What was going on when I was born?

A DIAGNOSTIC and resource center for Alzheimer's disease opened at Rutgers Medical School here last week, the first step in a statewide effort to coordinate and improve services for about 200,000 New Jerseyans who suffer from the fatal, degenerative brain disorder. Officials of the new state-sponsored facility say that it will offer specialized medical and social services for Alzheimer's patients and their families, as well as educational and research opportunities for doctors and other health professionals. ''There is no cure for Alzheimer's, but manifestations of the disease can be much better managed than they usually are,'' said Lee Joslin, director of the center, the Institute for Alzheimer's Disease and Related Disorders. ''Our intention is to help professionals learn to treat the symptoms in order to reduce the stress on Alzheimer's patients and their families.''

A 54-acre forested area less than four miles from downtown White Plains is the site for a $40 million residential community that will have 97 attached and free-standing homes. To be known as Wrenwillow, the development, situated between Rosedale Avenue and the Hutchinson River Parkway, will be a homeowners' association, which, unlike a condominium community, allows buyers to take title to the property under and immediately surrounding their homes.

The Metropolitan Museum never hesitates to think big, as we all know. Thinking big is not always such a great idea, but there are times when thinking big, thinking straight, and thinking brave are one and the same thing, and one of them will come about on Saturday, Oct. 26, when the very large loan exhibition called ''Liechtenstein: The Princely Collections'' opens to the general public after several weeks of members' previews. ''Thinking big'' can sometimes be taken literally, in this context. The great late Rubens altarpiece, ''The Assumption of the Virgin'' may well be the largest Old Master painting ever to be brought into the Met. (Before it could be got safely inside, it had to be uncrated in the street. Door frames had then to be removed, and walls to be taken down.) But in the end it is not, of course, the dimensions of the ''Assumption'' that count. (To be precise, they are 198 1/2 inches by 138 5/8 inches). It is the fact that this is Rubens's last and largest account of a subject to which he had returned again and again. It is also relevant that no comparable Rubens has ever been seen, or can be seen today, in this country, and that the ''Assumption,'' though shown briefly in Lucerne, Switzerland, in 1948, has not been seen in public since, and has recently been cleaned for the present exhibition with entirely happy results.

Deeply in debt and with less than $1,000 in its bank accounts, this steel city laid off its entire 14-member police force and 10-member fire department in early September. ''We've cut the fat to the bone and now we have to cut essential services,'' Mayor Daniel Pastore said. ''We're broke. But what's the point in filing for bankruptcy? You've got to pay your bills anyway. We've got to show the banks we're doing something and then they'll talk.''

Housing Finally Starts Housing starts have been a disappointment this year. With mortgage interest rates down, housing activity should be up. Instead, housing starts soared to an encouraging 1.9 million unit annual rate in April and never hit that level again. But Rosanne Cahn, of Goldman Sachs Economics, says that housing may still wind up the year on the strong side of the ledger. She expects starts of single and multifamily housing units to total 1.85 million for 1985, solidly ahead of last year's 1.75 million units. The September number, due out next week, will show the housing sector's growing strength, said Mrs. Cahn. She expects a 6 percent jump in starts over the August level, the second strong monthly rise in a row. Michael Carey, of Citicorp Investment Bank, is also optimistic about this key sector. ''We expect housing starts to continue to rise through the fourth quarter,'' he said, as lower mortgage rates and gains in real personal income encourage home building and buying.

WITH a blitz of diplomacy last week, Mikhail S. Gorbachev attempted to set the agenda for an arms control dialogue with the United States and its NATO allies. The Soviet leader met a response that was wary but intrigued, as Americans and Western Europeans sifted between the imposing Gorbachev style - risk-taking, energetic, even flamboyant - and the rather familiar content of his offer. At the Geneva arms talks, Mr. Gorbachev's negotiators formally submitted a proposal that would ostensibly cut the two superpowers' strategic nuclear armories in half. As a condition for an accord, the Reagan Administration would have to halt research into a space-based shield against ballistic missiles. Stopping ''Star Wars'' has evidently become the overriding priority of Mr. Gorbachev's foreign policy.

