What was going on when I was born?

A group of present and former New York City investigators has charged that city officials consistently hindered their efforts to investigate large-sca le fraud in the city's f ood-stamp program. The group includes the former chief of the largest fraud-prevention unit in the Human Resources Administration. In interviews this week, the investigators - all of whom had extensive experience with Federal or city government before joining the Human Resources Administration - said they believed that city employees were involved in organized theft from the program. They said that whenever their investigations focused on organized criminal activity and city employees, they were told they were limited to investigating fraud by recipients. The investigators now say that instead of looking into the fraud, the city is persecuting them for having talked to reporters about their charges of obstruction.

Faced with stiffening resistance in Congress to further budget cuts, the Reagan Administration is planning immediate reductions on its own, averaging 12 percent in most areas outside the military, by seeking to have spending deferred. Edwin L. Dale Jr., the spokesman for the Office of Management and Budget, said today that the Administration would make the cuts itself by instituting administrative deferrals. However, such proposed reductions could be overturned by a majority vote of either the House of Representatives or the Senate.

The Nobel Prize for medicine was awarded yesterday to one scientist at the California Institue of Technology and two at Harvard University for research that has proved vital to understanding the organization of the brain. Dr. Roger W. Sperry, 68 years old, of Caltech, was honored for research demonstrating that the right and left hemispheres of the human brain had different, sometimes virtually independent functions. The total award came to about $18,000, and Dr. Sperry received half of this. The other half of the prize, officially called the Nobel Prize in Physiology or Medicine, went to Dr. David H. Hubel, 55, and Dr. Torsten N. Wiesel, 57, of Harvard for studies of the complex manner in which the brain processes visual information. 'I was Afraid of That!'

The Voyager 2 spacecraft discovered a cloud of electrified gases circling Saturn that is 300 times hotter than the Sun's outer regions and the hottest spot ever detected in the solar system, a team of space scientists reported yesterday. The discovery was not only surprising but also extraordinarily provocative because of the mystery it raises as to the origin of the cloud. It added yet another puzzle to the many that Saturn has posed to observers on Earth as the result of spacecraft exploration in recent years. Dr. S.@M. Krimigis of the Applied Physics Laboratory at Johns Hopkins University, who headed the research team, said in a telephone interview that there was no obvious explanation for the phenomenal temperatures. Another unusual solar event was reported yesterday by scientists at the Naval Research Laboratory in Washington, who found evidence in satellite data of a violent collision by a comet with the Sun two years ago. (Page 11.)

After 24 hours of clashes between policemen and Moslem fundamentalists, quiet returned today to this southern city. Policemen reinforced by soldiers brought in yesterday and today were hunting remaining snipers. According to officials, at least 20 people - 14 policemen and 6 Moslem fundamentalists - were killed in the fighting that began at dawn yesterday with an attack on security forces here. Some intermittent firing was reported this morning.

Prime Minister Menachem Begin of Israel met for 40 minutes today with Hosni Mubarak, the new Egyptian leader, and promised that the search for peace in the Middle East would go on. Mr. Begin was one of a host of world figures, including three former American Presidents, assembling here for the funeral tomorrow of President Anwar el-Sadat, who was assassinated three days ago. Shortly after arriving at Cairo Airport, Mr. Begin drove to the suburban home of Mr. Mubarak, who is virtually certain to be approved as Mr. Sadat's successor in a referendum Tuesday. When the two met, Mr. Begin hugged the 53-year-old Vice President and former air force commander and patted him on the back. He asked Mr. Mubarak about the assassination on Tuesday, and the Egyptian leader was heard to reply, ''It happened so suddenly. ...''

The Government's Producer Price Index for finished goods, an important indicator of inflationary trends, crept up by two-tenths of 1 percent in September, the smallest rise in more than three years. A report today by the Bureau of Labor Statistics said the September rise was moderated by price-cutting on the last of the 1981 cars and trucks and by lower prices for some foods. The report was a further sign that inflation has receded from double-digit rates and that food prices this year have risen less than expected. Nevertheless, the September figures were less favorable than they appeared at first glance.

The two farmers faced real dangers on opposite sides of the war that turned Rhodesia into Zimbabwe. Both have now had a piece of the first big postwar harvest, which has made this the only black-ruled country in Africa that has to worry about overproduction of food. Yet, although they are separated by only 25 miles and a range of hills, the two farmers - Nichodamas Manomano and Hermanus Conradie Jr. - exist in different worlds. One of these worlds knows bumper crops as a matter of course; the other still shares in the crisis of rural Africa, where population pressure and ruinous cultivation practices are part of a cycle that ends in malnutrition and the depletion of the soil itself. Although Zimbabwe may rank as black Africa's major example of a country with a food surplus, it is too soon to say that it has found a way to unlock the productive potential of Africa's farmers. Of the 76 million bushels of corn that will eventually find its way to market from Zimbabwe's farms this year, 67 million were grown by only 4,000 white commercial farmers.

Enrico Berlinguer, the head of Italy's Communist Party, left today for Cuba at the start of a 12-day tour of the Central American region.

China pressed its new campaign for reconciliation with Taiwan today by inviting the leaders of the island's Nationalist party to return to the mainland to visit their ancestral homes. (The invitation was rejected within hours in a statement by a Nationalist Government spokesman, who denounced the move as a ''big show'' and part of the Communist leadership's ''smiling offensive'' that the Nationalists had previously rebuffed.) The invitation was made by China's Communist Party Chairman, Hu Yaobang, at an afternoon ceremony commemorating the 70th anniversary of the 1911 revolution, which led to the creation of the first Chinese Republic under Dr. Sun Yat-sen. The event is also celebrated as a Nationalist holiday on Taiwan. It is being officially observed on the mainland for the first time in the 32 years since the Communists took power, becoming an extension of the Chinese Communist Party's own holiday on Oct. l.

The State Department accused the Soviet Union today of using forgery, ''disinformation'' and blackmail ''to discredit and weaken the United States and other nations.'' The accusation was contained in a four-page special report made public today. The department has printed 14,000 copies of the report for distribution in this country and abroad, apparently as part of a Reagan Administration campaign to publicize Soviet activity that is regarded as inimical to Western interests. In what was appeared to be the opening of this campaign last month, the Defense Department published a 99-page booklet to demonstrate the growth of Soviet military activity.

Prime Minister Indira Gandhi, whose Government has recognized the Vietnamese-backed regime in Cambodia, said here today that India would welcome any conference that would seek a resolution of the conflict there. The United Nations voted last month to recognize the Pol Pot forces as the legitimate Government of Cambodia, even though it has been accused of genocide.