Degeneration of core neural tracts for emotional regulation in a patient with traumatic brain injury: A case report

RATIONALE

Several brain structures, including the orbital prefrontal cortex, ventrolateral prefrontal cortex, dorsolateral prefrontal cortex, amygdala, and anterior cingulate cortex, are considered key structures in the neural circuitry underlying emotion regulation. We report on a patient showing behavior changes and degeneration of core neural tracts for emotional regulation following traumatic brain injury (TBI).

PATIENT CONCERNS

A 51-year-old male patient suffered an in-car accident. The patient lost consciousness for approximately 30 days, and his Glasgow Coma Scale score was 3. He underwent stereotactic drainage for traumatic intraventricular and intracerebral hemorrhages. At approximately 6.5-year after onset, he began to show disinhibition behaviors such as shouting with anger, which worsened over time. At approximately 8-year after onset, he showed severe depression signs and disinhibition, including violence.

DIAGNOSES

The patient who showed delayed-onset behavioral changes (disinhibition and depression).

INTERVENTIONS

Diffusion tensor imaging data were acquired at 3 months and 8 years after TBI onset.

OUTCOMES

The patient showed degeneration of core neural tracts for emotional regulation that was associated with delayed behavioral changes following TBI. On both 3-month and 8-year diffusion tensor tractographies (DTTs), the right dorsolateral prefronto-thalamic tract, ventrolateral prefronto-thalamic tract, orbital prefronto-thalamic tract, uncinate fasciculus, and both cinguli were reconstructed whereas other neural tracts were not reconstructed. Compared with the 3-month DTT, all reconstructed neural tracts on the 8-year DTT were narrow, except for the left cingulum, which showed new transcallosal fibers between both anterior cingula. The fractional anisotropy and tract volume of all reconstructed neural tracts were lower on the 8-year DTT than the 3-month DTT, except for the tract volume of left cingulum.

LESSONS

The evaluation of dorsolateral, ventrolateral, and orbital prefronto-thalamic tract, uncinate fasciculus, and cingulum using follow-up DTTs is useful when a patient with TBI shows delayed-onset behavioral problems.

Functional reorganisation and recovery following cortical lesions: A preliminary study in macaque monkeys

Damage following traumatic brain injury or stroke can often extend beyond the boundaries of the initial insult and can lead to maladaptive cortical reorganisation. On the other hand, beneficial cortical reorganisation leading to recovery of function can also occur. We used resting state FMRI to investigate how cortical networks in the macaque brain change across time in response to lesions to the prefrontal cortex, and how this reorganisation correlated with changes in behavioural performance in cognitive tasks. After prelesion testing and scanning, two monkeys received a lesion to regions surrounding the left principal sulcus followed by periodic testing and scanning. Later, the animals received another lesion to the opposite hemisphere and additional testing and scanning. Following the first lesion, we observed both a behavioural impairment and decrease in functional connectivity, predominantly in frontal-frontal networks. Approximately 8 weeks later, performance and connectivity patterns both improved. Following the second lesion, we observed a further behavioural deficit and decrease in connectivity that showed little recovery. We discuss how different mechanisms including alternate behavioural strategies and reorganisation of specific prefrontal networks may have led to improvements in behaviour. Further work will be needed to confirm these mechanisms.

The allocentric neglect due to injury of the inferior fronto-occipital fasciculus in a stroke patient: A case report

RATIONALE

We report on a patient who developed allocentric neglect due to injury of the inferior fronto-occipital fasciculus (IFOF) following intracranial hemorrhage, diagnosed using diffusion tensor tractography (DTT).

PATIENT CONCERNS

Her cognition seemed normal (A 17-year-old, right-handed female patient). However, in spite of a normal visual field, her perception was missing on the left side, and she had no awareness of her deficit. She was unable to perceive the left side in each of 2 objects, regardless of position of the 2 objects, and failed at detail exploration of the left side of 1 object. In addition, the line bisection test, the most representative neglect test, did not reveal any abnormality.

DIAGNOSES

She was diagnosed with an intracerebral hemorrhage (right thalamus), intraventricular hemorrhage, and subarachnoid hemorrhage due to arteriovenous malformation in the right thalamus.

INTERVENTIONS

Seven weeks after onset, she began rehabilitation. Consequently, the apple cancellation test to discriminate between allocentric and egocentric neglect was performed, with the result of severe allocentric neglect.

OUTCOMES

The right superior longitudinal fasciculus and inferior longitudinal fasciculus were well-reconstructed without definite injury compared with those of the left side. However, the right IFOF was discontinued in the anterior portion around the frontal lobe.

LESSONS

Allocentric neglect due to injury of IFOF was demonstrated in a stroke patient using DTT. It appears that DTT would be helpful in demonstrating the neglect type and pathway in patients with neglect.

Recovery of injured Broca's portion of arcuate fasciculus in the dominant hemisphere in a patient with traumatic brain injury

RATIONALE

Recovery of injured AF in patients with traumatic brain injury (TBI) has not been reported. In this study, we report on a patient with TBI who recovered from an injury to Broca's portion of AF in the dominant hemisphere, diagnosed by diffusion tensor tractography (DTT).

PATIENT CONCERNS

A 28-year-old right-handed male patient suffered head trauma resulting from sliding while riding a motorcycle.

DIAGNOSES

He was diagnosed with a traumatic contusional hemorrhage in the left frontal lobe, subarachnoid hemorrhage, and subdural hemorrhage in the left fronto-temporal lobe.

INTERVENTIONS

He underwent craniectomy on the left fronto-temporal area, and hematoma removal for the subdural hemorrhage in the neurosurgery department of a university hospital. Two weeks after the injury, he was transferred to the rehabilitation department of another university hospital. He showed severe aphasia and brain MRI showed leukomalactic lesion in the left frontal lobe.

OUTCOMES

The result WAB for the patient showed severe aphasia, with an aphasia quotient of 45.3 percentile. However, his aphasia improved rapidly by 9 months with an aphasia quotient at the 100.0 percentile. 2-week DTT detected discontinuity in the subcortical white matter at the branch to Broca's area of left AF. By contrast, on 9-month DTT, the discontinued portion of left AF was elongated to the left Broca's area.

LESSONS

Recovery of injured Broca's portion of AF in the dominant hemisphere along with excellent improvement of aphasia was demonstrated in a patient with TBI. This study has important implications in brain rehabilitation because the mechanism of recovery from aphasia following TBI has not been elucidated.

Protective effect of resveratrol against nigrostriatal pathway injury in striatum via JNK pathway

Nigrostriatal pathway injury is one of the traumatic brain injury models that usually lead to neurological dysfunction or neuron necrosis. Resveratrol-induced benefits have recently been demonstrated in several models of neuronal degeneration diseases. However, the protective properties of resveratrol against neurodegeneration have not been explored definitely. Thus, we employ the nigrostriatal pathway injury model to mimic the insults on the brain. Resveratrol decreased the p-ERK expression and increased the p-JNK expression compared to the DMSO group, but not alter the p38 MAPK proteins around the lesion site by Western blot. Prior to the injury, mice were infused with resveratrol intracerebroventricularly with or without JNK-IN-8, a specific c-JNK pathway inhibitor for JNK1, JNK2 and JNK4. The study assessed modified improved neurological function score (mNSS) and beam/walking test, the level of inflammatory cytokines IL-1β, IL-6 and TNF-α, and striatal expression of Bax and Bcl-2 proteins associated with neuronal apoptosis. The results revealed that resveratrol exerted a neuroprotective effect as shown by the improved mNSS and beam latency, anti-inflammatory effects as indicated by the decreased level of IL-1β, TNF-α and IL-6. Furthermore, resveratrol up-regulated the protein expression of p-JNK and Bcl-2, down-regulated the expression of Bax and the number of Fluoro-Jade C (FJC) positive neurons. However, these advantages of resveratrol were abolished by JNK-IN-8 treatment. Overall, we demonstrated that resveratrol treatment attenuates the nigrostriatal pathway injury-induced neuronal apoptosis and inflammation via activation of c-JNK signaling.

