Improved behavior, motor, and cognition assessments in neonatal piglets

Abstract

The alterations of animal behavior after traumatic brain injury (TBI) can be subtle, and their quantitative characterization can present significant methodological challenges. Meeting these challenges is a critical need, because quantitative measures are required in studies that compare the efficacy of different clinical interventions. We developed a battery of assessments to quantify behavioral, motor, and cognitive changes in neonatal piglets with good sensitivity and specificity to the detection of persistent deficits that correlate with axonal injury severity after a rapid non-impact head rotation with a diffuse pattern of axonal injury. The battery of measures developed included open field behaviors of sniffing and moving a toy, locomotion measures of Lempel-Ziv complexity and the probability of remaining in the current location, and a novel metric for evaluating motor performance. Our composite porcine disability score was able to detect brain injury with a sensitivity of 100% and specificity of 85.7% at day +4 post-injury for n=8 injured and n=7 sham piglets and significantly correlated with the percent axonal injury in these animals (day +4: ρ=0.76, p=0.0011). A significant improvement over our previous assessments, this new porcine disability score has potential use in a wide variety of porcine disease and injury models.

FIG. 1.

Diagram of T-maze testing setup. During training and normal trials, food was found in arm A. During reversal trials, food was moved to arm B. Hash-marked circles indicate position of bowls of milk replacer outside of the maze that were used to mask olfactory cues. Dotted lines indicate zone markings.

FIG. 2.

T-maze data from both post-injury days combined. Normal trial time, p=0.4542, reversal trial time, p=0.0541, time spent at old food location, p=0.0125. Mean and standard error shown.

FIG. 3.

Motor proficiency scores for injured and sham animals on each study day. Day +1, p=0.021 and Day +4, p=0.75. Mean and standard error shown.

FIG. 4.

Porcine disability score values for injured and sham animals across each study day. Mean and standard error shown.

FIG. 5.

(A) Representative coronal brain slice from injured animal on study day +6 with areas of axonal injury circled. (B) Representative micrograph corresponding to the marked area on the coronal slice image showing areas of β-amyloid precursor protein positive immunostaining (scale bar=100 μm). Color image is available online at www.liebertpub.com/neu