For the most part, this series grows largely out of my personal experience and  observations.  For a recent, expert medical compilation, you might want to read the Mayo Clinic Guide to Alzheimer's Disease: The Essential Resource for Treatment, Coping and Caregiving.  That said…
    My first experience with mental senility, aka senile dementia, was with my mom.  I learned a lot from her experience.  But before I describe her dementia, I need to sketch  her as she was before.
    Mama was an avid, though not a particularly focused, learner.  She learned English in 1st grade (apparently kindergartens hadn't spread to the Duluth public school system at the beginning of the 1900s).  But she'd already read the entire New Testament aloud to her parents in Swedish.  As she laughingly described the experience: "I didn't know what all the words meant, but I could read them." 
    Many of her classmates also learned English in 1st grade.  Most spoke Swedish, Finnish or Norwegian at home, and many had learned to read from the prayer book and "Luthers Lilla Katekis."  She explained that because those languages were mostly spelled phonetically, learning to read was easy.  And having absorbed the principles — learned what reading was about — learning to read English was easy for them, too.  She insisted that the kids whose home language was other than English, learned to read English more quickly than kids who spoke English at home.
    Of course, this reflected cultures that greatly valued reading.
    At school she graduated from 8th grade, not bad in 1908, and went no further.  But because her parents got mad at the preacher in their neighborhood Swedish church, she'd been going to a Norwegian church since age seven, and could speak, read and sing Norwegian, too.  No great stretch, especially for a child; the languages are a lot alike.  Also she had lessons in voice, piano, and pipe organ, went to nursing school, and as a young widow, aced a night school course in hotel management. 
    In her late fifties she went to work in the Michigan State University library, and after only four years was promoted to supervisor of technical processing.  
Not bad for a gray-haired eighth-grade graduate.  Her boss had recommended her.  The library board asked where she'd gotten her master's degree, an informal prerequisite for the job.  He said she didn't have one.  He didn't tell them she didn't have a bachelor's degree, either, let alone a high school diploma; he just let them assume she did.  They gave her a provisional appointment, and a few months later it was made permanent.
    It didn't hurt, of course, that she was alert, effervescent, confident, and very responsible.  
    That was then.  She retired in 1961, at age 66, and moved from Michigan to Fort Collins, Colorado, where I lived.  I knew at once something was different about her, and had a notion what it was: she was in an early stage of senile dementia.  (Alzheimer's was a term not much used then).  On the basis of her resume and recommendations, she got a job at the Colorado State University (CSU) library— and quickly lost it; she couldn't learn a new system, nor adjust well to her new challenges  
    So we moved her in with us.  Soon she couldn't distinguish things she dreamed from things in the real world.  She'd tell us what seemed clearly to be dreams, but tell them as if they were reminiscences — for example, of watching Hitler speak on television while she was deep underwater in a German submarine...in World War One!  Our kids were big-eyed.   And the stories she told of my early childhood were stories I'd heard years before, of her little cousin Dewey, whom as a young girl she used to sit: Dewey and the streetcar, Dewey and the "fiskegubbe," Dewey and Jesus, Dewey's intimate mixing of Swedish and English… (Dewey died in a diptheria outbreak, probably around 1905-1910.  Diptheria killed lots of children, back in "the good old days.")
    Finally she insisted on an apartment of her own — and on choosing it herself.  She picked the first one she looked at, upstairs over a jewelry store.  It was within easy walking distance of my office, so I dropped in frequently, usually on my lunch hour. 
    One day she wasn't home.  The next day I got a phone call, from a man, a good Samaritan, who seemed upset.  Mama was at a bus station, and had asked him to dial me.  She'd shown him an index card I'd given her with my home and work numbers.  Having established my identity, he put mama on.  She sounded panicky.  She was lost, she said, in New York City!  She'd decided to go to Red Wing, Minnesota, to (visit? live with?) her cousin Violet, and gotten lost.  (Violet and Frank could chat in Swedish with her.)  I got the caller back on the line, and he got the agent in charge of the station.  The agent looked at her ticket — it was for Red Wing, but she hadn't transferred when she should have.  He assured me he'd give her a ticket for Fort Collins, and make sure the driver was aware of her problem.  
