Biological Basis of Cognition

Lecture 1b Revision

• Lecture 1b provides an overview of the research and key cognitive psychologists associated with behaviourism between 1913-1956.
• Reliable research conducted on cognition prior to 1956 is provided
• Focus on the key moments and theorists that contributed to the cognitive revolution in 1956 is included.
• Strengths and weaknesses associated with the field of Cognitive Psychology are provided

Cognitive Neuropsychology

• An approach to studying brain lesion patients in order to identify where mental processes occur is used
• Modern research started roughly in 1861
• Prior to 1861, there was confusion about what the brain is used for.
• Evidence that brains is involved in mental processing was scarce
• Hippocrates/Plato (400/387 B.C.) felt mental processing occurred in the brain
• Aristotle (335 B.C.) felt mental processing occurred in the heart, stating that the brain was a radiator
• Roman's illegalization of human dissection (150 B.C.) slowed understanding of human anatomy
• Galen (157 A.D.) became a gladiators' physician, studying the effects of their brain injuries on their behaviour.
• Galen suggested mental processes occur in the ventricles of the brain, and also practiced animal vivisection
• Murder Act 1752 (UK) allowed dissection of executed murderer's bodies
• 1819 - Gall published work on phrenology, arguing that the brain has 27 organs with unique functions
• Phrenology is the first theory suggesting localisation of function
• Anatomy Act 1832 (UK) allowed bodies to be donated to science to stop grave robberies

The Birth of Cognitive Neuropsychology

• Medical schools access to bodies improved to study problems patients with mental processing problems
• Broca (1861) performed autopsies on patients with speech production problems with lesions in the same area of the left hemisphere
• This was the first study showing localisation of function, although it was demonstrated in 1836 by Marc Dax
• Wernicke (1874) found speech comprehension patients all have brain damage in another area of the left hemisphere
• Damage to Broca's area causes an area slow, non-fluent, and non-grammatical speech which is meaningful, this is called Broca's Aphasia
• Damage to Wernicke's area causes fast, fluent, and grammatical speech which is meaningless, this is called Wernicke's Aphasia
• Broca's and Wernicke's Areas is is a double-dissociation indicating that speech production and comprehension are associated with two separate processes
• Ground-breaking research was conducted on brain lesion patients to identify brain areas responsible for cognitive processes in the 20th century
• HM is a famous patient whose hippocampi were removed in 1953 to reduce epileptic seizures
• Post surgery, HM had difficulty forming new long-term memories, showing hippocampus function

Strengths of Cognitive Neuropsychology

• Strength 1: Allows drawing of causal inferences about the relationship between brain areas and mental processes
• Strength 2: Helps develop theories about how mental processes work, using patient HM
• e.g. Episodic (Life events) and Semantic (General knowledge) or Procedural (Skills) Memories

Challenges of Cognitive Neuropsychology

• Brain damage is often diffuse, making it difficult to pinpoint which areas control which mental process
• General impairments may result from damage to several areas with different functions
• Functional plasticity is the brain's reorganization to counteract damage
• Incorrect conclusions about which brain areas ordinarily perform a mental process may be drawn if functional plasticity has occurred
• Structural plasticity is the brain's ability to change structure because of age, expertise, health, etc.
• If individual brains vary highly due to structural plasticity, findings from small samples may not generalize
• Patients with lesions can develop coping strategies so impaired mental processes appear normal
• Damage to the Fusiform Gyrus causes prosopagnosia, leading to the use of coping strategies to recognize people

Origins of Cognitive Neuroscience

• This approach used technology to identify where mental processes occur in the brain.
• Modern cognitive neuroscience research began in 1976
• Influenced by Neuroscience, of the study of the entire nervous system including neurotransmitters, hormones, etc.

Important Advances in Neuroscience

• Pre-1800's: it was unclear that brains are composed of millions of individual neurons
• 1873: Golgi immerses a brain slice in silver nitrate, staining 1% of neurons, which were then able to be seen under a microscope
• 1888: Ramón y Cajal used Golgi stains to study newborn animals' brains
• Cajal identified that brains are composed of individual neurons that communicate with one another after studying said brains
• Golgi and Cajal shared the Nobel Prize in 1906 for their findings
• 1920's: It was unclear how neurons communicated
• 1923: Loewi electrically stimulated a dead frog's heart releasing acetylcholine
• The second dead frogs heart initiated beating after acetylcholine from first heart was applied
• Indicated that neurons communicated via electro-chemical signals and Loewi won the 1936 Nobel Prize
• 1920's to 1950's: Single cell recording methods were developed and refined:
• A tiny electrode is inserted into a single neuron
• Participants complete cognitive tasks as the researchers examine whether the neurons are activated

Hubel and Wiesel

• 1960's: Hubel and Wiesel used single cell recording to study neuronal activation in the primary visual cortex (area V1)
• V1 Neurons had different firing rates depending on angle, movement and length
• This lead to the discovery of feature detectors
• 1969/72: Gross et al. used single cell recording to examine perception in the temporal lobe.
• Temporal Lobe Neurons responded to complex stimuli
• 1980's: some studies show some temporal lobe neurons respond to faces, while others respond for objects
• Perception is hierarchical

Hierarchical Processing

• V1 Neurons respond to stimulus like lines with the information combined into more complex shapes that neurons in the temporal lobe process
• Temporal lobe neurons process squares
• The combined shapes are formed by the neurons of process faces

Outstanding Issues in Cognitive Neuroscience

• How neurons retain information about specific stimuli (e.g., specific faces, objects, words etc.) is unclear
• Specificity Coding: Individual neurons for specific faces, objects, words, etc.
• Population Coding: Many neurons fire in unique combinations/intensities for specific stimuli
• Sparse Coding: A few neurons fire in unique combinations/intensities for specific stimuli