Here is a draft I wrote about flashbacks and PD
 
  1  L-Dopa Flashbacks in Parkinson Disease
 
  1.1     Introduction
 
  1.2     Flashbacks - Past Reality
 
  Flashbacks are a vivid reliving of real but historical
  events, for example Vietnam veterans and  combat.
  1.3     Emotional Reality
 
  The veteran knows he is no longer in Long Tan. He
  experiences the feelings. The quick reacting, emotional
  "Right Brain" is still expecting danger.  Part of him
  doesn't know the war is over. A car backfiring or a
  helicopter triggers the experience.
  1.4     Hallucinations - Distortion of Reality
 
  Hallucinations, like seeing an ocean liner cross the
  highway, are a distortion of reality
  1.5     Treatment
 
  Drug treatment is difficult, especially in Parkinson Disease
  where dopamine antagonists are contraindicated.
  Psychological treatment is based on reality. The experience
  is real, but it is a past reality. Guided visualisation is
  one way of helping the  "subconscious" to come home from the
  war.
  1.6     Method
 
   This report is based on support group  workshops  and
  discussion with Parkinsonians.
  1.7     Report of Cases
 
  The cases are the stories of people with PD, from their
  perspective. Each case is chosen to illustrate a point, and
  is based on a real experience.
  1.8     Anthropology
 
  The perspective is somewhat anthropological, as the author
  has PD.
  1.9     Cases
 
  1.9.1   I Had to Take Hold of Myself
 
  Vignette
  A gentle person, she saw people standing around the foot of
  her bed, talking. They wore suits. She recognised them as
  people from her past. She "had to take hold of herself"  to
  distinguish present from past reality. She only took two
  Carbidopa/L-Dopa  100mg/25mg per day. Her flashbacks
  corresponded to the estimated  peak L-Dopa brain levels. She
  was advised to try slow release C/L to minimise peaking.
  1.9.2   This case illustrates
 
  1.9.2.1 Vivid memories
 
  Her memories were not merely history book narratives.
  Sights, sounds, tastes, smells and emotions accompany
  flashbacks. The person is in danger of becoming a
  participant in a vitual reality
  1.9.2.2 Real memories
 
  The men were real. Her experience superficially resembles an
  hallucination.
  1.9.2.3 Reality maintained
 
  She was able to keep in touch with reality, to look at the
  past and the present and to know the difference, somewhat
  like knowing the difference between live tv and videotape.
  This is called reality testing, and we do it all the time.
  1.9.2.4 Peak dose effects.
 
  A constant level of drug enables the brain to adjust. Levels
  that rise and fall rapidly cause symptoms because the brain
  cannot adjust quickly. This is why short acting
  benzodiazepines such as halcion can cause strange effects.
  1.9.3   Happy Memories
 
  1.9.4   Vignette
 
  The past for this 70 year old was full of real but happy
  memories. There were no terrors because his parents had been
  loving and wise. His memories of life on the farm were many
  and varied. Strong men making haystacks, gardens full of
  mulberries, plums, grapes, and figs. Women who made jam,
  washed in coppers and fed shearers and harvest workers.
  Great gentle horses pulling ploughs that turned the sod in
  one long never ending strip. People who treated him with
  warmth and compassion, who celebrated death even as they
  grieved for those who died.
  Happy Memories had a normal subconscious, which is a place
  of happiness. Visiting the normal subconscious is like
  visiting a happy, playful child who lives with nurturing
  people in a tropical rainforest, full of amazing and
  wonderful sights and sounds
 
  1.9.5   This case illustrates
 
  1.9.5.1 Vivid memories
 
  These memories are the first and most permanent, and persist
  when Alzheimer's disease plays havoc with later memory.
  1.9.5.2 Happy memories
 
  People with happy memories can tolerate larger doses of L-
  Dopa. Loss of contact with reality is still possible.
  1.9.5.3 Happy normal subconscious
 
