Deja Vu

Hmmm...yes. But what about them times where you just know its been exactly the same before? Surely thats a little more than familiar with the situation. But then, I guess, that can be down to personal experience.

I'd always assumed deja vu was just a sense of familiarity of the characteristics of the situation, and not so much an actual sharing of two different times.

That is, It's largely a psychological phenomena, rather than one of time or space.

Dèjá vu experiences are a common feature of temporal lobe seizures and have often been reported after stimulating healthy subjects' medial temporal lobes. Such evidence suggests that the middle area of the temporal lobes gives rise to such experiences.

I realize that Zooby is well read on the subject of simple partial seizures, but the supporting evidence for the statements in the linked thread is pretty thin. A few references beyond a drug site would be nice.

Actually, I just realized I could take a pic of the EEG of a deja vu and post it:

This guy has depth electrodes implanted right into various parts of his limbic system through holes drilled in his skull in an attempt to locate his seizure focus prior to epilepsy surgury.
This is from a paper called The Role Of The Limbic Sysytem in Experiential Phenomena of Temporal Lobe Epilepsy by Pierre Gloor, et. al. Annals of Neurology, Vol12 No2 August 1982

Also, does this account for all experiences? If I walk into a room and have a sense of deja vu, and later I remember that I was once there as a small child, have I experienced a simple partial seizure?Clearly there are other reasons why one might have a feeling like this. And here is another problem with this sort of thing: If I feel a breeze on my arm or hear a buzzing sound, it may be a breeze or a buzzer, or it may be a simple partial seizure, but the existence of simple partial seizures does not exclude the existence of wind or buzzers.

I definitely am not that knowledgeable about it since I am more interested in parietal lobe functions and focus most of my studying there.

I've identified that i get the feeling of Deja Vu, for example, in the following scenario:
- at one point i see an object, like a toothbrush, and i think of something, or the toothbrush reminds me of something.
- later on, if i see the same object and think the exact same thing, i get the feeling of Deja Vu,.

I think the reason sometimes the feeling is hard to explain is because either the first or, more likely, the second thought might happen unconsciously, as a reflex, so you might not be aware of what triggered the feeling.
For example, have you ever, while flipping through the pages of a book, have a word pop into your head without you ever actually seeing (or remembering seeing) the word? Whenever this happens to me i always scan the page for what might have triggered the word to get into my head. If i closely study the path my eyes followed when they moved across the page i always either find the word or some syllables, maybe in different lines, that form the word.
Similarly, in the same way the word got into my head when i was flipping through the pages, sometimes, unconsciously, maybe from seeing an object from the corner of my eye, something may trigger a thought to get into my head. If this has happened before i will get the feeling of Deja Vu. If i'm unable to identify what triggered this then i won't be able to explain it, which is common.
I'm pretty confident that this is what deja vu is, i usually pay close attention whenever i get the feeling, and i find that this explanation works for me.

You should have read the whole thread:

Of course authentic memories, sounds, and buzzers aren't simple partial seizures.

What interests you about the parietal lobes? Most people seem to get interested in the frontal or temporal lobes.

I looked it over and only saw one link. The other references can't easily be verified.

* Motor simple partial seizures

o Clonic discharges in the sensorimotor cortex cause jerky, rhythmic movements that may remain restricted to one body segment or spread by “jacksonian march.”

o Benign focal epilepsy of childhood accounts for 15-25% of childhood epilepsy and eventually remits by age 16 years.

+ Typical seizures are simple and motor, affect the face or arm, and occur soon after falling asleep or awakening.

+ As it usually remits by age 16 years, this syndrome does not always require treatment.

o Another subtype, epilepsia partialis continua (ie, Kojewnikoff syndrome), includes stereotypical periodic to semiperiodic clonic activity that may persist for years and is often refractory to treatment.

+ Clonic jerking usually involves the thumb or great toe, and may or may not spread to other body parts.

+ This activity has been associated with stroke, tumor, trauma, hypoxia, Rasmussen encephalitis, syndrome of mitochondrial encephalomyopathy, lactic acidosis, and stroke (MELAS), subacute sclerosing panencephalitis (SSPE), and adult nonketotic hyperglycinemia.

o Tonic-supplementary motor area (SMA) and premotor region discharges produce sustained contractions and unusual postures of a limb.

