Search PubMed⌕ Search

Biomedical subjects

F R Brush

Publications and source records attributed to F R Brush.

28 records · Page 2Linked to original sources
PubMed1979

Central mediation of hormonal influences on instrumental avoidance conditioning.

Two behaviorally active hormones of the pituitary-adrenal system are adrenocorticotropic hormones (ACTH) and corticosterone, and their behavioral effects are facilitation and inhibition of performance of previously learned avoidance responses, respectively. Their uptake, distribution and effects on central nervous system are reviewed. Hypothalamic neurotransmitter control of corticotropin releasing hormone (CRH) is described together with hypothalamic and extra-hypothalamic (hippocampal) regulation of pituitary-adrenal activity. Extra-hypothalamic mediation of the behavioral effects of ACTH is evaluated. Recent isotopic mappings of the efferents of the hippocampal formation have identified pathways from hippocampal subiculum to hypothalamus and posterior lateral and anterior thalamic nuclei. The evidence reviewed suggests a complex circuit involving hippocampal subiculum, thalamus and hypothalamus may be involved both in regulating pituitary-adrenal responses to stress and in mediating the effects of ACTH on avoidance behavior.

Adrenocorticotropic Hormone↗
PubMed1976

Does the rat with hereditary hypothalamic diabetes insipidus have impaired avoidance learning and/or performance?

Avoidance learning and extinction of rats with hereditary hypothalamic diabetes insipidus (Brattleboro strain) were studied in 2 experiments that differed only in shock intensity. In both experiments rats homozygous for diabetes insipidus were more deficient in both escape and avoidance responding than were their heterozygous or normal controls. Although the hterozygous animals showed improved escape performance at the higher shock intensity, their avoidance behavior was not improved. The superiority of normal and heterozygous animals in extinction performance, relative to the homozygous animals, was eliminated or reversed when the differences in terminal acquisition performance were taken into account by analyses of covariance. Deficiency of ADH, therefore, may not result in faster extinction of avoidance behavior.

Animals↗
PubMed1975

Positive and negative behavioral contrast in the rat.

Three groups of rats received either 8, 23, or 53 sessions of multiple variable-interval variable-interval baseline training before being shifted to a multiple extinction variable-interval schedule. The rate of responding during the unaltered component was higher for the groups shifted to multiple extinction variable-interval than for control groups remaining on multiple variable-interval variable-interval (positive contrast). Furthermore, when the multiple variable-interval variable-interval schedule was re-instated, stable negative contrast was found in the groups that had received 23 or 53 baseline sessions, but not for the group that had received only eight sessions. Positive and negative contrast were also demonstrated in the eight and 23-session groups when the multiple extinction variable-interval and multiple variable-interval variable-interval schedules were re-administered in further phases of the experiment. These results suggest that both positive and negative behavioral contrast can be obtained reliably in a species other than the pigeon.

Journal Article↗
PubMed1975

Rapid acquisition of discrete-trial lever-press avoidance: effects of signal-shock interval.

Acquisition of discrete-trial lever-press avoidance learning was studied in three experiments. Experiment I compared a new training procedure, which produces rates of lever-press avoidance learning comparable to those obtained in shuttle boxes, with a "conventional", less efficient training procedure. A factorial design was used to compare continuous versus intermittent shock and a long-variable versus a short-fixed signal-shock interval. Learning was best in the groups trained with the long and variable interval and poorest in those trained with the short and fixed interval. Type of shock had no effect. Experiment II separated the effects of duration from those of variability of the signal-shock interval. Fixed and variable intervals of 10 and 60 sec were tested and duration was the only significant factor. Experiment III addressed the effect of the differential opportunity to avoid provided by long signal-shock intervals by varying this interval from 10 to 60 sec in 10-sec steps. Only the 10-sec group showed slow acquisition relative to the others. Analysis of avoidance response latencies showed that the distributions for all groups were positively skewed and that skewness increased with increasing duration of the signal-shock interval. At intervals longer than 20 sec, the animals made progressively less use of their increased opportunity to respond. The data do not support the opportunity-to-respond interpretation of the effects of duration of signal-shock interval and suggest that some type of inhibitory process may block lever-press avoidance learning at intervals as short as 10 sec. The significance of these findings for species-specific defense reaction and preparedness theories was emphasized.

Journal Article↗
PubMedDate not supplied

Opposite effects of naltrexone on ETOH intake by Syracuse high and low avoidance rats.

Rats which were selectively bred for good (Syracuse High Avoidance: SHA) and poor (Syracuse Low Avoidance: SLA) shuttle-box avoidance learning were used to assess the effects of naltrexone on ethanol ingestion. Male rats from both strains were offered a free choice of water and ethanol (10%, v/v) for two 8-day periods between which was inserted a 4-day period of forced ethanol consumption. The net ethanol consumption and ethanol preference ratio were significantly greater in control SHA rats than in control SLA rats in the first choice period, but they did not differ in the forced and the second choice periods. Chronic naltrexone administration from an implanted 30-mg pellet showed bidirectional effects, i.e., suppression of ethanol consumption in SLA animals and enhancement in SHA rats.

Alcohol Drinking↗