A characteristic feature of developing neural circuits is that they exhibit spontaneous, patterned activity. The effects of this activity have been well characterized in the developing visual system, where the spontaneous activity, called retinal waves, is known to be important in the establishment of retinotopic and eye-specific maps. However, there has been little focus on the issue of cell autonomous effects of spontaneous activity. Retinal waves, like other forms of spontaneous activity in the spinal cord and hippocampus, are characterized at the single neuron level by periodic increases in intracellular calcium concentration with a periodicity on the order of a minute. One likely mechanism by which neurons can "decode" these slow oscillations is through activation of second messenger cascades that either influence transcriptional activity or drive post-translational modifications. Recently, genetically encoded, fluorescent reporters have been developed that allow imaging of second messenger pathways other than calcium, such as the cAMP/PKA pathway. This dissertation focuses on the use of these FRET-based, reporters of the cAMP/PKA pathway to study the activity of second messenger cascades during retinal waves. In chapter 1, recent advances in efficacy and utility of genetically encoded, fluorescent indicators of the cAMP/PKA pathway are described. In chapter 2, we report the spontaneous activation of the cAMP/PKA pathway in retinal ganglion cells (RGCs). Spontaneous activation of the cAMP/PKA pathway is dependent on, and maintains a temporally consistent relationship with retinal waves and is dependent on calcium influx. Chapter 3 describes the mechanism by which calcium influx leads to an increase in PKA activity, specifically focusing on the role of calcium activated adenylate cyclases and phosphodiesterases. We present evidence that multiple adenylate cyclases underlie the calcium-induced PKA activation in RGCs. Chapter 4 concludes with a model of the cAMP/PKA pathway in retinal ganglion cells and discussion of the possible function of periodic PKA transients in the development of visual circuits

Theories attempting to explain the evaluation of subjective values often stress the importance of the context in whicha judgment is made. One such theory, the General Evaluability Theory (GET; Hsee & Zhang, 2010), suggests judgments areparticularly sensitive to evaluation mode (i.e., a single or joint evaluation). Importantly, deviations in the patterns of judgmentsof a value across single and joint modes are argued to reflect the degree to which individuals can consistently evaluate thatvalue (i.e., the extent of evaluability). We applied this framework to a novel context, specifically the evaluation of effort.Individuals made judgments of effort across memorial, motor, and perceptual domains in single and joint evaluation modes.Results demonstrated that memorial and motor effort judgments remained largely consistent across modes, whereas perceptualeffort judgments did not. These results provide initial evidence that at least some types of effort may not be evaluable.

Neurons undergo long term, activity dependent changes that are mediated by activation of second messenger cascades. In particular, calcium-dependent activation of the cyclic-AMP/Protein kinase A signaling cascade has been implicated in several developmental processes including cell survival, axonal outgrowth, and axonal refinement. The biochemical link between calcium influx and the activation of the cAMP/PKA pathway is primarily mediated through adenylate cyclases. Here, dual imaging of intracellular calcium concentration and PKA activity was used to assay the role of different classes of calcium-dependent adenylate cyclases (ACs) in the activation of the cAMP/PKA pathway in retinal ganglion cells (RGCs). Surprisingly, depolarization-induced calcium-dependent PKA transients persist in barrelless mice lacking AC1, the predominant calcium-dependent adenylate cyclase in RGCs, as well as in double knockout mice lacking both AC1 and AC8. Furthermore, in a subset of RGCs, depolarization-induced PKA transients persist during the inhibition of all transmembrane adenylate cyclases. These results are consistent with the existence of a soluble adenylate cyclase that plays a role in calcium-dependent activation of the cAMP/PKA cascade in neurons.

Understanding how we judge effortfulness promises insight into the myriad choices we make each day. Here, we present research investigating a curious finding: In Dunn et al., 2019, individuals anticipated reading a single rotated word as more effortful than reading two upright words. This contravenes the expectation that the latter will take significantly longer. In Dunn et al. (2019) participants had limited experience engaging in the task beyond judging anticipated effort. In the present investigation participants performed demand selection and forced-choice tasks for which they read either one rotated or two upright words. We analyze results in terms of choice, accuracy, vocal onset time, and task duration. Participants still generally considered reading two words as less effortful (and preferable) to one rotated word but, interestingly, this tendency diminished as the task wore on. We discuss implications for understanding individuals’ effort-based choices.

Motivation

The BioTIME database contains raw data on species identities and abundances in ecological assemblages through time. These data enable users to calculate temporal trends in biodiversity within and amongst assemblages using a broad range of metrics. BioTIME is being developed as a community-led open-source database of biodiversity time series. Our goal is to accelerate and facilitate quantitative analysis of temporal patterns of biodiversity in the Anthropocene.

Main types of variables included

The database contains 8,777,413 species abundance records, from assemblages consistently sampled for a minimum of 2 years, which need not necessarily be consecutive. In addition, the database contains metadata relating to sampling methodology and contextual information about each record.

Spatial location and grain

BioTIME is a global database of 547,161 unique sampling locations spanning the marine, freshwater and terrestrial realms. Grain size varies across datasets from 0.0000000158 km² (158 cm²) to 100 km² (1,000,000,000,000 cm²).

Time period and grain

BioTIME records span from 1874 to 2016. The minimal temporal grain across all datasets in BioTIME is a year.

Major taxa and level of measurement

BioTIME includes data from 44,440 species across the plant and animal kingdoms, ranging from plants, plankton and terrestrial invertebrates to small and large vertebrates.

Software format

.csv and .SQL.