module 2

• Cerebrum

  • Cerebral Hemispheres
  • Forebrain
  • Cerebellum
  • Hind brain

  
• Cerebral Hemispheres

  • Two Hemispheres, divided by Longitudinal Fissure or Inter-Hemispheric Fissure

  
• Cerebral Cortex

  • The outermost surface layer of the cerebrum
  • Grey matter
  • 2 to 4 mm thick
  • Contains the cell bodies of the brain's neurons
  • Highly folded to maximize surface area
  • White matter underneath the grey matter is all the "wiring" i.e. axons of the neurons, connecting to the spinal cord and to other areas of the cortex

  
• Frontal Lobe

  • Executive Functions: reasoning, planning, problem-solving
  • Inhibitory control
  • Working memory
  • Motor functions: Premotor cortex – motor planning, Primary motor cortex – execution
  • Speech production (Broca's area)

  
• Parietal Lobe

  • Primary Somatosensory Cortex: Perception of touch
  • Sense of space and locations: Gives sense of stable world around us relative to our body position
  • Spatial attention: Directing attention and eye-movements to explore visual world
  • Linking vision to action: Represents spatial location of objects around us for guiding actions

  
• Occipital Lobe

  • Primary Visual Cortex (V1): All visual perception
  • Higher visual areas: Different regions process shape, colour, orientation, motion

  
• Temporal Lobe

  • Primary Auditory Cortex: Perception of sound
  • Language Comprehension (Wernicke's area)
  • Medial Temporal Lobe: Limbic system, amygdala and hippocampus
• Limbic System

  • Amygdala: Fear and arousal, Responds to threat / danger, Fear / learning Phobias
  • Hippocampus: Learning and Memory, Forming new episodic memories, Damage causes anterograde amnesia (can't form new memories of events)
• Corpus Callosum

  • Neuron connections between the left and right hemispheres
  • Allows brain communication between hemispheres
  • "Split-Brain" patients – left and right hemispheres disconnected. The two hemispheres cannot communicate with each other.
• Important role of frontal lobe for executive control of behaviour
• Broca's Area

  • Speech Production
• Broca's Aphasia

  • Speech is slow and non-fluent
  • Difficulty finding appropriate words (anomia)
  • Speech still carries meaning
  • Comprehension is (mostly) unaffected
• Wernicke's Area

  • Language Comprehension
• Wernicke's Aphasia

  • Unable to understand language – deficit in comprehension
  • Speech is fluent with normal prosody (rhythm, intonation)
  • Speech has no meaning, nonsense speech
• Left Hemisphere: Broca's and Wernicke's area, Speech production and Language comprehension
• Homunculus


  • Primary Sensory cortex and Primary Motor cortex
  • Brain function "mapped" by electrical stimulation
  • Brain stimulation leads to sensation or movement (muscle twitch)
  • Size of area on cortex determines sensitivity or fine motor control

  
• Brainstem

  • Central Nervous System: Brain and spinal cord
  • Peripheral Nervous System: Somatic Nervous System (Voluntary, Motor and Sensory), Autonomic Nervous System (Involuntary, Heart-rate, respiration, sweating, Stress, arousal, "fight-or-flight")

  
• Autonomic Nervous System

  • Sympathetic Nervous System: Emotional arousal, stress, fear, "Fight or Flight" response, Increases heart-rate, respiration, perspiration, pupils dilate
  • Parasympathetic Nervous System: "Rest and digest", Lowers heart-rate, respiration, Increases stomach, intestine activity (digestion), "opposes" the sympathetic nervous system
• Brainstem: Medulla


  • Autonomic nervous system functions, Controls heart-rate, respiration, regulation of blood pressure, body temperature, Reflex centres for coughing, sneezing, swallowing, vomiting
• Persistent Vegetative State


  • Severe damage to upper brain (hemispheres and cortex)
  • If brainstem is not damaged, autonomic nervous system functions can remain
  • Sometimes normal respiration, control of heart rate, some face and eye movements remain
  • Patients have no conscious awareness

