BIO 320 Lab 1 Fall 2024 PDF

Lab 1 PowerLab 1 - Electroencephalogra- phy (EEG), Psychophysiology & Wii Lab Objectives: 1. EEG artifacts. In this exercise, you will learn to recognize common artifacts seen while recording an EEG. 2. Alpha and Beta Rhythm. Here you will learn how best to elicit alp...

Lab 1 PowerLab 1 - Electroencephalogra- phy (EEG), Psychophysiology & Wii Lab Objectives: 1. EEG artifacts. In this exercise, you will learn to recognize common artifacts seen while recording an EEG. 2. Alpha and Beta Rhythm. Here you will learn how best to elicit alpha waves in an EEG recording. 3. Effects of mental activity. In this part of the laboratory, you will do some simple arithmetic and observe the effects on EEG activity. 4. Effects of auditory stimulation. Here you will examine the effects on the EEG of the volume and type of music listened to. 5. Psychophysiology. Here you will use the GSR amplifier to measure skin conductance. You will use surface electrodes to measure a facial EMG. You will also measure skin conductance, respiration, and EMG in response to visual stimuli. 6. Wii Lab. You will test the effects of distraction. This PowerLab was developed in part by ADInstruments and Human Anatomy & Physiology 9th edition by Marieb & Hoehn. ** You will need closed-toe shoes for this lab.** 2 Lab 1: PowerLab 1 - Electroencephalography (EEG), Psychophysiology and Wii Lab Introduction Very little contribution normally comes from action po- In this laboratory, you will explore the electrical activity tentials propagated along nerve axons. As with the ECG of the brain. You will record and analyze electroencepha- & EMG, the EEG reflects the algebraic sum of the elec- lograms (EEGs) from a volunteer, look at interfering sig- trical potential changes occurring from large popula- nals, and examine the effect on alpha and beta waves by tions of cells. Therefore, large amplitude waves require opening and shutting the eyes, auditory and mental cues. the synchronous activity of a large number of neurons. The rhythmic events that these waves reflect often arise Background in the thalamus, whose activity is, in turn, affected by a Normal brain function involves continuous electrical variety of inputs including structures in the brain stem activity of neurons, and the cerebral cortex contains huge reticular formation. numbers of these neurons. An electroencephalogram (EEG) records some aspects of this activity. An EEG is Components of the EEG Waveform made by placing electrodes on the scalp and then con- Each of us has a brain wave pattern that is as unique necting the electrodes to an apparatus that measures as our fingerprints. Each wave is a continuous train of electrical potential differences between various corti- peaks and troughs, and the wave frequency, expressed in cal areas. The patterns of neuronal electrical activity hertz (Hz), is the number of peaks in one second. A fre- recorded, called brain waves, are generated by synaptic quency of 1 Hz means that one peak occurs each second. activity at the surface of the cortex, rather than by action potentials in the white matter. EEG signals are affected The amplitude or intensity of any wave is represented by by the state of arousal of the cerebral cortex and show how high the wave peaks rise and how low the troughs characteristic changes in different stages of sleep. EEG dip. The amplitude of brain waves reflects the synchro- signals are also affected by stimulation from the external nous activity of individual neurons. Usually, brain waves environment, and brain waves can become entrained to are complex and have low amplitude. During some external stimuli. Electroencephalography is used, among stages of sleep, neurons tend to fire synchronously, pro- other things, in the diagnosis of epilepsy and the diagno- ducing similar, high-amplitude brain waves. sis of brain death. The EEG waveform contains component waves of dif- Recording the EEG ferent frequencies. These can be extracted and provide EEG recording is technically difficult, mainly because information about different brain activities. The Lab- of the small size of the voltage signals (typically 50 µV Tutor software is set up so that the raw EEG signal is peak-to-peak). The signals are small because the record- displayed in channel 1. Digital filtering allows this to ing electrodes are separated from the brain’s surface by be analyzed into the component frequencies of interest the scalp, skull, and a layer of cerebrospinal fluid. A spe- that are displayed in other channels. Each of these waves cially designed amplifier, such as the Bio Amplifier built (or rhythms) provides information about different brain into the PowerLab, is essential. It is also important to use states. These waves are shown in Figure 1. electrodes made of the right material and to connect them properly. Even with these precautions, recordings may be spoiled by a range of unwanted interfering influences, known as artifacts. In this laboratory you will record EEG activity with three electrodes: two frontal electrodes on the forehead and a third (ground or earth) electrode attached to the mas- toid process, to reduce electrical interference. In clinical EEG, it is usual to record many channels of activity from multiple recording electrodes placed in an array over the head. Origins of the EEG Signals The EEG results from slow changes in the membrane po- tentials of cortical neurons, especially the excitatory and inhibitory postsynaptic potentials (EPSPs and IPSPs). Figure 1. Brain waves Lab 1: PowerLab 1 - Electroencephalography (EEG), Psychophysiology and Wii Lab 3 1. Alpha (8 to 13 Hz; average amplitudes 30 to 50 µV) rhythm reflects the mental activity involved in integrating Alpha waves are relatively regular and rhythmic, low-am- various aspects of an object (color, shape, movement, etc) plitude, synchronous waves. In most cases, they indicate to form a coherent picture. Interestingly, recent research a brain that is “idling” – a calm, relaxed state of wakeful- has shown that gamma waves are enhanced in Buddhist ness. Alpha rhythm is seen when the eyes are closed and monks during meditation and are absent in schizophren- the subject relaxed. It is abolished by eye opening and by ics. mental effort such as doing calculations or concentrat- ing on an idea. It is thus thought to indicate the degree of It is not presently possible to relate the EEG waves to cortical activation where, the greater the cortical activa- specific underlying neuronal activities. In general, the tion, the lower the alpha wave activity. Alpha waves are more active the brain, the higher the frequency and the strongest over the occipital cortex (back of the head) and lower the amplitude of the EEG. Conversely, the more the frontal cortex. inactive the brain, the lower the frequency and the higher the amplitude of the signal. 2. Beta (14 to 30 Hz;