Spatiotemporal trajectories of reactivation of somatosensory cortex by direct and secondary pathways after dorsal column lesions in squirrel monkeys

After lesions of the somatosensory dorsal column (DC) pathway, the cortical hand representation can become unresponsive to tactile stimuli, but considerable responsiveness returns over weeks of post-lesion recovery. The reactivation suggests that preserved subthreshold sensory inputs become potentiated and axon sprouting occurs over time to mediate recovery. Here, we studied the recovery process in 3 squirrel monkeys, using high-resolution cerebral blood volume-based functional magnetic resonance imaging (CBV-fMRI) mapping of contralateral somatosensory cortex responsiveness to stimulation of distal finger pads with low and high level electrocutaneous stimulation (ES) before and 2, 4, and 6weeks after a mid-cervical level contralateral DC lesion. Both low and high intensity ES of digits revealed the expected somatotopy of the area 3b hand representation in pre-lesion monkeys, while in areas 1 and 3a, high intensity stimulation was more effective in activating somatotopic patterns. Six weeks post-lesion, and irrespective of the severity of loss of direct DC inputs (98%, 79%, 40%), somatosensory cortical area 3b of all three animals showed near complete recovery in terms of somatotopy and responsiveness to low and high intensity ES. However there was significant variability in the patterns and amplitudes of reactivation of individual digit territories within and between animals, reflecting differences in the degree of permanent and/or transient silencing of primary DC and secondary inputs 2weeks post-lesion, and their spatio-temporal trajectories of recovery between 2 and 6weeks. Similar variations in the silencing and recovery of somatotopy and responsiveness to high intensity ES in areas 3a and 1 are consistent with individual differences in damage to and recovery of DC and spinocuneate pathways, and possibly the potentiation of spinothalamic pathways. Thus, cortical deactivation and subsequent reactivation depends not only on the degree of DC lesion, but also on the severity and duration of loss of secondary as well as primary inputs revealed by low and high intensity ES.

Neurobiology of Unilateral Spatial Neglect

Hemispatial neglect is a common and disabling consequence of stroke. Earlier studies aimed to identify a single area of the brain where damage caused neglect and sought a single disrupted process that could account for the symptoms. Recent studies have shifted toward identifying component processes and representations underlying spatial attention required for various tasks and identifying areas of the brain responsible for each component that together constitute the network of regions responsible for neglect. This review focuses on recent insights into the mechanisms of neglect, regions of neural dysfunction that cause disruption of particular components or forms of neglect, and potential means of ameliorating neglect. Converging evidence supporting these insights comes from new imaging modalities in acute stroke, functional imaging, transcranial magnetic stimulation, electrophysiological studies in humans, and single-cell recording studies in nonhuman primates.

Injury of the Arcuate Fasciculus in the Dominant Hemisphere in Patients With Mild Traumatic Brain Injury: A Retrospective Cross-Sectional Study

Little is known about injury of the arcuate fasciculus (AF) in patients with mild traumatic brain injury (TBI). We investigated injury of the AF in the dominant hemisphere in patients with mild TBI, using diffusion tensor tractography (DTT). We recruited 25 patients with injury of the left AF among 64 right-handed consecutive patients with mild TBI and 20 normal control subjects. DTTs of the left AF were reconstructed, and fractional anisotropy (FA), apparent diffusion coefficient (ADC), and fiber number of the AF were measured. Among 64 consecutive patients, 25 (39%) patients showed injury of the left AF. The patient group showed lower FA value and fiber number with higher ADC value than the control group (P < 0.05). On K-WAB evaluation, aphasia quotient and language quotient were 95.9 ± 4.1 (range 85-100) and 95.0 ± 5.4 (range 80-100), respectively. However, 23 (92.0%) of 25 patients complained of language-related symptoms after TBI; paraphasia in 12 (48.0%) patients, deficits of comprehension in 4 (16.0%) patients, deficits of speech production in 1 (4.0%) patient, and >2 language symptoms in 6 (24.0%) patients. We found that a significant number (39%) of patients with mild TBI had injury of the AF in the dominant hemisphere and these patients had mild language deficit. These results suggest that DTT could provide useful information in detecting injury of the AF and evaluation of the AF using DTT would be necessary even in the case of a patient with mild TBI who complains of mild language deficit.

Multiple resting state network functional connectivity abnormalities in mild traumatic brain injury

Several reports show that traumatic brain injury (TBI) results in abnormalities in the coordinated activation among brain regions. Because most previous studies examined moderate/severe TBI, the extensiveness of functional connectivity abnormalities and their relationship to postconcussive complaints or white matter microstructural damage are unclear in mild TBI. This study characterized widespread injury effects on multiple integrated neural networks typically observed during a task-unconstrained "resting state" in mild TBI patients. Whole brain functional connectivity for twelve separate networks was identified using independent component analysis (ICA) of fMRI data collected from thirty mild TBI patients mostly free of macroscopic intracerebral injury and thirty demographically-matched healthy control participants. Voxelwise group comparisons found abnormal mild TBI functional connectivity in every brain network identified by ICA, including visual processing, motor, limbic, and numerous circuits believed to underlie executive cognition. Abnormalities not only included functional connectivity deficits, but also enhancements possibly reflecting compensatory neural processes. Postconcussive symptom severity was linked to abnormal regional connectivity within nearly every brain network identified, particularly anterior cingulate. A recently developed multivariate technique that identifies links between whole brain profiles of functional and anatomical connectivity identified several novel mild TBI abnormalities, and represents a potentially important new tool in the study of the complex neurobiological sequelae of TBI.

Impaired head direction cell representation in the anterodorsal thalamus after lesions of the retrosplenial cortex

The retrosplenial cortex (RSP), a brain region frequently linked to processes of spatial navigation, contains neurons that discharge as a function of a rat's head direction (HD). HD cells have been identified throughout the limbic system including the anterodorsal thalamus (ADN) and postsubiculum (PoS), both of which are reciprocally connected to the RSP. The functional relationship between HD cells in the RSP and those found in other limbic regions is presently unknown, but given the intimate connectivity between the RSP and regions such as the ADN and PoS, and the reported loss of spatial orientation in rodents and humans with RSP damage, it is likely that the RSP plays an important role in processing the limbic HD signal. To test this hypothesis, we produced neurotoxic or electrolytic lesions of the RSP and recorded HD cells in the ADN of female Long-Evans rats. HD cells remained present in the ADN after RSP lesions, but the stability of their preferred firing directions was significantly reduced even in the presence of a salient visual landmark. Subsequent tests revealed that lesions of the RSP moderately impaired landmark control over the cells' preferred firing directions, but spared the cells directional stability when animals were required to update their orientation using self-movement cues. Together, these results suggest that the RSP plays a prominent role in processing landmark information for accurate HD cell orientation and may explain the poor directional sense in humans that follows damage to the RSP.

Neural mechanisms of individual and sexual recognition in Syrian hamsters (Mesocricetus auratus)

Recognizing the individual and sexual identities of conspecifics is critical for adaptive social behavior and, in most mammals this information is communicated primarily by chemosensory cues. Due to its heavy reliance on odor cues, we have used the Syrian hamster as our model species for investigating the neural regulation of social recognition. Using lesion, electrophysiological and immunocytochemical techniques, separate neural pathways underlying recognition of individual odors and guidance of sex-typical responses to opposite-sex odors have been identified in both male and female hamsters. Specifically, we have found that recognition of individual odor identity requires olfactory bulb connections to entorhinal cortex (ENT) rather than other chemoreceptive brain regions. This kind of social memory does not appear to require the hippocampus and may, instead, depend on ENT connections with piriform cortex. In contrast, sexual recognition, through either differential investigation or scent marking toward opposite-sex odors, depends on both olfactory and vomeronasal system input to the corticomedial amygdala. Preference for investigating opposite-sex odors requires primarily olfactory input to the medial amygdala (ME) whereas appropriately targeted scent marking responses require vomeronasal input to ME as well as to other structures. Within the ME, the anterior section (MEa) appears important for evaluating or classifying social odors whereas the posterodorsal region (MEpd) may be more involved in generating approach to social odors. Evidence is presented that analysis of social odors may initially be done in MEa and then communicated to MEpd, perhaps through micro-circuits that separately process male and female odors.

