Comparative experimental animal studies of the effects of various nuclear pharmaceuticals on the EEG

Some of the radiopharmaceuticals presently recommended for cisternoscintigraphy were compared, in experiments on animals, for their effects upon bioelectric activity. On relaxed cats, electroencephalography did not show any effects upon bioelectric activity for 198 Au and 169 Yb Ca DTPA. One test animal each of seven and six cats examined using 169 Yb DTPA and 131 J HSA showed changes in the electroencephalogram subsequent to suboccipital application.     

Gene x environment interaction and cognitive performance: animal studies on the role of corticosterone

A fundamental question in the neurobiology of cognition is how stress and glucocorticoids modify learning and memory processes. Why some individuals develop cognitive deficits after stress, while other individuals improve in cognitive performance under similar adverse conditions is still unresolved. To address these questions we focus on those issues. First, corticosterone, which appears to be the preferred glucocorticoid for the rodent and human brain, acts via brain mineralocorticoid (MR) and glucocorticoid receptors (GR) on the expression of networks of corticosteroid-responsive genes. Different effects are achieved by MR and GR activation. Second, the experimental context that determines the timing and the consequences of corticosterone action during the various stages of information processing is reviewed. Third, the genetic context and the environmental context are investigated. Using apolipoprotein E knockout (apoE0/0) mice we show that apoE (apoE4 is a genetic risk factor for Alzheimer's disease) is a candidate gene with an important function in shaping the cognitive outcome (genotype x environment interaction).     

Relevance of non-human animal studies to the understanding of human sexuality

There are several reasons for studying sexual behavior in animals other than the human. Prominent among these is probably the use of sexual behavior as a model system for analyzing hormone actions on the brain. In this kind of study, lordosis behavior in the female rat has frequently been used as the behavioral end-point. Recently, the mouse has become a popular subject because of the availability of strains lacking estrogen or progesterone receptors. Animal sexual behavior is also studied for its own sake by biologists, by agricultural scientists and by those interested in the management of wildlife resources. Finally, there are some researchers interested in human sexual behavior who prefer to approach their problems through studies in non-human subjects, as they thereby gain access to techniques of experimentation impossible in human subjects. This is particularly important when the neurobiological basis of sexual behavior is the subject of study. Two striking similarities between humans and other mammals are the hormone dependency of sexual motivation and the fundamentally bisexual organization of the nervous system. In addition, animal studies have revealed how learning with sexual reinforcement can be an important determinant of sexual behavior. The role of learning has been largely ignored in human studies, and this has led to many misconceptions. Paramount among these is the idea that sexual behavior is associated with reproduction.     

Developmental dyslexia and animal studies: at the interface between cognition and neurology

Recent findings in autopsy studies, neuroimaging, and neurophysiology indicate that dyslexia is accompanied by fundamental changes in brain anatomy and physiology, involving several anatomical and physiological stages in the processing stream, which can be attributed to anomalous prenatal and immediately postnatal brain development. Epidemiological evidence in dyslexic families led to the discovery of animal models with immune disease, comparable anatomical changes and learning disorders, which have added needed detail about mechanisms of injury and plasticity to indicate that substantial changes in neural networks concerned with perception and cognition are present. It is suggested that the disorder of language, which is the cardinal finding in dyslexic subjects, results from early perceptual anomalies that interfere with the establishment of normal cognitive-linguistic structures, coupled with primarily disordered cognitive processing associated with developmental anomalies of cortical structure and brain asymmetry. This notion is supported by electrophysiological data and by findings of anatomical involvement in subcortical structures close to the input as well as cortical structures involved in language and other cognitive functions. It is not possible at present to determine where the initial insult lies, whether near the input or in high-order cortex, or at both sites simultaneously.     

Body tilt effect on the reproduction of orientations: studies on the visual oblique effect and subjective orientations

Body tilt effects on the visual reproduction of orientations and the Class 2 oblique effect (E. A. Essock, 1980) were examined. Body tilts indicate whether the oblique effect (i.e., lower performance in oblique orientations than in vertical-horizontal orientations) is defined in an egocentric or a gravitational reference frame. Results showed that the oblique effect observed in upright posture disappeared in tilted conditions, mainly due to a decrease in the precision of the vertical and horizontal settings. In tilted conditions, the subjective visual vertical proved to be the orientation reproduced the most precisely. Thus, the oblique effect seemed to be not purely gravitationally or egocentrically defined but, rather, to depend on a subjective gravitational reference frame tilted in the same direction as body tilts.     

Further studies of the McCollough effect

Following prolonged viewing of black and white striped pattems in colored light, red and green aftereffects that lasted as long as 3 days were seen on the patterns, illuminated with white light. Altemate exposures of a vertical pattern of stripes in green light and a horizontal in white light (or a vertical in white light and a horizontal in red light) produced a red aftereffect on the vertical pattern and a green on the horizontal. The red and green aftereffects were also produced with a single vertical pattern. Adaptation colors that were at all greenish produced a red aftereffect on a vertical pattern and a green on a horizontal, whereas colors that were at all reddish produced a green aftereffect on a vertical pattern and a red on a horizontal. Colors near pure blue and pure yellow, which had little red or green content, produced weak aftereffects. The saturation of the aftereffects on the vertical grating varied in proportion to the red or green content of the adaptation color. Vivid red and green aftereffects were frequently obtained with the vertical and horizontal adaptation patterns paired with colors that closely bracketed pure yellow or pure blue. In all cases, the aftereffects gradually desaturated as the head was gradually tilted down to the side; the colors on each test pattern, vertical and horizontal, vanished at 45-deghead tilt and reversed beyond 45 deg.     

Developmental effects of acute, chronic, and withdrawal from chronic nicotine on fear conditioning

Pre-adolescence and adolescence are developmental periods associated with increased vulnerability for tobacco addiction, and exposure to tobacco during these periods may lead to long-lasting changes in behavioral and neuronal plasticity. The present study examined the short- and long-term effects of nicotine and nicotine withdrawal on fear conditioning in pre-adolescent, adolescent, and adult mice, and potential underlying substrates that may mediate the developmental effects of nicotine, such as changes in nicotinic acetylcholine receptor (nAChR) binding, CREB expression, and nicotine metabolism. Age-related differences existed in sensitivity to the effects of acute nicotine, chronic nicotine and nicotine withdrawal on contextual fear conditioning (no changes in cued fear conditioning were seen); younger mice were more sensitive to the acute effects and less sensitive to the effects of nicotine withdrawal 24 h post treatment cessation. Developmental differences in nAChR binding were associated with the effects of nicotine withdrawal on contextual learning. Developmental differences in nicotine metabolism and CREB expression were also observed, but were not related to the effects of nicotine withdrawal on contextual learning 24 h post treatment. Chronic nicotine exposure during pre-adolescence or adolescence, however, produced long-lasting impairments in contextual learning that were observed during adulthood, whereas adult chronic nicotine exposure did not. These developmental effects could be related to changes in CREB. Overall, there is a developmental shift in the effects of nicotine on hippocampus-dependent learning and developmental exposure to nicotine results in adult cognitive deficits; these changes in cognition may play an important role in the development and maintenance of nicotine addiction.