Animal Behavior
February 4th, 2007
Evolution of behavior, the driver of nervous system evolution, is reviewed emphasizing concepts developed in ethology and sociobiology. Examines foraging and feeding, defensive and aggressive behavior, courtship and reproduction, migration and navigation, and various social activities and communication. Students consider the contributions of inherited patterns and cognitive abilities as well as the roles of various types of plasticity. Both field and laboratory studies are reviewed; human behavior is considered in the context of primate studies.
Categories: Teaching
RISE (Random Image Sequence Evolution) – One of the least understood aspects of mammalian vision is the ability to recognize scenes through significant degradations in image quality. Neural receptive fields have traditionally been described with coherent structures – for example, oriented gratings in V1. However, this does not address how neurons respond to noisy, less coherent visual input, which is arguably more prevalent in the natural world. Previous studies with natural images show that recognition is highly non-linear with respect to noise, and more importantly, that recognition in noise is facilitated by prior experience with the stimuli (Sadr and Sinha, 2004). We extend these studies by using RISE sequences (Random Image Structure Evolution) to present structured images evolving from noise in fMRI, intrinsic optical imaging, and electrophysiological paradigms. Specifically, the direction of RISE evolution – ascending or descending in information content – allows us to control for low-level image features, such as luminance, while trending towards or away from a neuron’s experimentally defined preferred stimulus. Any difference in response to ascending and descending stimuli thus reflects prior knowledge facilitating neural recognition in noise. In line with previous behavioral studies, we present evidence for this hysteretic facilitation throughout the visual hierarchy. Furthermore, we show a graded signature of hysteresis from V1 through IT, suggesting that prior knowledge affects lower and higher visual areas in different ways. With Jitendra Sharma, Hiroki Sugihara, Mriganka Sur, and Pawan Sinha.
Nitric Oxide - Nitric oxide (NO) has recently generated an explosion of interest as it acts as a novel type of neurotransmitter; unlike conventional neurotransmitters, which are released from one neuron to another in a predefined synaptic pathway, NO is produced on demand and theoretically can diffuse between neurons to affect signaling in the surrounding area. These properties suggest that NO plays a role in widespread signaling, and has specifically been implicated in the light/dark adaptation process in the vertebrate retina. Though NO synthase (NOS), the producer of NO, is present in all major retinal cell types, the actual production and behavior of NO in vivo has yet to be fully characterized. By loading retinas with the fluorescent NO-binding dye diaminofluorescein (DAF), NO induced fluorescence (NO-IF) can be imaged in real time. This study used real-time imaging techniques in turtle (Pseudemys scripta elegans) retinal slices to characterize the production and behavior of NO. Though specific stimulation patterns could not be replicated or isolated due to methodological constraints, it was found that NO-IF is produced in two discrete kinetic profiles that are not correlated with cell types, and that, contrary to theory, extracellular NO-IF diffusion is highly restrained, or nonexistent.