A mouse freely exploring a labyrinth where it can encounter tactile stimuli that will predict choices and rewards.
To make sense of the world around us, the brain must discriminate stimuli that are structured in space and time. Our group explores the principles that make this possible. Recent and ongoing work analyzes how different processing stages in a sensory pathway represent, use and transform information, leading from the raw physical signals that are sampled by sensory receptors to the elaborate stimulus features that underlie sensation, perception and prediction.
We work mainly on the neocortex or cerebral cortex, the sheet that forms the outer surface of the mammalian brain. Neural circuits in this area underpin perception, decision making and cognition. Diseases that perturb the normal establishment of cortical circuits, such as schizophrenia and autism spectrum disorders, often cause impairments in the transformation and integration of sensory information. Our experiments focus mainly on the part of sensory cortex that receives somatosensory (tactile) input from the whiskers, known as the “barrel cortex” for the particular shape of the clusters of neurons that constitute the first cortical stage for whisker processing.
Our work has highlighted how, in this part of sensory cortex, sensory responses mesh with neuronal activity reflecting an animal's upcoming actions and their consequences. Neurons in sensory cortex are involved in task-specific processing and – as a consequence – an animal does not, in effect, sense the world independently of what it needs to feel in order to guide behaviour. Instead, the sensations are deeply enmeshed in the task itself. These findings connect to ideas of predictive coding and with theories of embodied sensing, and these inform our thinking about the experiments we do to improve our understanding of "sensory" neuronal circuits and the responses they produce.
We use multiple experimental approaches and levels of description.
- We assess performance on sensory tasks in mice and in humans, allowing us to compare and benchmark animal and human capacities on analogous types of sensory discrimination.
- We measure neuronal responses using single-cell and population electrophysiological recording and two-photon fluorescence imaging in animals performing sensory tasks. We also manipulate responses using optogenetics.
- An important part of our work involves tailoring and applying new analytical tools to extract information from these data. We have applied methods of information theory, dimensional reduction and decoding to sensory responses in the whisker system and this has produced new insights into how neuronal populations process information.
We also enjoy collaborative projects that inform and enrich our perspective. Topics of recent collaborations have ranged widely, including the arrangement of neurons in the developing cortex (Oscar Marín, King's College London), human temporal perception (Warrick Roseboom, Βι¶ΉΣ³»), or the development of new open-source tools for neuroscience research and education (Andre Maia Chagas, Βι¶ΉΣ³»/PUC Campinas; and Tom Baden, Βι¶ΉΣ³»).
Diagram showing a mouse receiving sequences of vibrations presented to the whiskers (above), while the activity of neurons in its primary somatosensory “barrel” cortex is recorded using two-photon calcium imaging (below). Using these techniques we have shown that neurons in barrel cortex respond to variables beyond sensory information, including the animal's upcoming task-related actions (licking for a reward when the target sequence is perceived) and the outcomes of those actions. We have also shown that neuronal activity in barrel cortex is needed to perform the task. Bale et al, 2021.