  
• "Locked-in" Syndrome

  • Amyotrophic Lateral Sclerosis (ALS) or Motor Neuron disease: Loss of motor neurons to spinal cord, or Brain injury (following accident)
  • Intact cerebrum and brainstem, but "disconnected" from spinal cord
  • Normal cognitive function, vision, and hearing, but patients cannot move
  • Patients may be fully conscious and aware, but totally unresponsive
• Low-level to High-level function


  • Cerebral Hemispheres – Cortex: Planning, reasoning, problem-solving (frontal lobe), Language and Perception
  • Brainstem: Autonomic nervous system functions (heart-rate, respiration, blood pressure)
• Cerebellum

  • Hind brain (latin for little brain)
  • Sense of balance and co-ordination of complex movement
  • Motor learning – fine adjustment of movement based on feedback
• Primary Motor and Sensory Areas

  • Primary motor cortex activity leads to movement (muscle contraction)
  • Primary sensory cortex activity leads to sensation
  • Different parts of motor and sensory cortex map to different parts of the body (homunculus)

  
• "Motor Programs" for movement

  • Movements planned and "programmed" in the brain before initiation, like a computer program
  • Brain creates program just before movement, or Brain retrieves program for learnt skilled actions
• Feedback control of Movement

  • Planned actions compared with feedback from actual actions performed
  • Vision, Sensation (hands on racquet), Proprioception (body position)
  • Brain computes difference between planned action and feedback during performed action, Rapidly correct action, Learn for future
• "Did I do that?" Sense of Agency

  • Brain automatically links sensory events and own-actions to infer causality
  • Sense that my action caused that event
  • Can't tickle yourself !!
  • When feedback matches predictions from planned actions
• Scales of Explanation in Psychology


  • Social group / community
  • Person
  • Brain
  • Neural circuits / networks
  • Neuron
  • Molecules
  • Synapse
• Neuron


  Common to all cells, contains nucleus and all structures necessary for cell functioning (DNA)
• Neuron


  • Cell Body - Unique to neurons, receives signals - input zone, many per neuron, receives input from many other neurons
  • Dendrites - Unique to neurons, sends signals - output from axon hillock at cell body to axon terminals, one per neuron - only one axon for output, wrapped in myelin for efficient transmission of signals along the axon
  • Axon - Terminal boutons / buttons form synapses with other neurons, secrete neurotransmitters to send signals across synapses to other neurons
• Glial Cells


  Supporting cells for neurons, 3 types: Oligodendrocytes - produce the myelin sheath that wraps around axons, Astrocytes - supply nutrients from blood to the neurons and maintain "blood-brain barrier", Microglia - brain's immune system, clean up foreign or toxic substances
• Myelin


  Oligodendrocytes form myelin sheath by wrapping around the axon, essential for efficient communication, for propagation of signals along axon, Multiple Sclerosis involves loss of myelin, disruption of efficient neural communication throughout the body
• Synapse


  Join axon terminals of one neuron to dendrites of another neuron for transmission of signals between neurons, neural signals go one-way - pre-synaptic (from cell body to axon terminal), post-synaptic (from dendrite to cell body)
• The Cognitive Neuroscience Toolbox

  • Lesion studies
  • Brain stimulation
  • Single neuron recording (animals)
  • EEG: Electroencephalography
  • MRI: Magnetic Resonance Imaging

  
• Membrane Potential


  Difference in the electrical charge (voltage) between inside and outside cell, across cell membrane wall
• ERPs: Event-Related Potentials


  Brain activity related to a specific event or stimulus

  
• fMRI: Functional Magnetic Resonance Imaging


  Measures change in blood oxygen level, change in blood flow associated with neural activity
• Neuropsychology – Brain Lesions


  • Explains normal brain function by examining what changes when part of the brain is damaged
  • Stroke or brain injury in humans
  • Induced lesions in animals (electrical/chemical)
  • Assumption: Whatever changes in behaviour/cognition must rely on that part of the brain that is damaged

  
• Resting Potential


  At rest (i.e. NOT during an action potential) more positive ions outside than inside the cell gives overall negative potential (voltage) inside compared with outside the cell, difference in electrical charge (voltage) at rest = -70mV
• Single Neuron Recording


  1. Place a thin electrode into an animal's brain

  2. Record action potentials "firing" from a single neuron

  3. Measure what that neuron encodes or detects