  Freud's view of the subconscious as the place where
  repressed feelings exist is simplistic in the extreme. Freud
  described only the pathology of the subconscious, a process
  like mistaking lung cancer for the normal lung. His view was
  further distorted because he took the adultist view that the
  people he saw were unreasonably angry with their parents,
  when in fact the parents had been violent towards the
  children. The normal subconscious is happy, but not to be
  confused with idealised memories. The normal subconscious
  has resolved panful events such as the death of a loved one,
  whereas idealised memories indicate amnesia for painful
  events.
  1.9.6   Four Leafed Clover
 
  1.9.7   Vignette
 
  L-Dopa caused a return to the Ireland of his childhood, with
  bonnets, baby carriages, and violence, namely people hitting
  each other with pieces of wood. Everything looked large, the
  way it would to a child.
  1.9.8   This case illustrates
 
  1.9.8.1 Reality confirmed by content
 
  The period clothes, the view from a child's perspective, and
  the historical record of growing up in Ireland where violece
  was commonplace support the diagnosis of flashbacks.
  1.9.9   Kokoda Veteran
 
  1.9.10  Vignette
 
  Despite the reality of the present world, Kokoda was
  spending much of his time fighting the Japanese in New
  Guinea in World War Two. Suggestions made included stopping
  bromocryptine, using a D2 blocker, talkig reality therapy,
  and possibly treating the Post Traumatic Stress Syndrome.
 
  1.10    This case illustrates
 
  1.10.1  Post Traumatic Stress
 
  Children exposed to stress while their personality is
  forming develope Post Traumatic Stress Syndrome. Because
  their personalities are still forming, they can also
  develope problems like multiple personality disorder.
  Kokoda has no such problems, but reliving war experience is
  torment enough.
  1.10.2  Failure to distinguish past from present
 
  Reality therapy is talking about and showing and touching
  real things, be they people, pets, cars, trees. The past
  reality is not denied, or treated with drugs, but calmly
  accepted for what it is - a painful, past reality. This is
  best done right at the time of stress. Prevention is better
  than cure.
  1.10.3  Reality confirmed by history
 
  External confirmation is helpful, but not always
  forthcoming, and not always sought after.
  1.10.4  Continued vigilance at subconscius level
 
  Kokoda still hits the ground when cars backfire. It is as
  though noone has told the subconscious person the war is
  over. Therapy is aimed at telling the symbolic 'Right brain'
  that the war is over.
 
  1.10.5  Lost Child
 
  1.10.6  Vignette
 
  This 50 year old professional found himself in a childhood
  where there was all kinds of violene - physical, verbal, and
  sexual. A terrifying, depressing, crazy reality of knives,
  fire torture, and rape. A reality previously experienced as
  nightmares, hidden by amnesia. Rather than give up
  treatment, he underwent counselling to try and live with the
  traumatic past and be able to move in the present.
  1.10.7  This case illustrates
 
  1.10.7.1     Anamnesia
 
  Sachs describes the breaking down of amnesia by L-Dopa, but
  no other references are known to me.
  1.10.7.2     Paucity of historical confirmation
 
  Very little external evidence existed to support the reality
  of these past experiences.
  1.10.7.3     Reality confirmed by content
 
  Some scenes were seen from a child's view, eg through the
  bars of a cot.
  1.10.7.4     Ease of confusion with schizophrenia
 
  It is easy to see that the absence of external evidence
  could lead to the view that Lost Child was out of touch with
  reality. A label of schizophrenia easily follows.
  1.10.7.5     Dilemma of dose
 
  The dose of L-dopa is hard to stabilise. Too much causes
  flashbacks, too little causes lethargy. There is a tightrope
  effect.
  1.10.7.6     Dilemma of Dopamine antagonists
 
  Possible selective L-Dopa antagonists such as clozapine may
  help suppress the psychiatric side effects. However, there
  is commonality amongst receptors. Giving dopamine blockers
  to PD sufferers goes against the grain, but there have been
  favorable reports. Bone marrow depression is said to be
  fatal one in 3,000 cases. There is a report of ondansetron
  being used in a letter to the BMJ.
 
  1.11    Discussion
 
  It is important to differentiate between schizophrenia and
  flashbacks, since the treatment may be very different.
 
     Lloyd Stewart