses being adequately stimulated and our ability to bring all these sensations together to form a picture of the world.
• Vision: seeing trees and flowers.
• Hearing: the sounds in nature.
• Touch: holding the flower.
• Smell: sweet scent from flowers.
• It is our nervous system that creates our picture of the world rather than the stimuli themselves.
• Mueller suggested that Kant's categories of thought might actually be the nervous system.
• The nervous system is the intermediary between sensation and perception.
• Our nervous system gives us phenomenal experience.

Nerve Impulses and Perception

• Advances in physiology and the functioning of the brain/nervous system further clarify the mind-body debate.
• An understanding of nerve conduction allows for reaction studies.
• Interest in the specificity of sensory nerves and sensory modalities, specifically vision, will allow for the creation of the ophthalmoscope and will allow doctors and researchers to learn more about the retina.
• This also extends to theories of colour vision.

Hermann von Helmholtz (1821 – 1894)

• Helmholtz can be considered one of the greatest scientists of the 19th century and a prolific researcher in physics and physiology.
• He made an instrumental contribution to psychology, specifically in terms of the study of metabolism as well as sensation/perception, specifically vision.
• Emphasized mechanism and determinism, fighting against vitalism, assuming that the human sense organs functioned like machines.

Principle of Conservation of Energy

• In 1847, von Helmholtz researched metabolic processes in frogs, discovering the food and oxygen could account for energy expenditure. He extended the principle of conservation of energy to all living things.
• Energy within a system is constant, cannot be added or subtracted, and can be transformed from one thing to another.

Rate of Nerve Conduction

• Assuming the materialist perspective, nothing was unmeasurable.
• Von Helmholtz sought to measure the rate of nerve conduction, which others believed to be impossible because of vitalism.
• Von Helmholtz used frogs and isolated the nerve that traveled to the frog's legs: stimulated this at different places and measured the response time.
• The difference in response time allowed him to calculate that the rate of nerve conduction was approximately 90 feet per second.

Studying Human Reaction Time

• Similar to the frog studies, von Helmholtz studied human reaction time in order to estimate the nerve impulse.
• For humans, von Helmholtz asked participants to push a button when they felt their leg being stimulated, finding that the location of the stimulation made a difference in response time.
• Stimulating the leg closer to the toe resulted in a longer response time, whereas stimulating the thigh resulted in a shorter response time.
• He noted that the rate of nerve conduction was between 165 to 196 feet per second.
• The slowness was also due to the reliance on reaction times which tend to be different between people.

Theory of Perception

• Von Helmoltz also contributed to Psychology in terms of perception.
• He believed sensations were raw elements of experience and that perceptions were due to the assigned meaning of the sensation.
• To explain the transformation from sensation to perception, he relied on the ideas of unconscious inference of past experience.

Creating the Ophthalmoscope

• In 1851, von Helmholtz invented the ophthalmoscope which allows doctors and researchers to look at the retina.
• The ophthalmoscope allowed access to the posterior portion of the eye.

Trichromatic Theory of Colour

• Von Helmholtz sought to challenge Mueller's idea that colour vision had one specific nerve energy.
• He suggested that there were three types of color receptors corresponding to the three primary additive colours (red, green, and blue).
• The firing of these receptors in various combinations results in subjective color experiences corresponding to various wavelengths of light.
• This is known as the Young-Helmholtz theory of colour or the Trichromatic Theory of Colour.

Resonance Theory of Hearing

• Challenging Muller's idea that hearing just had one specific nerve energy, Helmholtz proposed a resonance place theory of auditory perception in which pitches of sound are determined by the location on the basilar membrane where most vibration occurs.
• The cochlea has different sized hair cells that are able to vibrate based on incoming sound.

Challenging Tri-Chromatic Theory

• In 1892, Hering proposed an alternative theory of colour vision to Helmholtz's tri-chromatic theory stating that some colours do not blend.

Opponent Process Theory

• There are photoreceptors, linked together to respond in an opponent process manner: red-green, blue-yellow, and black-white.
• Activation of one, inhibits the other.

Opponent Process Theory: Summary

• When one of the receptors is fatigued, the opposing receptor will be engaged.
• Remember the pairings: red-green, blue-yellow, and black-white, activation of one inhibits the other.
• Both von Helmholtz and Hering were correct--Von Helmholtz's theory is correct at the retina level, but that neural processes further up in the system work in Hering's opponent process manner.

Christine Ladd-Franklin (1847 – 1930)

• In 1892, Ladd-Franklin also proposed a theory of colour vision, but was based on evolutionary theory and evolution of the physiology of the system.
• She believed that the ability to perceive colour combinations evolved over time.
• Achromatic vision came first, then blue-yellow sensitivity, and finally red-green sensitivity.
• In 1926, Ladd-Franklin received her PhD at age 78; she completed her studies in logic and mathematics and all of the requirement for a PhD in 1882, but was denied the degree because of her gender.

Psychophysics and Early Experimental Psychology

• There was a growing interest in how the body was perceiving the stimulus presented.
• Key researchers: Johann Friedrich Herbart, Ernst Heinrich Weber and Gustav Theodor Fechner.
• Researchers began to use varying stimuli to measure a response and thus, psychophysics was born.

