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Anomalous patterns of response learning and transfer in decorticate rats.

Behavioural flexibility in decorticate rats was examined by testing response transfer in an obstructed alleyway. In the first experiment, rats were trained to push a ball out of a cylindrical alleyway in order to gain access to the goal box. When this 'push' habit was prevented by blocking forward movement of the ball, decorticate rats were much quicker than sham-operated rats in successfully developing the novel clearance response of pulling the ball into the start box. Both groups were subsequently able to reverse effectively between responses. In a second experiment, sham-operated and decorticate rats were first shaped to pull the ball clear from the alleyway, and then required to adopt a push-type clearance response when movement of the ball towards the start box was prevented. Here, the decorticates showed difficulty both in learning to pull the ball out of the alley and in transferring to a push-type clearance response, but having transferred they coped well with subsequent reversals. This asymmetrical pattern of transfer results is not readily attributed to response preference and raises the possibility that, in some situations at least, decorticated animals may show greater behavioural flexibility than had previously been supposed.

Animals↗

Perinatal decortication impairs performance on an 8-arm radial maze task.

Two experiments evaluate the role of the neocortex in rodent spatial learning. In Experiment 1, perinatally decorticated rats and sham-operated controls began ten training sessions at day 200 on an 8-arm radial maze. Decorticated rats made more errors than controls, but showed improvement by the tenth session. In the second experiment, training was extended to determine whether decorticates could eventually match control performance levels if given sufficient training. Spontaneous activity levels were also recorded and compared to maze performance to investigate the relationship between poor performance on the radial maze and activity. More than half of the decorticates reached criterion performance. Decorticates had significantly elevated spontaneous activity levels when compared to controls, and the magnitude of this hyperactivity was related to performance deficits on the radial maze. These results suggest that with extended training decorticates can learn a spatial task. Performance deficits may reflect the hyperactive tendency of decorticates rather than a specific impairment of spatial learning abilities.

Animals↗

Visual fields of cats with cortical and tectal lesions.

When cats were tested for visual field perimetry, the field of vision for each eye separately was from 45 degrees contralateral to 90 degrees ipsilateral. After either bilateral occipitotemporal lesions (with a split of the tectal commissure) or bilateral area 17, 18, and 19 lesions, the cats could see with each eye only from the midline to 90 degrees ipsilateral. A cat that became nearly totally blind as a result of bilateral occipitotemporal decortication had a subsequent tectal split which enabled it to see with each eye from the midline to 90 degrees ipsilateral.

Animals↗

Effects of cholecystokinin and vasoactive intestinal peptide on locomotion and rearing in neofrontal decorticated rats.

Cholecystokinin octapeptide (CCK-8) and vasoactive intestinal peptide (VIP) have been shown to be antagonistic in various parameters in the rat in our previous studies. In the present investigation the effects of CCK-8 and VIP on spontaneous motility and rearing activity were observed in sham-operated and neofrontal decorticated rats. The results indicate that VIP antagonizes the effects of CCK-8 on spontaneous motility and rearing, and the effects are more apparent in the decorticated rats. It was suggested that CCK-8 affects presynaptic dopaminergic systems, while VIP is likely to stimulate post-synaptic dopaminergic mechanisms.

Animals↗

Striatal and cortical acetylcholine release in vivo in rats with unilateral decortication: effects of treatment with monosialoganglioside GM1.

Striatal and cortical extracellular acetylcholine (ACh) and choline (Ch) levels were determined in samples collected under in vivo conditions using microdialysis in normal (naive) and decorticated rats treated with saline or the monoganglioside GM1. ACh and Ch were assayed using a sensitive high performance liquid chromatography technique coupled to a postcolumn reactor with immobilized enzymes. Picomole amounts of ACh could be measured in the presence of an acetylcholinesterase inhibitor (neostigmine) in the microdialysis perfusion medium (striatal ACh = 0.2-0.4 microM; cortical ACh = 0.03-0.04 microM). Ch was detected both in the presence and in the absence of neostigmine (striatal Ch = 0.5-0.6 microM; cortical Ch = 0.6-2 microM). ACh, but not Ch, was strongly stimulated by 100 mM of KCl included in the perfusion medium. Decortication produced by devascularization did not significantly modify the cortical or striatal basal levels of ACh. However, in the cortex, KCl produced a higher ACh stimulation in the GM1-treated than in the saline-treated decorticated or naive rats. The present results indicate that GM1-treatment increases the ability of cortical cholinergic terminals to release ACh and support the idea that trophic factors such as monoganglioside GM1 can promote recovery following injuries of the central nervous system.

Acetylcholine↗