Abstract
Is there a relationship between peri-ictal slow waves, loss of consciousness, memory, and slow-wave sleep, in patients with different forms of epilepsy? We hypothesize that mechanisms, which result in peri-ictal slow-wave activity as detected by the electroencephalogram, could negatively affect memory processes. Slow waves (≤4 Hz) can be found in seizures with impairment of consciousness and also occur in focal seizures without impairment of consciousness but with inhibited access to memory functions. Peri-ictal slow waves are regarded as dysfunctional and are probably caused by mechanisms, which are essential to disturb the consolidation of memory entries in these patients. This is in strong contrast to physiological slow-wave activity during deep sleep, which is thought to group memory-consolidating fast oscillatory activity. In patients with epilepsy, slow waves may not only correlate with the peri-ictal clouding of consciousness, but could be the epiphenomenon of mechanisms, which interfere with normal brain function in a wider range. These mechanisms may have transient impacts on memory, such as temporary inhibition of memory systems, altered patterns of hippocampal–neocortical interactions during slow-wave sleep, or disturbed cross-frequency coupling of slow and fast oscillations. In addition, repeated tonic–clonic seizures over the years in uncontrolled chronic epilepsy may cause a progressive cognitive decline. This hypothesis can only be assessed in long-term prospective studies. These studies could disentangle the reversible short-term impacts of seizures, and the impacts of chronic uncontrolled seizures. Chronic uncontrolled seizures lead to irreversible memory impairment. By contrast, short-term impacts do not necessarily lead to a progressive cognitive decline but result in significantly impaired peri-ictal memory performance.
Highlights
Memory deficits cause severe impairment of quality of life in patients with epilepsy (Thompson and Corcoran, 1992; Motamedi and Meador, 2003; Elger et al, 2004; van Rijckevorsel, 2006; Butler and Zeman, 2008)
Is memory affected by structural brain damage, which eventually causes seizures, or is memory impairment a result of the seizures, being possibly related to the occurrence of ictal slow waves? The authors support the view that it is highly likely that both possibilities are eligible, but the amount of contribution of one or the other of these two processes may vary with epilepsy subtype, its age of onset, localization, lateralization, time-scale of the affected memories, age, type, and number of seizures – especially the occurrence of generalized tonic–clonic seizures, status epilepticus, and discharges during slow-wave sleep (Elger et al, 2004; Stefan and Pauli, 2008)
One may say speculative review we examined the literature on possible relationships between slowwave activity in the EEG and memory performance in patients with epilepsy
Summary
Memory deficits cause severe impairment of quality of life in patients with epilepsy (Thompson and Corcoran, 1992; Motamedi and Meador, 2003; Elger et al, 2004; van Rijckevorsel, 2006; Butler and Zeman, 2008). In the network inhibition hypothesis, Englot and Blumenfeld (2009) proposed that peri-ictal sleep-like slow rhythms could mediate the impairment of consciousness in TLE Is it possible, that the slow wave activity (≤4 Hz) as measured by the electroencephalogram (EEG) is the link between seizures affecting consciousness and memory? The authors support the view that it is highly likely that both possibilities are eligible, but the amount of contribution of one or the other of these two processes may vary with epilepsy subtype, its age of onset, localization, lateralization, time-scale of the affected memories, age, type, and number of seizures – especially the occurrence of generalized tonic–clonic seizures, status epilepticus, and discharges during slow-wave sleep (Elger et al, 2004; Stefan and Pauli, 2008). It was suggested that acetylcholinergic neurons are lesioned in refractory epilepsy (Hayashi et al, 2012)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
