Biomedical subjects
Publications and source records attributed to J F Hobbelen.
Descending pathways were studied in 5 adult rabbits by means of HRP, injected in the cervical spinal cord (in C2 and C3) at the right side. Results indicate the existence of pathways from the contralateral motor cortex, bilateral projections from the red nuclei, from the vestibular nuclei and from several nuclei in the reticular formation.
In 5 groups of rabbits (0-1, 2-3, 4-5, 6-7 and 12-13 weeks old) the left frontal, parieto-temporal and occipital cortex were removed. Beginning two weeks after the operations the hopping reaction was tested during 15 weeks. It was found in the groups operated 0-1, 2-3 and 4-5 weeks after birth, that the hopping reaction developed normally. This was not the case in the animals operated 6-7 and 12-13 weeks after birth. Brightness descrimination with the left and right eye was tested in the same animals, beginning 12 weeks after the operation. Contrary to the motor system, no age-development recovery was found in the visual system. In all age groups, brightness discrimination with the eye contralateral to the lesion was impaired.
In a group of 14 rabbits aged between 14 and 21 days a hemidecortication was performed in the left hemisphere. A normal monopedal lateral hopping response developed in both forelegs. At adult age, 13 weeks after the first lesion, the remaining cortex on the right side was ablated. Three days afterwards the hopping response was tested again. In all animals, the hopping response remained positive in the right foreleg, contralateral to the lesioning at early age. However, in 10 out of 14 animals the response was absent on the left side, contralateral to the recent lesion. These results show that the hopping response is not mediated by corticofugal connections of the remaining hemisphere of the foreleg contralateral to the early lesion.
In 5 groups of rabbits (0-1, 2-3, 4-5, 6-7 and 12-13 weeks old) the left frontal, parieto-temporal and occipital cortex were removed. Beginning two weeks after the operations the hopping reaction was tested during 15 weeks. It was found in the groups operated 0-1, 2-3 and 4-5 weeks after birth, that the hopping reaction developed normally. This was not the case in the animals operated 6-7 and 12-13 weeks after birth. Brightness discrimination with the left and right eye was tested in the same animals, beginning 12 weeks after the operation. Contrary to the motor system, no age-dependent recovery was found in the visual system. In all age groups, brightness discrimination with the eye contralateral to the lesion was impaired.
Unilateral lesions of the sensorimotor cortex were made in rabbits either 24 h or 6 months after birth. Four months after the operation the hopping reaction in the leg contralateral to the lesion was still absent in the animals operated in adulthood. In the animals operated one day after birth a normal hopping reaction was found when tested 1.5 and 4 months after the operation.
The role of the visual cortex in brightness and pattern vision was re-examined in the rabbit. Animals were trained on both a brightness and a horizontal-vertical striation discrimination. Bilateral removal of the dura mater overlying the entire visual cortex produced no impairments in either brightness or pattern vision. When the visual cortex was devascularized by removal of the pia mater bilaterally, total loss of pattern vision was found with no impairment of brightness discrimination ability. The significance of the finding that the effects of slowly developing degenerative lesions are the same as those of surgical ablation was discussed.
Rabbits were tested binocularly and with each eye separately, in pattern discriminations sensitive to the removal of the visual cortex opposite the exposed eye before and after the middle cerebral artery was unilaterally coagulated. Following surgery, the rabbits were not impaired in performing the discriminations with either eye; nor were any pathological changes found in the hemisphere in which surgery was performed. These findings imply that deficits in performing tasks dependent on the integrity of the visual cortical areas in rabbits may require interruption of the posterior and middle cerebral arteries, both of which supply the visual cortical areas.
Rabbits were trained on a brightness and a vertical vs horizontal discrimination. After bilateral removal of the visual cortex the threshold of brightness discrimination was significantly higher. In addition, there was a severe impairment of striated pattern discrimination.
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