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Biomedical subjects

R G Coss

Publications and source records attributed to R G Coss.

25 records · Page 2Linked to original sources
PubMed1980

Crowded jewel fish show changes in dendritic spine density and spine morphology.

This study demonstrates that neuronal development can be adversely affected by short-term crowding. Compared with uncrowded siblings (15 fish/73-litre), juvenile jewel fish (15 fish/3.6-litre) crowded for 60 days exhibited 50-58% fewer dendritic spines and spines with narrower heads on pyriform interneurons in deep tectal strata. These findings indicate that crowded environments can produce aberrant neuronal development similar to that seen in socially deprived jewel fish.

Aggression↗
PubMed1979

Delayed plasticity of an instinct: recognition and avoidance of 2 facing eyes by the jewel fish.

A model depicting 2 horizontally positioned black spots resembling facing eyes, as compared with models depicting other spot arrangements, elicits intense flight activity in young African jewel fish (Hemichromis bimaculatus) under 5 months of age and 7-month-old subadults reared apart from conspecifics with eyeless cave fish (Anoptichthys jordani). In contrast, subadults permitted to observe or interact fully with conspecifics during development exhibited attenuated discriminative flight activity. These findings suggest that visual experience with facing conspecifics, irrespective of physical contact, modifies the flight-eliciting properties of the innat mechanism subserving eye-schema recognition, but only during later maturation.

Age Factors↗
PubMed1979

Social experience affects the development of dendritic spines and branches on tectal interneurons in the jewel fish.

African jewel fish reared with eyeless cave fish, but without visual-tactile contact with conspecifics, exhibit hyperresponsive behavior after release in community aquaria. Because the optic tectum might be affected by these restraints on visual experience, unreleased members of the same social isolate group were compared histologically with controls reared in community aquaria. Using the rapid Golgi method, we counted dendritic spines and branches on pyriform interneurons between 402 and 529 days of age. As compared with isolates, control group interneurons exhibited significantly more spines and primary branches on apical dendrites in deep tectal layers. Our focus is the relation between experiential differences in rearing conditions and synaptic changes in the deep tectal layers.

Animals↗
PubMed1978

Spine stems on tectal interneurons in jewel fish are shortened by social stimulation.

Spined pyriform interneurons in community-reared jewel fish have more dendritic branches and spines in the deep tectal layers than those in isolates reared without visual-tactile contact with conspecifics. Furthermore, in the same dendritic loci in which the community-reared fish had more spines, the spine stems were shorter. The findings suggest that social stimulation induces localized formation of spines, which swell with synaptic activation. Shortening of the spine stem through elongated swelling of the spine head is likely to alter synaptic effectiveness through changes in electrotonic conductance.

Animals↗
PubMed1976

Gaze aversion in autistic and normal children.

Autistic children rarely engage in eye contact, and whilst observation suggests this is due to a specific avoidance of eye contact, some experimental studies have challenged this. In this study the effects on autistic and normal children of an adult looking at them with both eyes, with one eye covered, or apparently not looking at them (both eyes covered) were investigated. As expected, autistic children looked more at the adult with his eyes covered, and also engaged in less flight behaviour. They looked less when two eyes were exposed than one, confirming the potency of the two-eye pattern in provoking gaze aversion. Normal children engaged in much more eye contact than the autistic children, with fewer flight behaviours and stereotypies, supporting the hypothesis that autistic children are predominatly flight motivated. Other, sometimes conflicting, results of previous studies are discussed. Teachers and nurses are recommened not to make efforts to engage autistic children even in friendly eye contact as this provokes more flight behaviour.

Animals↗