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| There are two fundamental ways in which the activity of a large of set of neurons will produce synchronous oscillations (rhythms): |
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Definition
A. A pacemaker or central clock:
i. neurons with self-generating activity
B. Collective interaction:
ii. neurons mutually excite one another |
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Term
| In a network of neurons (which the cortex represents), neurons interact among themselves via synaptic connections to form .... |
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| What has massive input to the cerebral cortex and can act as a powerful pacemaker? |
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| During sleep, thalamic discharge is synchronous or de-synchronized? |
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| an episode of abnormally synchronized and high frequency firing of neurons in the brain that result in abnormal behavior or experience |
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Term
| A generalized seizure involves |
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Definition
| the entire cerebral cortex of both hemispheres. |
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Term
| A partial (focal or local) seizure involves |
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Definition
| only a defined area of the cortex. |
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Definition
| immediately after a seizure |
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Term
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Definition
| disorder characterized by recurrent unprovoked seizures |
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Term
| Examples of partial seizures are: |
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Definition
| Temporal lobe (psychomotor) and Jacksonian |
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Term
| In simple partial seizures |
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Definition
| consciousness is spared, and signs are directly related to the region of cortex involved |
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Term
| In complex partial seizures |
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Definition
| consciousness is impaired and signs are more complex, being related to more than one region of cortex. |
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Term
| Examples of generalized seizures are... |
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Definition
| Absence (petit mal) and Tonic-clonic (grand mal) |
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Term
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Definition
A. most frequently, epilepsy is idiopathic (cause unknown); >50% of cases
B. tumors
C. trauma (causing brain damage and scarring); may occur during birth process, too
D. metabolic dysfunction (e.g., hypoglycemia; uremia)
E. infection
a. bacterial meningitis
b. Rasmussen's encephalitis, a viral-like condition in the brain that causes progressively more severe seizures)
F. stroke (vascular disease)
G. hyperthermia (febrile seizures, especially in infancy; sometimes later in life the patient is predisposed to non-febrile seizure activity; fever can trigger seizure more readily in an epileptic than in a normal individual)
H. genetic predisposition; family history
I. Drugs that block GABA receptors (potent convulsants)--GABA is an inhibitory neurotransmitter. |
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Term
| Temporal lobe (psychomotor) Seizures |
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Definition
1. Characterized by an odd combination of behavioral and motor activities
2. Clouding of consciousness and amnesia
3. Inappropriate movements at the time of seizure
A. tying and untying shoes
B. buttoning and unbuttoning clothes
C. robot-like activities are common
D. laughing or talking strangely
E. walking in circles
F. striking furniture or walls as though angry (often an expression of religious convictions)
4. Attacks last 30 sec. to 2 min., with little memory of the attack itself |
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Term
| Jacksonian Seizures (Frontal Lobe) |
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Definition
Jacksonian march: describes the progression of seizure activity along the motor cortex. Seizure often starts on one side, with twitching of the thumb, which then progresses to the hand, wrist, arm, shoulder, to leg.
3. Conscious is not lost unless seizure activity spreads to the other hemisphere and becomes generalized. |
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Term
| Absence (Petit Mal) Seziures |
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Definition
1. Generalized, but less serious than grand mal epilepsy
2. Brief loss of consciousness
3. There is a general loss of body motion (akinetic seizure), but may be slight muscle movements in limbs, eyes and mouth
4. "Absence" refers to absence of awareness and lack of participation in activity during attack
5. Blank facial expression during attack and lack of awareness of surrounding conversation
6. Duration is ~1-2 min.
7. Hyperventilation (produces respiratory alkalosis) can precipitate an attack and increase susceptibility of CNS to seizure
8. Some patients develop tonic-clonic (grand mal) seizures and some people outgrow seizure activities. Females are mores susceptible to developing tonic-clonic activity when they reach puberty. Most don’t fall. |
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Term
| Tonic-Clonic or Grand Mal Seizures |
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Definition
1. Generalized seizure activity; serious in nature
2. Stiffening of limb muscles (increased tonus), followed by symmetric twitching movements of limbs (clonus)
3. Loss of consciousness
4. Urinary and fecal incontinence
5. Frothing at the mouth
6. Dyspnea (difficulty in breathing), temporary cyanosis; may cause asphyxiation and death
A. seizure interferes with respiratory muscle activity
B. severe laryngospasm
C. blocking of airway with tongue
7. Seizure sometimes, but not always, preceded by an aura
A. peculiar taste or odor
B. flashes of light or sound
C. complete visual scene or tune
D. aura is usually specific and recognized by the patient, so that he can sometimes predict the onset of an impending seizure
8. Flashing lights (e.g., strobe light) can produce synchronous neuronal discharge and trigger a tonic-clonic seizure. (In December, 1997 in Japan, 729 children were sent to the hospital in one day for seizures they experienced watching brilliantly flashing blue/red/white scenes in a Pokemon TV cartoon. Varying symptoms included convulsions, spasms, nausea and loss of consciousness.)
9. Seizure phase itself is called the ictal period.
10. Post-ictal confusion, stupor, near unconscious, quiet, listless, unresponsive.
11. Grand mal epileptics are candidates for commissurotomy.
12. Susceptibility to seizure activity decreases with age:
A. 0-9 years: 47% of seizures
B. 10-19 years: 30%
C. 20-29 years: 13%
D. 30-39 years: 6%
E. 40+ years: 4% |
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Definition
1. Adequate rest; balanced diet
2. Abstinence from alcohol (alcohol depresses CNS; seizures can occur as CNS rebounds from depressive effects)
3. Anticonvulsant drugs (~19 different drugs are FDA approved)
A. ~80% of epileptics have seizure activity controlled by currently available drugs.
4. Commissurotomy (corpus callosum and anterior commissure severed)
5. Hemispherectomy: removal of the entire cortex on one side, leaving intact the thalamus, brainstem and basal ganglia. Vacant space fills with fluid. Patients have hemiplegia, especially in the hand and arm; vision in one eye may also be affected. Patients can walk, run, most of the patients's physical and cognitive abilities are intact; they are freed from seizures. Used for intractable seizures (many seizures a day, that impair a person’s ability to function and are causing brain damage). Results are better the younger the child, due to greater CNS plasticity in younger persons.
6. Other surgery to remove epileptic focus.
7. Placement of a small pacemaker placed under the skin, to periodically stimulate the vagus nerve in the side of the neck with a low amount of electrical current. This process can reduce seizure frequency and severity.
8. Low carbohydrate diet |
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Term
| The summed collective behavior of many thousands of neurons of the cerebral cortex can be studied non-invasively with |
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Definition
| electroencephalogram (EEG) |
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| deep relaxation and mediation, mental imagery |
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| relaxed, calm, lucid, not thinking |
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| awake, normal alert, consciousness |
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