Lecture 8Outline of Last Lecture I. Neurotransmitter systemsOutline of Current Lecture I. ElectrophysiologyII. Invasive and noninvasive measuresIII. Event related potentialsIV. Electrophysiology of the PNS Current LectureI. Electrophysiologya. Intracellular recording: measure the changing voltage inside of a neuroni. Intracellular microelectrode records the membrane potential from one neuron as it firesii. Cell recordings are used for postsynaptic potentials (PSPs)iii. Neuron fires an action potential  voltage value rapidly spikes  returns to baselineb. Extracellular recording: measure the changing voltage outside of one of more neuronsi. Single unit1. Record the electrical disturbance that is created each time an adjacent neuron fires2. Cannot measure the membrane potential3. All we see are spikes of passing action potentialsii. Multiple units1. When there is a build up of PSPs (e.g. many neurons are getting ready to fire)  can measure their group activity2. These neurons must be in sync with one anotherc. Some methods are more often used for central nervous system (e.g. intracellular recording)d. Other methods are almost exclusively peripheral nervous system (e.g. electromyogram)II. Invasive and noninvasive measures a. Most single unit and multi unit recording is done in vitro or requires invasive surgeryb. In vitro: in the glassc. Stereotaxic surgery: method used to implant devices or manipulate small brain regions of a living organism  done by using an “atlas” of a typical braind. On humans? Most brain research is done with non-invasive methodse. Electroencephalogram (EEG)  modern EEG systems use many electrodes to record from different regions on the scalpIII. Event-related potentials (ERPs)a. ERP: average voltage change that occurs when a person encounters a stimulusb. Signal averaging: background noise unrelated to the experiment cancels out by taking the average of a brain response over many hundreds of trialsc. P300: the third positive peak in an ERP. P300 levels are higher if the stimulus that elicited it “means” something to the person (e.g. mentioning a person’s name, encountering a stimulus that the person has been instructed to respond to)IV. Electrophysiology of the PNS a. Single and multi unit reordings, invasive EEG, and EEG/ERP all measure the CNSb. EMG, SCL/SCR, and EKG/ECG measure PNSc. Electromyography (EMG): measure muscle contractionsd. Skin conductance: measures sweat-gland activitye. Electrocardiogram: plethysmography blood