Main Research Lines
Our overall goal is to study how the brain encodes and processes information to give rise to our thoughts, perceptions, memories, feelings and even the awareness of ourselves. For this, we pursue an interdisciplinary research program based broadly around six research lines.
I - Human single cell recordings
In epileptic patients implanted with intracranial electrodes for clinical reasons, we study multiple single neurons and local field potentials while the patients do different tasks. With this clinical setup we found a new type of neuron, the so-called “concept cells” (a.k.a. “Jennifer Aniston neurons”) that respond to the identity of a given individual, disregarding visual details. For example, one neuron responded to different pictures of Jennifer Aniston, but not to other persons, objects, etc. These neurons also responded to the written or spoken name of the particular person and not to other names. We argue that these neurons represent concepts for creating and recalling declarative memories and we perform experiments to show how exactly this is done.
II - Modeling and Analysis of Neural data
Key neuroscience questions rely on the optimal analysis of neural data. For this, we develop and use advanced methods of signal processing, especially for the analysis of large-scale neurophysiological recordings. In particular, we developed an automatic “spike sorting” algorithm (Wave_clus) for identifying the activity of single neurons from extracellular recordings, which is currently used by several neurophysiology laboratories world-wide. We are also working on a low-power on-chip implementation of the algorithm for wireless transmission to external devices. Although we already got excellent results with the current algorithm, we are always trying further optimisations. Given that there is no ground truth with real recordings, we also work on realistic simulations of extracellular recordings (NeuroCube) to test algorithms and electrode designs. Another related line of research involves extracting information from neural populations. For this we use machine learning (decoding algorithms) and information theory. In general, our goal is to identify as many neurons as possible and extract as much information as possible from neural recordings.
III – EEG and Eye-Tracking
We use EEG and Eye-Tracker recordings to study visual perception. In this respect, we have been pushing two paradigm shifts. First, whereas the standard approach is to average several presentations and then study ensemble averages, we developed a method based on the wavelet transform, EP_den, to study single-trial evoked responses (responses in the ongoing EEG to stimulation). The main advantage of single-trial analyses is that we can study trial-by-trial variations and correlate these to perception and learning processes. Second, whereas the classic approach is to flash stimuli at the centre of the screen (where subjects are required to fixate), we combine EEG and Eye-Tracking recordings to study visual responses while subjects move their eyes, freely exploring complex scenes. Using Eye-Tracking information we can analyse the timing of different fixations and study evoked response in much more natural conditions.
IV – Neuroprosthetics
Paralysed patients (or amputees) can have the will to, for example, reach to a particular object, but are not able to execute the movement. The idea of neuroprosthetics is to develop brain-machine-interfaces to drive external devices, such as a robot arm, directly from brain signals. With this application in mind, we study different strategies to reach at objects using real or simulated brain and eye-tracking signals.
V – Art and Science
Historically, there has been very little interaction between arts and science, but clearly artists and neuroscientists have complementary knowledge and expertise about perception and behaviour. Our goal is to create links between science and arts to study how we perceive, remember, attend, make decisions, etc. On the one hand, we aim to bring scientific methodologies, like Eye-Tracking recordings, to museums and art galleries in order to study art perception in its natural environment. On the other hand, we seek interactions with painters, writers or magicians, among other artists, to get new insights into visual perception, decision making and memory processes. As a result of this interaction we have had an Art and Science exhibition at the Embrace Arts gallery in Leicester (“The art of visual perception”) and have organised a minisymposium about science and magic (“The Neuroscience of Magic”).
VI – Electrophysiology and 2-photon imaging recordings
We have recently started work on an animal model of concept cells to perform both electrophysiology and 2-photon imaging recordings in the mouse hippocampus, while the animals navigate in a virtual reality environment. The goal is to compare concept representations in mice with those we have found in humans and to extend the studies in humans by having recordings of larger number of neurons, in different areas and at different stages of concept formation.