We study neuroscience because we want to understand our own minds and behaviours. Behaviour is therefore of fundamental importance in neuroscience research: As exciting and powerful our new techniques for observing and manipulating the nervous system, the neurotech is only as good as the behaviour, because it is the neural basis of the behaviour that we are using the techniques to try to understand.
C2C seeks to set an example of adhering to the highest standards of behaviour. A number of strategic desirables for behaviour follow from this principle:
C2C is based on a number of values shared by researchers in the consortium
HIGH STANDARDS FOR BEHAVIOUR
- Reproducible and accurate behaviour. The major behavioural approach taken by C2C is touchscreen testing using mice. Touchscreen testing systems have standardised behavioural protocols that are under the control of a computer system, allowing for increased standardisation of outcomes. Furthermore, the automation of high-level cognitive testing can provide significant reductions in experimenter and environmental influence, by providing a standard operant environment and standardised output file formats (Horner et al., 2013; Mar et al., 2013). The consistency of this method has been demonstrated to achieve more accurate, efficient, and reproducible phenotyping of mice across laboratories, in addition to providing higher throughput than standard methods (Beraldo et al., 2019).
- Non-aversive methodology. C2C adheres to the principle that unnecessary stress as a feature of a cognitive test is best avoided. Stress can interfere with experimental manipulations, and can have strong modulatory effects on cognition (Joels and Baram, 2009). Furthermore, stressful methods often model aspects of cognition that are rarely experienced by humans (e.g., fear conditioning, which assesses extreme fear of a specific place that can be caused by a single exposure). Moreover, while cognition is being assessed in such methods, the mouse is in a state of extreme physiological stress, and so does not model the normal physiological state of humans, or even other mice. This approach extends to the study of freely-moving animals. Levels of the stress hormone corticosterone increase ten-fold during the head-fixed method, and the difference in corticosterone levels between head-fixed and control animals persist longer than 60 days (Juczewski et al., 2020). Instead of this approach, C2C uses approaches such as miniscopes and fibre photometry which allow the study of cells and circuits in freely-moving animals. This approach yields more information than head-fixed methods without the major confound of major stress.
- Translational behaviour. Many of the major methods used in behavioural neuroscience do not easily translate to humans. In contrast, a major impetus behind the development of the touchscreen approach is translation, by testing animals in the same way as we test humans in experimental and clinical settings. Indeed a number of studies now feature rodents and humans tested on identical tests (refs). There are now over 30 touchscreen tests available for mice that tap into disease-relevant aspects of high-level cognition including attention, memory, executive function and motivation. This allows the use of a test-panel approach, similar to touchscreen test panels for humans, in which all tests use the same types of stimuli, responses, and feedback, facilitating comparison between tests and generating a cognitive profile of the subject. C2C takes the powerful approach of combining this flexible cognitive testing platform with molecular, circuit, and cognitive levels of analysis, in a way that is directly relevant to human patients.
FOCUS ON CIRCUITS
Structures in the brain do not work in isolation; this is why attempts to label regions of the brain as ‘the memory area’ or ‘the fear centre’ have met with such limited success. Furthermore, diseases of the brain are almost never easily understood and treated in terms of dysfunction in a specific brain structure. Instead it has become clear that understanding cognition and brain disease must involve enquiry at the level of molecules, cells, and especially circuits – including the coordinated effort of a number of brain areas in the service of cognition. It is therefore of great benefit to neuroscience that innovators have gifted us with a number of tools with which to study the brain circuits of cognition. These tools include miniscopes, fibre photometry, optogenetics, next-generation humanized mouse models, and DREADDs. Indeed these techniques allow us to manipulate and observe the nervous system in a cell-specific manner, including not just different neuronal sub-types but astrocytes, microglia and other cell types. We can also observe the dynamics of neurotransmitter release, including dopamine, acetylcholine and others. It is therefore the circuit level, using these tools to probe the nervous system at that level, that are at the centre of the activities of the C2C initiative.
OPEN SCIENCE: KNOWLEDGE AND DATA SHARING VIA A WORLD-WIDE EPISTEMIC COMMUNITY
C2C pushes forward cooperative, open science in several ways:
- Knowledge and data sharing. To encourage other researchers to adopt common methodology, and to increase replicability and reliability, we have created extensive resources that facilitate engagement in open knowledge-sharing of our expertise, platform developments and data, aligned with Canada’s Roadmap for Open Science:
- www.touchscreencognition.org serves as a central hub for state-of-the-art know-how about using touchscreen cognitive testing systems in combination with circuit-level techniques. This knowledge-sharing platform provides access to the latest publications, a forum for discussion, training videos and resources such as standard operating procedures (SOPs).
- www.mousebytes.ca is the first open science data repository for mouse cognitive and physiological data. This data sharing platform follows the FAIR principles of open science and has received support from and is being linked to the Brain Canada funded Canadian Open Neuroscience Platform (CONP) as well as Neuroscience Without Borders (NWB).
- Training. We have developed a 2-day on-site advanced training course on the use of touchscreens and circuit-level techniques. It was first offered in June 2019 and it received an overwhelming response—with participants from China, Australia, Brazil, USA, and Canada—such that we repeated the course to accommodate all requests for participation. Symposium participants contributed to a special issue of Genes, Brain and Behavior on touchscreens. Approximately 40% of attendees came from other centres, with international attendees hailing from 11 different countries.