[Effects of unilateral lesion of the nigrostriatal pathway by 6-OHDA on the neuronal activities of the pedunculopontine nucleus and the ventrolateral thalamic nucleus]

AIM

To investigate the changes in neuronal activities of the pedunculopontine nucleus (PPN) and the ventrolateral thalamic nucleus (VL) after unilateral 6-hydroxydopamin (6-OHDA) lesioning of the striatum in rats.

METHODS

Extracellular single-unit recordings were perin normal rats and 6-OHDA lesioned rats to observe the firing rate and firing pattern occurring in PPN and VL neurons.

RESULTS

The firing rate of PPN neurones significantly increased from (8.31 +/- 0.62) Hz in normal rats to (10.70 +/- 0.85) Hz in 6-OHDA lesioned rats. The firing pattern changed towards more irregular and bursty when compared with the normal rats, with the firing rate increasing in regular pattern. The firing rate of VL neurones in normal rats and 6-OHDA lesioned rats were (6.25 +/- 0.54) Hz and (5.67 +/- 0.46)Hz respectively, whereas to normal animals. Surthere were no significant differences in these two groups. In addition, the firing pattern did not change in VL compared prisingly, the firing rate in burst pattern decreased significantly.

CONCLUSION

These findings demonstrate that PPN neurons are overactive in 6-OHDAlesioned rats, indicating the participation of this nucleus in the pathophysiology of parkinsonism and the activities of VL neurons might be regulated by projection from PPN to VL.

Adult zebrafish as a model for successful central nervous system regeneration

Adult fish, in contrast to mammals, are capable of regenerating axonal tracts as well as cells and even entire tissues in the central nervous system (CNS). The zebrafish is a powerful genetic model for studies on the developing CNS and is now emerging as a CNS regeneration model. Here we review recent progress in adult regeneration paradigms in zebrafish ranging from axonal re-growth models to those of tissue regeneration. Moreover, we review the tools that have become available in zebrafish to elucidate the factors contributing to successful CNS regeneration. Since many molecular pathways are shared between zebrafish and mammals, it is hoped that insights from zebrafish may contribute to future therapeutic approaches in CNS injury and disease.

Kernohan's notch phenomenon in chronic subdural hematoma: MRI findings

We report two cases of Kernohan's notch phenomenon secondary to chronic subdural hematoma detected by MRI. In the first case, the patient was drowsy with an oculomotor palsy and a hemiparesis ipsilateral to the chronic subdural hematoma. MRI in the post-operative period showed no abnormal signal or deformity of the crus cerebri. The neurological signs immediately resolved after trephination. In the second case, the patient was admitted with progressive decrease in their level of consciousness and ipsilateral hemiparesis with the chronic subdural hematoma. MRI on admission revealed an abnormal signal in the contralateral crus cerebri against the chronic subdural hematoma. After surgery, the mental state gradually recovered to normal with some degree of residual hemiparesis. In patients with chronic subdural hematoma, a compressive deformity of the crus cerebri, without abnormal signal on MRI, may predict a better neurological recovery in patients with Kernohan's notch phenomenon.

Simultaneous application of two neurotrophic factors after spinal cord injury

We have studied the application of voltage gradients to injured spinal cord which enhanced regeneration of axons and reduced their retrograde degeneration after injury. This led to an implanted electronic device producing electrical fields sufficient to induce regeneration in both ascending and descending tracts of white matter (called oscillating field stimulation [OFS]), which has been associated with behavioral recovery in animal models of spinal cord injury (SCI). OFS has also proven to benefit neurologically complete spinal cord injured dogs and humans in clinical trials. These studies, however, have failed to confirm benefit if applied after the sub-acute period of SCI. Here we report on combining OFS with the application of a non-toxic neurotrophic factor, inosine, using a behavioral model for "chronic" SCI, the cutaneous trunci muscle (CTM) reflex in adult guinea pigs. Inosine was delivered subcutaneously in guinea pigs for 28 days using implantable "osmotic pumps"--alone or in combination with OFS. In all animals, experimental and control treatments were withheld for three months after a right lateral hemisection of the thoracic spinal cord. Both inosine and the combination therapy produced a statistically significant recovery of CTM receptive fields silenced permanently by spinal cord hemisection in controls--though the combination therapy enhanced the time of the appearance of recovered regions of skin. Retransection of the cord in three recovered animals eliminated the CTM recovery confirming changes in neural connections were restricted to the cord and not due to changes in cutaneous peripheral innervation. Morphometry of anterogradely labeled white matter revealed a statistically enhanced regeneration of ascending and descending projections in animals treated with the combination "therapy" compared to inosine alone. These data suggest that combining neurotrophic factors of differing modes of action likely enhance the outcome from "chronic" SCI.

Overground Locomotion after Incomplete Spinal Lesions in the Rat: Quantitative Gait Analysis

In rats with incomplete low thoracic spinal cord lesions of different extents, the basic indices of gait such as locomotor velocity, step and stance phase duration and the duty factor (i.e., the relative duration of the stance phase) during overground runway locomotion were analyzed using contact electrodes on each paw for data recording. In animals with lesions confined to the dorsal columns (DC), tested 3 weeks postsurgery, these gait indices were essentially unchanged compared to the preoperative period. After the same recovery period, rats with larger lesions, comprising the dorsal columns plus a major part of the dorsolateral funiculi (DL), showed a transient increase in the hindlimb stance phase duration and the duty factor. More extensive injuries, with additional damage to parts of the ventrolateral and ventral funiculi (VL), produced increments in the stance phase duration and duty factor much above that which would be expected from changes in step cycle duration due to slowing down of locomotion. These changes, which lasted for at least 3 months, were more conspicuous in animals with extensive spinal cord injuries and were due to an altered relationship between the stance phase and step cycle duration. It is suggested that the excessive increment in the hindlimb stance phase and the duty factor constitute a reliable indicator of impairment in locomotor movements, which is correlated with the extent of spinal cord injury.

HVC microlesions do not destabilize the vocal patterns of adult male zebra finches with prior ablation of LMAN

The songs of adult male zebra finches (Taeniopygia guttata) arise by an integration of activity from two neural pathways that emanate from the telencephalic nucleus HVC (proper name). One pathway descends directly from HVC to the vocal premotor nucleus RA (the robust nucleus of the arcopallium) whereas a second pathway descends from HVC into a basal ganglia circuit (the anterior forebrain pathway, AFP) that also terminates in RA. Although HVC neurons that project directly to RA outnumber those that contribute to the AFP, both populations are distributed throughout HVC. Thus, partial ablation (microlesion) of HVC should damage both pathways in a proportional manner. We report here that bilateral HVC microlesions in adult male zebra finches produce an immediate loss of song stereotypy from which birds recover, in some cases within 3 days. The contribution of the AFP to the onset of song destabilization was tested by ablating the output nucleus of this circuit (LMAN, the lateral magnocellular nucleus of the anterior nidopallium) prior to bilateral HVC microlesions. Song stereotypy was largely unaffected. Together, our findings suggest that adult vocal production involves nonproportional integration of two streams of neural activity with opposing effects on song--HVC's direct projection to RA underlies production of stereotyped song whereas the AFP seems to facilitate vocal variation. However, the rapid recovery of song in birds with HVC microlesions alone suggests the presence of dynamic corrective mechanisms that favor vocal stereotypy.

