WEEK 1: The brain through the ages

• What is neuroscience?

  • The scientific study of the nervous system
  • our nervous system controls behaviour
  • Interdisciplinary - Biology, psychology, computer science, mathematics, physics, philosophy, medicine
• What is the nervous system?

  • A network of neurons in the brain, spinal cord and periphery
  • Central Nervous System (CNS)
  • Brain and Spinal Cord
  • Peripheral Nervous System (PNS)
  • Nerves (Cranial and Spinal)
  • Ganglia (a mass of nerve cell bodies)
• Neuroscience and modern psychology

  • Behaviour is initiated by the nervous system
  • neuroscience can therefore be used to help understand behaviour
  • Psychologists who study biological bases of behaviour → Behavioural neuroscientists (biological psychologists, Biopsychologists)
  • Use physical measurement s of brain function
• Origins of neuroscience 


  Human prehistory -> Ancient Egypt -> Ancient Greece -> Roman empire
• Human prehistory

  • Dates from roughly 2.5 million years ago to 1,200 B.C.E
  • Stone Age, Bronze Age, Iron Age
• Human prehistory

  • Neolithic period
  • Blunt force cranial trauma
  • Cranial trepanation
  • “5-10% of all skulls found from the Neolithic period were trepanned with single or multiple skull openings of various sizes"
• Ancient egypt

  • Earliest written reference to the brain (1600 BCE) – the Edwin Smith Surgical Papyrus
  • Body and most organs were preserved (mummified) after death… but not the brain
• Ancient Greece

  • Hippocrates (c. 460-377 BCE)
  • the theory of the four humours “… the source of our pleasure, merriment, laughter and amusement, as of our grief, pain, anxiety, and tears is none other than the brain”
• Ancient Greece

  • Aristotle (384-322 BCE)
  • “… the brain is not responsible for any of the sensations at all, the correct view is that the sear and source of sensation is the region of the heart”
• Roman empire

  • Galen (130-200 CE)
  • Leading physician of the Roman Empire
  • Saw the brain as the ruling organ of the body
  • Common sense, cognition and memory were all functions of the brain
  • Discovery of ventricles fitted with Hippocrates’ theory of humourism
• The Renaissance

  • Leonardo da Vinci (1452-1519)
  • Sensation, cognition and memory attributed to the “3” ventricles
• The Renaissance

  • Andreas Vesalius (1514-1564)
  • Added more detail to the understanding of brain structure
  • Identified errors in Galen’s anatomy
• The Renaissance

  • René Descartes (1596-1650)
  • Fluid-mechanical theory of brain function
  • Reflexive theory
  • Dualism
• The 18th and 19th century

  Four key insights

  • Nerves are wires
  • Localisation of specific brain functions
  • The neuron
  • Evolution of the brain
• Nerves are wires - 18/19th century

  • Luigi Galvani (1737-1798)
  • Stimulation of nerves in frogs caused muscle contractions
• Nerves are wires - 18/19th century

  • Hermann von Helmholtz (1821-1894)
  • Human physiology is subject to the laws of nature
  • Measured the speed of nerve conduction
  • ~90 ft/sec
  • Slow – not just electrical, but physiological
• Localisation of specific brain functions

  • Johannes Müller (1801-1858)
  • Proposed the “law of specific nerve energies”
  • same nerves which go to different areas of the brain
• Localisation of specific brain functions

  • Marie-Jean-Pierre Flourens (1794 1867)
  • Experimental ablations
  • Intellect = cerebral cortex
  • Lower brain = vital bodily functions
  • Cerebellum = coordination and motor control
• Localisation of specific brain functions

  • Paul Broca (1824-1880)
  • Damage to left frontal cortex = difficulties in language production
• Localisation of specifc brain functions

  • Gustav Fritsch & Eduard Hitzig
  • Muscle contractions contralateral to brain hemisphere
• The neuron

