Aim

To understand the role that posterior parietal cortex (PPC) and other cortical areas play in representing dynamic body posture, and to characterize how cortical networks integrate active sensing and posture during natural behavior.

Background

One of the ultimate goals of neuroscience is to link brain activity to behavior. As a complex organ, the brain offers no shortage of areas and sub-circuits to investigate. Likewise, a large repertoire of behaviors can be studied. While the Whitlock lab has chosen to investigate the specific link between rodent postural behavior (standing, rearing, reaching, etc.) to cortical brain activity, his team’s research provides a window into answering a larger question about how the brain computes and supports behavior in the first place.

Key Research Questions

• What role do the posterior parietal cortex (PPC) and linked cortical areas play in coding posture? 
• How do these networks represent different levels of behavior?
• How does the brain integrate postural signaling with other streams of information, like sensory input?

Tools & Methods

The Whitlock group uses several tools to tackle their research questions: (1) tracking and visualization software (developed in-house), which allow the reconstruction of a rat and its movement through three-dimensional space, (2) facial tracking, especially of the whiskers and eyes, and (3) large-scale electrophysiological recordings of the rat’s brain while it moves through that three-dimensional space. These rich series of information (behavior and neural activity) are then analyzed using a variety of statistical and visualization methods. The group has also undertaking anatomical work to define the PPC in mice, and developed anatomical reconstruction software to map out relevant neuroanatomy and to guide recording locations.

Research

The core line of work in the Whitlock group focusses on how higher-motor and sensory cortices encode 3D kinematics of the head and body in unrestrained rodents. The goal of this work in the lab is to build a foundational understanding of how cortex coordinates the movement of the body during natural behavior. Our first insights came neural recordings in the posterior parietal cortex (PPC) and frontal motor cortex (M2) in freely moving rats using a 3D tracking platform pioneered in the lab. We found that the majority of neurons were strongly driven by the posture of the head or trunk, and that body posture was encoded topographically over the cortical surface. With spiking activity from just a few dozen cells in PPC and M2, we found we could decode the ongoing posture of a freely foraging rat. More recent work has shown that posture and movement are read out with similar precision across numerous sensory and motor cortices, indicating that this may be a general feature of cortex when animals are free to move about. What’s intriguing is that visual and auditory cortices appeared to favor features that would enable them to localize visual or auditory stimuli during natural forms of movement—like running over a surface or tilting the head.

With this idea in mind, we have incorporated facial video recordings in our tracking platform. We are investigating how the deployment of the sense organs of the face (eyes and vibrissae) guide the head and body—both at the level of behavior and neurally—using Neuropixels recordings in associative (PPC) and sensory cortical areas simultaneously. Other projects in the lab are investigating how prefrontal cortex encodes natural behavior in rats, and how another associative area, the retrosplenial cortex, enables animals to predict the movement of a goal and move the body accordingly.