Psy 200 Lecture 3 Current Lecture The 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 synapses Extensive 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 send Many different types of neurons Neural Signaling Transmission within a neuron electrical Transmission between neurons chemical Communication 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 none These 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 stuttering Experimental Applications Creation of virtual lesions by transient inhibitions of stimulated cortex Reversible Time sensitive Limitations 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 Function