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Biomedical subjects

R T Robertson

Publications and source records attributed to R T Robertson.

At least 109 records · Page 6Linked to original sources
PubMed1980

A subcortical pathway links sensory and limbic systems of the forebrain.

The subcortical afferents and cortical projections of the lateral dorsal nucleus of the thalamus were investigated using anterograde and retrograde axonal transport of horseradish peroxidase (HRP). The lateral dorsal nucleus receives afferent projections from several nuclei of the pretectal complex, and sends efferent projections to several subdivisions of limbic cortex. These connections constitute a two stage pathway that could convey visual and somatosensory information to the limbic system.

Afferent Pathways↗
PubMed1979

Aspirin: teratogenic evaluation in the dog.

Beagle bitches were administered aspirin at either 100 or 400 mg/kg/day between Days 15 and 22 or Days 23 and 30 postmating, and corresponding control groups were dosed with vehicle during one of these same time periods. Maternotoxicity was evident in all dogs dosed with 400 mg/kg/day of aspirin, but no signs of toxicity were observed when 400 mg/kg/day of aspirin was administered from Days 15 to 22 postmating. Teratogenicity, as evidenced by 50% malformation rate, was seen in fetuses from dams treated with 400 mg/kg/day on Days 23 to30 postmating. Observed malformations included, but were not limited to cleft palate,micrognathia, anasarca, cardiovascular malformations, and tial anomalies. No evidence of embryotoxic or teratogenic effects was seen in fetuses from either 100 mg/kg/day dosage level group. Examination of fetuses from 12 untreated litters and 4 vehicle-control litters revealed a very low spontaneous malformation rate confined almost entirely to minor tail abnormalities. These data support use of the dog as an acceptable alternative species in teratogenic screening.

Abnormalities, Drug-Induced↗
PubMed1977

Thalamic projections to parietal cortex.

Thalamic projections to parietal regions of cerebral cortex were investigated in the cat by retrograde degeneration and retrograde transport techniques. Studies of retrograde cellular changes indicate cortically projecting cells in the lateroporterior nucleus (LP), rostral pulvinar (Pul), and the ventral part of the laterodorsal nucleus (LD). When lesions were placed in the cortex of young kittens, clear chromatolytic changes and cell loss were also consistently observed in middle and caudal parts of the ventroanterior nucleus (VA). Investigations of retrograde transport following intracortical injections of horseradish peroxidase have confirmed the results of retrograde degeneration studies by demonstrating cortically projecting cells in VA, LP, LD, and Pul. Retrograde transport studies also indicate cortically projecting cells in the central lateral nucleus. Material from both experimental techniques demonstrates a loose topographic organization of the projections from the lateral thalamus. Anterior parts of LP project to the anterior lateral gyrus and anterior middle suprasylvian gyrus. Middle LP and rostral Pul project to the middle suprasylvian gyrus.

Animals↗
PubMed1975

Unit activity in posterior association cortex of cat.

1. "Association" neurons in the posterior middle suprasylvian gyrus of cat were found to be predominantly polysensory, with 82% of the units in the chloralose-anesthetized preparation responding to auditory, visual, and somatic stimuli. There was no evidence of response differentiation associated with cortical depth distribution. Most units responded with a short-latency response (median 35-60 ms) to all stimulus modalities, with the response to visual stimulation occurring at the shortest latency. Among polysensory cells, almost half responded with equal probability to auditory, visual, and somatic stimulation. The visual stimulus was the most potent for those cells responding with a higher probability to a single modality. Varying degrees of response complexity were noted in some cells in terms of changes in responsivity over time, discharge to stimulus offset, and inhibition of spontaneous activity. The unitary discharge was seen to occur on the negative peak and slope of the locally recorded evoked potential. When only the larger amplitude spikes were analyzed, most of the unitary activity occurred on the negative peak of the evoked potential. Almost half of trimodally responsive cells displayed similar phase relationships between unitary activity and evoked potentials for all three modalities. The absolute refractory period for most cells was from 200 to 300 ms, with relative refractory periods extending up to 30 s...

Anesthesia, General↗
PubMed1971

Development of polysensory responses in association cortex of kitten.

Sensory responsiveness of single neurons in posterior association cortex of kittens that were 7 to 50 days old was investigated. The percentage of trimodal cells (that is, cells that respond to visual, auditory, and somesthetic stimulation) increased gradually until day 50, when percentages of trimodally responsive cells approached the adult level. In the youngest kittens, cells were predominantly responsive to only visual stimulation. With maturation, responsiveness to auditory and then to somesthetic stimulation was observed in increasing percentages of cells.

Age Factors↗
PubMed1970

Number coding in association cortex of the cat.

In electrophysiological investigations of single neurons in cortical association response areas of the cat, cells have been encountered that appear to code the property of number. In a sequence of stimulus presentations, these cells characteristically discharge to a particular numbered stimulus in the series. This effect is independent of stimulus modality, intensity, and interstimulus interval; thus, the cells seem to be responding to the number of stimulus presentations.

Animals↗