Biomedical subjects

J L Ringo

Publications and source records attributed to J L Ringo.

4 recordsLinked to original sources

PubMed1991

Memory decays at the same rate in macaques with and without brain lesions when expressed in d' or arcsine terms.

Data from the literature on the effect of lesions upon recognition memory in the monkey have been examined. On the basis of percentage scores the published data can be interpreted as showing that the ability to recognize a previously seen object decays faster in macaques with brain lesions than it does in normal animals. A reanalysis of the extensive data in terms of d' of Signal Detection Theory or by arcsine transform suggests, on the contrary, that the rate of decay from 0 to 600 s, is essentially the same in normal animals and in those with lesions (particularly temporal lobe lesions). Indeed, in d' or arcsine terms, the effect of the lesions is fully developed at the shortest times used, and shows no increase as a function of the delay between initial presentation and test. Thus, very different conclusions stem from the choice of scale.

Animals↗

PubMed1991

Bi-versus monohemispheric performance in split-brain and partially split-brain macaques.

Experiments comparing binocular with monocular abilities of monkeys working on visual mnemonic tasks were performed. First, it was shown that even in split-brain monkeys performance was more accurate when both hemispheres were utilized than when the task was performed with only the single (better) hemisphere. Some form of noncommissural integration is thus possible. However, when the forebrain commissures are present, as in four other animals (with only optic chiasm transected) it was shown that integration occurs via callosal mechanisms as well. This was demonstrated by the fact that here, too, binocular performance was normally more accurate than monocular performance, but when different images to be remembered were presented concurrently to the two eyes, the binocular advantage was lost. Finally, in three monkeys with only the anterior commissure allowing interhemispheric communication the superiority of binocular assessment remained even when the two hemispheres simultaneously received such differing images.

Animals↗

PubMed1991

Neuronal interconnection as a function of brain size.

The effect of increasing brain size upon the degree of interconnection between neurons is analyzed. An explicit model suggests that as the brain is scaled up there must be a corresponding fall in percent connectedness (the fraction of cells with which any one cell communicates directly). The reason for this is that if the percent connectedness is to be maintained in the face of increased neuron number, than a large fraction of any brain size increase would be spent maintaining such interconnection while the increasing axon lengths would reduce neural computational speed. One implication is that larger brains, being necessarily limited in allowable interconnectedness, may tend to show more specialization.

Animals↗

PubMed1990

Interhemispheric transfer of visual discriminations in split-chiasm monkeys (Macaca nemestrina) and its measurement.

The interhemispheric transfer of visual discriminations in split-chiasm monkeys (Macaca nemestrina) was assessed by training with one eye to a criterion level, then testing either with that same eye (control) or with the other eye (transfer). The difference between these two values was the loss due to transfer. A computer simulation suggested that the usual savings score could grossly misestimate transfer ability. In addition, stimuli with comparable left and right halves were used to minimize the effect of the bilateral hemianopia caused by chiasm section. Performance with the untrained eye was slightly, but statistically significantly, poorer than with the trained eye. No evidence of the phenomena of "learning to transfer" was found (i.e., there was no improvement in transfer ability in relation to concurrent intrahemispheric controls).

Animals↗