this phenomenon belongs to the group of derealization disorders , which also includes states such as dj vcu ( already experienced ) , dj entendu ( already heard ) , and jamais vu ( never seen ) . according to another classification , dv is a memory - based illusion . the term was coined by the french psychologist emile boirac ( 18511917 ) in his monograph l'avenir des sciences psychiques ( the future of psychology , 1918 ) . the dv phenomenon attracts special interest because , on the one hand , it occurs in most healthy individuals ( up to 97% of the general population ) , spontaneously or in association with sleeping disorders or anxiety . on the other hand , it can be a sign of certain psychoneurological diseases , such as charles bonnet syndrome , temporal lobe epilepsy ( tle ) , depression , or schizophrenia , and it can be an early symptom of a mass lesion of the brain [ 25 ] . thus , dv is observed both in healthy people and in patients with organic brain damage or dysfunction . under these circumstances , it seems reasonable to identify differential diagnostic criteria to discriminate whether dv represents a normal phenomenon or a sign of a disease . a number of modern publications are concerned with the mechanisms underlying dv and its characteristics and prevalence [ 2,48 ] . we also described major clinical differential diagnostic characteristics of dv in healthy individuals , in patients with mass lesions of the brain , and in patients with epilepsy . a dv aura occurs in 10% of patients with tle ; dv as a sign is present in 2/3 of patients with idiopathic generalized epilepsy . in our previous paper , autosomal dominant temporal lobe epilepsy ( adtle ) is characterized by focal seizures with auditory symptoms or aphasia . recently , adtle cases with psychic presentations ( dv and fear ) but lacking classic aphasia and auditory symptoms have been described . these patients had a previously unknown lgi1 mutation , arg407cys , which , in contrast to the mutations described earlier , did not prevent protein secretion in vitro . to identify the brain regions involved in dv , patients with tle with and without dv episodes were investigated using voxel - based analysis of fdg - pet brain scans . patients with tle with dv episodes exhibited unilateral focal hypometabolism in the superior temporal gyrus and the parahippocampal region , in the vicinity of the perirhinal and entorhinal cortices . gloor   implanted electrodes on 35 patients with tle with pharmacoresistant seizures and found that most dv episodes were associated with stimulation of the right hemisphere . performed a spect investigation in a patient with frequent dv auras and detected hyperperfusion in the right temporal and frontal lobes . following pharmacotherapy , the frequency of seizures and dv episodes decreased , and the perfusion characteristics returned back to normal . the main clinical problem unsolved is whether dv can be considered as a sign of epilepsy . neppe   found that dv occurred more frequently in patients with tle ( 86% ) than in control individuals ( 68% ) but did not show the significance of this difference . some other authors argue that dv can occur as a simple partial seizure , as a part of a complex partial seizure , or as an aura of a secondarily generalized tonic apparently , the problem can not be solved without describing the specific ictal eeg pattern of dv , which has not been done so far to our knowledge . the aim of the present study was to investigate the electroencephalographic characteristics of the dv phenomenon in patients with epilepsy and in healthy subjects . we performed eeg monitoring in 20 healthy volunteers with frequent dvs and in 23 patients with epilepsy . in the course of ambulatory eeg monitoring , dv episodes were registered in one healthy volunteer and in three patients with epilepsy . we did not find any description of eeg patterns of dv in the available literature . this investigation involves autonomous registration of eeg on a memory card of the recording device , without phono- or photostimulation , while the patient is free in his movement and activities , and independent of the computer . it provides a possibility to detect the pattern of rare seizures ( including dv ) during a subject 's normal wakefulness . this investigation involves autonomous registration of eeg on a memory card of the recording device , without phono- or photostimulation , while the patient is free in his movement and activities , and independent of the computer . it provides a possibility to detect the pattern of rare seizures ( including dv ) during a subject 's normal wakefulness . for a long time ( since the age of 15 ) , the subject had been complaining of moderate tension headaches with a predisposition to meteosensitivity . at approximately the same age , she began to experience dv episodes , which had been growing more frequent . at examination , dj vu episodes occurred several times per day , lasting up to 10  s , and were accompanied by positive emotions ( surprise , interest ) and no fear . a routine eeg showed moderate diffuse changes of bioelectric brain activity , without epileptiform signs . the patient was in the kitchen , when she experienced a feeling of unreality and expected a dv . she pressed the marker button . she felt interest and pleasant emotions and became attentive to her condition . she had a feeling that everything had happened before and knew what was going to happen next ( anticipation ) . the episode lasted about 10 to 15  s ( fig .  