The Neural Population Imaging Group focuses on understanding the principles underlying neuronal activity during decision making and object perception in behaving rodents.
The goal of our research is to understand how rodents use their vision to make decisions during free behavior and the underlying principles of the neural circuits involved in this process. Motivation underlies the performance of self-determined behavior and is fundamental to decision making, especially with regard to seeking food, mates, and avoiding peril. As many decision making based behaviors in rodents involve a combination of head movements, vestibular driven eye movements, vestibular driven cortical activity and active sensing of the environment to guide their behavior, studying the freely moving animal is of great advantage. The network imaging group focuses on recording activity from neural circuits activated during decision making in the freely moving rodent. To achieve this aim we have taken a multidisciplinary approach that has centered around using and developing Opens internal link in current Opens internal link in current windowmultiphoton imaging techniques, eye and head tracking techniques, computational approaches, and behavioral paradigms to record from Opens internal link in current Opens internal link in current windowneuronal populations in the trained and freely moving animal. What this has afforded is measuring spatiotemporal organization of activity from populations of neurons during decision making in the freely moving animal, and the precise behavioral strategies that underlie this behavior.
With the aim of using multiphoton imaging in freely moving and behaving animals, we developed in collaboration with Winfried Denk (MPI for Medical Research, Heidelberg) a miniaturized microscope small enough to be carried on the head of a freely moving rat.
This microscope, or fiberscope, has all of the features of a conventional 2-photon microscope, and can accurately measure activity from populations of neurons in the visual cortex of a freely behaving animal for extended periods of time.
We have now added to this the capacity to track the position and orientation of the animals head and simultaneously image the high-speed movements of both eyes during these recordings, and have shown that the range and independence of eye movements in freely moving rats is far greater than previously documented.
Imaging in awake
Imaging activity from neuronal populations using a combination of multi-photon imaging, targeted electrophysiology, and calcium indicators affords several advantages over traditional activity recording techniques.
Multi-photon imaging of neuronal activity, not only provides spatial resolution and morphological identification, but also spike activity detection in all neurons within the imaging area, even those that respond at low rates or respond infrequently. This allows both a complete picture to be formed of the local circuit and quantification of higher-order statistics across the population. Population imaging allows the simultaneous mapping of the receptive-fields of many identified neurons and, even more importantly, the detection of activity correlations in neuronal activity that can be related back to spatial location and cell type. The development of genetically encoded calcium indicators (GECIs) allows the same neuronal populations to be imaged over months during the learning process.