| dc.description.abstract | Our brains transform the patterns of light on the two retinae into a singular view. Prior work demonstrated that neurons in the lateral geniculate nucleus of the dorsal thalamus (LGN) and in the primary visual cortex (V1) play critical roles in this transformation. However, despite decades of research delineating the circuitry connecting the retinae, LGN, and V1, we still lack a definitive answer to the question of where the outputs of the two eyes first meet in the primate primary visual pathway. This dissertation takes advantage of recent advances in neurophysiological recording techniques to answer this question by investigating whether and where single neurons in the LGN and V1 of awake behaving primates are sensitive to both eyes. The prevailing model of binocular integration suggests that the signals from each eye remain segregated in the primary input layer of V1. However, a small fraction of LGN neurons modulated responses under binocular viewing, suggesting that this structure is at least somewhat involved in binocular interactions. Moreover, this study revealed that the vast majority of V1 neurons are sensitive to both eyes. In other words, most V1 input neurons encode what is viewed by both eyes, suggesting that the signals from the two eyes meet at an earlier processing stage than previously appreciated. The second aim of this dissertation is focused on the convergence of incoming feedforward signals, such as those investigated in the first aim, with ongoing activity. In V1, low frequency (7-14 Hz) alpha fluctuations are pronounced in the deep layers of cortex, which receive both inputs from other cortical areas as well as feedback projections from layer 2/3. Correlating alpha fluctuations with neural responses revealed that spiking activity in all layers, especially layer 2/3, co-varied with the phase of alpha fluctuations in deep layers. This alpha-spike coupling occurred during rest and was more pronounced during active visual stimulation. Overall, this work sheds light on two different types of signal interactions in the primary visual pathway, both in the feedforward and feedback directions. | |
