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Neuroscience & Animal Behavior
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Hillary R. Rodman, Ph.D.

Research

My research focuses on the development, plasticity and evolution of brain systems that govern high-level visual abilities such as object recognition and the awareness of stimuli.

Comparative organization of vision

Why and how are individual brains and brains of different animals similar and different? Comparative neuroscience seeks to identify components of brain systems which make up the ‘common plan’, to identify variations in brain structure that correlate with species and individual differences in behavior, and help understand evolutionary relationships. Our studies to date show that highly visual rodents (ground squirrels) have an overall organization of the visual cortical mantle that is strikingly similar to that of diurnal primates, along with compelling differences. Recently, we have also begun addressing a different component of visual capacity, namely the use of light to control circadian rhythms and thus influence individual differences in behavior across the day-night cycle.

Questions we are addressing or plan to research include:

  1. Do rodents show cortical specializations for motion and form vision analogous to visual areas MT and IT of primates?
  2. How do the brains of highly visual species such as squirrels differ from those of less visual species (rats and hamsters) regarding organization of main visual structures?
  3. How is the circadian system organized in nocturnal vs. diurnal species?
  4. How are individual differences in activity at different times of day (eg ‘early bird’ vs. ‘night owl’ behavioral patterns) reflected in underlying differences in neural circuitry?
Visual plasticity and ‘blindsight’

What gives us our awareness of what we see? How is experience compromised by brain damage? In humans, blindness after damage to primary visual cortex (V1) is sometimes followed by recovery of reflex-like visual capacity (‘blindsight’). Amazingly, if the damage is sustained early in life, some awareness of the stimuli can also be present. Earlier, my collaborators and I showed that nonhuman primates (monkeys) exhibit parallel phenomena.

Current projects in animals use anatomical methods to identify changes in specific neuronal circuits following early V1 damage, focusing on chemically specific populations in the thalamus and on the cortical regions which contribute to conscious perception of stimuli in intact brains. I also collaborate with researchers in the Departments of Rehabilitation Medicine and Neurology to study human patients with visual system damage using fMRI and behavioral techniques.

Questions we are currently addressing or plan to research include:

  1. Are there specialized types of neurons in the thalamus which survive damage to the cortex, and how are they recruited differentially after lesions in infancy or later in life?
  2. What individual variations are seen in patterns of reorganization, and how do they relate to behavioral differences?
  3. Is recovered vision after cortical damage the property of specific structures and cell populations, or more a property of an interconnected network spanning much of the brain?
  4. What individual and sex differences are present in the subcortical substrates of vision?
Other research interests

Sleep, especially individual differences in sleep timing and behavior, and neural mechanisms. Face and object recognition and their development.

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