Developmental Neuroscience & Nutrition Research
Pigs and humans have remarkably similar brains and digestive tracts. This affords the pig great potential as a preclinical model for biomedical research. In particular, the neonatal piglet model provides a window into understanding how early-life nutrition influences neural development. Using the piglet model is advantageous because its perinatal brain anatomy and growth trajectory translate well to human infants. Consequently, the Piglet Nutrition & Cognition Laboratory (PNCL) is exploring how nutrient intake or supplementation affect brain structure and function during this vulnerable stage of life.
The Piglet Nutrition & Cognition Laboratory (PNCL) was created by a group at the University of Illinois at Urbana-Champaign (UIUC) to study nutrition, brain health, and their interactions with the gut microbiota and immune system. PNCL is a one-of-a-kind, high-throughput facility with an artificial rearing system, capable of raising 48 newborn piglets simultaneously. Piglets are individually housed and receive unlimited access to milk replacer treatments using an automated feeding system.
PNCL was also specifically created to monitor pig behavior as a response to dietary interventions. For example, each pig’s daily activity and sleep patterns are monitored 24/7 via home-cage cameras. Additionally, PNCL contains a dedicated behavioral suite, equipped with state-of-the-art technologies to assess the pig’s ability to learn and retain information. PNCL pig behavior tests are designed to mimic the tests conducted with human infants. The PNCL team seek to translate their findings from pigs to humans. In doing so, PNCL can elucidate the complex interactions between our diet, the bacteria in our gastrointestinal tract, and their influence on cognitive development in the host.
PNCL uses multiple behavioral paradigms that are sensitive to different cognitive processes. These paradigms include eye-blink conditioning (EBC), novel object recognition (NOR), and operant conditioning (OC).
With EBC, pigs are connected to a system that turns on a light before releasing a small puff of air into the pig’s eye. Over repeated trials, the pig learns to close its eye upon seeing the light, as to avoid the puff of air. Using sensitive tracking equipment, we can analyze exactly when the pig closes its eye (down to the millisecond) in relation to both the light and the air puff. A pig with well-developed cognitive processes will be more successful at closing its eye before delivery of the air puff. How quickly the pig learns to close its eye in reaction to the light can also provide insight into the effects of dietary treatments.
The NOR paradigm starts with arena habituation, during which the pig is placed in the empty arena to acclimate to the new environment. In a second phase, two identical objects are placed in the arena for the pig to investigate. In the final phase, two objects are placed in the arena, one familiar object and one novel object. From the final phase, PNCL measures the amount of time spent investigating the novel object and compares it to the total time spent investigating either object, in order to identify whether the pig has “recognized” the new object as novel. A pig with damaged or underdeveloped cognitive processes will not show novel object recognition.
For the OC paradigm, pigs are trained to perform a specific behavior to obtain a reward. How quickly the pig learns the association between performing the behavior and receiving the reward provides information about the pig’s cognitive development. PNCL is currently developing touchscreen OC, in which the pig must use its nose to touch a stimulus on the screen to get a reward. Human infant testing often already includes touchscreens, so this will be an exciting technological advancement for PNCL behavioral testing that enhances the translatability of the pig model.
Studying behavior is an important step towards understanding brain development, but the PNCL laboratory takes it a step farther by pairing these findings with structural assessments of the pig brain.
Specifically, PNCL scans individual pig brains using magnetic resonance imaging (MRI) techniques through a partnership with the Beckman Imaging Center (BIC) at UIUC. Pigs housed at PNCL are brought to the BIC where they are anesthetized and monitored during all neuroimaging procedures. Human brain imaging sequences have been altered to work with pig brains in order to obtain anatomical images, as well as other types of images, to assess the brain’s microstructure (i.e., nerve fiber organization and other characteristics).
By obtaining a plethora of anatomical pig brain images, PNCL developed a brain map, called The Pig Brain Atlas. This atlas identifies 24 structural regions of interest in the brain, such as the cerebellum (a controller of balance and voluntary body movements) and the hippocampus (the memory and learning center of the brain). Using this atlas and downstream statistical analyses, we can estimate the volumes of each region and make comparisons between experimental groups. This can then help us understand how environmental stimuli differentially affect the growth of individual brain regions.
To evaluate microstructural aspects of the brain, PNCL uses techniques such as diffusion tensor imaging and myelin water fraction imaging. Diffusion scans show how water moves throughout the brain in various directions. By tracking this movement, PNCL can gain insight into how individual pathways form in the brain. With myelin water fraction imaging, PNCL can learn how the brain is myelinated. The myelin sheath is an insulating coating that forms around nerves throughout the body. This coating is an important structure that allows signals to be transmitted quickly and efficiently along neurons. Myelin development occurs rapidly during early-life and can substantially influence cognitive and behavioral development. This supports the value of pairing neuroimaging procedures with behavioral paradigms.
PNCL aims to ask and answer intriguing questions at the intersection of nutrition, behavior, and brain development. PNCL approaches, tools, and infrastructure continue to evolve as they strive to design interdisciplinary projects that facilitate collaborations with both academia and industry. Efforts from PNCL group, as well as other research groups, will help harness the pig’s potential, as well as advance the understanding of human neural development and early-life nutrition.
Katie is a postdoctoral associate in Dr. Ryan Dilger's lab at the University of Illinois at Urbana-Champaign (UIUC). Katie completed her PhD in Nutritional Sciences at UIUC in 2020, and her BS in Nutritional Sciences at Iowa State University in 2015. She thanks Rebecca Golden and Loretta Sutkus (PhD students in the Dilger lab) for their contributions to this article.