The contribution of prefrontal cortex to global perception

Recent research suggests a role of top-down modulatory signals on perceptual processing, particularly for the integration of local elementary information to form a global holistic percept. In this study we investigated whether prefrontal cortex may be instrumental in this top-down modulation in humans. We measured detection thresholds for perceiving a circle defined by a closed chain of grating patches in 6 patients with prefrontal lesions, 4 control patients with temporal lesions and 17 healthy control subjects. Performance of patients with prefrontal lesions was worse than that of patients with temporal lesions and normal controls when the patterns were sparse, requiring integration across relatively extensive regions of space, but similar to the control groups for denser patterns. The results clearly implicate the prefrontal cortex in the process of integrating elementary features into a holistic global percept, when the elements do not form a "pop-out" display.

cerebellar atrophy after moderate-to-severe pediatric traumatic brain injury

BACKGROUND AND PURPOSE

Although the cerebellum has not attracted the same degree of attention as cortical areas and the hippocampus in traumatic brain injury (TBI) literature, there is limited structural and functional imaging evidence that the cerebellum is also vulnerable to insult. The cerebellum is emerging as part of a frontocerebellar system that, when disrupted, results in significant cognitive and behavioral consequences. We hypothesized that cerebellar volume would be reduced in children following TBI and wished to examine the relation between the cerebellum and known sites of projection, including the prefrontal cortex, thalamus, and pons.

MATERIALS AND METHODS

Quantitative MR imaging was used to measure cerebellar white and gray matter and lesion volumes 1-10 years following TBI in 16 children 9-16 years of age and 16 demographically matched typically developing children 9-16 years of age. Cerebellar volumes were also compared with volumetric data from other brain regions to which the cerebellum projects.

RESULTS

A significant group difference was found in cerebellar white and gray matter volume, with children in the TBI group consistently exhibiting smaller volumes. Repeating the analysis after excluding children with focal cerebellar lesions revealed that significant group differences still remained for cerebellar white matter (WM). We also found a relation between the cerebellum and projection areas, including the dorsolateral prefrontal cortex, thalamus, and pons in 1 or both groups.

CONCLUSION

Our finding of reduced cerebellar WM volume in children with TBI is consistent with evidence from experimental studies suggesting that the cerebellum and its related projection areas are highly vulnerable to fiber degeneration following traumatic insult.

High-frequency stimulation of the subthalamic nucleus modulates the activity of pedunculopontine neurons through direct activation of excitatory fibres as well as through indirect activation of inhibitory pallidal fibres in the rat

Recent data suggest a potential role of pedunculopontine nucleus (PPN) electrical stimulation in improving gait and posture in Parkinson's disease. Because the PPN receives fibres from the subthalamic nucleus (STN), we investigated the effects of STN-high-frequency stimulation (HFS) on PPN neuronal activity in intact rats and in rats bearing either an ibotenate lesion of the entopeduncular nucleus (EP) or a lesion of the substantia nigra (SN). The main response of PPN neurons to STN single-shock stimulations in the three experimental groups was a short latency (4.5 +/- 2.1 ms) and brief (15.3 +/- 6.5 ms) excitation. This response was maintained during 1-5 s of STN-HFS (130 Hz, 60 micros, 100-1000 microA). In EP-lesioned rats the percentage (75.0%) of PPN neurons showing a modulation of activity following STN-HFS was significantly higher compared with that observed in intact (39.7%) and in SN-lesioned rats (35.4%). Furthermore, in EP-lesioned rats the most frequent response of PPN neurons following STN-HFS was a 5-20 s excitation, which was present in 76.6% of responsive neurons in comparison to 15.4% and 9.1% of neurons responsive in intact and in 6-hydroxydopamine-lesioned rats, respectively. Neurons responsive to STN-HFS in the three experimental groups showed either a sharp positively skewed distribution of interspike intervals or multisecond oscillations in autocorrelograms. The results support that STN-HFS modulates the PPN through a balance of excitatory and inhibitory influences, which may be independent from the dopaminergic nigral neurons. In the absence of inhibitory EP fibres, the direct excitatory influence exerted by the STN on the PPN appears to predominate.

Protease-activated receptor-1 induces generation of new microglia in the dentate gyrus of traumatised hippocampal slice cultures

The protease thrombin is not only known as a major component in the blood coagulation cascade but is also involved in proinflammatory processes in the central nervous system (CNS). Here we used an in vitro model, to investigate the effect of thrombin and protease-activated receptor-1 (PAR-1) on proliferation and microgliosis after traumatic injury. A 5-day exposure to thrombin after cutting the Schaffer collaterals induced a proliferation and microgliosis in the dentate gyrus of organotypic slice cultures. This effect is at least partially mediated by PAR-1 since the selective peptide agonist TRag shows similar effects. Thus, thrombin effects after injury might involve microglial proliferation.

Proteomic identification of biomarkers in the cerebrospinal fluid in a rat model of nigrostriatal dopaminergic degeneration

We have performed proteomic analysis in the cerebrospinal fluid in an animal model of Parkinson's disease induced by axotomy of the medial forebrain bundle. In this model, the degeneration of dopaminergic neurons was completed in 14 days, with a loss of about 50% dopaminergic neurons in the substantia nigra and a loss of more than 80% dopamine terminals in the striatum, with a similar diminution of dopamine levels in both structures. Proteins were separated by 2D electrophoresis and identified by matrix-assisted laser desorption-ionization time-of-flight (MALDI-TOF). We found significant increases of haptoglobin and transthyretin along with a decrease of Apo E concentrations in the cerebrospinal fluid of axotomized animals. Changes for haptoglobin and transthyretin were further confirmed in cerebrospinal fluid and plasma by Western blotting. These results suggest that monitoring plasma levels of these signals appears to be a promising biological marker of neuronal degeneration of the nigrostriatal dopaminergic system.

Brain plasticity: From pathophysiological mechanisms to therapeutic applications

Cerebral plasticity, which is the dynamic potential of the brain to reorganize itself during ontogeny, learning, or following damage, has been widely studied in the last decade, in vitro, in animals, and also in humans since the development of functional neuroimaging. In the first part of this review, the main hypotheses about the pathophysiological mechanisms underlying plasticity are presented. At a microscopic level, modulations of synaptic efficacy, unmasking of latent connections, phenotypic modifications and neurogenesis have been identified. At a macroscopic level, diaschisis, functional redundancies, sensory substitution and morphological changes have been described. In the second part, the behavioral consequences of such cerebral phenomena in physiology, namely the "natural" plasticity, are analyzed in humans. The review concludes on the therapeutic implications provided by a better understanding of these mechanisms of brain reshaping. Indeed, this plastic potential might be 'guided' in neurological diseases, using rehabilitation, pharmacological drugs, transcranial magnetic stimulation, neurosurgical methods, and even new techniques of brain-computer interface - in order to improve the quality of life of patients with damaged nervous systems.

Selective dopaminergic lesions of the ventral tegmental area impair preference for sucrose but not for male sexual pheromones in female mice

The role of the meso-accumbens dopaminergic pathway in reward-related behaviours is the subject of intense investigation. In this regard, here we analyse the effects of specific lesions of dopaminergic cells of the ventral tegmental area (VTA) of female mice on two goal-directed behaviours, namely sucrose preference (intake of sucrose solution vs. water) and preference for male sexual pheromones (exploration of male-soiled vs. clean bedding). The results indicate that partial lesions of the VTA that impair neither locomotion nor general exploratory behaviour reduce the preference for sucrose (over a 48-h period) but do not alter the innate attraction that females display for male sexual pheromones (in 5-min tests). This differential effect of the lesions can be interpreted as demonstrating the existence of separate neural mechanisms and circuits for signalling the reward of different natural reinforcers (e.g. sweet taste of sucrose and sexual pheromones). Alternatively, VTA lesions may result in an impaired attribution of incentive salience (which depends on the dopaminergic tegmento-striatal system) of sucrose-predicting cues, thus leading to a long-term decrease in sucrose consumption. By contrast, the same lesions do not affect the unconditioned attraction to male-derived pheromones, which may depend on amygdalo-striatal pathways.