    She arrived back in Fort Collins late the next day.  (I'd accepted her report that she was in New York City, but her arrival time in Spokane suggests Madison, Wisconsin.  When I picked her up, she told me happily what a good time she'd had with Violet.  I did not correct her. 
    She didn't even seem terribly tired.   
    Not long afterward she asked me to eat lunch with her.  We had chicken.  A day or two later I was there, and something didn't smell right.  It was spoiled, left-over chicken, which she'd heated and put on the table.  I put the chicken in the garbage, which she cheerfully allowed, and we ate something else.  I asked if she'd like to live with us again.  She wasn't interested.     Meanwhile there was no longer any "normal" communication — any development of whatever subject was addressed.  It's hard to describe.  One of us would say something, the other would respond, but it never went anywhere.
    Within a year or so she was unhappy with her jeweler landlord, so she found another apartment, probably with the help of the jeweler or his wife.  At any rate I helped her move, and she was happy with the change.  
    In the months to come, I was twice called to different addresses.  She'd gone to the market a block and a half from her place, and coming out, had turned in the wrong direction.  She was immediately lost, walked onto someone's porch, and asked for help.  Then she seemed to get a handle on it.  
    After a bit she developed a rash on her hands and feet, and Dr. Hilliard told her, and us, she should keep her hands and feet dry until the ointment he prescribed suppressed the rash.  So Gail and I started taking turns going to her place after supper and washing dishes.  That was after we realized she was using them unwashed.  
    A few days later I arrived to find her sitting with her feet in a pan of hot water, well salted probably, to sooth the itching.  "Mama," I said, "you're supposed to keep your feet dry."
    "Oh, I do!" she assured me, with her feet in the water.
    A few days later I left on a work trip to Alpine, Arizona (from late May to late October I was gone a lot), and a few evenings later phoned Gail from there.  Mama, Gail reported, was in the hospital.  She'd painted her itchy feet with iodine, and her shrieks had drawn her landlady, who'd called Dr. Hilliard, who'd sent an ambulance. 
    Dr. Hilliard assured Gail that mama would be okay, and he had a strategy to get her into a nursing home.  It worked.  He told her it would be for 2 or 3 weeks.  But this was a home for people who were able to socialize, and mama loved it!  Always social, she quickly had a circle of friends, some of whom would ask her to play old favorites on the piano (an actual baby grand!) in the social  room.  She never, so far as I know, asked to leave. 
    She was happier than I'd seen her for years, and her condition actually seemed to improve.  Some of those new friends, folks not conspicuously demented, became quite fond of mama.  One was a World War II paratrooper institutionalized with muscular dystrophy.  A cheerful Irish-American a year or two older than I was, he was confined to wheelchair and bed, but mama would stroll in and chat with him.  
    She did best in the morning.  Once we went to an Italian place for supper.  Gail was driving, and mama and I were sitting in back with one of the kids.  On the way, mama piped out: "Who is that nice young man driving?   
    Occasionally she reported having guests from outside the home.  She sometimes seemed consciously aware of her mental decline(!), and on one occasion told me that old friends had dropped in from East Lansing, Michigan.  "Who were they?" I asked.  "I don't know.  I didn't remember ever seeing them before," she confided, "but I pretended to, and they never suspected."

    At the home, the dining room tables were round, with five in-house diners assigned.  And with one extra chair for a guest.  Each assigned diner could have a lunch guest once a week.  My day was Thursday.   The group conversations were pleasant but tended to be somewhat random. 
    In 1968, my research project was transferred to Flagstaff, Aizona.  I knew about it several months in advance, but hadn't said anything to Mama.  I did the arithmetic, and soon realized we couldn't afford to take her with us.  Colorado provided major support to families with a member in a care faciility.  Arizona provided none.  And it seemed to me that to move her in with us would result in more problems than when she'd lived with us 6 years earlier.  Both kids were in school by then, and we'd be living out of town at an experimental forest,
    On the Thursday before Departure Day, I had my weekly lunch with mama, and after dessert broke the news to her.  It ran off her as if I'd told her I needed to buy new socks.  "Would you like me to play for you?" she asked.
