Psy 200 Lecture 3Current LectureThe Brain and Behavior-Human brains are really complicated- There are 100 billion neurons and each one has 1000+ synapses- there is an average 10,000 connections.-100 trillion synapsesExtensive Interconnections-There is no 1:1 connection.-Each neuron is only a few synapses away from other neurons.-Each neuron makes a small contribution to overall function.Neurons- 3 Main Parts-Dendrites- receive -Cell body (Soma)- summate-Axon- sendMany different types of neuronsNeural Signaling-Transmission within a neuron- electrical-Transmission between neurons- chemicalCommunication within a Neuron-Excitatory and inhibitory signals come in through dendrites.-Soma sums all inputs- one neuron does not have a big effect-If signal reaches threshold, action potential will occur.The Action Potential-A neuron at rest has a -70mv resting potential.-As a cell becomes more positive (-50mv), voltage gated channels open allowing positive ions to flow into the cell.-Once the cell gets to +50mv the sodium channels close.Moves like a Wave Down Axon-Always the same magnitude- all or noneThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.-Intensity of a stimulus is signaled by rate of firing, not amplitude.Communication Between Neurons-Messages from one neuron to another pass over a microscopic gap called a synapse.Brain Structure-Four different lobes of the brain- frontal, central, parietal, and occipital.-Hippocampus controls memory.-Amygdala controls emotion.How is the Brain Organized?-Equipotentiality- all brain areas work as one, any area has potential to support any function. VS.-Specialization- brain areas are specialized for certain functions. -Phrenology was the earliest attempt to understand the organization of the brain. -If you used one skill more than another, that area of the brain grew (i.e. bumps on the skull)-Neural stimulation is mostly done on animals, but sometimes humans.Limitations-Works well for sensory and motor functions. -Not so well for more complex cognitive processes like memory or decision making. -These processes are computed by ensembles of neurons in multiple regions. Transcranial Magnetic Stimulation (TMS)-Most methods with humans are correlational.-Can’t create lesions in humans, we are not causing neurons to fire in fMRI. -With TMS, we can test questions about causation. Method for Non-Invasive Stimulation of Cerebral Cortex-Trigger current flow through coil.-Generates magnetic field over cortex. -Causes massive firing of neurons in underlying cortex.-Minimal side effects-occasional headaches.-Can use to excite or inhibit.Excite-Stimulation over motor cortex causes body part to twitch. -Stimulation over visual cortex causes light to flash.Inhibit-Can cause stutteringExperimental Applications -Creation of “virtual” lesions by transient inhibitions of stimulated cortex.-Reversible-Time sensitiveLimitations-Can’t stimulate deep structures like basal ganglia.-Difficult to know when to give a pulse.-Compensatory processes in other hemisphere? Neuropsychological Assumptions-Damage (area x) + Poor Performance (task y) = Neural