Apoptosis in the rat basal forebrain during development and following lesions of connections

Evidence suggests that neurotrophins are essential for the survival and phenotypic maintenance of cholinergic basal forebrain (BF) neurons. We evaluated the pattern of programmed cell death in the BF of the rat during development and after ablations of the cerebral cortex, a major target area and source of neurotrophins for BF neurons. We identified dying cells using the TUNEL (terminal deoxynucleotidyl-transferase-mediated dUTP-biotin nick end labelling) method and confirmed their apoptotic morphology with electron microscopy. Moreover, we demonstrated the expression of the apoptotic marker active caspase-3 in cells with features of apoptosis. TUNEL(+) cells were present in the developing BF during the first two postnatal weeks. Their frequency peaked at postnatal day (P)1 and at P5. TUNEL used in conjunction with immunofluorescence for neuronal nuclear protein (NeuN) showed that, at both peak stages, the majority of apoptotic cells were neurons. Extensive lesions of the cerebral cortex at different ages (P0, P7 and P14) did not induce significant changes in the frequency of apoptotic BF neurons. However, they resulted in alterations in the morphological phenotype of choline acetyltransferase (ChAT)-immunoreactive neurons in the BF, and a reduction in their number which was inversely proportional to the age at which the lesions were performed. We suggest that: (i) apoptosis is temporally coordinated with the morphological and neurochemical differentiation of BF neurons and the establishment of connections with their target areas; and (ii) cortical ablations do not affect the survival of BF neurons, but they influence the phenotype of cholinergic BF neurons.

Differential motor and electrophysiological outcome in rats with mid-thoracic or high lumbar incomplete spinal cord injuries

We have investigated the motor changes in rats subjected to a moderate photochemical injury on mid-thoracic (T8) or high lumbar (L2) spinal cord segments. Fourteen days after surgery, L2 injured animals presented gross locomotor deficits (scored 10+/-2.8 in the BBB scale), decreased amplitude of motor-evoked potentials (MEPs) recorded on tibialis anterior (TA) and plantar (PL) muscles (24% and 6% of the preoperative mean values, respectively), reduced M wave amplitudes (75%, 62%), and also facilitated monosynaptic reflexes evidenced by an increase of the H/M amplitude ratio (158% and 563%). On the other hand, T8 injured animals had only slight deficits in locomotion (18+/-0.6 in the BBB scale), a minimal reduction in MEP amplitudes (78% and 71% in TA and PL muscles), normal M wave amplitudes, and a milder increase of the H/M ratio in the TA muscle (191%) but less pronounced in the PL muscle (172%). The percentage of spared tissue at the site of injury was similar in both experimental groups (L2: 79% and T8: 82%). Taken together, these results indicate that lumbar spinal injuries have more severe consequences on hindlimb motor output than injuries exerted on thoracic segments. The causes of this anatomical difference may be attributed to damage inflicted on the central pattern generator of locomotion resulting in dysfunction of lumbar motoneurons and altered spinal reflexes modulation.

Cooperativity between hippocampal–prefrontal short-term plasticity through associative long-term potentiation

The hippocampal-medial prefrontal cortex (mPFC) pathway provides highly convergent input to the mPFC in rats and shows two types of short-term plasticity in terms of paired-pulse facilitation (PPF) of the field potential under urethane anesthesia. We now report that stimulating either the dorsal or ventral subregions of the posterior hippocampus elicited PPF (by about 335 and 120%, respectively) of field potentials recorded in the mPFC at 100 ms interpulse interval. This PPF-like interaction occurred when projections were stimulated in the ventral-dorsal order (by about 200% of the single-pulsed response), but not vice versa. When weak long-term potentiation (LTP) of the dorsal projection was evoked simultaneously with strong LTP of the ventral projection, an associative effect was revealed (about +55%), although the magnitudes of LTP in each projection were not correlated. Even when the impermutable PPF-like facilitation was further enhanced (by about +120%), the enhancement was not correlated with either form of LTP, but exhibited the interaction of changes in the dorsal PPF, rather than in the heterotopic priming effect through the ventral projection. Moreover, this change was correlated with the associated LTP ratio of dorsal to ventral projection LTP (i.e., LTP associativity). Larger increases in LTP associativity correlated with greater impermutable PPF-like facilitation; in addition, there was hardly attenuation of the response to the dorsal projection by subsequent electrolytic lesions of the ventral subregion. These results indicate that the mPFC functionally integrates discrete sources of hippocampal information via cooperativity between short- and long-term plasticity.

Vulnerability of the anterior commissure in moderate to severe pediatric traumatic brain injury

In relation to the adult brain, the immature brain might be more vulnerable to damage during and following traumatic brain injury, particularly in white-matter tracts. Given well-established evidence of corpus callosum atrophy, we hypothesized that anterior commissure volume (using quantitative magnetic resonance imaging [MRI]) in this structure would be decreased in children with moderate to severe traumatic brain injury relative to typically developing children. Second, given the purported role of the anterior commissure in interhemispheric axon conveyance between temporal lobes, we hypothesized that temporal lobe white matter, temporal lesion volume, and injury severity (Glasgow Coma Scale score) would be predictive of decreased anterior commissure cross-sectional volume in patients with traumatic brain injury. Finally, we wished to establish the relationship between the anterior commissure and the temporal stem, a major white-matter tract into the temporal lobes, using diffusion tensor imaging fiber-tracking maps for each patient. We also hypothesized that children with traumatic brain injury would exhibit decreased fractional anisotropy in relation to typically developing children in a fiber system including the anterior commissure and the temporal lobes. Decreased anterior commissure cross-sectional volume was observed in patients with traumatic brain injury, and, as predicted, anterior commissure and temporal white-matter volumes were positively related to each other and to higher Glasgow Coma Scale scores. Lesion volume was not independently predictive of anterior commissure volume in the overall model. Diffusion tensor imaging fractional anisotropy values differed between the groups for the temporal stem-anterior commissure system, with the traumatic brain injury group exhibiting decreased fractional anisotropy. The anterior commissure, like the corpus callosum, appears to be highly vulnerable to white-matter degenerative changes resulting from mechanisms such as the direct impact of trauma, progressive axonal injury as tissue in other brain regions atrophies, or myelin degeneration. This is the first systematic examination of anterior commissure atrophy following traumatic brain injury using in vivo quantitative MRI and diffusion tensor imaging fiber tracking in pediatric subjects.

Impaired behavioural and molecular adaptations to dopamine denervation and repeated L‐DOPA treatment in Nur77‐knockout mice

We have previously shown that dopamine (DA) denervation and repeated L-DOPA treatment modulate the pattern of Nur77 mRNA expression in the striatum. However, the exact role of this nuclear receptor in L-DOPA-induced molecular and behavioural adaptations observed in animal models of Parkinson's disease is still unknown. In the present study, we investigated the effects of Nur77 gene deletion on the development of behavioural sensitization and on changes in the regulation of neuropeptides and DA D(3) receptor expression following DA denervation and repeated L-DOPA treatment in Nur77+/+ and Nur77-/- hemiparkinsonian mice. One week postsurgery, hemiparkinsonian mice were treated with L-DOPA (10 mg/kg) plus benserazide (3 mg/kg) once a day for 7 days. Despite similar extents of nigrostriatal denervation, L-DOPA-induced rotational response was exacerbated in Nur77-/- mice compared to Nur77+/+ ones. However, the rate of increase of the rotational behaviour after repeated L-DOPA injections was similar in the two mouse strains. Lesioning the nigrostriatal pathway increased enkephalin (ENK) and neurotensin (NT) mRNA levels in both mouse strains. However, the up-regulation of these neuropeptides was significantly reduced in Nur77-/- mice. There was no difference in the modulation of D3 receptor density and dynorphin (DYN) mRNA expression between the two mouse strains. The present results suggest that Nur77 is involved in setting the threshold level for L-DOPA-induced rotational behaviour, rather than controlling the development of behavioural sensitization. This specific behavioural change is associated with a selective regulation of neuropeptide expression specifically in the indirect striatal output pathway.