Can We Use Math as a Means to Study the Mind?

• Herbart, a German philosopher, took Kant's contention that psychology needed to be mathematical to be a true science and set out to do just that.
• He proposed that numbers could be assigned to psychological experiences of different intensities.

Psychic Mechanics

• Herbart believed that ideas had a force or energy of their own and the laws of association were not necessary to bind them--psychic mechanics.
• Ideas have the power to attract or repel other ideas, depending on their compatibility.
• Compatible ideas come together and form an apperceptive mass--a group of compatible ideas that are in consciousness to which we are attending at any given moment.
• Ideas outside the apperceptive mass (incompatible ideas) will be repressed by the powers of the ideas in the mass.
• Herbart distinguished a limen or the threshold between conscious and unconscious.
• Anything below the limen will not be consciously perceived--it is subliminal.

Ernst Heinrich Weber (1795 – 1878)

• Weber was interested in kinesthesis, which is the study of muscle sense or the ability to detect changes in body position and movements without relying on information from the five senses.

Two-Point Sensitivity

• Weber investigated the sense of touch by using a two-point caliper.
• The more sensitive the region, the closer together the two points of the caliper can be while being detectable as two individual points.
• Sensitivity ranged from most sensitive on the tongue to least sensitive on the back.
• Touch was actually several senses: pressure, temperature, and pain.

Just Noticeable Difference

• Weber also experimented on the smallest amount of change that is required to notice a change in the stimulus--a just noticeable difference (JND), which is essentially the threshold of perception.
• Weber studied this with a series of weight discrimination experiments.
• Participants were given one standard weight and one comparison weight, this varied over multiple trials.

The Results

• The weight of the standard stimulus influenced the JND, such that as the weight of the standard stimulus increased, so did the JND.

Calculating the JND

• JND was a constant fraction of the original weight. Participants lifting: 1/40; Keeping hand on the table: 1/30.

Weber's Law

• This calculation became known as Weber's Law (later Weber – Fechner's law).
• Weber's law shows that the amount of change necessary to notice a difference (JND) is a constant fraction relating to the stimuli.
• This was the first quantitative law in psychology and a clear method for investigating the relation between body and mind, between stimulus and sensation.

Gustav Theodor Fechner (1801 – 1887)

• Fechner was interested in the mind-body connection, using Weber's work and math to study sensation/perception.
• Fechner's goal was to find a way to measure perceptions in the same way temperature can be measured.

The Birth of Psychophysics

• A systematic relation between physical and mental experience could be demonstrated by varying a stimulus and asking participants to report the changes in sensation.
• Psychophysics is a branch of study involving physical measurement and quantification of psychological phenomena.

Threshold Theory: Signal Detection

• The stimulus must reach a threshold before it is consciously detected.
• Fechner assumed that the intensity started at zero and all the while asking if the participant could perceive it.
• Signal Detection:
  • Hit: The stimulus was present and the participant detected it.
  • False Alarm: The stimulus was detected, but wasn't actually there.
  • Miss: The stimulus was presented but the participant did not detect it.
  • Correct Rejection: The stimulus was not there and the participant did not detect it.

Absolute Threshold

• If the signal is perceived at a certain intensity 50% of the time, that is the absolute threshold.
• Absolute threshold is the lowest intensity at which a stimulus can be detected.
• Quantified for different sensory modalities by Fechner:
  • Vision: candle flame 30 miles away.
  • Hearing: watch ticking 20 feet away.
  • Smell: drop of perfume in a 6-room house.
  • Taste: teaspoon of sugar in a gallon of water.
  • Touch: wing of a fly on your cheek, dropped at 1 centimeter.

Threshold Theory: Discrimination

• Fechner also studied discrimination of stimuli.
• Difference threshold is also known as the just noticeable difference (JND).
• Fechner devised different methods of research for psychophysical measures:
  • Method of limits (stimulus changes in ascending/descending order)
  • Method of constant stimuli (stimuli are shown in a randomized manner)
  • Method of adjustment (participant is in charge of the change in intensity)

Wrap Up

• The empiricist-mechanistic view gave us the body as a machine which led to advances in physiology as researchers began to discover how the gears and pulleys work.
• Key physiological functions identified in this lesson: brain region for language formation, different one for language comprehension, and one responsible for executive functioning such as planning/inhibition.
• The nervous system was also found to be specific versus general conveyers of vibrations or spirits: Bell and Magendie proved separate sensory and motor nerves.
• We are able to experience colour because the visual cortex processes light waves and allows us to experience colour.
• Rationlist Influence: saw that consciousness can be quantified in terms of a limen (threshold)
• Freud's dynamic unconscious has roots in Herbart's apperceptive mass.

Consciousness

• Through psychic mechanics, ideas come together and form an apperceptive mass, crossing the limen into conscious awareness.

Psychophysics

• Using Weber's two-point sensitivity tests, different levels of sensitivity in different body regions was described.
• Scientists use the just noticeable difference to indicate the level of change between two stimuli.
• This is known as Weber's law--the first math formula and law in psychology.
• Fechner set up lab experiments/testing procedures to create psychophysics, establishing absolute/difference thresholds.