    "Yes I would."
    So she led me into the social room, sat down at the piano, and asked "what would you like me to play?"
I suggested an old favorite of hers.  "Sæterjentens Søndag," I said.  
    "Oh," she said, looking up at  me, "I don't know that one.  Can you hum it for me?"  (Think about it.  That reply called for off-the-cuff reasoning.)
    I began to whistle, and she began to play.  Flawlessly. "Can you sing it?" she asked.
    "Not in that key."
    Instantly she changed keys, transposing into a key—in fact the only key—I could sing it in, and I did.  That in an era when Fort Collins provided just three TV channels from Denver and one from Cheyenne, switched by a simple knob — and mama couldn't change channels!  
    Two days later, Gail and the kids and I left Fort Collins for Flagstaff, Arizona, a 782-mile drive.  In the next couple of years I got back to Fort Collins perhaps twice a year, for a project leaders conference and other, occasional meetings.  I'd go to the home after supper and spend an hour or so with mama.  With visits set apart by such long absences, her slippage was more conspicuous, but still she knew me, and responded easily.  But while we chatted, there was nothing you could call a real conversation. 
    Then came a phone call from Dr. Hilliard: mama was being transferred to the "intermediate home" in the chain, for persons deemed too far gone for the morale of the others.  Specifically, she'd shoved a wobbly old man, knocking him down.
    In 1972, son Jack and I drove to Fort Collins specifically to see mama.  We took her out to a nice restaurant for supper, and when the hostess came to seat us, mama told her brightly, "I'd like you to meet my brother Albert."  (Indicating me.)  And the hostess, God love her, said she was pleased to meet me.
    When the waiter came to take our orders, she trumped that first introduction.  Gesturing to me, she said, "I'd like you to meet my husband Jack."  Dad had died in 1933, but she still remembered his name.  While her  dearly loved grandson Jack, standing there with us, seemed to have disappeared from her plaque-riddled brain.  
    At this home, there was no social room, but in a corridor there was a piano, a garden variety upright, and after our "evening on the town," she asked if there was something I'd like her to play.  Remembering that day four years earlier, I  said "Sæterjentens Søndag."
    Smiling she played "Rocked in the Cradle of the Deep."  With many clinkers.  Briefly.  Then asked if I had another.  "Elegie," I answered, another favorite of hers.  Again she played "Rocked in the Cradle of the Deep."  For my next request I tried something very different.  "Rachmaninoff's Prelude in C Sharp Minor."  Same result.

    Not long  afterward, Dr. Hilliard phoned to say mama had had "another stroke" and was essentially a vegetable.  In the bottom rung home, for the folks who were far gone.  About then the experiment station RIFed some folks; combined and refocused some projects; and I was no longer a project leader.  Which meant I seldom flew to Fort Collins for meetings.  Instead I began busily tying up the work of 15 years of the Aspen and Mixed Conifers Project, and planning a new program.  Thus I did not see Mama till the last week in 1976.
    The lab had hired a free-lance editor to work over my manuscript for a book on quaking aspen, and I spent the week after Christmas in Fort Collins reviewing the task with her.  But the lunch hours, and an hour in the evening, I spent with mama.  
    The first visit shook me.  By then she had Parkinson's Syndrome, something I hadn’t known.  No more piano; instead a wheelchair, and tubes that disappeared into her bedclothes,  Her left hand had a major and constant tremor; her right hand was a tiny unmoving claw that lay neglected on her lap.  About every 20 seconds her head would rock back a little, and her eyes would roll back in her head.
    "She hasn't responded to anything for several months," the aide said, "but she might hear if you talk really loudly in her ear."
    So I did.  Nothing.  Then, on an impulse, I  lay two  of my fingers in the motionless hand and almost shouted: "Mamma, om Du förstår, så kan Du trycka på fingrarna."  Swedish, ragged but Swedish, meaning "Mama, if you understand, squeeze my fingers."
    And that seemingly useless hand squeezed;  somewhere inside, sentience remained.  