Behavioral and hypothalamic‐pituitary‐adrenal responses to anterodorsal thalami nuclei lesions and variable chronic stress in maternally separated rats

In maternally separated rats, variable chronic stress decreased the emotional reactivity and provoked a state of hypoactivity of the hypothalamic-pituitary-adrenal system at 3 months old but increased its activity after the open field test. The anterodorsal thalami nuclei control of the endocrine response under stress conditions was not manifested however its seems activate grooming behavior. The development of behavioral and endocrine response to stress is influenced by early postnatal environment. On the other hand, the anterodorsal thalami nuclei exert an inhibitory influence on the hypothalamic-pituitary-adrenal system under basal and stressful conditions. The aim of this work is to determine the magnitude of behavioral and hypothalamic-pituitary-adrenal responses to variable chronic stress in adult female rats with anterodorsal thalami nuclei lesions, previously isolated for 4.5 h daily during the first 3 weeks of life. The groups were: non-maternally separated sham and lesioned, maternally separated sham and lesioned with variable chronic stress with and without open field test. At 3 months old, under variable chronic stress, maternal separation provoked an increase in ambulation in sham and lesioned animals (P<0.01) but this parameter was not modified by lesion in either non-maternally separated or maternally separated groups. Neither the lesion nor the maternal separation changed the defecation and rearing parameter. Grooming behavior was lower in maternally separated lesioned rats (P<0.05). Under variable chronic stress maternal separation decreased adrenocorticotrophin hormone in comparison with non-maternally separated (P<0.001) and the lesion did not alter this response. Regarding corticosterone concentrations, maternal separation did not affect this hormone under variable chronic stress conditions and after the open field test there was an increase of this in both non-maternally separated and maternally separated sham and lesioned (P<0.001).

Retrograde amnesia following hippocampal lesions in the shock-probe conditioning test

The present experiment examined the role of the hippocampal formation (HPC) in long-term memory of an association between an object and a fear-eliciting event. Rats either received sham or neurotoxic lesions of the HPC 1 or 14 days after learning that contacting a wire-wrapped probe (i.e., object) elicits a shock. After recovery from the surgery, rats were re-exposed to the wire-wrapped probe and burying and avoidance of the probe were assessed and used as memory and fear indices. Regardless of the learning-to-surgery interval, the rats with hippocampal lesions buried and avoided the probe significantly less than sham rats and no more than rats that never experienced shock from the probe. These findings suggest that the lesions caused severe retrograde amnesia and that the HPC has a long-lasting role in memory of a discrete stimulus associated with a fear-eliciting event.

Consequences of unilateral nigrostriatal denervation on the thalamostriatal pathway in rats

The position of the caudal intralaminar nuclei within basal ganglia circuitry has largely been neglected in most studies dealing with basal ganglia function. During the past few years, there has been a growing body of evidence suggesting that the thalamic parafascicular nucleus in rodents (PF) exerts a multifaceted modulation of basal ganglia nuclei, at different levels. Our aim was to study the activity of the thalamostriatal pathway in rats with unilateral dopaminergic depletion. The experimental approach comprised first unilateral delivery of 6-OHDA in the medial forebrain bundle. Thirty days post-lesioning, animals showing a clear asymmetry were then subjected to bilateral injection of Fluoro-Gold (FG) within the striatum. Subsequently, expression of the mRNA encoding the vesicular glutamate transporter 2 (vGLUT2) was detected within thalamostriatal-projecting neurons (FG-labeled) by in situ hybridization and the results were confirmed by laser-guided capture microdissection microscopy followed by real-time PCR. The data showed that there was a marked neuronal loss restricted to PF neurons projecting to the dopamine-depleted striatum. Moreover, PF neurons innervating the dopamine-depleted striatum were intensely hyperactive. These neurons showed a marked increase on the expression of vGLUT2 mRNA as well as for the mRNA encoding the subunit I of cytochrome oxidase as compared with those neurons projecting to the striatum with normal dopamine content. Thus, the selective neurodegeneration of PF neurons innervating the striatum together with the increased activity of the thalamostriatal pathway coexist after nigrostriatal denervation.

Abulia following penetrating brain injury during endoscopic sinus surgery with disruption of the anterior cingulate circuit: case report

BACKGROUND

It is common knowledge that the frontal lobes mediate complex human behavior and that damage to these regions can cause executive dysfunction, apathy, disinhibition and personality changes. However, it is less well known that subcortical structures such as the caudate and thalamus are part of functionally segregated fronto-subcortical circuits, that can also alter behavior after injury. CASE PRESENTATION We present a 57 year old woman who suffered penetrating brain injury during endoscopic sinus surgery causing right basal ganglia injury which resulted in an abulic syndrome.

CONCLUSION

Abulia does not result solely from cortical injury but can occur after disruption anywhere in the anterior cingulate circuit--in the case of our patient, most prominently at the right caudate.

Effects of Post-Training Lesions in the Hippocampus and the Parietal Cortex onldiothetic Information Processing in the Rat

Dead reckoning can be defined as the ability to navigate using idiothetic information based on self-movement cues without using allothetic information such as environmental cues. In the present study, we investigated the effects of hippocampal and parietal cortex lesions on homing behavior using dead reckoning in rats. Experimentally naive Wistar rats were trained with a homing task in which rats were required to take a food pellet from a cup in the arena and to return home with the pellet. After training, rats were divided into a control (CONT) group (n = 16), hippocampal lesioned (HIPP) group (n = 16), and parietal cortex lesioned (PARC) group (n = 16), and rats in the lesioned groups underwent surgery. After surgery, Test 1 (with four cups) and Test 2 (with one cup but the outgoing path was diverted by a barrier) were conducted. The HIPP group showed severe impairment in homing, but the performance of the PARC group did not differ from that of the CONT group. HIPP rats either approached wrong doors or ate the pellet in the arena. Circular statistics showed that homing directions of CONT and PARC rats showed concentration towards home, whereas those of HIPP rats did not. Our results exhibiting HIPP rats' failure in homing agree with many previous studies, but the results obtained from PARC rats were different from previous studies. These results indicate that the intact hippocampus is important for dead reckoning, but the role of the parietal cortex in dead reckoning is still not clear.

Spatial Memory and Hippocampal Function in a NonFoodstoring Songbird, the Zebra Finch (Taeniopygia guttata)

Spatial memory and hippocampal function have as yet been investigated mainly in pigeons and food storing songbirds. We show here that the zebra finch, a songbird not specialized in food storing and caching, is also able to learn a spatial memory task and uses a spatial map for finding food in a 'dry water maze'. Hippocampal lesions prevent learning and retention of this spatial task. The immediate early gene (IEG) products Zenk and Fos are expressed within the hippocampus when the bird is learning the task. Spatial learning cannot be assigned to any hippocampal subregion; IEG expression within the hippocampus is patchy and seems almost arbitrarily located. The IEG activation pattern in spatial memory experiments is compared with those in other learning experiments with zebra finches.

Combined Treatment with Neurotrophin-3 and LSD Facilitates Behavioral Recovery from Double-Hemisection Spinal Injury in Neonatal Rats

We explored functional recovery in two spinal cord injury models following a novel combination treatment (NT-3 + LSD). One group of rats received a staggered double hemisection (DH) at postnatal day 2 (P2) of the left hemicord at T11 and the right hemicord at T12. Another group received complete transection (CT) at T11 on P2. A third group was sham operated. Each of these groups was also treated with the drug combination. Drugs were administered intrathecally above the lesion during surgery, and again s.c. at P4, P6, P8, and P10. Intracellular recording in an in vitro spinal cord preparation at P10-P12 in DH rats revealed weak polysynaptic connections to lumbar motoneurons through the injury region, but only in those receiving NT-3 + LSD; NT-3 or LSD alone had no effect. In behavioral experiments, the frequency of rearing in an open field and hindlimb kicks during swimming was assessed every 3-4 days from P9 to P58. Both CT and DH injury severely impaired rearing and hindlimb kicking during swimming. DH rats treated with NT-3 + LSD showed significantly more kicks during swimming than untreated DH or CT rats and treated CT rats beginning as early as P9 and lasting through the duration of testing. Rearing behavior was also improved by treatment but beginning only in the 3rd postnatal week, the time at which it normally develops. Rearing frequency reached sham control levels by P40. Our results suggest this combination treatment may be a promising new strategy for facilitating recovery from moderate spinal cord injury.

