Reinstatement of binocular depth perception by amphetamine and visual experience after visual cortex ablation

Cerebral and cerebellar diaschisis following carbamazepine therapy

1. The regional cerebral blood flow was studied by SPECT in patients with partial epilepsy before and after 30 days of monotherapy with carbamazepine (CBZ). 2. Both a qualitative visual interpretation and a semiquantitative analysis of SPECT was performed. All patients underwent EEG, CT scan, and MRI studies. The CBZ serum concentrations were assayed. 3. After therapy, in three patients with focal epilepsy, both a crossed cerebral and cerebellar diaschisis were observed, with respect to the side of the epileptic focus in the opposite hemisphere. No morphologic changes were detected at MRI in the cerebral or cerebellar remote hypometabolic areas found at SPECT. 4. CBZ may have a depressant action on the corticopontocerebellar pathways and on the corticocallosal connections.

Prescribing of potentially harmful drugs to patients admitted to hospital after head injury

Fundamental studies in laboratory animals show that certain drugs influence behavioural recovery after brain injury. Although some drugs have the potential to enhance recovery, others may be detrimental. The purpose of the present study was to determine how often these potentially detrimental drugs are used in the management of patients with traumatic brain injury. The medical records of 100 patients with head trauma admitted to a university hospital during one year were reviewed and the frequencies of medication prescriptions during the stay in hospital were recorded. Only 14% of patients with head injury were taking medications at the time of injury. All of the patients were prescribed medications during their stay in hospital. Seventy two per cent of the patients received one or a combination of the drugs (neuroleptics and other central dopamine receptor antagonists, benzodiazepines, and the anticonvulsants phenytoin and phenobarbitone) that animal studies suggest may impair recovery. Until the true impact of these classes of drugs on the recovery process is better understood, care should be exercised in their use.

Methylphenidate treatment following ablation-induced hemiplegia in rat: experience during drug action alters effects on recovery of function

Two experiments examined the effects of single or multiple administrations of methylphenidate (MPH; Ritalin) and differing amounts of beam-walking trials (symptom relevant experience) during the period of drug action on recovery from hemiplegia following unilateral sensorimotor cortex ablation in rat. The first study tested multiple doses of MPH (10 mg/kg) or sterile saline given once daily, followed by four beam-walk (BW) trials at 1, 2, 3, and 6 h on 3 consecutive days. A significant and enduring enhancement of recovery was only observed 24 h after the third administration of MPH, compared to saline controls. In the second study, a single dose of MPH (10 mg/kg) or saline was administered 24 h after ablation, followed by 12 BW trials beginning 1 h and continuing at 15-min intervals until 3 h after MPH or saline administration. A significant and enduring facilitation of BW ability was produced by this single MPH treatment regimen. These data further support the importance of an interaction between symptom-relevant experience and drugs that increase norepinephrine transmission to enhance functional recovery after brain damage.

Pharmacotherapy of aphasia. A critical review

BACKGROUND

Communication problems are a common sequela of cerebrovascular disease and other central nervous system disorders. Behavioral treatment of these disorders aims to harness uninjured parts of the brain to improve the communicative life of the individual. While pharmacotherapy has held promise for the treatment of aphasia for over 50 years, it has not fulfilled this promise. This article reviews both the promise and the disappointment of aphasia pharmacotherapy.

SUMMARY OF REVIEW

Diverse theories of the underlying neurological deficits in aphasia have led to different pharmacologic rationales for therapy. Animal studies have demonstrated decreased levels of brain catecholamines after cortical stroke and more rapid stroke recovery with therapy aimed at augmenting brain norepinephrine and dopamine. These studies have led to recent attempts to hasten or extend language and sensorimotor rehabilitation after human stroke by administration of catecholaminergic drugs. When used as an adjunct to behavioral therapy, such pharmacotherapy appears to have benefit.

CONCLUSIONS

While drug therapy is unlikely to revolutionize the treatment of aphasia, it nonetheless holds promise as an adjunct to behavioral speech and language therapy to decrease performance variability and consequently to improve mean performance in patients with mild to moderate language dysfunction. Additional studies with carefully designed methods are necessary to assess the full potential of aphasia pharmacotherapy.

