... says it all, eh?

Jeff Radel, Ph.D.

Ph.D. `87; Dalhousie University, Halifax, Nova Scotia, Canada
M.A. `82; Dalhousie University, Halifax, Nova Scotia, Canada
B.A. '79; Oberlin College, Oberlin, Ohio, USA
Associate Professor
Dept. Occupational Therapy Education
School of Allied Health
and
the Kansas Mental Retardation Research Center
University of Kansas Medical Center

Research Interests:

  • Developmental neuroscience
  • Neuronal plasticity
  • Anatomy & function of the visual system

My research efforts address issues of neural plasticity and function by investigating how anatomic relations and functional capacities of the visual system are altered following perturbations during development. Determining how neural information from multiple sources is integrated, how functional behaviors are influenced by that integration pattern, and how neural processing may be enhanced are factors fundamental to understanding the process of neural development. A wide range of techniques are used to address these issues, including microsurgery and transplantation of neural tissue, a variety of histological procedures at the light microscopic and ultrastructural levels, behavioral and electrophysiological assessments of function, and systems analysis methodology.

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Intracranial retinal transplants:
One set of goals for these investigations include 1) evaluating the functional consequences of neural plasticity during development and aging, 2) study of interactions among transplanted neurons and host neural systems, 3) determining if it is possible to enhance efficiency of retinal function experimentally, and 4) the correlation of structural and functional features contributing to optimal efficiency in transplanted and normal retinae. Findings emerging from this research program will be important for understanding the capacity of an ectopic sensory input to influence normal behaviors, and factors contributing to this capacity. The findings also will have implications for the development of behaviors based on multiple inputs in the normal nervous system. Finally, the proposed studies provide an alternative model for evaluating anatomic and functional factors relating to the therapeutic potential of in oculo transplantation procedures prior to widespread clinical application of such technology.

Anatomical studies generate interesting images, and here are a few related to the retinal development and aging studies.

For a review:

Eye movements, reading, and the aging brain:
A second research interest is study of factors influencing control of eye movements in humans, particularly those made during daily life tasks (such as reading). A rich experimental literature addresses the physiological aspects of oculomotor control, and there is a similarly-rich literature on cognitive changes associated with aging. Reading is a highly complex activity, which requires precise integration of sensory, cognitive, and motor functions. In this situation, eye movements become a sensitive indicator of cognitive processing capacity. We are evaluating changes in eye movement patterns made by young and older adults during reading tasks which vary in contextual complexity in order to detect subtle cognitive changes associated with normal aging.

Here are some images related to the eye movements & cognition project.

Related publications:

DHA and the developing visual system:
A third, recent avenue of research is directed at examining the influence of dietary docosahexanenoic acid (DHA) on neural development and function - particularly functional capacity expressed at maturity. DHA is a long-chain (22:6n-3) fatty acid recognized as being essential for normal neural development. The demand for DHA is high during periods of rapid neural development; the primary source of DHA for mammals prenatally is the maternal blood supply, and the mother's breast milk postnatally. Only recently, however, has DHA been included in commercial baby formulae. Moreover, low levels of DHA have been linked to both subtle and overt cognitive and behavioral deficits.

In these experiments, dietary levels of alpha-linolenic acid (the essential fatty acid precursor of DHA) are manipulated systematically during gestation and early development in rats. In one series of studies, we have evaluated the influence of brain DHA levels on sensory processing in the adult central nervous system. Graded series of visual and auditory stimuli are used to evoke central neural responses 50 - 60 days after birth. After a delay of several weeks, naturally-expressed and drug-induced behaviors are investigated in the same animals. Diet-related changes in evoked responses and behaviors are then evaluated and compared to the lipid composition of the brains of these mature rats. Although all diet conditions yield steady increases in brain levels of DHA, rats fed a diet deficient in alpha-linolenic acid consistently possess much less DHA than age-matched controls and animals fed a diet supplemented with DHA. Low brain DHA levels correlate with increased neural activity of central brain regions, and with alterations in behavior. Supplementing the deficient diet with DHA at weaning, however, reverses the increased neural activity elicited by visual - but not auditory - stimuli. Similarly, some but not all behavioral alterations are reversed upon supplementation.

Very recent data suggests that this increased activity in DHA-deficient rats may be due to disinhibition of cortical activity elicited by sensory stimulation. With single-point binding using radioligand at the KD, we've documented a 30% reduction in GABA-A receptor binding in the occipital cortex of DHA-deficient adult rats. Ongoing experiments address the source of this reduction in GABA-A receptor binding through saturation analyses.

In another series of studies, we have evaluated the influence of dietary fatty acids on the severity of blood vessel formation caused by changing oxygen levels in newborn rats. This work suggests that dietary fatty acids have little effect on neovascularization, but that cyclic variations in oxygen levels does reduce the DHA content of the retina. In these rats, normal levels of retinal DHA are maintained only in rats fed a diet high in DHA. The combination of these preliminary findings suggests a neutral role for DHA supplementation of diets fed to very low birth weight human infants who also require oxygen supplementation in relation to neovascularization of the retina (retinopathy of prematurity), but a beneficial role for maintaining normal levels of retinal DHA, and thus better visual acuity for those infants who do not progress to end stage ROP.

Images, etc.: I've posted some images related to the DHA & development projects.

Related publications:

Send e-mail to: Jeff Radel

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