NNS 2015 Program & Abstract Book

mild non-significant deficits in learning the location of a platform in a

water maze. In contrast, male mTBI rats did not differ significantly

from shams during recovery but displayed marked deficits during

spatial learning. A memory retention test conducted a week after

spatial learning revealed deficits in both male and female mTBI rats.

Conclusion:

These findings confirm the validity of this novel

model at the behavioral level and research on adverse neural outcomes

is underway; preliminary data indicate that mTBI may reduce hip-

pocampal plasticity. This research has the potential to facilitate a new

way to study mTBI and may better complement research on sports-

related concussion in humans.

Keywords: Hippocampus, mTBI, Behavior, Injury

D2-02

CLOSED-HEAD SINGLE AND REPEAT CONTROLLED

CORTICAL IMPACT IN THE ADULT RAT: EFFECTS ON

BEHAVIOR, PHYSIOLOGY, AND PATHOLOGY

Naseem Jamnia

, Sarah Scheinman

, Grace Stutzmann

2,3

, Robert

Marr

2,3

, Janice Urban

, Daniel Peterson

2,3

, Dorothy Kozlowski

DePaul University, Dept. Biological Sciences, Chicago, USA

RFUMS, Center for Stem Cell Regenerative Med, North Chicago,

USA

RFUMS, Dept. Neuroscience, North Chicago, USA

RFUMS, Dept. Physiol. & Biophysics, North Chicago, USA

Recently, cases of multiple concussions in athletes have received in-

creased attention. Compared to single concussions (sTBI), repeat

concussions (rTBI) can produce significant long-term consequences

and increased risk for neurodegenerative disease. However, mecha-

nisms underlying this difference are poorly understood. We developed

a clinically relevant closed-head injury model of concussion in the

adult rat using a Leica Controlled Cortical Impact (CCI) device. Rats

were placed in a stereotax without ear-bars, on a foam-bed base. The

head was stabilized against a Plexiglas frame to control impact while

allowing head movement. A 6.5 m/s impact was delivered onto the

head surface over the sensorimotor-cortex at a depth of 10.0 mm from

the skin. rTBI animals received three injuries, 48h apart. At 5–7 days

post-injury, rats were assessed using tests of memory (Novel Object

Recognition), forelimb coordination (foot fault) and activity/anxiety

(open field). Blood corticosterone levels were measured pre-injury

and pre-sacrifice (day 8). Results indicate that both sTBI and rTBI

animals show deficits in coordination and hypo-locomotion. sTBI rats

showed no anxiety but rTBI rats showed a trend towards less time

spent in the center of an open field. sTBI rats displayed memory

deficits 3d but not 7d post-injury while rTBI rats still showed memory

deficits at 7d. Both had higher resting corticosterone levels post-

injury. No obvious gross pathology was observed on the cortical

surface or in coronal sections. Our data presents a model of closed-

head CCI in an adult rat that results in clinically relevant markers of

concussion and a delineation between sTBI and rTBI.

Keywords: memory, concussion, motor, anxiety, repeat concussion

D2-03

A COMPUTATIONAL MODEL OF CORTICAL NETWORK

FOR QUANTIFYING NEUROBEHAVIORAL SEQUELAE OF

CONCUSSION LINKED TO TRAUMATIC AXONAL INJURY

Jianxia Cui

, Laurel Ng, Vladislav Volman

L-3 Communications/Applied Technologies, Inc., Simulation, Engineer-

ing & Testing, 10770 Wateridge Circle Suite 200, San Diego, USA

Background:

Mild traumatic brain injury (mTBI) often results in

neurobehavioral alterations such as impaired attention, increased re-

action time, and deficits in working memory. Diffusion imaging, post

mortem studies, and animal models suggest that mTBI primarily af-

fects myelinated axons in white matter tracts. We sought to quantify

the neurobehavioral manifestations of concussive mTBI that are

linked to traumatic injury of myelinated axons.

Methods:

A large-scale biophysically plausible model of cortical

tissue was created for studies of neurobehavioral manifestations of

traumatic axonal injury. The network was composed of 5120 pyra-

midal neurons and 1280 inhibitory neurons, communicating via glu-

tamatergic and GABAergic synapses. Importantly, the model

architecture reflected intra- and inter- hemispheric cortical organiza-

tion, including the distribution of non-myelinated and myelinated

(callosal) axons and axonal conduction delays. Injury was applied to

model corpus callosum axons for quantifying the resulting alterations

in cortical dynamics.

Results:

The intact model exhibited collective oscillations in the

alpha band (8–12 Hz) that are routinely observed in resting non-

attending human subjects. Callosal injury induced several clinically

observable changes, including injury dose dependent increases in: 1)

theta-to-alpha spectral power, as observed in qEEG studies, 2) re-

duced response to attention-like stimulation, and 3) increased popu-

lation response time, similar to increased reaction time as observed in

neurobehavioral tests on mTBI subjects.

Conclusions:

The model results were in a good semi-quantitative

agreement with the existing experimental data. This effort is part of a

larger goal to link a series of models together in an end-to-end

fashion to identify a neurologically based mechanism of concussion

and its implication regarding the prognosis and diagnosis of con-

cussion. Computational models of white matter biomechanical re-

sponse and neurological changes have been developed and are used

in conjunction with the present model to complete the linkage of

external loading conditions to neurological outcomes. The present

model can be used as a platform for modeling neurobehavioral se-

quelae of mTBI and for linking the observed outcomes to specific

injury scenarios.

Keywords: cortical network, neurobehavioral sequelae, reaction

time, qEEG

D2-04

VISUAL DYSFUNCTION SCREENING IN MICE AFTER TBI

USING AN OPTOMOTOR ASSESSMENT OF THE OPTOKI-

NETIC RESPONSE

Scott Ferguson

, Benoit Mouzon, Destinee Aponte, Michael Mullan,

Fiona Crawford

Roskamp Institute, Neurobehavior, Sarasota, USA

Introduction:

Our mouse model of repetitive mild TBI (r-mTBI)

produces chronic optic nerve pathology and retinal degeneration.

In order to assess the visual function of the mice, we have opti-

mized a mechanical optomotor assay to assess the optokinetic

response.

Methods:

The optomotor apparatus consisted of a rotating drum

containing black and white stripes at varying angular resolutions.

Mice were acclimated to the apparatus for a period of 5 minutes in

phototopic lighting. Optomotor testing at each resolution consisted

of pairs of 2 minute trials with 1 trial in a clockwise rotation fol-

lowed by 1 trial in a counter-clockwise rotation with an inter-trial

time of 30 seconds. Following the completion of the first pair of

trials in photopic conditions, lighting was dimmed to scotopic

A-101