Some determinants of an amnesic phenomenon in a light-sensitive epileptic child

Verbal and visual memory impairment in children with epilepsy

Verbal and visual memory performances were evaluated in 60 epileptic children and 60 normal control subjects with Signoret's Memory Battery scale. Eighteen patients had idiopathic generalized epilepsy and 42 had partial epilepsy, mostly of the temporal (n = 28) and frontal (n = 10) lobes. Memory scores were statistically lower in epileptics than in controls and significant differences were found within each group: (1) children with idiopathic generalized epilepsy had a slight depression of visual memory; (2) memory disorder was more severe in partial epilepsy; and (3) children with left and right temporal lobe epilepsy had marked memory deficits related to hemispheric specialization.

Focal spike-induced cerebral dysfunction is related to the after-coming slow wave

By means of a computerized system of spike detection, presentation of visual stimuli, and registration of reaction times (RTs), we have shown previously that focal posterior interictal spikes cause transiently prolonged RT and increased nonperception and misperception of stimuli, especially contralateral to the spike. We report here the temporal profile of this phenomenon, ascertained by systematically increasing a delay between spike and stimulus-flash, until the latter was well beyond the limits of the entire spike-wave complex. In each of two subjects, the spike effect began just before the spike and ended with the termination of the after-coming slow wave. For stimuli with identical delays following spikes, RTs were significantly prolonged if the end of the slow wave overlapped the stimulus, and not otherwise. In one subject, who had an amplitude dissociation between spikes and after-coming slow waves, the prolongation of RT was associated with the larger waves, regardless of spike amplitude. These findings suggest that the after-coming slow wave (surround hyperpolarization) transiently disrupts aspects of cortical functioning, in addition to whatever effect the spike itself may have. Focal spike-wave-induced cortical dysfunction may be relevant to a variety of interictal cognitive disorders.

Effects of evoked spike-wave discharges upon short term memory in patients with epilepsy

Memory for digits was examined during EEG examination in five female children suffering from light sensitive epilepsy. Sequences of random digits equal to the patients' digit span, span-less-one and span-less-two were presented, followed by a 2 sec. interval, after which recall of the digits was required. The 2 sec. interval could be filled in any of four possible ways by: a burst of photic stimulation which evoked a paroxysm of generalised spike-wave in the EEG; a burst of slow (3 Hz) photic stimulation having no discernible effect upon the EEG; a burst of fast (30 Hz) stimulation, again having no observable effect; or a period of silence with no photic stimulation. It was found that recall of digits series of all three lengths was impaired if a paroxysm of spike-wave had been generated between the end of presentation and the beginning of recall. There were no significant differences in correctness of recall when the slow, fast and no-stimulation photic conditions were compared. It was found that the last two digits in the digit span were more vulnerable to recall failure than were the first two. On the basis of recent work in human experimental psychology, the initial and final digit pairs appear to be retrieved from functionally different storage systems. It is tentatively suggested therefore, that since different parts of the digit span are dislocated to different extents by spike-wave activity, they may depend upon different neural substrates.