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Biomedical subjects

H Davis

Publications and source records attributed to H Davis.

At least 217 records · Page 12Linked to original sources
PubMed1974

The measurement of response force during a lever-press shock-escape procedure in rats.

Three albino rats were given extensive exposure to an escape procedure in which shocks were scheduled to occur 30 sec apart. The amount of downward force exerted on the lever was continuously recorded and compared with traditional discrete measurement in which only responses above an arbitrary force threshold were recorded. Subjects typically remained in contact with the lever throughout the shock-free intertrial interval. Shock onset reliably occasioned a brief lurch from and return to the lever, which resulted in a lever-press escape response being recorded. Lever contact, which occupied an average of 90% of session time, showed great stability in force after a brief (e.g., 5-sec) period of instability after each shock terminated. In general, continuous measurement revealed considerably different results than discrete measurements of on-lever behavior. For example, continuous lever contact fluctuating near response threshold was often recorded as discrete responding, and sustained lever contact occurring below response threshold was omitted from discrete measurement.

Animals↗
PubMed1973

Assessment of vaccination coverage, vaccination scar rates, and smallpox scarring in five areas of West Africa.

In 1966, nineteen countries of West and Central Africa began a regional smallpox eradication and measles control programme in cooperation with the World Health Organization. This paper summarizes sample survey data collected to assess the results of the programme in Northern Nigeria (Sokoto and Katsina Provinces), Western Nigeria, Niger, Dahomey, and Togo. These data indicate that the programme, which used mass vaccination campaigns based on a collecting-point strategy, was generally successful in reaching a high proportion of the population. Analysis of vaccination coverage and vaccination scar rates by age underlined the importance to the programme of newborn children who accumulate rapidly following the mass campaign. Of all persons without vaccination scars at the time of the surveys, 34.4% were under 5 years of age; in the absence of a maintenance programme, this figure would rise to 40% after 1 year.

Adolescent↗
PubMed1972

Conditioned suppression of an avoidance response by a stimulus paired with food.

Three food-deprived Long-Evans rats were exposed to a non-discriminated shock avoidance procedure. Superimposed upon this operant avoidance baseline were periodic presentations of a conditioned stimulus that was paired with food, the unconditioned stimulus. These pairings resulted in increases in the rate of shock over that recorded when the conditioned stimulus was not present. A traditional suppression ratio failed to reveal any differential effect of the conditioned stimulus on the overall rate of avoidance responding, although all subjects showed a consistent pattern of pausing and postshock response bursts during presentations of the conditioned stimulus. When food was withheld during a final extinction phase, the conditioned stimulus ceased to occasion increases in shock rates and disruptive postshock response bursts were eliminated. An analysis of conditioned suppression procedures is proposed that stresses not only operant-Pavlovian or appetitive-aversive incompatibility, but also the manner in which the baseline schedule of reinforcement affects operant behavior changes that are elicited by the superimposed Pavlovian procedure.

Animals↗