Page 156 - NNS 2014 Program & Abstract Book

due to hearing impairment. Histopathological evidence was overall
mild, with presence of scattered blast intensity-dependent intracra-
nial microhemorrhages. The most striking pathological feature was
dose-dependent FD neurosilver and Fluorjade B staining of the su-
perior colliculus, with some evidence of astroglia and microglia
activation in the same areas. Molecular evaluations showed evidence
of a mild increase in levels of spectrin breakdown products, sug-
gestive of calpain activation, and of several cytokines both in frontal
cortex and hippocampus. Levels of neuron specific enolase and
brain-derived neurotrophic factor, were increased in plasma after
blast exposure. Overall, a single blast exposure did not appear to
cause more than mild evidence of brain injury in rat, with maximum
impact on neurosensory structures and pathways.
Key words
primary blast, rat, TBI
D2-31
ROLE OF THE CONTRALESIONAL CORTEX IN FORELIMB
RECOVERY AFTER EXPERIMENTAL TBI
Verley, D.R., Torolira, D., Kleess, A., Hessell, B.A., Hovda, D.A.,
Sutton, R.L., Harris, N.G.
UCLA, Los Angeles, USA
Deficits in sensorimotor function after clinical TBI are a significant
problem with up to 30% of patients experiencing chronic impair-
ment. Previously, we have shown that left-lateralized controlled
cortical impact (CCI) injury in the rat sensorimotor cortex induces a
trans-hemispheric shift in affected, right forelimb-evoked fMRI
cortical activation over to the homotopic, contralesional cortex
(CLCx). While spontaneous recovery of affected limb-use occurs in
this model, it is unclear whether CLCX-shifted activation is an in-
dicator of beneficial map plasticity or if this is maladaptive. In order
to determine if the CLCx plays a functional role during post-injury
recovery of limb-use, forelimb-reaching was tested before and dur-
ing temporary silencing of the CLCx using intraparenchymal mus-
cimol injection (versus vehicle, n = X/group) and this was performed
longitudinally at 1 and 4 weeks after CCI injury in the adult rat. The
results showed that at 1 week post-injury and before silencing, TBI-
affected forelimb-reaching was reduced by 71% from pre-injury
levels as expected from prior work (P < 0.05). Silencing the CLCx 1
day later resulted in deficits in the TBI-unaffected limb compared to
pre-silencing levels (P < 0.05), simply indicating a correctly targeted
cortical injection. In addition however, there was a complete reversal
of the TBI-affected limb-reaching deficits to pre-injury levels
(P < 0.05) indicating significant involvement of the CLCx in TBI-
affected limb function acutely post-injury. By 4 wks post-injury,
deficits in TBI-affected forelimb-reaching measured before a second
period of silencing had spontaneously recovered to within 20% of
pre-injury levels (P > 0.05). Although CLCx silencing one day later
induced deficits in the TBI-unaffected limb as expected (P < 0.01),
opposite to 1wk post-injury, TBI-affected-limb function was also
significantly reduced to 32% of pre-injury levels (45% of pre-si-
lencing, P < 0.05). This indicates that prior fMRI data showing an
ipsilesional-to-CLCx-shift in activation likely underpins affected
forelimb function chronically. The absence of any new ipsilesional
regions of cortical fMRI activation during CLCx silencing further
indicates the importance of the CLCx to affected limb function.
Support: UCLA BIRC
Key words
cortical silencing, fMRI, neuroplasticity, staircase reaching task
D2-32
FINITE ELEMENT SIMULATION OF BRAIN DEFORMA-
TION FROM SIX DEGREE OF FREEDOM ACCELERATION
MEASUREMENTS OF MILD TRAUMATIC BRAIN INJURY
Hernandez, F.1, Wu, L.C.1, Yip, M.C.1, Hoffman, A.R.1 , Lopez, J.1,
Grant, G.1 , Kleiven, S.2, Camarillo, D.B.1
1Stanford University, Palo Alto, CA, USA
2KTH Royal Institute of Technology, Stockholm, Sweden
Human mTBI biomechanics are complex and poorly understood,
rendering screening efforts ineffective. Inertial rotation and translation
are thought to cause diffuse brain trauma, but human tolerance to
acceleration in all rotational and translational directions (six degrees
of freedom, 6DOF) has not been measured for a human injury. Using
novel instrumented mouthguards that rigidly couple to the upper
dentition, we measured head collision biomechanics in full 6DOF,
including the first complete measurements of human mTBI. Over 500
collisions among 31 subjects were measured at American football,
boxing, and mixed martial arts events. Two subjects sustained a
concussion during competitive play: one suffered loss of conscious-
ness (LOC) while the other self-reported more subtle post-concussive
symptoms, including headache, impaired concentration, and slowed
reaction. Using the KTH finite element (FE) model, we mapped
complex spatiotemporal kinematics measured in vivo onto the brain’s
anatomy. The LOC injury reported the highest principal strain (50%)
among 50 randomly-selected non-injury collisions and the self-
reported injury. Six non-injury collisions produced higher strains than
the self-reported injury (18%), but in different anatomical regions.
Maximum strain in both injuries occurred in the corpus callosum, and
no non-injuries reached injury strain levels in this region. The LOC
injury also predicted large strains in the brainstem. Our 6DOF mea-
surement system predicted deformation in brain structures consistent
with observed neurological deficits. Injury and non-injury collisions
were distinguished by the severity and location of maximum tissue
strain. Damage to the corpus callosum has been shown to disrupt
interhemispheric communication and affect perception, while damage
to the brainstem has been shown to induce LOC. While more data is
required to characterize brain tissue mechanics across a wider spec-
trum of injuries, congruity between our measured kinematics, pre-
dicted tissue deformations, and observed symptoms indicates the
promise of this system as a clinical tool.
Key words
biomechanics, finite element modeling, mild traumatic brain injury
(mTBI), screening, sensors, sports concussion
D2-33
ANXIETY-LIKE BEHAVIOR IN MICE AFTER TRAUMATIC
BRAIN INJURY: DISCUSSION AND COMPARISON OF
COMMONLY-USED TESTS AND MEASUREMENTS
Tucker, L.B.1,2, Ozl, J.1,2, Fu, A.1,2, Kim, Y.1,2, McCabe, J.T.1,2
1Center for Neuroscience and Regenerative Medicine, Bethesda, MD,
USA
2Uniformed Services University of the Health Sciences, Bethesda,
MD, USA
Traumatic brain injury (TBI) survivors often exhibit long-term
symptoms of anxiety, and anxiety-like behaviors in animal TBI
models are a common functional measure. However, anxiety measures
in experiments in brain-injured rodents have yielded variable results.
A-124