Mechanisms underlying recovery from cortical injury: reflections on progress and directions for the future

Perspectives on creating clinically relevant blast models for mild traumatic brain injury and post traumatic stress disorder symptoms

Military personnel are returning from Iraq and Afghanistan and reporting non-specific physical (somatic), behavioral, psychological, and cognitive symptoms. Many of these symptoms are frequently associated with mild traumatic brain injury (mTBI) and/or post traumatic stress disorder (PTSD). Despite significant attention and advances in assessment and intervention for these two conditions, challenges persist. To address this, clinically relevant blast models are essential in the full characterization of this type of injury, as well as in the testing and identification of potential treatment strategies. In this publication, existing diagnostic challenges and current treatment practices for mTBI and/or PTSD will be summarized, along with suggestions regarding how what has been learned from existing models of PTSD and traditional mechanism (e.g., non-blast) traumatic brain injury can be used to facilitate the development of clinically relevant blast models.

Propentofylline after focal cortical lesion in the rat: impact on functional recovery and basic fibroblast growth factor expression

The effects of propentofylline, a xanthine derivative and adenosine transport inhibitor, were evaluated following anteromedial cortex lesion in the rat. Propentofylline (2x/10 mg/kg, intraperitoneally) was administered for 7 days post-insult and basic fibroblast growth factor (bFGF) immunoreactivity measured at designated time points in the peri-lesional cortex and ipsilateral dorsal striatum. The spatiotemporal pattern of bFGF expression was then compared to functional recovery patterns. Propentofylline-treated animals displayed increased bFGF expression in the peri-lesional cortex which may have contributed to the observed early facilitation of functional recovery. Drug administration did not, however, produce a change in bFGF expression in the ipsilateral dorsal striatum compared to saline-treated animals. These findings taken together with other positive findings regarding propentofylline, support the drug's therapeutic potential.

Environmental influence on outcome after experiment brain infarction

After permanent ligation of the middle cerebral artery the motor function of rats housed in an enriched environment, i.e. cages with opportunities for various activities but not forcing the rats to do any particular task, is significantly better than in rats housed in individual cages. Rats kept in an enriched environment before and after MCA ligation improved sooner and slightly more than those placed in the enriched environment after ischemia but with no lasting significant difference except for climbing. Preliminary studies suggest that social stimulation is more important than physical activity. Rats with fetal neocortical grafts implanted into the infarct cavity performed better if exposed to enriched environment than grafted control rats housed in standard laboratory cages with 5 rats in each cage. However, they did not perform better than non-grafted rats housed in the same enriched environment. The infarct size did not differ between rats housed in an enriched environment and control rats. There was no correlation between infarct size and performance in rats exposed to an enriched environment. The improved motor function suggest that a rich environment may stimulate mechanisms that enhance brain plasticity.

Lateralized effect of unilateral somatosensory cortex contusion on behavior and cortical reorganization

Previous studies have shown that rats recover function after unilateral somatosensory cortex lesions, possibly by transfer of information processing to other brain areas not normally involved in those functions. In the present study, adult rats underwent unilateral contusions of the somatosensory cortex with ablation of the barrel receptor field. Behavioral testing with modified beam-walking and sensory neglect tasks demonstrated persistent somatosensory deficits in rats with left contusions but no apparent deficits in right injured animals. After 2 months, the [14C]2-deoxyglucose (2-DG) method was used to show the metabolic activity produced by unilateral stimulation of the facial vibrissae. In left injured animals, cortical metabolic activity rostral and caudal to the injury site was depressed both under basal conditions and during right vibrissal stimulation. On the other hand, comparison of the pattern of [14C]2-DG uptake in the intact, right cortex revealed changes in the pattern of glucose utilization associated with left injury combined with right vibrissal stimulation. Pattern changes were quantified by measuring the area in which glucose utilization was within the highest 25% of this range (high activity area; HAA). Right vibrissal stimulation in left injured rats caused an expansion of this HAA in the intact occipital/temporal cortex. Also, in the intact somatosensory cortex of left injured rats, there was an enlarged HAA whether or not vibrissal stimulation was performed. Thus, a combination of depressed peri-injury metabolic activity and aberrant activity in remote brain areas occurs following unilateral somatosensory cortex injury. It remains to be shown whether these factors ameliorate or contribute to persistent behavioral deficits.

Biochemical and physiological parameters of recovery in acute severe head injury: responses to multisensory stimulation

We investigated the efficacy of applying a programme of multisensory stimulation to patients with severe diffuse traumatic brain injury, during their admission to a tertiary neurosurgical intensive care unit. We attempted to determine the nature and extent of any physiological or biochemical changes occurring as a result of the multisensory stimulation in the initial period of their comatose state. The findings were inconclusive with no significant treatment effect demonstrated.