Epilepsy, Sleep, NeuroImaging Flashcards

Question

NEURAL CIRCUITS: REM Sleep paralysis

Answer 1

1. Relative paralysis arises from increased activity in GABAergic neurons in the pontine reticular formation 2. Through projections, the lower motor neurons in the spinal cord are inhibited

Answer 2

1. Electrical stimulation of the RAS causes a state of arousal and wakefulness 2. Located at the junction of the pons and midbrain

Answer 3

Electrical stimulation of the Thalamus with low- frequency pulses in an awake cat causes slow-wave sleep

Answer 4

1. During REM sleep, EEG waves originate in the PRF and propogate through the LGN to the occipital cortex. These PGO waves provide a useful marker of the beginning of REM sleep and are another marker of the brainstem activating the cortex. 2. Without visual stimuli, the pontine reticular formation endogenously signals the superior colliculus 3. Collicular neurons project to the PPRF, which is involved in the saccade 1. Increased limbic system activity 2. Decreased influence of the frontal cortex

Answer 5

1. Cholinergic nuclei are characterized by high discharge rates during wake/REM and low discharge during non-REM sleep 2. These nuclei cause “desynchronization” of the EEG when activated 3. Lateral hypothalamus activates the Tuberomammillary nucleus of the hypothalamus 4. TMN activates both the locus coeruleus and raphe nucleus 5. These circuits are responsible for the awake state 6. Ventrolateral preoptic nucleus of the hypothalamus can inhibit the TMN 7. Activation of the VPLO is responsible for the onset of sleep 8. VPLO lesions cause insomnia

Answer 6

1. The sleep/wake effects of the brainstem nuclei are achieved by modulating the interactions between the thalamus and the cortex 2. The activity of several ascending systems from the brainstem decreases both the rhythmic bursting and the related synchronized activity of cortical neurons 3. Thalamocortical neurons receive projections from brainstem nuclei and project to cortical pyramidal cells 4. Thalamocortical neurons have only two stable states: bursting or tonically active 5. Bursting occurs when neurons in the thalamus become synchronized with those in the cortex, "disconnecting" the cortex from the outside world 6. This is maximal during slow-wave sleep 7. The tonically active state is generated when the neurons are depolarized, which happens when the RAS generates wakefulness 8. TC neurons transmit information to the cortex related to spike trains encoding peripheral stimuli

Answer 7

1. Bursting can be transformed to tonically active by cholinergic or monoaminergic projections 2. Bursting is stabilzed by hyperpolarization of thalamic cells -- Hyperpolarization occurs by GABAergic projections from the reticular nucleus - These neurons receive ascending information from reticular cells and descending information from cortex 3. Sleep spindles are generated when neurons in the RAS have a burst of activity 4. In turn this causes TC cells to generate short bursts of action potentials

Answer 8

- - Short term insomnia has many causes and can usually be avoided by improving sleep habits, avoiding stimulants, and (sometimes) by taking sleep-promoting medications - - Debilitating insomnia can be associated with major depression and is a problem in the elderly - - Depression and aging likely affect the cholinergic, adrenerigic, and serotinergic systems

Answer 9

1. Pattern of interrupted breathing during sleep 2. - - A person wakes many times a night and experiences little or no slow-wave sleep and REM sleep - - Continual tiredness and depression are symptoms - - Can even lead to death due to airway restriction - - In normal sleep, breathing slows, muscle tone decreases. If the output of the brainstem circuitry regulating commands to the chest wall or to pharyngeal muscles is decreased enough, or if the airway is compressed due to obesity, the pharynx collapses as muscles relax. Carbon dioxide levels rise, which causes a reflex inhalation, which generally wakes the individual. - - Most widely used remedy is a positive-pressure max that enhances airflow during sleep

Answer 10

1. Unpleasant crawling, prickling, or tingling sensations in one or both legs and feet, and the urge to move them to obtain relief - - Occurs after sitting or lying down for long periods - - Constant leg movement during the day and fragmented sleep at night - - Mild cases can be helped by heat, massaging the legs, or avoiding stimulants - - Severe cases can be helped by benzodiazepines

