Visually-guided timing and its neural representation
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Stimulus-driven timing is a fundamental aspect of human and animal behavior. This type of timing can be subdivided into three principal axes: interval generation, storage, and evaluation. In this thesis, we present results related to each of these axes and describe their implications for how we understand timed behavior. In Chapter 2, we address interval generation, which is the process of creating an internal representation of an ongoing temporal interval. While several studies have found evidence for neural oscillators which may subserve this function, it has remained an open question whether such a mechanism can be useful for timing at even the lowest level of cortex. To address this question, we analyze electrophysiological data collected from rats performing a timing task and find evidence that, indeed, timed reward-seeking behavior tracks oscillatory states in primary visual cortex. This kind of finding raises an important question: how is this temporal information stored after the interval has been generated? This process is called interval storage, and we address the sources of noise that might corrupt it in Chapter 3. Specifically, we devise a novel timing task for humans (BiCaP) to address whether memory biases can account for performance on a classification task, in which a subject must decide whether a test interval is more similar to one or another reference interval. We find that they do, and argue that these sources of noise must be accounted for in theories of timing. In Chapter 4, we deal with interval evaluation which is the process of using this stored temporal information to make valuation decisions. We study this process through the lens of foraging behavior. Specifically, we develop and test a framework that rationalizes observed spatial search patterns of wild animals and humans by accounting for the temporal information they gather about their environment, and how they discount delayed rewards (temporal discounting). Lastly, in Chapter 5, we discuss how these processes are integrated and the implications of these findings for theories of timing.