T channel dynamics in a silicon LGN
This dissertation describes my efforts, in silicon, to study the role of the low threshold calcium channel in the processing of visual information in the lateral geniculate nucleus. Historically, neuroscientists have considered the LGN as simply a relay station for retinal transmission to the visual cortex. However, the LGN does not function alone; rather, it exists within a complicated network of feedback from both the reticular nucleus and the cortex. ^ The approach that I use to study geniculate function involves the design of silicon circuits of increasing model complexity. I begin at the channel level, modelling the low threshold calcium channel using a transistor analog of state transition rates for a voltage gated channel. Following validation of this model, I integrate this channel into a silicon cell and demonstrate how its state influences the cell's response. The next level of complexity involves the dynamics between a thalamocortical and an inhibitory reticular cell, probing their response to inputs at both retinal and cortical synapses. Finally, the system is extended to include many cells, in an effort to illuminate network operation. ^ Using this approach, I demonstrate the role of the low threshold calcium current in enhancing strong features within visual stimuli. In addition, through influence of synapses to both thalamic and reticular layers, the cortical feedback acts as an attentional mechanism by which the response to weaker features can be markedly enhanced, through both increased bursting and increased excitability. ^
Biology, Neuroscience|Engineering, Biomedical
Kai Michael Hynna,
"T channel dynamics in a silicon LGN"
(January 1, 2005).
Dissertations available from ProQuest.