Immunolesions of glucoresponsive projections to the arcuate nucleus alter glucoprivic-induced alterations in food intake, luteinizing hormone secretion, and GALP mRNA, but not sex behavior in adult male rats

Metabolic signals such as insulin, leptin and glucose are known to alter hypothalamic function. Although insulin and leptin are known to directly alter hypothalamic areas that regulate reproduction, the mechanisms by which glucose alters reproductive function are not as clear. Catecholaminergic neurons in the A1/C1 region in the hindbrain are glucose-responsive and project to the arcuate nucleus. To determine if this pathway is involved in the regulation of sex behavior and luteinizing hormone (LH) secretion, this catecholaminergic pathway was lesioned with injections of saporin conjugated with anti-dopamine-beta-hydroxylase (DSAP) or unconjugated saporin (SAP) in adult male rats. Rats were given glucoprivic challenges and feeding and sex behavior was observed. As was expected, the DSAP-treated rats showed decreased feeding during glucoprivation (250 mg/kg 2-deoxy-D-glucose, 2DG) compared to SAP controls. Glucoprivation caused a significant reduction in sex behavior in both SAP and DSAP animals equally, compared to saline treatments (p < 0.05). At the end of the experiment, animals were given a final challenge with 2DG or saline, euthanized by decapitation and trunk blood was assayed for plasma LH levels. In situ hybridization analysis revealed that 2DG treatment caused a significant reduction in GALP mRNA in SAP controls compared to saline treatment. This reduction in GALP mRNA was prevented with DSAP treatment. In SAP animals, 2DG elicited a significant decrease in plasma LH levels (p < 0.05); this reduction in plasma LH was absent in the DSAP-treated male rats. These data indicate that the A1/C1 efferents to the ventromedial hypothalamus are involved in the glucostatic regulation of GALP mRNA, feeding behavior and LH secretion, but not sex behavior in the adult male rat.

Effects of Partial Hippocampal Lesions by IbotenicAcid on Repeated Acquisition of Spatial Discrimination in Pigeons

Pigeons were trained on a spatial discrimination task using a repeated acquisition procedure. In this procedure, the pigeons were trained to discriminate between the positions of three keys. One of them was designated the correct key. When the subjects reached the criterion, the discrimination task was changed, with one of two previously incorrect keys now being made the correct key. This procedure was repeated at least 15 times. Then, lesions to the whole hippocampus, the medial hippocampus or to the lateral hippocampus were made by injections of ibotenic acid (Experiment 1). Only the subjects with damage to the whole hippocampus showed deficits in learning after the lesions. The deficits were similar to those caused by aspiration lesions /37/. Knife cuts separating the medial and lateral hippocampi were made in Experiment 2. The subjects did not show deficits in the spatial discrimination task after the sections. Although studies of the connectivity in the avian hippocampus suggested functional differences between the medial and lateral hippocampi, the present results show that pigeons can learn spatial discrimination with the medial and lateral parts of hippocampus separated.

Relationship between inspiratory muscle strength and cough capacity in cervical spinal cord injured patients

STUDY DESIGN

Prospective single centre study.

OBJECTIVES

Pulmonary rehabilitation focuses on improving the expiratory muscle function in order to increase the reduced cough capacity in patients with cervical spinal cord injuries (SCI). However, an improvement in the inspiratory function is also important for coughing effectively. Therefore, this study was to examine the significance of the inspiratory muscle strength on the cough capacity in the patients with a cervical SCI.

SETTING

SCI unit, Yonsei Rehabilitation Hospital, Seoul, Korea.

METHODS

The vital capacity (VC), maximum inspiratory pressure (MIP), and maximum expiratory pressure (MEP) were measured. Moreover, the unassisted peak cough flow (PCF) and assisted PCF under three conditions were evaluated.

RESULTS

All three assisted cough methods showed a significantly higher value than the unassisted method (P < 0.001). The VC correlated with the voluntary cough capacity and the MIP (R = 0.749) correlated more significantly with the VC than the MEP (R = 0.438) (P < 0.01). The MIP showed a higher correlation with both the unassisted PCF and all three assisted PCFs than the MEP (P < 0.001).

CONCLUSIONS

The management of the inspiratory muscle strength should be considered in the pulmonary rehabilitation at cervical SCI patients.

Deficits in decision-making in head injury survivors

Many survivors of head injury suffer chronic personality changes, such as increased impulsivity and a lack of insight and poor judgment. These changes are well recognized and likely to affect the ability to make decisions. However, systematic investigations into their nature have been limited. This study aims to explore the nature of decision making in head injury survivors using a computerized task. Forty-three head injury survivors and a group of 29 matched controls completed the computerized task. The task required participants to make a probability-based choice and to further qualify this choice with an associated "bet." This betting component allows an assessment of the participant's level of confidence in the decision, via the affective evaluation of its possible consequences in terms of points won or lost. The survivors were found to be slow at making the probability- based choice. Whilst at highly favorable odds, the survivors chose the most likely option in a similar manner to the controls, they chose the most likely option less often than the controls at less favorable odds. Examination of the survivors' betting behavior revealed that they responded impulsively compared to controls. This pattern of prolonged decision making and poor quality of decisions is similar to that found in patients with orbitofrontal cortex lesions, whilst impulsive betting has been associated with abnormalities of the dopamine system. These complex deficits in decision making may contribute to difficulties with poor judgment and inhibition in head injury survivors.

Lesions to the subthalamic nucleus decrease impulsive choice but impair autoshaping in rats: the importance of the basal ganglia in Pavlovian conditioning and impulse control

Although the subthalamic nucleus (STN) is involved in regulating motor function, and inactivation of this structure relieves the motor symptoms in Parkinsonian patients, recent data indicate that corticosubthalamic connections are involved in both the regulation of attention and the ability to withhold from responding. Considerable evidence suggests that the neural circuitry underlying such behavioural disinhibition or impulsive action can be at least partially dissociated from that implicated in impulsive decision-making and it has been suggested that the tendency to choose impulsively is related to the ability to form and use Pavlovian associations. To explore these hypotheses further, STN-lesioned rats were tested on the delay-discounting model of impulsive choice, where impulsivity is defined as the selection of a small immediate over a larger delayed reward, as well as in a rodent autoshaping paradigm. In contrast to previous reports of increased impulsive action, STN lesions decreased impulsive choice but dramatically impaired the acquisition of the autoshaping response. When the STN was lesioned after the establishment of autoshaping behaviour, lesioned subjects were more sensitive to the omission of reward, indicative of a reduction in the use of Pavlovian associations to control autoshaping performance. These results emphasize the importance of the STN in permitting conditioned stimulus-unconditioned stimulus associations to regulate goal-seeking, a function which may relate to the alterations in impulsive choice observed in the delay-discounting task. These data bear a striking similarity to those observed after lesions of the orbitofrontal cortex and are suggestive of an important role for corticosubthalamic connections in complex cognitive behaviour.

Impaired concentration due to frontal lobe damage from two distinct lesion sites

BACKGROUND

Investigations of cognitive deficits after frontal lobe damage have commonly relied on multidimensional tests and relatively coarse specification of lesion anatomy. Some form of impairment in attention is often asserted to cause the revealed deficits.

OBJECTIVE

To describe a disorder of attention in patients with frontal damage using a theoretical model of the fundamental cognitive processes that underlie attention.

METHODS

The ability to perform a task of concentrated responding was studied in 43 patients with well-defined chronic frontal lesions and 38 control subjects using a continuous reaction time (RT) test. Performance measures were mean RT, RT across blocks of the test, and errors. Lesion measures were coarse localization and a hot-spot analysis to detect finer grained lesion effects.

RESULTS

Only patients with lesions in the right superomedial (SM) frontal regions had significantly prolonged RT consistently across the entire test. The critical lesion was in Brodmann's areas 24, 32, 9, and 46 days and in the adjacent corpus callosum. Patients with lesions in left lateral frontal (LL) regions made significantly more errors on the 20% of trials in the first block. The critical lesion was in areas 44, 45, and 47/12.

CONCLUSION

Concentrating attention to respond is affected by lesions in two different frontal regions for reasons that reflect impairments in different cognitive processes. Right superomedial lesions cause an insufficient energizing of attention to respond. Left lateral lesions cause defective setting of specific stimulus-response contingencies. Constrained tests of attention can demonstrate impairments in specific cognitive operations following lesions to different regions of the frontal lobes.