IT is midday at the Forgotten Woman shop on New York's Upper East Side. Large shoppers whirled around Nancy Radmin, its owner, who is large herself. There wasn't anyone close to a petite in sight. ''Here's how it all happened,'' Mrs. Radmin said. ''Eight years ago, I was a size 6 and I had a son and I gained 80 pounds. I went out looking for clothes in size 16 to 18. There was nothing. There were no gabardine wool pants. No cashmere sweaters. I got so mad.''

HOUSE By Tracy Kidder. Illustrated. 341 pp. Boston: Houghton Mifflin Company. $17.95. THIS book is the story of the building of a house, and it is told with such clarity, intelligence and grace it makes you wonder why no one has written a book like it before. In the way that a well-told story of a marriage, or of a love affair or of a child's coming of age fills you with a sense that you are reading about a fundamental human experience for the first time, so it is with ''House.'' Tracy Kidder makes us feel with a splendid intensity the complex web of relationships and emotions that inevitably comes into play in the act of bringing a work of architecture to fruition.

There are those who understand the New York City Police Department to be a crime-fighting organization, but people in the entertainment industry know better. In truth, the department is an idea factory. Sure it cracks cases, but more important is what lurks inside the cases: concepts, such as the one personified by the bald, lollipop-sucking detective who served as the model for ''Kojak.'' The department has traditionally been an inspiration for popular culture. But in the past 15 years its mystique has grown enough to generate a spinoff industry. On most days, a television viewer can follow the Celluloid Finest in such shows as ''Ryan's Hope,'' ''Cagney & Lacey,'' ''Our Family Honor,'' ''Night Heat'' and repeats of such long-running hits as ''Kojak'' and ''Barney Miller.'' To help fill the need for extras in these efforts and in a few score films, including the current ''Year of the Dragon,'' more than 300 past and present officers have become card-carrying members of the Screen Actors Guild. According to SAG officials, a main reason for this is that producers save wardrobe costs by having real officers show up in their uniforms.

TERMING homelessness in Westchester ''a disaster,'' the Homeless Crisis Action Group, a blue-ribbon panel named last April by County Executive Andrew P. O'Rourke, issued a report last week, criticizing the municipalities for failing to address the issue and stressing the need for them to assume more responsibility if solutions are to be found. It says that, ''The county has a right to expect each unit of government in Westchester, in concert with not-for-profit organizations, to develop options that provide housing for families and individuals in various homeless situations.'' Specifically, it outlined steps it said local communities should immediately take, including the development by early next year of emergency housing for 15 to 18 families each in the eight different areas served by the county's Social Service Department's district offices. While the report acknowledges that the county will ''by necessity, have a stimulating and catalytic role in the development and implementation of solutions,'' it said that the County Executive ''must be able to call on municipal leaders to take measures as well.'' It warned that ''if they will not act, the legislative backing to advise solutions without local collaoration will have to be found.''

ECONOMISTS and Congressmen are still guessing about the impact President Reagan's tax-reform proposals would have on the market for condominiums and cooperatives, but the complex measure has already clouded the marketplace. Sales and development slowed in many parts of the country while lenders, developers and buyers calculated their investment risks. The proposals, in effect, worsened an already poor national sales picture for condominiums. Sales were strong in only a few metropolitan areas, like Boston and New York. Real-estate professionals are taking the likelihood of some tax reform - if not the President's exact plan - very seriously. ''Nobody here in Washington believes it will pass as proposed, but nobody knows what will pass,'' said C. James Dowden, executive vice president of the Community Associations Institute, a trade group for developers and managers of condominiums and cooperatives.

Once regarded as an unproductive wasteland, New Jersey's 32-square-mile Meadowlands district across the Hudson River from Manhattan in recent years has attracted more than $1 billion worth of industrial, commercial and residential development. In Secaucus, most of the projects so far have gone up north of Route 3.