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The Brain and Behavior Outline • • • • • • • • Functions Evolution: structure and behavior Basic Unit: The Neuron Generation: How does a signal get started? Action Potential: How does a signal move? Synapses: What does the signal do? Reflexes: A model Brain Organizing Principles and Functions Functions • • • • • Communication Coordination Control Cognition Complexity Outline: Start With A Mechanistic View • • • • • • • • Functions Evolution: structure and behavior Basic Unit: The Neuron Generation: How does a signal get started? Action Potential: How does a signal move? Synapses: What does the signal do? Reflexes: A model Brain Organizing Principles and Functions Evolution • • • • None Nerve net Segmented Cephalization: an organizing principle (brainmind correlation not always obvious!) • Kineses • Taxes • Reflexes Evolution Brain Structure Brain Structure Brain Structure DRUGS Evolution • • • • • • • None Nerve net Segmented Cephalization: organizing principle + brain-function rel. Kineses Taxes Reflexes Reflexes • Kinesis (potato bug) • Taxis (moth / maggot / fly / tick) • Reflex: (knee jerk) – Descartes 161 St. Germaine on the Seine – Pineal – Mechanist Reflexes • Braightenberg: Vehicles Outline • • • • • • • • Functions Evolution: structure and behavior Basic Unit: The Neuron Generation: How does a signal get started? Action Potential: How does a signal move? Synapses Reflexes: A model Brain Organizing Principles and Functions The Neuron • 100 billion • Varied in size, shape, function • Function of neuron sending signals in real time (ex.) • What is the signal? - electrical / chemical Outline • • • • • • • • Functions Evolution: structure and behavior Basic Unit: The Neuron Generation: How does a signal get started? Action Potential: How does a signal move? Synapses Reflexes: A model Brain Organizing Principles and Functions Origin of nerve signal • Function of neuron sending signals in real time (ex.) • What is the signal? - electrical / chemical Generation • Two forces: – Electrical (ionic) – Chemical (concentration) – Give rise to steady-state voltage “resting potential” – Universal in cells Outline • • • • • • • • Functions Evolution: structure and behavior Basic Unit: The Neuron Generation: How does a signal get started? Action Potential: How does a signal move? Synapses Reflexes: A model Brain Organizing Principles and Functions Action Potential Movement of a Signal Action Potential • Cell actions • Speed: Muller (light), Helmholtz (43 m/sec) • Refractoriness • All or none law • Coding of intensity: analog-digital + recruitment (organizing principle) Neuron Communication • Propagation is much faster if the axon is myelinated: • Depolarization proceeds down the axon by a number of skips or jumps. • The action potential obeys the all-ornone law: • Once it’s launched, further increases in stimulus intensity have no effect on its magnitude. Neuron Communication • Propagation is much faster if the axon is myelinated: • Depolarization proceeds down the axon by a number of skips or jumps. • The action potential obeys the all-ornone law: • Once it’s launched, further increases in stimulus intensity have no effect on its magnitude. • Frequency signals intensity Outline • • • • • • • • Functions Evolution: structure and behavior Basic Unit: The Neuron Generation: How does a signal get started? Action Potential: How does a signal move? Synapses Reflexes: A model Brain Organizing Principles and Functions Synapses: What happens when signal reaches end of neuron? • Two types of actions - excitatory / inhibitory • Chemical model with multiple & functionally different neurotransmitters • Temporal & spatial summation Synapses Release of Neurotransmitter Synapses Outline • • • • • • • • Functions Evolution: structure and behavior Basic Unit: The Neuron Generation: How does a signal get started? Action Potential: How does a signal move? Synapses Reflexes: A model Brain Organizing Principles and Functions A Model for building behavior out of simple building blocks • • • • Reflexes Voting behavior Mirror neurons Other examples to follow Reflexes: A model Outline • • • • • • • • Functions Evolution: structure and behavior Basic Unit: The Neuron Generation: How does a signal get started? Action Potential: How does a signal move? Synapses Reflexes: A model Brain Organizing Principles and Functions Principles and Functions • • • • • • • • • Cephalization All-or-None Law Frequency Coding of Intensity Doctrine of Specific Nerve Energies Localization of Function (+ Integration) Topographic Projection (& Distortion) Split Brain (Crossed Connections) Connectivity & Functional Connectivity Neuro-plasticity & Reorganization Brain Structure (midline) Structure: Central Core Structure: X-Ray View Localization of Function • Different parts of the brain serve specialized functions • Sensory Information • Motor Control • Perception • Language • Planning and Social Cognition Localization of Function Localization/Topographic Projection Localization/Topographic Proj. Localization/Topographic Proj. Cerebral Cortex • Most projection areas have contralateral organization: – Left hemisphere receives information from right side of body (sensory), or controls right side of body (motor) – Right hemisphere receives information from left side of body (sensory), or controls left side of body (motor) Split Brain Split Brain Cortical Damage • Much of what we know about the cortex comes from studying brain damage. • Damage at identifiable sites can produce: • Apraxias (disorders in action) • Agnosias (disorders in perception) • Aphasias (disorders of language) • Disorders of planning or social cognition Apraxias • Difficulty in carrying out purposeful movements without the loss of muscle strength or coordination – Disconnection between primary and nonprimary motor areas – Able to carry out each part of a complex movement, but disruption lies in coordination of the movements Agnosias • Visual agnosia: disturbance in recognizing visual stimuli despite the ability to see and describe them • Prosopagnosia: inability to recognize faces (fusiform face area) – http://www.youtube.com/watch?v=vwCrxomPbtY&feature=related – http://www.youtube.com/watch?v=VKa-PuJCrO4&feature=related • Neglect Syndrome: complete inattentiveness to stimuli on one side of the body – http://www.youtube.com/watch?v=ADchGO-0kGo&feature=related • Akinetopsia: inability to perceive movement – “I see the world in snapshots – like frames of a move but most of the frames are missing” Aphasias • Broca’s Aphasia: disturbance in speech production, caused by damage to Broca’s area – http://www.youtube.com/watch?v=f2IiMEbMnPM • Agrammaticism • Anomia • Difficulty with articulation • Wernicke’s Aphasia: disturbance in speech comprehension, caused by damage to Wernicke’s area – http://www.youtube.com/watch?v=aVhYN7NTIKU&feature=r elated • Disruption in recognition of spoken words • Disruption in comprehension of the meaning of words • Inability to convert thought into words Disorders of Planning and Social Cognition • Caused by damage to prefrontal area – Disrupts executive control– processes that allow us to direct our own cognitive activities • e.g., setting priorities, planning, strategizing, ignoring distractors Plasticity • The brain is plastic—subject to alteration in the way it functions, such as: • Changes in the brain’s overall architecture • The central nervous system can grow new neurons: • But appears unable to do so with cortical injury • This promotes stability in the brain’s connections but is an obstacle to recovery from brain damage. Plasticity • Neurons are subject to alteration in the way they function, such as: • Changes in how much neurotransmitter a presynaptic neuron releases • Changes in neuron sensitivity to neurotransmitters • Creating new connections by growing new dendritic spines