Berger (1929) was the first person to recognise spike wave activity during epileptic seizures using the electroencephalograph. However, since this major discovery it has been argued that paroxysmal, abnormal neuronal discharges do not always produce clinical manifestations of seizures, (Binnie 1991). Because of the lack of any clinical manifestations, such discharges were described as ‘sub-clinical’, ‘larval’ or ‘inter-ictal’, (Binnie 1991). Schwab (1939) investigated ‘sub-clinical activity’ in petit mal epilepsy (absence seizures) by conducting an experiment using an electroencephalograph and a simple reaction time task. Schwab found that spike and wave activity recorded on the electroencephalograph that was not associated with clinical manifestations of absence seizure behaviour did however correlate with reaction time. That is to say, spike and wave activity appeared to increase reaction time and also the failure to respond. Since Schwab’s study, over forty other experiments have supported Schwab’s findings.
Aarts et al. (1980) defined the impairment in cognitive ability during spike and wave activity as ‘transitory cognitive impairment’ because the cognitive impairment is not permanent but appears from time to time. Furthermore, Binnie (1991) has argued that inter-ictal epileptiform activity is a more appropriate term to use rather than sub-clinical activity because it can be argued that transitory cognitive impairment is a type of clinical manifestation. Binnie has also argued that the term Inter-ictal epileptiform activity should be used because it describes epileptiform activity between ictal phases (seizures).

Click here to buy generic Lamictal (Lamotrigine) 25mg online - 270 pills $156.60

In their study, Tizard & Margerison (1963) found that participants were able to respond to most stimuli during spike and wave activity and even during overt absence seizures. Prechtl et al (1961) conducted experiments to see if there was relationship between paroxysmal EEG patterns and changes in the behaviour of participants. Prechtl et al (1961) designed a test for use with a group of ‘normal’ participants and a group of participants with clinical symptoms of epilepsy. A test of performance was used that would engage the participant in continuous activity but would not allow the participant to automate the activity. The test consisted of five small lamps with five buttons. One button corresponding to each of the lamps. In the test, only one lamp lit up at a time and the pushing of the corresponding button would extinguish the lamp. The lamps lit up in a random order and the participants were requested to extinguish the lamps as quickly as possible. During the test, each individual participant was connected to an EEG machine. Correct and incorrect button pushes were recorded on the EEG by the way of markers. The test lasted three minutes followed by a short break and then the participant was asked to take a further test of three minutes.

Click here to buy generic Topamax (Topiramate) 25mg online - 200 pills $122.00

The results from the study indicated that epileptiform activity and EEG recordings did not show simple temporal correlations. One of the participants in the study managed to complete the experiment without any errors whilst displaying ten seconds of generalised spike and wave activity. Focal spike and wave activity also appeared to have little affect on the performance of the test. However, Prechtl et al found that changes in test performance correlated with an undifferentiated flattening of the EEG, which is known as suppression. Overall, the results indicated that spike and wave activity did not show any significant correlation with changes in test performance as opposed to suppression which did. Prechtl et al have argued that suppression is usually followed by an epileptic discharge and is not seen in non-epileptic patients. It was also noted that the frequency of epileptic discharges in the epileptic patient was reduced during periods of concentrated attention opposed to relaxed periods when the participant displayed alpha rhythms. It could therefore be argued that alpha blocking might have a relationship with the reduction of epileptic discharge.

Click here to buy generic Tegretol (Carbamazepine) 100mg online - 400 pills $92

Davidoff et al (1963) conducted a study that involved the participation of people with epilepsy who had met a number of criteria prior to entering the study. To enter the study, the participants needed to have a referring diagnosis of idiopathic epilepsy, absences of neurological disorders including disease and an EEG recording that had shown abnormal paroxysmal, bilaterally synchronous bursts of activity that appeared abruptly. The EEG readings must also have shown normal electrical activity prior to the paroxysmal burst and normal electrical activity following the paroxysmal burst.
The participants in the study, which was undertaken at an army medical research centre, were referred with differing diagnoses of epilepsy. Of the thirty-six participants that were referred, nineteen were diagnosed as suffering from Grand Mal epilepsy, eighteen were diagnosed with Petit Mal epilepsy and Nine others were diagnosed as having miscellaneous types of epilepsy. 
In the study, the participants were requested to undertake four tasks, which were tapping with the right index finger rhythmically, repeating digits, serial subtraction of seven from one hundred and counting backwards. The participants undertook the tasks whilst exposed to intermittent photic stimulation. Prior to the tasks been undertaken using photic stimulation the participants undertook the tests without photic stimulation so that they could act as their own controls.

Click here to buy generic Valparin (Valproic Acid) 500mg online - 90 pills $113.19

After the experiment, EEG paroxysms were classified into four categories which were petit mal type (PMT), atypical spike and slow wave (ASW), multiple spike bursts (MSB) and slow wave burst (SWB). The EEG paroxysms were also classified as either clinical or subclinical depending on the observations of the participant made by the experimenters during the test. Behaviour such as blinking, head movements or reports by the participant of feelings of strange sensations by the participant during paroxysmal discharges was classified as clinical discharges. If no movements or the participant did not report any unusual sensations during paroxysmal discharges, the discharges were classified as subclinical discharges.
After the completion of the experiment, the duration of paroxysmal discharges were measured and classified in terms of whether or not they were induced by photic stimulation or spontaneous. The participants were also divided into two groups dependent on whether or not they showed breaks in functioning with regard to the tests. That is to say, if the participant paused during a particular test such as the finger-tapping test, it would be classed as a break if both experimenters agreed that it was. Breaks in the finger tapping experiment included pauses and irregularities in finger tapping rhythm. It was noted that the halting of finger tapping behaviour completely was unusual. It was also noted that participants who stopped finger tapping at the beginning of a paroxysmal burst usually restarted the finger tapping and continued to do so despite the continuation of the discharge.

Click here to buy generic Mysoline (Primidon) 250mg online - 270 pills $175.50

The results from the study displayed a wide variability between individual participants and bursts of activity. The results indicated that participants with clinical bursts of paroxysmal activity were more likely to have breaks in functioning during the tests than the participants with subclinical bursts of activity. Fifty four percent of the clinical paroxysmal bursts were associated with breaks in activity as opposed to twenty six percent of subclinical bursts that were associated with breaks in activity.
The results also showed that there was a significant difference in the mean number of paroxysmal bursts between the twenty-four participants in the break group and the thirty-six participants in the no break group. Participants in the break group had significantly longer bursts of paroxysmal activity with greater variability of duration.
The results also indicated that fifty seven percent of discharges from the break group were photically stimulated as opposed to twenty six percent in the no break group. It was therefore argued that breaks in functioning were more likely to be associated with photically induced paroxysmal bursts than spontaneous paroxysmal bursts of activity.

Click here to buy generic Trileptal (Oxcarbazapine) 150mg online - 120 pills $45.60

The subtraction test was most effected by paroxysmal discharges. Eighty percent of participants who had an error on the test showed paroxysmal discharges as opposed to thirty four percent of errors correlating with paroxysmal discharges in the digit repetition test. Overall the results from Davidoff et al indicate that Clinical paroxysmal bursts are more likely to cause breaks during tests, the length of paroxysmal bursts are likely to increase the chance of a break in performance, photically stimulated paroxysmal bursts are more likely than spontaneous paroxysmal bursts to cause a break in performance and breaks in performance are more likely to be caused by clinical paroxysmal activity as opposed to subclinical activity.

Click here to buy generic Neurontin (Gabapentin) 300mg online - 120 pills $100.12