Web sites Society for Neuroscience www.sfn.org International Brain Research Organization www.ibro.org

The brain carries out calculations at synapses, the sites at which neurons interact. While hundreds of neuro-transmitters and receptors have been identified, they can be functionally classified into two types: excitatory and inhibitory. Excitatory neurotransmitters increase the likelihood that the postsynaptic neuron will generate an action potential, while inhibitory neuro-transmitters make it less likely that the postsynaptic neuron will be active. The balance of excitation and inhibition determines how information is processed in the nervous system.

Some synapses are excitatory: An action potential in one (pink) neuron releases a chemical that turns on the second (blue) neuron. The second neuron therefore is more likely to transmit an action potential to other neurons.

BCP 5-13 e.g. glutamate

Some synapses are inhibitory: An action potential in one (pink) neuron releases a chemical that turns off the second (blue) neuron. So the second neuron is less likely to send action potentials to other neurons.

BCP 5-14 e.g. GABA gamma-amino- butyric acid

Information is carried around the nervous system as trains of action potentials At any given moment, the sum of excitatory & inhibitory inputs to a neuron determines the probability that it will generate an action potential. Circuits of interconnected neurons represent & process information in various ways. Information is represented as patterns of electrical activity in groups of neurons.

Human Physiology Chapter 8 The Mechanisms of Body Function Vander’s Human Physiology The Mechanisms of Body Function Tenth Edition by Widmaier • Raff • Strang © The McGraw-Hill Companies, Inc. Figures and tables from the book, with additional comments by: John J. Lepri, Ph. D., The University of North Carolina at Greensboro

Consciousness, Brain, and Behavior Chapter 8 Consciousness, Brain, and Behavior Electroencephalography: a window on the brain States of wakefulness and sleep Limbic system: motivation and reward Neurochemistry of drug abuse Learning and memory

Figure 8-1 The electroencephalograph (EEG) is the printout of an (typically 20-100 microvolts) VOLTAGE The electroencephalograph (EEG) is the printout of an electronic device that uses scalp electrodes to monitor the internal neural activity in the brain; this is a record from the parietal or occipital lobes of an awake person. The units and scale of the axes are not included in my original– there should be some information about these on the figure.

19-3: Generation of very small electrical fields by synaptic currents in pyramidal cells. When thousands of cells contribute their small voltages, the signal is strong enough to see at the surface of the scalp.

19-4: (a) In a population of pyramidal cells under an EEG electrode, each neuron receives many synaptic inputs. (b) If the inputs fire at irregular intervals, the pyramidal cell responses are not synchronized, & the summed activity detected by the electrode has small amplitude. (c) If the same inputs fire within a narrow time window so the pyramidal cell responses are synchronized, the resulting EEG sum is much larger.

Figure 8-2 EEGs provide diagnostic information about the (20 to 100 microvolts) VOLTAGE EEGs provide diagnostic information about the location of abnormal activity in the brain, such as shown in this record typical of a patient undergoing an epileptic seizure. The units and scale of the axes are not included in my original– there should be some information about these on the figure.

Figure 8-3 EEGs reflect mental state: contrasted here are (20 to 100 microvolts) VOLTAGE (20 to 100 microvolts) VOLTAGE The units and scale of the axes are not included in my original– there should be some information about these on the figure. EEGs reflect mental state: contrasted here are mental relaxation (a) versus concentration (b). Figure 8-3

Figure 8-4 EEG patterns undergo characteristic shifts in a (20 to 100 microvolts) VOLTAGE The units and scale of the axes are not included in my original– there should be some information about these on the figure. EEG patterns undergo characteristic shifts in a sleeping person, reflecting the four stages of sleep; the duration of the series is typically ~90 minutes, and the entire pattern cycles 4 to 8 times per night.

Figure 8-5 The EEG pattern was analyzed to produce this graph of a full night’s sequence of sleep stages; also shown are cyclic patterns in the periphery.

Figure 8-6 A model of some of the neurochemical changes across the sleep-wake continuum; cause-and-effect relationships are under study.

19-20: In the SCN, clock genes produce proteins that inhibit further transcription. Gene transcription & the firing rates of SCN neurons cycle up & down over 24 hr. The cycles are synchronized by light exposure (input from the retina.). SCN = suprachiasmatic nucleus

Figure 8-7 Neuronal changes in these CNS structures appear to be essential participants in sleep-wake transitions and in biological rhythms.

Figure 8-8 Neural damage in the right parietal lobe of this patient results in the unilateral visual neglect seen in this drawing task. Although patient is not impaired visually, does not perceive part of visual world.

20-17: Self-portraits during recovery from a R parietal stroke that caused neglect syndrome. Upper L: 2 months after stroke, virtually no L side to face. Upper R: After 3.5 months, there is some detail on L. Lower L & R: After 6 & 9 months, there is increasing treatment of the L side of the painting.

Figure 8-9 Alterations in the mesolimbic dopamine pathway (shown here) appear to be a primary mechanism by which psychoactive drugs change behavior.

Figure 8-10 Animal models, such as this rat performing lever-presses stimulator Animal models, such as this rat performing lever-presses to receive rewarding neural stimulation through electrodes implanted in its brain, have provided detailed insights into the anatomical and neurochemical organization of the brain.

Figure 8-11 Changes in activity of the limbic system underlie some of the primary needs of the organism, including learning, motivation, appetite, and emotional response; its malfunction is associated with affective disorders.

Figure 8-13 Psychoactive drugs that affect serotonin- receptors share structural similarities with serotonin. Psychoactive drugs that affect dopamine- receptors share structural similarities with dopamine.

Figure 8-14 Declarative memory is associated with actual events in a person’s direct experience. Procedural memory is associated knowledge of the sequence of events and relationships between events.

23-1: Types of memory.

23-8: Removing the medial temporal lobe from both sides to alleviate severe epilepsy caused severe anterograde amnesia in H.M.

PET scan showing blood flow in the cortex during language tasks

Images of the active areas in the brain in a male (left) & a female (right) during a language task. Note that both sides of a woman’s brain are used in processing language, but a man’s brain is more compartmentalized.

Figure 8-17 The primary loci underlying the comprehension of speech are in Wernicke’s area, whereas the primary loci for the production of speech are located in Broca’s area.

20-p641: Wada test for hemispheric dominance.

20-9: Language comprehension in R hemisphere of split-brain subject.

The End.