+ In 72% of cases SMA seizures are not associated with impaired consciousness.

+ Versive-smooth or jerky, tonic contractions of head and eye muscles, usually on the side contralateral to the discharge, often are followed by a secondarily generalized tonic-clonic seizure.

+ Phonatory activation of the primary or supplementary motor cortex produces vocalizations, speech arrest, or aphasia.

* Sensory simple partial seizures

o Somatosensory-primary sensory cortex seizures usually elicit positive or negative sensations contralateral to the discharge.

o Symptoms associated with seizures from the postcentral gyrus include tingling, numbness, pain, heat, cold, agnosia, phantom sensations, or sensations of movement.

o Abdominal pain usually originates from the temporal lobe, and genital pain from the mesial parietal sensory cortex.

o The posterior parietal cortex is the likely origin of limb agnosia.

o Supplemental sensory-secondary sensory cortex seizures may have ipsilateral or bilateral positive or negative sensations or vague axial or diffuse sensations.

o Visual-calcarine cortex discharges produce elemental hallucinations including scintillations, scotomata, colored lights, visual field deficits, or field inversion.

o The visual association cortex is the probable location of origin of complex visual hallucinations and photopsias.

o Auditory SPS from the auditory cortex typically are perceived as simple sounds, rather than words or music.

o Olfactory-uncinate seizures originate from the orbitofrontal cortex and the mesial temporal area. Perceived odors are usually unpleasant, often with a burning quality.

o Gustatory seizures usually are associated with temporal lobe origin, although the insula and parietal operculum also have been implicated. Perceived tastes are typically unpleasant, often with a metallic component.

o Vestibular seizures originate from various areas, including frontal and temporal-parietal-occipital junction. Symptoms include vertigo, a tilting sensation, and vague dizziness.

o Psychic SPS arise predominantly from the temporal and limbic region, including the amygdala, hippocampus, and parahippocampal gyrus. Perceptual hallucinations or illusions are usually complex, visual or auditory, and are rarely bimodal.

+ Includes the déjà vu and jamais vu phenomena

+ Emotional: Fear is usual, but SPS can elicit happiness, sexual arousal, anger, and similar responses.

+ Cognitive: These responses include feelings of depersonalization, unreality, forced thinking, or feelings that may defy description.

* Autonomic simple partial seizures

o Abdominal sensation phenomena

+ These are common in mesial temporal epilepsy but can arise from the operculum and occipital region.

+ Symptoms include nausea, pain, hunger, warmth, and “epigastric rising” sensations, and may be associated with piloerection (ie, gooseflesh).

o Cardiovascular sensations

+ The most common cardiac manifestation of any seizure is sinus tachycardia with arrhythmias, with bradycardia occurring infrequently.

+ Some patients have chest pain or a sensation of palpitation that mimics cardiac disease.

+ Respiratory inhibition has been reported with electrical stimulation of the temporal regions.

o Pupillary symptoms - Miosis, mydriasis, hippus, and unilateral pupillary dilatation

o Urogenital symptoms

+ Seizures from the superior portion of the posterior central gyrus can result in genital sensations, while sexual auras arise more from the limbic or temporal regions.

+ Ictal orgasms have been reported, although rarely, in association with seizures arising from various cerebral locations.

o Other autonomic symptoms - Rarely perspiration, lacrimation, ictal enuresis, or flushing

* Postictal neurological deficits can occur after an SPS as a negative manifestation of the function affected by the seizure (eg, Todd paralysis).

o Psychic SPS arise predominantly from the temporal and limbic region, including the amygdala, hippocampus, and parahippocampal gyrus. Perceptual hallucinations or illusions are usually complex, visual or auditory, and are rarely bimodal.

+ Includes the déjà vu and jamais vu phenomena

+ Emotional: Fear is usual, but SPS can elicit happiness, sexual arousal, anger, and similar responses.

+ Cognitive: These responses include feelings of depersonalization, unreality, forced thinking, or feelings that may defy description.

If there is such a thing as a genuine precognitive or similar experience, then it might also be mistaken for what you describe as deja vu.

I was struck recently by a story from a woman who, due to what was described as precognition, insisted that her husband not take one of the doomed AA flights on 911. It saved his life.

The question is not whether clinical observations and explanations for deja vu are correct. The question is whether or not there could be more to the story.