1 ) . as visible in the eeg fragment , there were no epileptiform changes during this dv episode in a subject without epilepsy . , d. has been experiencing rare dv episodes , such as perceiving things as already seen in the same circumstances , up to 5  s long . at the age of 24 , he suffered a closed craniocerebral injury and cerebral concussion as a result of a traffic accident . six to seven months after the injury , the patient began to suffer from generalized tonic dj vu episodes occurred once or twice per week , lasting up to 30  s , and were accompanied by fear and unpleasant feelings ; however , the patient was willing to relive the experience . a routine eeg showed rhythm disorganization with moderately decreased amplitude and paroxysmal activity , predominantly frontal and central , more on the left , enhanced by hyperventilation . during a 12-hour eeg monitoring , at 23:30 , the patient experienced derealization and anxiety , followed by dv accompanied by an unpleasant feeling of anguish . the episode lasted up to 32  s. the episode was accompanied by the following changes in eeg ( figs .  2 , 3 , 4 ) . several fractions of a second before the patient pressed the button ( the beginning of the seizure ) , a galvanic skin response was registered . the dominant alpha rhythm changes to a polymorph epileptiform activity with slow waves of theta band and sharp waves ( fig .  2 ) . the amplitude of the slow and sharp waves gradually increased up to 200  mv as the episode began . the total duration of the seizure was 32  s. the pathological activity lasted for a total of 32  s , after which it was replaced by background activity . a dipole localization procedure using the brainlock program localized the focus of both the initial activity and the subsequent slow - wave activity in the medial temporal lobe and the medial frontal lobe of the right hemisphere ( fig .  5 ) . in two other ambulatory eeg records of dv episodes , the polyspike activity lasted for 8  s and also showed distinct right hemisphere lateralization , predominantly in the temporal lobe . for a long time ( since the age of 15 ) , the subject had been complaining of moderate tension headaches with a predisposition to meteosensitivity . at approximately the same age , she began to experience dv episodes , which had been growing more frequent . at examination , dj vu episodes occurred several times per day , lasting up to 10  s , and were accompanied by positive emotions ( surprise , interest ) and no fear . a routine eeg showed moderate diffuse changes of bioelectric brain activity , without epileptiform signs . the patient was in the kitchen , when she experienced a feeling of unreality and expected a dv . she pressed the marker button . she felt interest and pleasant emotions and became attentive to her condition . she had a feeling that everything had happened before and knew what was going to happen next ( anticipation ) . the episode lasted about 10 to 15  s ( fig .  1 ) . as visible in the eeg fragment , there were no epileptiform changes during this dv episode in a subject without epilepsy . , d. has been experiencing rare dv episodes , such as perceiving things as already seen in the same circumstances , up to 5  s long . at the age of 24 , he suffered a closed craniocerebral injury and cerebral concussion as a result of a traffic accident . six to seven months after the injury , the patient began to suffer from generalized tonic dj vu episodes occurred once or twice per week , lasting up to 30  s , and were accompanied by fear and unpleasant feelings ; however , the patient was willing to relive the experience . a routine eeg showed rhythm disorganization with moderately decreased amplitude and paroxysmal activity , predominantly frontal and central , more on the left , enhanced by hyperventilation . during a 12-hour eeg monitoring , at 23:30 , the patient experienced derealization and anxiety , followed by dv accompanied by an unpleasant feeling of anguish . the episode lasted up to 32  s. the episode was accompanied by the following changes in eeg ( figs .  2 , 3 , 4 ) . several fractions of a second before the patient pressed the button ( the beginning of the seizure ) , a galvanic skin response was registered . the dominant alpha rhythm changes to a polymorph epileptiform activity with slow waves of theta band and sharp waves ( fig .  2 ) . the amplitude of the slow and sharp waves gradually increased up to 200  mv as the episode began . the total duration of the seizure was 32  s. the pathological activity lasted for a total of 32  s , after which it was replaced by background activity . a dipole localization procedure using the brainlock program localized the focus of both the initial activity and the subsequent slow - wave activity in the medial temporal lobe and the medial frontal lobe of the right hemisphere ( fig .  