    I told the aide.  I don't know what she thought.  I told the shift nurse.  I don't know what she thought, either.  
    That was the big event of those several days.  Mostly I just sat with her, holding the hand that didn't tremble… On the final visit, it seemed as if I should try to break through again.  And again the aide was in the room.  "Mamma" — this time I spoke in  English — "I won't be back to see you tomorrow.  I have to go back to Arizona."
    She turned her head slightly!  And answered!  One word, shaky, broken in the middle, but distinct and easily heard.  "Al…ready?"  She'd known, seemingly the whole time, that I was there.  Brother, husband, son? — someone who cared — was there with her.
    Today I'd have wept; my eyes are spilling over as I write this.  But then I did not.  Instead I looked at the aide.  "Did you hear that?" I  asked.  She nodded.  She was staring.
    As I was leaving, I paused and told the shift nurse, adding that the aide had heard it.
    That was a Friday, New Years Eve, 1976.  More than 32 years ago.  

At the end of April, 1979, unemployed, and driving from Florida to L.A., I routed myself by way of Fort Collins.  I'd had an idea: music for mama.  So I bought a tape player and several tapes of music I knew she loved.  Had loved.  "Swan  Lake," "The Fire Bird," probably "Rachmaninoff's 2nd Piano Concerto"....
    She didn't seem much changed, except that something had stilled the tremor, her eyes didn't roll back, and they told me she had diabetes.  When I talked to her, she showed no sign she knew anyone was there.  After a little I put the headset on my own head, and clicked on "Swan Lake."  So far, so good.  Now, how much amplification?  As deaf as she'd seemed earlier, I'd give it as much as I could take without pain, then rewind it so she'd hear it from the start.  When I put the headset on her, she showed the first awareness that anyone was there.  
    I turned on the music…and she began to shake!  Alarmingly, almost violently.  Quickly I took the headset off her, thinking it was too loud, and put it on my own head.  Not too loud for me.  Still — I turned it down a smidge, then put it back on her.  Again the extreme shaking; again I took it off — and looked at her, face to face.  She really knew, then, that someone was there.  "Mama," I said loudly, "do you want the music?"
    I asked the question automatically, without thought.  I had no reason to expect an answer.  But once more she spoke: "Uh huh!  Uh huh!"  Almost desperately.  So there we were, she in her wheel chair, me standing beside her, while she listened to "Swan Lake."  I'd never realized, never wondered what it was like to be a prisoner in a gutted brain with no input of beauty — and no loving contact. 
    I still don't know, not really, but I'd confronted the  question.
    Before I left, I spoke to the administrator, asking if anyone there spoke Swedish; that I thought it might be good for mama if someone spoke Swedish to her.
    Now Fort Collins was not a town where you'd expect to find someone who speaks Swedish.  Volga Deutsch yes, lots of good Volga Deutsch — at least two churches of them — but not Swedish.  So when the administrator answered that she spoke Swedish, and she'd look in on mama now and  then,  It seemed to me we'd lucked out, mama and I.  Then I gave the administrator the tape player and tapes, and asked her if someone could play music for mama daily.  She said she'd arrange it.  Mama had become more than a name, more than a patient; she'd become a person to her.
    And as I left, it seemed to me that mama might not be as deaf as they'd thought — that in a world with no loving input, she might have become inattentive.  As for being a prisoner in a gutted brain — Shakespeare asked rhetorically: who knows "what dreams may come when we have shuffled off this mortal coil...?"  Shakespeare spoke, of course, of death, but the question may apply as well to consciousness within the mental walls of extreme senile dementia.  Did mama once more watch Hitler speak on television to submariners beneath the Atlantic?  Or Abraham Lincoln to astronauts in space? Wait again with little Dewey at a streetcar stop in Duluth?  Or chat again with Frank and Violet in Red Wing?  Does dreaming depend on the brain?  Or can dreams come even to the brain-dead, perhaps interacting with sleeping friends, or friends who have died?  
    Mama lingered until October 1984.  And she'd had the same doctor for 23 years, a caring man rich in empathy if not in time.  We were blessed in that, and I hadn't fully realized it.
    Meanwhile I'd learned a few things.