Children's spatial behavior is differentially affected after traumatic brain injury

Can we gain translational insights into the functional roles of cerebral cortex from acortical rodent and naturally acortical zebrafish models?

Cerebral cortex is found only in mammals and is particularly prominent and developed in humans. Various rodent models with fully or partially ablated cortex are commonly used to probe the role of cortex in brain functions and its multiple subcortical projections, including pallium, thalamus and the limbic system. Various rodent models are traditionally used to study the role of cortex in brain functions. A small teleost fish, the zebrafish (Danio rerio), has gained popularity in neuroscience research, and albeit (like other fishes) lacking cortex, its brain performs well some key functions (e.g., memory, consciousness and motivation) with complex, context-specific and well-defined behaviors. Can rodent and zebrafish models help generate insights into the role of cortex in brain functions, and dissect its cortex-specific (vs. non-cortical) functions? To address this conceptual question, here we evaluate brain functionality in intact vs. decorticated rodents and further compare it in the zebrafish, a naturally occurring acortical species. Overall, comparing cortical and acortical rodent models with naturally acortical zebrafish reveals both distinct and overlapping contributions of neocortex and 'precortical' zebrafish telencephalic regions to higher brain functions. Albeit morphologically different, mammalian neocortex and fish pallium may possess more functional similarities than it is presently recognized, calling for further integrative research utilizing both cortical and decorticated/acortical vertebrate model organisms.

Individual differences in executive attention and inhibitory control are related to spatial memory biases in adults

Executive attention is involved in working memory; however, the role of executive attention in the maintenance of information in spatial working memory is debated. This study examined whether inhibitory control was related to spatial working memory biases in adults in a simple spatial memory task where participants had to remember one location on an otherwise blank computer screen. On some trials, a distractor was presented during the maintenance period. Eighty-four participants completed the spatial working memory task and a battery of cognitive control measures. When a distractor was presented during the maintenance period of the spatial memory task, performance on two of the cognitive control measures, a measure of overall attention and a measure of inhibitory control was related to memory errors. When a distractor was not presented during the spatial memory task, memory errors were not related to performance on the cognitive control tasks. Overall, these effects demonstrated that attention is related to maintaining locations in spatial working memory in adults, and inhibitory control may also be related such that those with more efficient inhibitory control were less influenced by distractors presented during the maintenance period.

Controlled Cortical Impact Leads to Cognitive and Motor Function Deficits that Correspond to Cellular Pathology in a Piglet Traumatic Brain Injury Model

Traumatic brain injury (TBI) is a leading cause of death and disability in the United States, with children who sustain a TBI having a greater risk of developing long-lasting cognitive, behavioral, and motor function deficits. This has led to increased interest in utilizing large animal models to study pathophysiologic and functional changes after injury in hopes of identifying novel therapeutic targets. In the present study, a controlled cortical impact (CCI) piglet TBI model was utilized to evaluate cognitive, motor, and histopathologic outcomes. CCI injury (4 m/sec velocity, 9 mm depression, 400 msec dwell time) was induced at the parietal cortex. Compared with normal pigs (n = 5), TBI pigs (n = 5) exhibited appreciable cognitive deficiencies, including significantly impaired spatial memory in spatial T-maze testing and a significant decrease in exploratory behaviors followed by marked hyperactivity in open field testing. Additionally, gait analysis revealed significant increases in cycle time and stance percent, significant decreases in hind reach, and a shift in the total pressure index from the front to the hind limb on the affected side, suggesting TBI impairs gait and balance. Pigs were sacrificed 28 days post-TBI and histological analysis revealed that TBI lead to a significant decrease in neurons and a significant increase in microglia activation and astrogliosis/astrocytosis at the perilesional area, a significant loss in neurons at the dorsal hippocampus, and significantly increased neuroblast proliferation at the subventricular zone. These data demonstrate a strong relationship between TBI-induced cellular changes and functional outcomes in our piglet TBI model that lay the framework for future studies that assess the ability of therapeutic interventions to contribute to functional improvements.

