Psychology 224: Neuroscience Lecture PDF

Psychology 224: Neuroscience Sensory Systems: Audition; Sleep and Biological Rhythms Reading: Carlson, Chapters 7 &9  Announcement Exam #3 Exam 3 will be on Thursday, 11/7. The Auditory System Anatomy of the Ear 3....

Psychology 224: Neuroscience Sensory Systems: Audition; Sleep and Biological Rhythms Reading: Carlson, Chapters 7 &9  Announcement Exam #3 Exam 3 will be on Thursday, 11/7. The Auditory System Anatomy of the Ear 3. 4. 1. 2. The Organ of Corti Central Auditory Pathways 4. The cortex is last 3. The inferior colliculus is the next synapse, followed by the medial geniculate 1. nucleus 2. The auditory nerve synapses Most cochlear in the cochlear axons cross nucleus over & synapse in the  Auditory Cortical Areas The primary auditory cortex is adjacent to the upper bank of the lateral fissure in the temporal lobe – Each hemisphere receives information from both ears, but primarily the contralateral one The auditory association cortex surrounds the primary auditory area Like the visual system, there are 2 streams of auditory information flow: – 1) the dorsal stream – terminates in the posterior parietal region and is involved in sound localization (the “where”) – 2) the ventral – terminates in the temporal lobe and is involved in processing of complex sounds (the “what”) What is Sleep?  The Study of Sleep In the lab, sleep is studied by measuring the activity of the brain and of 2 different muscle groups: – 1) Electroencephalogram (EEG) – attach electrodes to the scalp to record the collective activity of thousands of brain cells (typically on the cortical surface) – 2) Electromyogram (EMG) – attach electrodes to the chin to monitor muscle activity – 3) Electrooculogram (EOG) – attach electrodes around the eyes to monitor eye movements  2 patterns of activity Alpha activity: state of relaxation 8-12 Hz 13-30 Hz Beta activity: state of arousal (desynchronized) 3.5-7.5 Hz Transitional 12-14 Hz 20-50% Delta < 3.5 Hz > 50% Delta (low frequency, **REM looks like synchronized) the awake state  2 patterns of activity Alpha activity: state of relaxation 8-12 Hz 13-30 Hz Beta activity: state of arousal (desynchronized) 3.5-7.5 Hz Transitional ** The EEG 12-14 Hz becomes more synchronized as 20-50% Delta sleep progresses from stages 1-4, < 3.5 Hz and the waves become slower > 50% Delta (low frequency, **REM looks like synchronized) the awake state  Non-REM Sleep Stages 1-4 of sleep are called typically called “non-REM sleep” Stages 1-2 are transitional; the subject typically is not aware s/he is asleep Stages 3-4 are known as slow wave sleep, mostly because the presence of low-frequency delta activity Slow-wave sleep is characterized by: – Light, even respiration – Presence of muscle tone – Difficulty in arousing subject  REM Sleep Occurs ~ every 90 mins throughout the night Characterized by: – Enhanced respiration and blood pressure – Rapid eye movements (REMs) – Complete loss of muscle tone (paralysis) – Vivid, emotional dreams  Cycles of Sleep We alternate between periods of REM and non-REM sleep. Each cycle of sleep is ~90min long. Each cycle of sleep contains ~ 20-30 minutes of REM sleep. In one night (8 hours), there will be 4-5 periods of REM sleep.  Time Mostly slow-wave sleep Mostly REM sleep and stage 2 Disorders of Sleep  Insomnia Difficultyfalling asleep after going to bed or after awakening during the night. People with sleep apnea fall asleep and the stop breathing, usually caused by obstruction in the airway. This is one form of insomnia.  Narcolepsy Characterized by sleep (or some of its components) at inappropriate times. Primary symptom: Sleep attack lasts usually 2-5 minutes. – Intense urge to sleep that can happen any time, but usually under monotonous, boring conditions. – Person usually wakes up feeling refreshed.  Narcolepsy Another symptom is cataplexy: muscle weakness, even muscular paralysis (like that during REM sleep) at an inappropriate time. – Person lies down for seconds to minutes fully conscious. – Brought on by strong emotional reactions or physical effort.  Additional Symptoms of Narcolepsy Sleep paralysis just before sleep or on waking. – A person can be snapped out of sleep paralysis by being touched or hearing someone call their name. Hypnagogic hallucinations: dreams that occur just before a person falls asleep. Accompanied by sleep paralysis.  