Ultrastructural and optogenetic dissection of V1 corticotectal terminal synaptic properties.

The superior colliculus (SC) is a major site of sensorimotor integration in which sensory inputs are processed to initiate appropriate motor responses. Projections from the primary visual cortex (V1) to the SC have been shown to exert a substantial influence on visually induced behavior, including "freezing." However, it is unclear how V1 corticotectal terminals affect SC circuits to mediate these effects. To investigate this, we used anatomical and optogenetic techniques to examine the synaptic properties of V1 corticotectal terminals. Electron microscopy revealed that V1 corticotectal terminals labeled by anterograde transport primarily synapse (93%) on dendrites that do not contain gamma aminobutyric acid (GABA). This preference was confirmed using optogenetic techniques to photoactivate V1 corticotectal terminals in slices of the SC maintained in vitro. In a mouse line in which GABAergic SC interneurons express green fluorescent protein (GFP), few GFP-labeled cells (11%) responded to activation of corticotectal terminals. In contrast, 67% of non-GABAergic cells responded to activation of V1 corticotectal terminals. Biocytin-labeling of recorded neurons revealed that wide-field vertical (WFV) and non-WFV cells were activated by V1 corticotectal inputs. However, WFV cells were activated in the most uniform manner; 85% of these cells responded with excitatory postsynaptic potentials (EPSPs) that maintained stable amplitudes when activated with light trains at 1-20 Hz. In contrast, in the majority of non-WFV cells, the amplitude of evoked EPSPs varied across trials. Our results suggest that V1 corticotectal projections may initiate freezing behavior via uniform activation of the WFV cells, which project to the pulvinar nucleus.

Learning chronobiology by improving Wikipedia.

Although chronobiology is of growing interest to scientists, physicians, and the general public, access to recent discoveries and historical perspectives is limited. Wikipedia is an online, user-written encyclopedia that could enhance public access to current understanding in chronobiology. However, Wikipedia is lacking important information and is not universally trusted. Here, 46 students in a university course edited Wikipedia to enhance public access to important discoveries in chronobiology. Students worked for an average of 9 h each to evaluate the primary literature and available Wikipedia information, nominated sites for editing, and, after voting, edited the 15 Wikipedia pages they determined to be highest priorities. This assignment (http://www.nslc.wustl.edu/courses/Bio4030/wikipedia_project.html) was easy to implement, required relatively short time commitments from the professor and students, and had measurable impacts on Wikipedia and the students. Students created 3 new Wikipedia sites, edited 12 additional sites, and cited 347 peer-reviewed articles. The targeted sites all became top hits in online search engines. Because their writing was and will be read by a worldwide audience, students found the experience rewarding. Students reported significantly increased comfort with reading, critiquing, and summarizing primary literature and benefited from seeing their work edited by other scientists and editors of Wikipedia. We conclude that, in a short project, students can assist in making chronobiology widely accessible and learn from the editorial process.