Answer 11

1. Frequent “REM attacks” during the day where the individual enters REM sleep directly from wakefulness. 2. Attacks can last from 30 seconds to 30 minutes or more 3. Affects mostly men; about 250,000 people in the US 4. Onset of sleep is abrupt and entails a temporary loss of motor control called cataplexy 5. In dogs, narcolepsy is caused by mutations to the orexin-2 receptor gene (found in the TRG) 6. Mutations either cause hyperexcitability or impairment of inhibition of the circuits that cause REM sleep 7. Treatment is usually with stimulants such as methylphenidate or amphetamines

Answer 12

1. Debilitating fatigue along with unrefreshing sleep, memory and concentration problems, a feeling of extraordinary tiredness following routine exercise 2. 6+ months of persistent or relapsing fatigue that impairs normal function 3. May also have sore lymph nodes, sore throat, muscle pain, joint pain, and headaches 4. Onset is generally after a flu-like illness, with only a minor number of patients returning to a normal level or figor 5. Treatment is usually symptom management and improving coping

Answer 13

1. All animals exhibit a restorative cycle of rest 2. Only mammals have REM/non-REM cycle 3. Why we need suspended consciousness and decreased metabolism is not known 4. Our organized sleep progression is generated by brainstem nuclei 5. This is achieved through modulation of activity of the thalamocortical loop 6. The circadian clock is located in the suprachiasmatic nucleus and VLPO of the hypothalamus and influences these systems 7. The “clock” adjusts sleep/wake to the appropriate durations

Answer 14

1. External Ionizing Radiation - CT, Angiogram/Arteriogram, X-Ray 2. Internal Ionizing Radiation - PET, SPECT 3. Non-Ionizing Radiation (Radio Waves) - MRI, fMRI, MR Angiography, Diffusion Imaging, MR Spectroscopy 4. Accessory (non-imaging) Methods - MEG, EEG

Answer 15

PROS: incredible images, advancing very rapidly extremely high resolution, extremely versatile, NO ionizing radiation CONS: moderately expensive, complex, some contraindications (ferrous metal in the body, cochlear implants ALWAYS, possibly pacemakers, vagal nerve stimulators, old surgical implants NOTE: the MR scanner is a giant magnet!

Answer 16

MRI studies brain ANATOMY - high resolution fMRI studies brain FUNCTION - low resolution - BOLD = Blood Oxygenation Level Dependent - As neural activity increases, blood oxygen increases, fMRI signal increases

Answer 17

1. Vegetative state: behavioral presentation of wakefulness in the absence of any evidence of awareness of self or environment 2. Autonomic functions with preservation of cranial and spinal reflexes but no evidence of behavioral responses or language comprehension 3. Distinct from coma (no wakefulness) on one side and minimally conscious state (response to environment, e.g. smooth pursuit) on other

Answer 18

Basic Principle of CT scan is to rotate machinery to take multiple x-rays with different paths thru the body PROS: widely available, very fast, cheaper than MRI, less hassle CONS: exposure to ionizing radiation (increased risk of cancer), poor tissue contrast, not versatile CT IS BEST FOR AN EMERGENCY!!!!!

Answer 19

PET = Positron Emission Tomography Basic principle is to inject radioactive isotope attached to metabolic compound (oxygen, glucose, etc.) and WAIT for it to decay, looking for radioactive decay products PROS: fairly cheap, shows function (metabolism) CONS: exposure to ionizing radiation (increased rick of cancer), low resolution, slow to very slow, not versatile

Answer 20

EEG Basic principle: electrodes on scalp surface record summed electrical activity (mainly synaptic) of many neurons (only difference w MEG is there aren't electrodes on the scalp, there are SENSORS near scalp surface) PROS: completely non-invasive -- this is the ONLY MODALITY THAT NEVER REQUIRES INJECTION OF A CONTRAST AGENT, no ionizing radiation, direct measurement of neuronal activity CONS: not really neuroimaging, limited clinical utility EEG: sleep studies MEG: epilepsy

Epilepsy, Sleep, NeuroImaging Flashcards

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