REM Sleep Behavior Disorder Involves acting out the dream while asleep – Failure to exhibit paralysis during sleep Oftenhas a genetic component. Caused by a neurodegenerative disease that damages brain mechanisms that produce paralysis during REM sleep. REM Sleep Behavior Disorder Sleep in a Dolphin Why Do We Sleep?  Sleep Deprivation Studies In animals, sleep deprivation appears to be harmful – Rats forced to lose sleep became weak, uncoordinated, lost their ability to regulate their body temperature, metabolism increased, and eventually died **the experimental animal’s EEG is monitored and the platform is rotated as soon as it falls asleep  Sleep Deprivation Studies In humans, sleep deprivation appears to have no outward physical effects – Motor skills intact – Stress hormones at normal levels – Primary function of sleep is not recuperation of the muscles. – Cognitive function is impaired (hallucinations, trouble concentrating, memory, etc)  Sleep Deprivation Studies When sleep deprived people are allowed to sleep again, they never regain all the sleep they lost. The percentage of recovery is not equal for all stages of sleep – 7% of stages 1 and 2 were made up – 68% of stage 4 was made up – 53% of REM sleep was made up age 4 and REM sleep may be more important than the other stag  Functions of Slow-Wave Sleep? Slow-wave & REM sleep may serve different functions One prominent hypothesis is that SWS may reflect a “restoration” process – Areas of the brain that are more stimulated during the day show more delta activity-and the lowest levels of metabolic activity-during slow wave sleep. – So the presence of SWS in a brain region indicates that region is resting. Functions of REM Sleep? REMsleep in children may reflect promotion of brain development – infants and children show the highest amounts of REM sleep – newborns spend about 70% of their sleep in REM  Functions of REM Sleep? In adults, REM and slow-wave sleep may reflect a memory consolidation process – Nondeclarative memory: Memories gained through experience (learning to drive a car or recognize a person’s face).  REM - Declarative memory: Memories that people can talk about (memories of past episodes)  SWS  Performance On A Nondeclarative Memory Task Performance After Slow- Wave Sleep Only Nap1 hour Mechanisms: The Neural Basis of Arousal  Neural Regulation of Arousal To understand what produces sleep, we must understand what causes us to remain awake! Electrical stimulation of the brainstem induces arousal & vigilance There are several common neurotransmitters involved in arousal: – Acetylcholine – Norepinephrine – Serotonin – Histamine  Acetylcholine (ACh) ACh is the primary neurotransmitter secreted by the motor axons of the PNS – All muscle movements are controlled by ACh ACh is also widely distributed in the brain; there are 3 brain regions that contain cholinergic neurons: – Dorsolateral Pons – involved in REM sleep (dreaming) – Medial Septum – involved in hippocampal function and certain types of memory – Basal Forebrain –involved in activating the cortex and facilitating learning; important for  Acetylcholine The ACh neurons in the nucleus basalis (in the basal forebrain) appear to be the most important for cortical arousal Stimulation of ACh neurons produces cortical activation and desynchrony of the EEG ACh levels in multiple brain regions are all increased when an animal is awake and alert The Nucleus Basalis  Norepinephrine Almost all NE effects are excitatory! – Release of NE by the sympathetic nervous system prepares you for “fight or flight”! Inthe brain, most NE neurons are clustered in the brainstem in a region called the locus coeruleus (LC) – Activation of the LC produces vigilance and anxiety  Norepinephrine Many catecholamine agonists, including amphetamine, cocaine, and MDMA, produce arousal & wakefulness These effects are mimicked by stimulation of the noradrenergic cells in the locus coeruleus (LC) (dorsal pons) – Activity of LC neurons shows a close correspondence with arousal and wakefulness – Activity of LC neurons falls during sleep until it reaches zero during REM sleep Norepinephrine and the Sleep-Wake Cycle in Freely Moving Rats