5 ) . in two other ambulatory eeg records of dv episodes , the polyspike activity lasted for 8  s and also showed distinct right hemisphere lateralization , predominantly in the temporal lobe . for a long time ( since the age of 15 ) , the subject had been complaining of moderate tension headaches with a predisposition to meteosensitivity . at approximately the same age , she began to experience dv episodes , which had been growing more frequent . at examination , dj vu episodes occurred several times per day , lasting up to 10  s , and were accompanied by positive emotions ( surprise , interest ) and no fear . a routine eeg showed moderate diffuse changes of bioelectric brain activity , without epileptiform signs . the patient was in the kitchen , when she experienced a feeling of unreality and expected a dv . she pressed the marker button . she felt interest and pleasant emotions and became attentive to her condition . she had a feeling that everything had happened before and knew what was going to happen next ( anticipation ) . the episode lasted about 10 to 15  s ( fig .  1 ) . as visible in the eeg fragment , there were no epileptiform changes during this dv episode in a subject without epilepsy . , d. has been experiencing rare dv episodes , such as perceiving things as already seen in the same circumstances , up to 5  s long . at the age of 24 , he suffered a closed craniocerebral injury and cerebral concussion as a result of a traffic accident . six to seven months after the injury , the patient began to suffer from generalized tonic dj vu episodes occurred once or twice per week , lasting up to 30  s , and were accompanied by fear and unpleasant feelings ; however , the patient was willing to relive the experience . a routine eeg showed rhythm disorganization with moderately decreased amplitude and paroxysmal activity , predominantly frontal and central , more on the left , enhanced by hyperventilation . during a 12-hour eeg monitoring , at 23:30 , the patient experienced derealization and anxiety , followed by dv accompanied by an unpleasant feeling of anguish . the episode lasted up to 32  s. the episode was accompanied by the following changes in eeg ( figs .  2 , 3 , 4 ) . several fractions of a second before the patient pressed the button ( the beginning of the seizure ) , a galvanic skin response was registered . the dominant alpha rhythm changes to a polymorph epileptiform activity with slow waves of theta band and sharp waves ( fig .  2 ) . the amplitude of the slow and sharp waves gradually increased up to 200  mv as the episode began . the total duration of the seizure was 32  s. the pathological activity lasted for a total of 32  s , after which it was replaced by background activity . a dipole localization procedure using the brainlock program localized the focus of both the initial activity and the subsequent slow - wave activity in the medial temporal lobe and the medial frontal lobe of the right hemisphere ( fig .  5 ) . in two other ambulatory eeg records of dv episodes , the polyspike activity lasted for 8  s and also showed distinct right hemisphere lateralization , predominantly in the temporal lobe . the major questions addressed in dv investigations are its clinical significance ( e.g. , whether it is a pathological phenomenon ) and , accordingly , the necessity of treatment and the mechanisms of its generation . most authors believe that dv is a neurologic analog of a seizure involving psychoactive zones , rather than a psychopathological phenomenon . it assumes that the functions of the hippocampus and the prefrontal cortex involve recognition of new information and relating it to previous experience . the parahippocampal system coordinates the comparison , and aberrations of its functioning cause novel information to seem familiar , i.e. , produce a dv . it was concluded that dvs occur as a result of an impaired contact between the neocortex and the medial temporal lobe structures , when the cortical influence weakens ( e.g. , during sleep , fatigue ) . electroencephalography ( eeg ) results together with clinical , psychological , and neuroimaging data , suggest that two dv types exist : pathological and nonpathological . on the other hand , show that there is a difference in brain structure between subjects who have felt dv and those who have never felt dv . authors investigated differences in brain morphology between healthy subjects with and without dv using source - based morphometry , a novel multivariate neuroimaging technique . the analysis revealed a set of cortical ( predominantly mesiotemporal ) and subcortical regions in which there was significantly less gray matter in subjects reporting dv . in these regions , most healthy individuals have the nonpathological - nonepileptic dv type , which does not show an epileptiform eeg pattern , has low frequency and low duration , and occurs mostly as an induced phenomenon . however , it can not be ruled out completely that such nonpathological dv might be associated with aberrations of neuron functioning and spontaneous neuron discharging . however , the activity is probably restricted to such a small area ( within the parahippocampal zone ) that it does not produce any distinctive eeg pattern . on the other hand , pathologic epileptic dvs occurring in epilepsy are characterized by a specific pattern of eeg activity and typical clinical features , such as increased frequency and duration and negative emotional perception . that is , a pathological dv