Quantification of Human Spatial Behavior in an Open Field-Locomotor Maze

To obtain and analyze the strategies of human spatial behavior, the Kiel Locomotor Maze, a maze-like analogue, was used. The Kiel Locomotor Maze automatically records different types of spatial memory errors, distances and rotation angles, decision time, and reaction times for each move. 18 patients with cerebral tumors within the frontal, temporal, or parietal lobes and 16 patients with Parkinson's disease were investigated with respect to “sense of direction.” These parameters provide information beyond error scores. It was expected that patients with focal cortical lesions would be characterised by loss of directional sense whereas basal ganglia-related brain disease is characterised by preserved directional sense but poor memory for cue-defined target locations. Based on the neuropsychological theory of head-direction sense, especially the 1991 model of McNaughton, the functionality of storage and update of the head-direction sense may be reflected with the help of these parameters. “Direction sense” parameters provide information about success or failure of the acquisition of a spatial task much earlier than error scores.

Cognitive recovery and development after traumatic brain injury in childhood: a person-oriented, longitudinal study

Influence of childhood traumatic brain injury (TBI) on cognitive recovery and subsequent development is poorly understood. In this longitudinal study we used cluster analysis to explore acute stage individual profiles of injury age and cognition in 118 children with traumatic brain injury. Repeated measures of cognitive function were conducted at 30 months, indicating recovery, and 10 years post-injury, indicating development. Nine clusters were identified. Recovery was evident in three clusters, two of them with low functioning profiles. Developmental gains occurred for three clusters and an acute profile of higher freedom from distractibility (FFD) and lower processing speed (PS) was related to positive differences. One cluster, average low functioning and especially low verbal comprehension, demonstrated a slower development than peers. This suggests that developmental change after TBI in childhood takes place on a continuum, with both chance of long-term catching up, and risk of poor development. An acute profile of higher FFD and lower PS seemed to reflect injury consequences and were followed by developmental gains. These results challenge previous findings, and warrant further investigation.

Ecological assessment of cognitive functions in children with acquired brain injury: a systematic review

BACKGROUND

Childhood acquired brain injury (ABI) often leads to impairment in cognitive functioning, resulting in disabilities in both the home and school environment. Assessing the impact of these cognitive deficits in everyday life using traditional neuropsychological tests has been challenging. This study systematically reviewed ecological measures of cognitive abilities available for children with ABI.

METHOD

Eight databases were searched (until October 2011) for scales: (1) focused on ecological assessment of cognitive functioning; (2) with published data in an ABI population; (3) applicable to children up to 17;11 years of age; and (4) in English. The title and abstract of all papers were reviewed independently by two reviewers.

RESULTS

Database searches yielded a total of 12 504 references, of which 17 scales met the inclusion criteria for the review, focusing on executive functions (n = 9), memory (n = 3), general cognitive abilities (n = 2), visuo-spatial skills (n = 2) and attention (n = 1). Four tasks used observation of actual performance in a natural environment, five were proxy-reports and six were functional paper and pencil type tasks, performed in an office.

CONCLUSION

Overall, few measures were found; eight were still experimental tasks which did not provide norms. Executive functions were better represented in ecological assessment, with relatively more standardized scales available.

Traumatic brain injury is a rarely reported cause of growth hormone deficiency

We determined the frequency of traumatic brain injury (TBI)-related growth hormone deficiency (GHD) from a large registry of growth hormone-deficient subjects and compared these subjects' clinical characteristics with those of children with idiopathic growth hormone deficiency (IGHD). A surprisingly small number of subjects with TBI-induced GHD (n = 141) were registered compared with those with IGHD (n = 23,722). At onset of treatment, the subjects with TBI-induced GHD were older (P = .045), had lower height velocity (P < .001), had a greater number of other pituitary hormone deficiencies (P < .001) and, after a year of recombinant human GH treatment, demonstrated a greater change in height velocity (P = .016). We speculate that TBI-induced GHD may be a neglected phenomenon in childhood, and recommend prospective longitudinal studies to explore its natural history and frequency.

Executive function outcomes following traumatic brain injury in young children: a five year follow-up

Little is known about the long-term effects of traumatic brain injury (TBI) in very young children. This study used a prospective, cross-sectional design to investigate the impact of TBI on executive function (EF) outcomes in children who sustained a TBI before the age of seven. The study aimed to identify specific or global EF deficits five years post-TBI, and to explore factors that predicted outcomes. Fifty-four children with a TBI and 17 uninjured comparison children participated. Their performance on several cognitive and behavioral EF measures was examined. Results suggested that executive difficulties were present following severe TBI, however children with mild and moderate injuries were relatively unaffected. Skills that develop early appeared to be relatively robust. Injury severity was found to be most predictive of long-term EF, however other injury, child and family-related variables also contributed to outcomes.

