Term
| What are some clinical applications of EEGs and evoked potential analysis? |
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Definition
| Diagnosis of sleep disturbances, epilepsy, determination of coma level, brain death |
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Term
| What are the two types of electrodes needed to obtain and EEG and why are two required? |
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Definition
1) An active electrode must be placed over the site of neural activity
2) An indifferent electrode must be places some distance form the active electrode
Two electrodes are needed because EEGs measure the difference in electrical potential. |
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Term
| How can clinicians enhance the detection of electrical potentials in the medial temporal lobes? |
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Definition
| By inserting nasopharyngeal or sphenoid electrods through he nose or jaw muscle |
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Term
| What are the four principal frequencies that are distinguished? |
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Definition
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Term
| T/F EEG activity recorded through the scalp is usually small amplitude (20-100 uV) and between 1-30 Hz (cycles per second) |
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Definition
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Term
| What is the name of activity measured between 13-30 Hz and what activities is it associated with? |
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Definition
| Beta waves are 13-30 Hz and they are associated with alert wakefulness and REM sleep |
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Term
| What are alpha waves associated with and what is their frequency range? |
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Definition
| Alpha waves have a frequency of 8-13 Hz and are generally associated with a state of relaxed wakefulness. They are most prominent over the parietal and occipital lobes. |
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Term
| What are the characteristics of theta waves? |
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Definition
| Measured at a frequency of 4-8 Hz and are more prominent in young versus adults. They are observed during awake, drowsy, and non REM sleep states |
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Term
| What are the characteristics of delta frequencies? |
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Definition
| Delta frequencies are .5-3.5 Hz and are prominent during non-REM sleep |
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Term
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Definition
| By currents flowing through the extracellular space, which are generated by the opening and closing of ions channels in the plasma membrane. |
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Term
| What is a current sink and what is its effect on the extracellular space? |
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Definition
| Current sinks are the flow of positive charge into the intracellular compartment (inward current) this leaves the extracellular space negative. |
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Term
| How is a current source formed? |
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Definition
| Current source is the return flow of current to the extracellular space forming a local transient increase in extracellular positivity. |
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Term
| Which has a lower resistance the extracellular space or the intracellular space? |
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Definition
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Term
| How can intracellular and extracellular potentials be calculated? |
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Definition
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Term
| T/F. EEG measure the summed activity of neurons located under a macroelectrode. |
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Definition
| True. Changes in extracellular field potential due to currents flowing across the membrane of a single neuron are too small to be detected by the distance electrode, however the electrode can detect the net current of flowing simultaneously across many membranes. |
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Term
| What is EEG amplitude primarily determined by? |
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Definition
| The degree of synchronization within the neuron population. |
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Term
| Describe the EEG of a very active but desynchronized population of neurons? |
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Definition
| A desynchronized population of neurons will yield an EEG with a small amplitude. |
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Term
| What is an electric dipole and how is it created? |
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Definition
| An electric dipole is spatially separated areas of positive and negative charge and it is created by synchronized electrical activity. |
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Term
| EEG primarily reflect synaptic activity of _______? |
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Definition
| Cortical pyramidal neurons because these are the most numerous cell type and they have larger apical dendrites which allow for the formation of larger dipoles. |
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Term
| Do EEG's differentiate between excitatory and inhibitory synaptic activity? |
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Definition
| No, because a current sink may be created by either local inward current llow at the site of excitatory synapses or by the return current flow at a site distant from inhibitory synapses. |
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Term
| What is sensory evoked potential and when is it observed? |
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Definition
| Sensory evoked potential is a specific change in ongoing EEG activity caused by stimulation of a sensory pathway. These are observed when a sensory pathway is stimulated. |
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Term
| What is the most common sensory evoked potential and what can this be used to determine in a clinical setting? |
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Definition
| The auditory sensory evoked potential is the most common and can be used to diagnose hearing impairments in young children or assess brainstem in integrity in unconscious patients. |
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Term
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Definition
| Abnormal patterns of neuronal activation. The outward behavior is dependent on the region of the brain affected. |
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Term
| What differentiates partial seizures from general seizures? |
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Definition
| Partial seizures are restricted to one area of the brain while general seizures affect many areas of the brain. |
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Term
| What is the difference between a simple and complex partial seizure? |
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Definition
| Simple partial seizures the patient retains consciousness but may experience unusual feelings or sensations. Complex partial seizures the patient has a change in consciousness. |
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Term
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Definition
| Repetitive motions that occur in patients suffering from complex partial seizures. |
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Term
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Definition
| An aura is a warning sensation of and impending seizure. |
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Term
| What is the term used to describe when a partial seizure originates within one area of the brain, but then spreads to others? |
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Definition
| Secondary generalization. |
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Term
| What causes generalized seizures? |
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Definition
| Abnormal nueronal activity occurring synchronously across many areas of the brain. |
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Term
| What type of seizure is a patient suffering from if they appear to stare into space and/or possibly exhibit muscle jerking? |
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Definition
| Generalized seizure-absence seizure previously known as petit mal seizure |
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Term
| Describe a tonic seizure. |
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Definition
| Stiffening of the muscles generally in the back, legs, and arms. |
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Term
| What type of seizure causes repetitive jerking movements of muscles on both sides of the body. |
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Definition
| Generalize seizure-clonic seizure |
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Term
| Describe an atonic seizure. |
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Definition
| Loss of normal muscle tone and the patient may fall down. |
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Term
| What is a tonic-clonic seizure and what is it also known as? |
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Definition
| Tonic-clonic seizures are a type of general seizure and is also known as a grand mal seizure. It causes the patient to have tonic and clonic muscle contractions, repeated jerks of the arms and or legs and loss of consciousness. |
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Term
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Definition
| Repeated absence seizures that cause momentary lapses in consciousness |
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Term
| What is psychomotor epilepsy? |
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Definition
| Recurrent partial seizures, especially of the temporal lobe. The term psychomotor refers to the strange sensations, emotions, and behavior accompanying these seizures. |
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Term
| Define temporal lobe epilepsy (TLE). |
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Definition
| This is the most common epilepsy syndrome involving partial seizures. TLE seizures are often associated with auras. Repeated temporal lobe seizures can cause hippocampal damage. |
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Term
| Define occipital lobe epilepsy. |
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Definition
| Occipital lobe epilepsy involves seizures that begin with visual hallucinations, rapid eye blinking, or other vision-related symptoms. |
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Term
| What is a commonality in all epilepsies? |
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Definition
| An imbalance in synaptic excitation of synaptic inhibition. |
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Term
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Definition
| Also know as interictal events, paroxysms are abnormal synchronized discharges which occur between seizures. |
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Term
| What are some things that occur after a seizure? |
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Definition
| Disorientation, depression, confusion, and an altered EEG (shift to lower frequency and/or reduced background amplitude. |
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Term
| What is a mechanism of antiepileptic medications such as barbiturates or benzodiazepines? |
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Definition
| Enhance the effectiveness of GABA neurotransmission or reduce the ability of neurons to generate repetitive trains of action potentials. |
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Term
| Other than surgery or medication what are some ways for controlling seizures? |
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Definition
| Vagal nerve stimulation or ketogenic diet (high fat, low carb) |
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Term
| What type of surgery do some focal epileptic patients choose to undergo? |
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Definition
| Removing the site of origin through a lesionectomy or lobectomy, with temporal lobe resection being the most common. |
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