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Biomedical subjects

R Granger

Publications and source records attributed to R Granger.

30 records · Page 2Linked to original sources
PubMed1991

Computation of frequency-to-spatial transform by olfactory bulb glomeruli.

A physiological simulation of 2.5% of the input and inhibitory neurons and 25% of the primary mitral/tufted cells in a single mammalian olfactory bulb glomerulus was constructed. This physiological simulation used the integrate-and-fire paradigm with realistic activation curves and synaptic delays. The dendritic integration incorporated non-linear interactive effects of individual cell excitatory and inhibitory post-synaptic potentials (PSPs) from both axodendritic and dendro-dendritic synaptic contacts. Refractory periods for granule-cell inhibition of mitral/tufted cell activity lead to relatively fixed-frequency rhythmic activity in the glomerulus, independent of the input frequency from the olfactory nerve. Though the frequency of mitral/tufted cell firing in bulb was approximately independent of input frequency, the number of cells active in the glomerulus was a roughly-linear function of input frequency to the glomerulus, indicating the mechanism's ability to function as a frequency-to-spatial encoder.

Animals↗
PubMed1991

Higher olfactory processes: perceptual learning and memory.

The past year has seen several important findings emerge from studies of higher olfactory processes. The identification of synaptic long-term potentiation in the olfactory cortex, induced via repetitive burst stimulation at the theta rhythm, and physiological activity patterns associated with learning, some of which mimic long-term potentiation induction patterns, have suggested relationships between rhythmic activity, behavioral learning and synaptic plasticity. In addition, the construction of computational models of the olfactory bulb and cortex have generated testable behavioral and physiological predictions which have been supported by experimental evidence.

Animals↗
PubMed1990

Simulation of paleocortex performs hierarchical clustering.

Simulations were performed of layers I and II of olfactory paleocortex, as connected to its primary input structure, olfactory bulb. Induction of synaptic long-term potentiation by means of repetitive sampling of inputs caused the simulation to organize encodings of learned cues into a hierarchical memory that uncovered statistical relationships in the cue environment, corresponding to the performance of hierarchical clustering by the biological network. Simplification led to characterization of those parts of the network responsible for the mechanism, resulting in a novel, efficient algorithm for hierarchical clustering. The hypothesis is put forward that these corticobulbar networks and circuitry of similar design in other brain regions contain computational elements sufficient to construct perceptual hierarchies for use in recognizing environmental cues.

Animals↗
PubMed1978

The Brighton resuscitation ambulances: review of 40 consecutive survivors of out-of-hospital cardiac arrest.

In three years 40 patients were resuscitated by ambulancemen after out-of-hospital cardiac arrest and survived to be discharged. Twenty-six of these had had circulatory arrest before an ambulance arrived and a further three had developed ventricular fibrillation before they were moved. Thirty-two patients were alive at the time of review six months to three and a half years later. Resuscitation by ambulancemen can be effective for patients with unheralded sudden cardiac arrest as well as for patients with recent myocardial infarction. Survivors of out-of-hospital ventricular fibrillation may have a favourable long-term prognosis.

Adult↗
PubMedDate not supplied

Differential patterns of c-fos mRNA expression in amygdala during successive stages of odor discrimination learning.

Expression of the activity-dependent gene c-fos was used to assess relative levels of neuronal activation in the amygdala and related structures of rats at different stages of odor discrimination learning. In situ hybridization was used to evaluate c-fos mRNA content within the amygdalar subdivisions, the bed nucleus of the stria terminalis, and the hippocampus. After initial exploration of the test apparatus, c-fos mRNA levels were increased in the medial and, to lesser extent, basolateral subdivisions and remained low in the central division. The balance of amygdala to hippocampal labeling favored hippocampus. Rats engaged in familiar nose-poke responses had comparably elevated labeling in the medial and basolateral divisions and low labeling densities in the central division. The ratio of hippocampal to amygdala labeling was at control levels. Rats required to switch from ad libitum responding to cued responding to odors had high basolateral to medial labeling ratios. This was in marked contrast to the medial dominance found in control and exploration rats. Hybridization was substantially more dense in basolateral amygdala than in hippocampal CA1; this imbalance was unique to the group required to form first associations between odors and rewards. Rats performing an overtrained odor discrimination had the least differentiation between amygdalar subdivisions of any behavioral group. The hippocampus-to-amygdala labeling ratio favored hippocampus and was nearly identical to the ratio in exploration rats. These results demonstrate that the balance of activity within the between limbic structures shifts according to behavioral demands. It is suggested that the balances reflect the availability of pertinent afferent cues, interactions between hippocampus and the extended amygdala, and relative levels of activity in the diffuse projections to the limbic system.

Amygdala↗
PubMedDate not supplied

Work-based antipoverty programs for parents can enhance the school performance and social behavior of children.

We assess the impact of the New Hope Project, an antipoverty program tested in a random assignment experimental design, on family functioning and developmental outcomes for preschool- and school-aged children (N = 913). New Hope offered wage supplements sufficient to raise family income above the poverty threshold and subsidies for child care and health insurance to adults who worked full-time. New Hope had strong positive effects on boys' academic achievement, classroom behavior skills, positive social behavior, and problem behaviors, as reported by teachers, and on boys' own expectations for advanced education and occupational aspirations. There were not corresponding program effects for girls. The child outcomes may have resulted from a combination of the following: Children in New Hope families spent more time in formal child care programs and other structured activities away from home than did children in control families. New Hope parents were employed more, had more material resources, reported more social support, and expressed less stress and more optimism about achieving their goals than did parents in the control sample. The results suggest that an anti-poverty program that provides support for combining work and family responsibilities can have beneficial effects on the development of school-age children.

Achievement↗