Differential effects of amphetamine and haloperidol on recovery after global forebrain ischemia

Gerbils subjected to sham surgery or to bilateral occlusion of the carotid arteries were given an injection, during the recovery period, of saline, d-amphetamine, or haloperidol. The animals were subsequently tested once daily for 50 days in an eight-arm radial maze. Global forebrain ischemia had no effect on learning to avoid unbaited arms (reference memory), but greatly increased the number of times animals reentered previously visited arms (working memory errors). Gerbils made ischemic and treated with amphetamine reduced working memory errors more rapidly than did saline-treated ischemic gerbils; conversely, animals made ischemic and treated with haloperidol made more working memory errors than the ischemic controls. Although all ischemic animals were hyperactive, the differential radial maze behaviors of the ischemic groups cannot be explained on the basis of increased activity.

Novel pharmacologic therapies in the treatment of experimental traumatic brain injury: a review

Delayed or secondary neuronal damage following traumatic injury to the central nervous system (CNS) may result from pathologic changes in the brain's endogenous neurochemical systems. Although the precise mechanisms mediating secondary damage are poorly understood, posttraumatic neurochemical changes may include overactivation of neurotransmitter release or re-uptake, changes in presynaptic or postsynaptic receptor binding, or the pathologic release or synthesis of endogenous "autodestructive" factors. The identification and characterization of these factors and the timing of the neurochemical cascade after CNS injury provides a window of opportunity for treatment with pharmacologic agents that modify synthesis, release, receptor binding, or physiologic activity with subsequent attenuation of neuronal damage and improvement in outcome. Over the past decade, a number of studies have suggested that modification of postinjury events through pharmacologic intervention can promote functional recovery in both a variety of animal models and clinical CNS injury. This article summarizes recent work suggesting that pharmacologic manipulation of endogenous systems by such diverse pharmacologic agents as anticholinergics, excitatory amino acid antagonists, endogenous opioid antagonists, catecholamines, serotonin antagonists, modulators of arachidonic acid, antioxidants and free radical scavengers, steroid and lipid peroxidation inhibitors, platelet activating factor antagonists, anion exchange inhibitors, magnesium, gangliosides, and calcium channel antagonists may improve functional outcome after brain injury.

Intraventricular norepinephrine facilitates motor recovery following sensorimotor cortex injury

Intraventricular norepinephrine, dopamine, or vehicle was administered to rats 24 hours after a unilateral sensorimotor cortex ablation to determine their potential roles in acceleration of motor recovery as measured by the beam-walking task. Norepinephrine was found to be the critical neurotransmitter in facilitating motor recovery. Blocking norepinephrine synthesis by dopamine-beta-hydroxylase inhibition coupled with dopamine administration failed to accelerate recovery, indicating a more important role for norepinephrine compared to its precursor dopamine in motor recovery after sensorimotor cortex injury.

Clonidine impairs recovery of beam-walking after a sensorimotor cortex lesion in the rat

Beam-walking in the rat is a useful model for studying the effects of drugs on motor recovery following brain injury. In the present experiment, the effect of clonidine HCl on beam-walking recovery was investigated. Groups of rats were first trained to traverse a narrow elevated beam and then subjected to a right sensorimotor cortex suction-ablation injury. After 24 h, each rat received a single dose of clonidine HCl (20, 60, or 200 micrograms/kg, i.p., salt weight) or saline. Recovery of beam-walking ability was scored over the next 12 days. Treatment with clonidine significantly slowed the rate of recovery (Kruskal-Wallis H = 8.755, df = 3; 0.02 less than P less than 0.05). Furthermore, the impairment persisted for at least 5 days after the rats were treated (Kruskal-Wallis H = 8.47, df = 3; 0.02 less than P less than 0.05). These data are consistent with the hypothesis that norepinephrine, working through central alpha 2-adrenergic receptors, influences motor recovery after a unilateral sensorimotor cortex lesion in the rat. Since many stroke patients are treated with centrally acting antihypertensive drugs, the potential effects of specific classes of these drugs during the recovery period, should be carefully considered.

Beam-walking in rats: studies towards developing an animal model of functional recovery after brain injury

While it has long been recognized that humans recover function after stroke or head injury, the direct impact of drugs on recovery has only recently received attention. The ability of rats to traverse a narrow, elevated beam has proven to be particularly useful when studying the effects of pharmacologic manipulations on motor recovery following cortical injury. However, the effect of testing conditions on the recovery of beam-walking performance has not been investigated. Treatment with amphetamine facilitated recovery of beam-walking following cortical lesions regardless of whether 'massed' or 'spaced' trials were employed. Unexpectedly, the performance of sham-operated controls declined when tested with 'massed' trials. 'Prodding' sham-operated rats by tapping on the rump abolished this decline in performance, but resulted in enhanced recovery in lesioned animals. The results indicate that testing conditions can exert a significant influence on beam-walking performance and are important to consider when interpreting the impact of pharmacologic agents on the recovery process.