  • Camillo Golgi (1843-1926)
  • Invented a new staining technique
  • Proposed “reticular theory” → interconnected network
• The neuron

  • Santiago Ramón y Cajal (1852-1934)
  • Worked out neural circuitry of many brains’ regions
  • Proposed the “neuron doctrine”
• Evolution of the brain

  • Charles Darwin (1809-1882)
  • “On the origin of species” (1859) considered the foundation of evolutionary biology
  • Natural selection
  • Evolution: Gradual change in structure of physiology of a species – generally producing more complex organisms –as a result of natural selection
  • theory can be attributed to both Darwin AND Russel Wallace
• Vertebrae brains

  • Vertebrate brains are similar in organization
  • All vertebrates have a forebrain, midbrain & hindbrain
  • Brain areas may be specialised in distinct ways in response to environmental constraints
  • e.g., crocodiles have huge olfactory bulbs (brain area for smell)
• Our brain has evolved

  • Brain size increased
  • Proportion of the different areas changed
  • Folding of cerebral cortex increased
• Brain size

  • Brain size has increased
  • But no link between brain size and behavioural complexity
• Proportion between brain and body

  • Brain size needs to be considered alongside body size
  • There is a relationship between proportional brain size and complexity of behaviour
  • Human brain is proportionally larger than any other large animal
• Evolution in hominids

  • The high, straight forehead of modern humans superseded the prominent brow ridges of ancestors due to expansion of cortex, especially prefrontal cortex
• Brain proportions

  • Proportions of parts of human brain are different than other primates
  • Differences in evolutionary development of parts of brain have more effect on behaviour than brain size
• The neocortex

  • Size increased in primates
  • Flexible & almost infinite learning abilities
  • Reflects growing complexity of social lives
  • Growth of certain parts of cortex responsible for social skills (e.g., language) because they improved this ability
• The prefrontal cortex

  • Developed greatly in primates
  • In other species it is primarily used for voluntary motor control
  • In humans: Responsible for unparalled planning & abstract reasoning abilities
  • Modern research:
  • Humans’ superior abilities are attributable to other specialized cortical regions & denser inter-connections between prefrontal cortex & rest of brain
• why is our brain so big?

  • Humans have larger volume of white matter in PFC (compared to most other primates)
  • White matter provides greater connectivity between PFC & rest of brain (compared to other species)
  • Connectivity is vital for working memory functioning
• Increased folding of cerebral cortex

  • Increase in cortex folding has been a major factor in brain evolution
  • Folding = cortical surface area to fit inside the skull
  • Allows better organization of complex behaviours
• Functionalism and inheritance of traits

  • the principle that the best way to understand a biological phenomenon (a behaviour of a physiological structure) is to try to understand its useful functions for the organism
  • e.g. to understand how the nervous system works , we should know what its functions are
• Mutations

  • a change in the genetic information contained in the chromosomes of sperm or eggs, which can be passed on to an organism’s offspring; provides genetic variability → can provide selective advantage
• Selective advantage

  • a characteristic of an organism that permits it to produce more than the average number of offspring of its species
• Neoteny

  • a slowing of the process of maturation, allowing more time for growth; an important factor in the development of large brains
• Triune brain theory

  • we have three brains
  • developed in the 1960s by Paul D. Maclean
  • Three distinct brains emerged through evolution which co-inhabit the human skull
  • reptilian brain
  • limbic brain (paleomammalian)
  • neocortex (neo mammalian)
• Triune brain theory - Reptilian brain

  • Oldest part
  • 300 million years
  • Main structures found in a reptiles brain
  • Brainstem
  • Cerebellum
  • “Regulating & Surviving”
  • Vital functions
  • Basic behaviours (survival)
  • Defending territory
  • Mating
  • Instinctive and automatic
• Triune brain theory - Limbic system

  • aka “paleomammalian” brain
  • Emerged in the first mammals
  • Limbic system i.e., the feeling centre
  • Main structures:
  • Hippocampus
  • Amygdala
  • Hypothalamus