Neuroprotective effects of resveratrol against traumatic brain injury in immature rats

Childhood trauma resulting in traumatic brain injury (TBI) due to accidents and abuse is the major cause of death and dysfunction in the young. Since there are no approved specific pharmacological agents that block the progression of the secondary injury, the current management of TBI is mainly supportive. We aimed to determine the effect of resveratrol on hippocampal damage and behavioral deficits in 7-day-old rat pups subjected to contusion injury. Resveratrol was injected intraperitoneally at the doses of 100 mg/kg of body weight immediately after induction of traumatic injury. Hippocampal damage was examined by cresyl violet staining and behavioral alterations were evaluated using open field and novel object recognition tests 2 weeks after trauma. Histopathological evaluation showed that treatment with a single dose of 100 mg/kg resveratrol (i.p.) after the trauma significantly ameliorated the trauma induced hippocampal neuron loss at ipsilateral and contralateral hippocampal brain regions of rats. Additionally, treatment with resveratrol decreased anxiety and increased cortex/hippocampus dependent memory of animals subjected to blunt head trauma. These results show that acute treatment of resveratrol has a neuroprotective role against trauma induced hippocampal neuron loss and associated cognitive impairment in rats.

Traumatic injury to the immature brain results in progressive neuronal loss, hyperactivity and delayed cognitive impairments

The immature brain may be particularly vulnerable to injury during critical periods of development. To address the biologic basis for this vulnerability, mice were subjected to traumatic brain injury at postnatal day 21, a time point that approximates that of the toddler-aged child. After motor and cognitive testing at either 2 weeks (juveniles) or 3 months (adults) after injury, animals were euthanized and the brains prepared for quantitative histologic assessment. Brain-injured mice exhibited hyperactivity and age-dependent anxiolysis. Cortical lesion volume and subcortical neuronal loss were greater in brain-injured adults than in juveniles. Importantly, cognitive decline was delayed in onset and coincided with loss of neurons in the hippocampus. Our findings demonstrate that trauma to the developing brain results in a prolonged period of pathogenesis in both cortical and subcortical structures. Behavioral changes are a likely consequence of regional-specific neuronal degeneration.

Assessment of visual-spatial deficits in patients with Parkinson's disease and closed head injuries using virtual environments

Cognitive spatial deficits have been reliably reported in patients with Closed Head Injury (CHI), though in patients with Parkinson's disease (PD) the phenomenon is disputed. CHI and non-demented PD patients were tested using a Judgement of Line Orientation Test, and two spatial tests using virtual environments (VEs). Performance on the Line Orientation and one VE test was worse in the CHI group than controls, but PD patients showed no apparent spatial deficits. However, performance on the second VE test (virtual tray of objects task) did reveal a deficit, both CHI and PD groups being significantly impaired. The data illustrate that particular spatial deficits can be differentiated using appropriate VE-based tasks, and that non-demented PD patients show a paradigm-specific visual-spatial impairment.

Neuropsychological progress during 14 years after severe traumatic brain injury in childhood and adolescence

OBJECTIVE

To investigate the impact of time since injury on neuropsychological and psychosocial outcome after serious TBI in childhood or adolescence.

METHODS

The subjects were eight patients with serious TBI sustained at a mean age of 14 years who had been assessed neuropsychologically at 1, 7 and 14 years after TBI. A retrospective longitudinal design was chosen to describe the development in six neuropsychological domains on the basis of the assessments. Psychosocial data were gathered from clinical knowledge and a semi-structured interview 14 years after TBI.

RESULTS

Performance of verbal IQ shows a declining trend over the three assessments, that the performance of attention and working memory is low and that verbal learning is the cognitive domain which exhibits the largest impairments. The main psychosocial result is that three of the eight subjects went from a school situation with no adjustments to adult life with early retirement.

CONCLUSIONS

Time since insult is an important factor when assessing outcome after TBI in childhood and adolescence and that assessment of final outcome should not be done before adulthood.