Depth perception in cats after cerebral hemispherectomy: comparisons between neonatal- and adult-lesioned animals

Depth perception was studied in adult cats following removal of the left cerebral hemisphere as a neonate or as an adult. Both monocular and binocular thresholds were determined using a visual cliff. Although both age-at-lesion groups showed depth perception deficits, the neonatal-lesioned animals performed much worse under binocular conditions on the visual cliff than either adult-lesioned or intact animals. This was primarily due to the lack of a binocular advantage in the neonatal-lesioned cats since their monocular thresholds were similar to that of adult-lesioned animals. Both lesioned groups showed higher monocular thresholds compared to intact animals but this effect reached significance only for the right eye. In addition, the neonatal-lesioned cats showed ocular misalignment which may have contributed to their lack of binocular depth perception. Regardless of these deficits neonatal-lesioned cats were more like intact controls regarding the types of errors made on the visual cliff. Neonatal-lesioned animals and intact controls made random errors, whereas adult-lesioned animals made most of their errors when the shallow shelf was presented on the animals' right side. This may indicate that the adult-lesioned animals have greater motor and/or visual field biases than do neonatal-lesioned cats.

Recovery of tactile placing after visual cortex ablation in cat: a behavioral and metabolic study of diaschisis

After bilateral visual cortex ablation, cats show a transient deficit in tactile placing and a permanent deficit in visual placing of both forelimbs. Amphetamine administration (four doses, 5 mg/kg, i.p., spaced at 4-day intervals beginning 10 days after surgery) accelerated the rate of recovery of tactile placing compared with saline controls whereas visual placing was not affected. The catecholamine antagonist, haloperidol (0.4 mg/kg, i.p.), blocked the amphetamine-enhanced recovery of tactile placing. Additionally, the visual cortex lesions produced a depression of oxidative metabolism, measured by cytochrome oxidase histochemistry, in subcortical regions remote from the injury. Animals treated with amphetamine exhibited an alleviation of this metabolic depression in the superior colliculus but not in other regions.

The effect of seizures on recovery of function following cortical contusion in the rat

The effect of seizures on recovery of motor function was studied in rats following unilateral contusion of the sensorimotor cortex. Animals receiving two electroconvulsive seizures (ECSs) within the first 24 hours postcontusion showed accelerated recovery of beam-walking ability, reduced volume of necrosis and less spontaneous activity compared to animals receiving only contusions. Animals receiving seven ECSs after contusion had an even smaller volume of necrosis and also reduced spontaneous activity compared to the two ECS group and to controls receiving contusions alone. However, for recovery of beam-walking ability, the seven ECS group did not differ from control rats receiving only contusions. The results are discussed in terms of the effects of seizures on catcholamines, gamma-amino butyric acid, cerebral blood flow and possible effects on remote functional depression after brain injury.

Recovery of function after neonatal or adult hemispherectomy in cats. II. Limb bias and development, paw usage, locomotion and rehabilitative effects of exercise

To investigate the relationship of age-related processes in the recovery of complex motor functions of the limbs, a variety of neurobehavioral assessments were applied to cats with either neonatal (n = 9) or adult (n = 11) removal of the entire left hemitelencephalon (hemispherectomy). Neonatal-lesioned kittens showed no paw preference in reaching for a manipulandum between 5 and 8 weeks of age; thereafter they developed a preference (5.6%) for the unimpaired left limb which persisted throughout adulthood. Adult-lesioned cats showed a significantly greater left bias (13.9%) than neonatal-lesioned cats and they exhibited more abnormal movements and postures when reaching with the impaired limb. Exercising the impaired limb, was effective in reversing the paw preference bias in all lesioned cats. To master a food retrieval task with the impaired limb, adult-lesioned cats required more trials than the neonatal-lesioned group, extensive food deprivation and at least 1 month of postsurgical recovery. However, after mastering this task all cats could continue to perform it indefinitely in their home cages. In a paw print analysis of locomotion, only adult-lesioned cats showed abnormalities including splayed paws, decreased stride length, and adduction of the right hind limb. The results support the 'Kennard Principle' of enhanced recovery following neonatal vs late brain lesions for the present complex motor patterns and are interpreted in the context of neural plasticity and anatomical reorganization during development.