Rapid functional recovery after spinal cord injury in young rats

Responses to traumatic injury in the immature spinal cord may be different from those in adults. We modified an adult model of weight-drop injury to characterize the histopathology and functional recovery after spinal cord injury (SCI) in rat pups at postnatal day 14-15. A 10-g weight was dropped from 2.5 or 5.0 cm at T8-T9. Hindlimb function was evaluated at 24 h and 1, 2, 3, and 4 weeks after injury using the Combined Behavioral Score that estimates overall hind limb sensorimotor function, and the BBB scale for open field locomotion. Histopathology was examined at 15 min, 24 h, and 4 weeks after SCI. The initial hemorrhagic lesion was similar to that seen in adults, but the time course of secondary loss of ventral horn motor neurons was extended. By 4 weeks, only a partial rim of white matter surrounding a central cavity was seen. The 5.0 cm injury group exhibited significantly less recovery of function at 4 weeks than the 2.5 cm group. In the latter, the degree of hindlimb deficit at 4 weeks was similar to that previously described for adults with 10 g x 2.5 cm SCI. However, pups in both injury groups exhibited a significantly faster rate of recovery than adults. Recovery was maximal by 1 week after SCI in pups as compared to 3-4 weeks in adults. The more rapid functional recovery observed in the pups suggests that this new model may be useful for studying mechanisms of functional plasticity after SCI.

Motoneuron loss associated with chronic locomotion impairments after spinal cord contusion in the rat

Information on the nature of deficits and adaptive mechanisms occurring after spinal cord injury is essential to the design of strategies for promoting functional recovery. Motor impairments and compensations were quantified by three-dimensional kinematic analysis in freely walking rats, 6 months after mild cervical (C7) or moderate lumbar (L2) spinal cord contusion. After C7 contusion, the animals showed reduced elbow extension and wrist movement, whereas reduced knee extension was the main impairment after L2 contusion. In both cases, the duration of the walking cycle increased and forward velocity was reduced due to a longer stance phase. Histology revealed reproducible lesions extending approximately to one spinal cord segment. In the transverse plane, the lesion involved the central gray matter and adjacent axons, including the dorsal corticospinal tract, but partially spared the ventrolateral tracts. Retrograde motoneuron tracing by nerve exposure to HRP or intramuscular injection of aminostilbamidine demonstrated that C7 contusion caused the loss of approximately 40% of triceps brachii motoneurons, whereas approximately 30% of quadriceps femoris motoneurons were lost after L2 contusion. These results demonstrate permanent deficits after incomplete lesions at the spinal cord enlargements and suggest that motoneuron loss contributes to their production.

A critical period for the impact of amygdala damage on the emotional enhancement of memory?

The amygdala is crucial in modulating enhanced memory for emotionally arousing material. The authors provide evidence that unilateral lesions of the human amygdala arising early in development, but not in adulthood, are associated with a loss of the expected superior retrieval of emotionally arousing over neutral material. This adds to evidence for an early critical period in the development of amygdala function.

Pro- and anti-apoptotic evidence for cholinergic denervation and hippocampal sympathetic ingrowth in rat dorsal hippocampus

In rat, injection of the specific cholinotoxin, 192 IgG-saporin, into the medial septum results not only in a selective cholinergic denervation of hippocampus, but in an ingrowth of peripheral sympathetic fibers, originating from the superior cervical ganglion, into the hippocampus. A similar process, in which peripheral noradrenergic axons invade hippocampus, may also occur in Alzheimer's disease. Since apoptotic cell death has been demonstrated in the selective neuronal loss found in Alzheimer's disease, the aim of this study was to measure apoptotic protein expression and DNA fragmentation in hippocampal sympathetic ingrowth and cholinergic denervation. Western blot, TdT-mediated dUTP nick end labeling, and oligo ligation techniques were used. Choline acetyltransferase activity and norepinephrine concentrations were also measured. As seen in our previous results, an increase in apoptotic markers was induced by cholinergic denervation alone (medial septum lesion + ganglionectomy), while hippocampal sympathetic ingrowth (medial septum + sham ganglionectomy) reduced or normalized apoptotic effects to control group levels. A decrease in choline acetyltransferase activity was also found in the dorsal hippocampus of hippocampal sympathetic ingrowth and cholinergic denervation groups. An increase in norepinephrine concentration was found in hippocampal sympathetic ingrowth but not in cholinergic denervation group. Results of this study suggest that cholinergic denervation is responsible for most of the proapoptotic responses, while hippocampal sympathetic ingrowth produces a protective effect in the process of programmed cell death in rat dorsal hippocampus. This effect may be a secondary to an altered relationship between norepinephrine-acetylcholine.

Histopathological and Behavioral Characterization of a Novel Cervical Spinal Cord Displacement Contusion Injury in the Rat

Cervical contusive trauma accounts for the majority, of human spinal cord injury (SCI), yet experimental use of cervical contusion injury models has been limited. Considering that (1) the different ways of injuring the spinal cord (compression, contusion, and transection) induce very different processes of tissue damage and (2) the architecture of the spinal cord is not uniform, it is important to use a model that is more clinically applicable to human SCI. Therefore, in the current study we have developed a rat model of contusive, cervical SCI using the Electromagnetic Spinal Cord Injury Device (ESCID) developed at Ohio State University (OSU) to induce injury by spinal cord displacement. We used the device to perform mild, moderate and severe injuries (0.80, 0.95, and 1.1 mm displacements, respectively) with a single, brief displacement of <20 msec upon the exposed dorsal surface of the C5 cervical spinal cord of female (180-200 g) Fischer rats. Characterization of the model involved the analysis of the temporal histopathological progression of the injury over 9 weeks using histochemical stains to analyze white and gray mater integrity and immunohistochemistry to examine cellular changes and physiological responses within the injured spinal cord. Accompanying the histological analysis was a comprehensive determination of the behavioral functionality of the animals using a battery of motor tests. Characterization of this novel model is presented to enable and encourage its future use in the design and experimental testing of therapeutic strategies that may be used for human SCI.

Novel muscle patterns for reaching after cervical spinal cord injury: a case for motor redundancy

A fundamental issue in the neuromotor control of arm movements is whether the nervous system can use distinctly different muscle activity patterns to obtain similar kinematic outcomes. Although computer simulations have demonstrated several possible mechanical and torque solutions, there is little empirical evidence that the nervous system actually employs fundamentally different muscle patterns for the same movement, such as activating a muscle one time and not the next, or switching from a flexor to an extensor. Under typical conditions, subjects choose the same muscles for any given movement, which suggests that in order to see the capacity of the nervous system to make a different choice of muscles, the nervous system must be pushed beyond the normal circumstances. The purpose of this study, then, was to examine an atypical condition, reaching of cervical spinal cord injured (SCI) subjects who have a reduced repertoire of available distal arm muscles but otherwise a normal nervous system above the level of lesion. Electromyography and kinematics of the shoulder and elbow were examined in the SCI subjects performing a center-out task and then compared to neurologically normal control subjects. The findings showed that the SCI-injured subjects produced reaches with typical global kinematic features, such as straight finger paths, bell-shaped velocities, and joint excursions similar to control subjects. The SCI subjects, however, activated only the shoulder agonist muscle for all directions, unlike the control pattern that involved a reciprocal pattern at each joint (shoulder, elbow, and wrist). Nonetheless, the SCI subjects could activate their shoulder antagonist muscles, elbow flexors, and wrist extensor (extensor carpi radialis) for isometric tasks, but did not activate them during the reaching movements. These results demonstrate that for reaching movements, the SCI subjects used a strikingly different pattern of intact muscle activities than control subjects. Hence, the findings imply that the nervous system is capable of choosing either the control pattern or the SCI pattern. We would speculate that control subjects do not select the SCI pattern because the different choice of muscles results in kinematic features (reduced fingertip speed, multiple shoulder accelerations) other than the global features that are somehow less advantageous or efficient.