occurs as a result of excessive mass neuron discharges and is , in fact , a simple partial psychogenic seizure . other authors also proposed a similar division with two dv types , although they did not provide any electrophysiological evidence to support the notion . the eeg data suggest that dv generation largely involves the right hemisphere . however , two eeg records of dv episodes showed polyspike activity in the right hemisphere , lasting for 8  s , while in a longer episode , polyspike activity was followed by slow - wave activity . it is possible that dv is not generated in any single hemisphere but results from impairment in their interaction . importantly , pet and spect studies detected hypometabolism areas in temporal lobe structures ( entorhinal and perirhinal cortices ) [ 2123 ] . the slow - wave activity detected in a patient with epilepsy during a dv episode can be an electrophysiological reflection of the previously described hypoperfusion . however , among the cases analyzed , dv episodes were present not only in focal forms but also in idiopathic generalized and undifferentiated epilepsy , which can probably be explained as follows : each seizure changes the functioning of individual neurons and neuronal networks ( up to neuronal death ) . secondary epileptogenesis is characterized by selective loss of specific gabaergic interneurons and formation of new excitatory glutamatergic pathways , which also determine future seizures . such newly formed synapses have a decreased activation threshold .in tle , neurons most commonly affected are those of the ca1 and ca3 zones , as well as of the dentate gyrus ; however , extrahippocampal zones , such as the piriform and entorhinal cortices and the amygdala , that is , zones , responsible for dv generation , are also involved . thus , the patterns of neuronal damage and death and synaptic reorganization constitute the fundamental mechanism of epileptogenesis , both in animal models and in human patients with tle . postseizure reorganization of neural networks in dv - generating zones ( irrespective of the epilepsy form ) can produce the phenomenon in the absence of a particular pathologic process in this area . each seizure changes the functioning of individual neurons and neuronal networks ( up to neuronal death ) . secondary epileptogenesis is characterized by selective loss of specific gabaergic interneurons and formation of new excitatory glutamatergic pathways , which also determine future seizures . neurons most commonly affected are those of the ca1 and ca3 zones , as well as of the dentate gyrus ; however , extrahippocampal zones , such as the piriform and entorhinal cortices and the amygdala , that is , zones , responsible for dv generation , are also involved . thus , the patterns of neuronal damage and death and synaptic reorganization constitute the fundamental mechanism of epileptogenesis , both in animal models and in human patients with tle . postseizure reorganization of neural networks in dv - generating zones ( irrespective of the epilepsy form ) can produce the phenomenon in the absence of a particular pathologic process in this area . also , dv in patients with idiopathic generalized epilepsy is characterized by a frequency of 12 times a month and duration of 510  s , accompanied by positive emotions and lack of fear . so , it was similar to the dv in healthy respondents but a bit more frequent . in patients with epilepsy , dv is equally frequent in cryptogenic and symptomatic focal epilepsy ; it can accompany nearly all seizure types and occur as a simple partial seizure or as a part of a secondarily generalized seizure . major clinical features distinguishing dv in patients with epilepsy from that in healthy individuals are its frequency , the fear preceding dv , and the emotional perception . a very important criterion is dv dynamics , such as increasing frequency and duration , or appearance of negative emotions . on eeg , dv began with polymorphic spike and slow - wave activity in the right temporal lobe . our combined clinical and electrophysiological investigation identified two separate dv types : epileptic dj vu , which is characteristic of patients with epilepsy and equivalent to an epileptic seizure , and nonepileptic dj vu , which occurs in healthy individuals and is basically a psychological phenomenon .
backgrounddj vu ( dv , from french dj vu   already seen  ) is an aberration of psychic activity associated with transitory erroneous perception of novel circumstances , objects , or people as already known.objectivethis study aimed to record the eeg pattern of dj vu.methodsthe subjects participated in a survey concerning dj vu characteristics and underwent ambulatory eeg monitoring ( 1216  h).resultsin patients with epilepsy , dv episodes began with polyspike activity in the right temporal lobe region and , in some cases , ended with slow - wave theta 
 delta activity over the right hemisphere . 
 there were no epileptic discharges in healthy respondents during dv.conclusiontwo types of dj vu are suggested to exist :  pathological - epileptic 
 dj vu , characteristic of patients with epilepsy and equivalent to an epileptic seizure , and  nonpathological - nonepileptic  dj vu , which is characteristic of healthy people and psychological phenomenon .