The brain’s left hemisphere contains frontal, temporal, and parietal nodes in a distributed network that is critical to the representation and selection of skilled tool actions. This contrasts with a bilateral network controlling actions to currently-visualized objects. In three decades of research in individuals with stroke and neurotypical individuals, our research using lesion-symptom mapping, resting-state functional connectivity, and fMRI is helping to clarify the functions and connections of these two action systems.

Because not all activated sensory or cognitive information can be selected for further processing or for motor output, competition is a fundamental mechanism used by the brain to winnow down alternatives, biased by task goals. Our research in the Cognition and Action Laboratory sheds light on the specific features of objects and actions that make them competitive with one another, how disruption in competitive selection processes affects behavior after stroke or in degenerative disorders, and how these representations can be strengthened to improve competitive selection and overt performance.

Concepts of manipulable objects (tools) are distributed representations with specific linked features – such as the shape and movements of the hand for using the tool – that are activated (or not) depending upon context and goals. Our research clarifies how activation of tool concepts differs as a function of the surrounding world (e.g., competitor objects) task demands, and intentions. This research enables us to understand how tasks can be structured to improve the activation of concepts, thereby facilitating performance.

The brain encodes representations of the body as well as surrounding space in relation to the body. After stroke or limb amputation, damage to these representations can markedly influence behavior and functioning. A frequently-observed disorder after stroke to the brain’s right hemisphere is spatial neglect, characterized by reduced awareness of the body and space on the left. A common consequence of limb amputation is phantom limb syndrome, often accompanied by pain. Our research in these domains has resulted in a number of reliable clinical assessment tools, and it explores how neural plasticity can be harnessed by providing augmented and virtual feedback to reduce pain.

Gesture is an important aspect of communication: when we speak, we often gesture. Language and tool-use are both strongly lateralized to the brain’s left hemisphere. Not surprisingly, language disorders (aphasia) and disorders of skilled action (apraxia) frequently co-occur in stroke and neurodegenerative disorders. Despite this fact, there is little research that has considered the role of apraxia in gestural communication. Our research in the Cognition and Action Lab is assessing how – and in whom – gestures may facilitate language comprehension and production in experimental and naturalistic tasks.