The turtle visual cortex, which comprises a significant portion of the turtle's brain, responds to visual stimuli with waves of activation that sweep across the entire visual cortex. The turtle visual cortex forms a part of a visual pathway that allows the turtle to engage in complex tracking activities for prey capture and predator evasion.
The Cor32 and Cor34 experiments, performed by David Senseman of UTSA, measure the the response of the turtle visual cortex to various flash and spot stimuli using voltage sensitive dye (VSD) imaging. The experiment uses an in vitro preparation of the intact visual system shown in Fig. 1 for two experiments.
| Fig. 1: Intact turtle visual system (Cor 32 and Cor 34 experiments). | |
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See experimental setup for additional information about the recording procedures and experimental set-up, and VSD Cor data mapping for an explanation of how detectors are mapped into Davis spatial elements for the examples in the Davis tutorials.
Location of prey and other visual activities cause waves of activation response to sweep across the turtle visual cortex as relected by the local field potential (LFP) measured in awake and behaving turtles in their environment. Fig. 2 shows the increase in LFP right before and during capture.
Fig. 2: LFP reflects prey tracking activity
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LFP measurements show a close relationship with the derivative of the VSD signal at detectors near the maximum observed activation as shown in Fig. 3.
Fig. 2: The LFP is highly correlated with the time derivative of the VSD signal
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Activity in the turtle visual cortex appears highly correlated with but lagging response in the optic tectum, as shown in Fig. 4.
Fig. 2: Activity in optic tectum leads response in visual cortex
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