visual perception is done in loops

Current Theoretical Understanding

The hypothesis of closed-loop perception (CLP)

In our current working hypothesis the perception of external objects is a closed-loop dynamical  process encompassing loops that integrate the organism and its environment and converging towards organism-environment steady-states. We call this process closed-loop perception (CLP).

Encoding principles of active vibrissal touch

Encoding of Active Touch

Using this technique, we found that the signals sent to the brain by the whiskers during active touch differ from those transmitted during passive touch.

Encoding of Location

Using the same technique we studied the neural codes used by vibrissal receptors to encode the coordinates of object location in three dimensions.


We examined the ability of rats to resolve horizontal object location and its dependence on whisker configuration and whisking parameters.

On-going computation of whisking phase by mechanoreceptors

In order to attribute spatial meaning to sensory information, the state of the sensory organ must be represented in the nervous system.

Parallel vibrissal sensory processing

Parallel processing - passive touch

We have previously found that sensory information in the vibrissal system is not processed the same way along the two main afferent pathways of the vibrissal system (the lemniscal and paralemniscal). Whereas spatial information is processed primarily along the lemniscal pathway, temporal information is processed primarily along the paralemniscal pathway.

Parallel processing - active touch

Using artificial whisking in anesthetized rats, we discovered that the three classes of signals are carried to the thalamus by three separate afferent pathways: the paralemniscal convey whisking related signals, a newly discovered "extralemniscal" pathway (discovered by the group of Martin Deschênes) conveys touch related signals, and the lemniscal pathway conveys whisking/touch related signals.

Thalamocortical functions

Thalamocortical code conversion

Our studies revealed that thalamic “relay” nuclei are not mere relays. Rather, they process sensory information.

Thalamocortical coding

We examined the coding schemes occurring at the first forebrain level that receives inputs necessary for generating such internal representations – the thalamocortical network.

Pre-neuronal morphological coding

In the vibrissal system, touch information is conveyed by a receptor-less whisker hair to follicle mechanoreceptors, which then provide input to the brain. We examined whether any processing, i.e., meaningful transformation, occurs in the whisker itself.

State-dependent perceptual memory

State-dependent learning is a phenomenon in which the retrieval of newly acquired information is possible only if the subject is in the same sensory context and physiological state as during the encoding phase. In spite of extensive behavioural and pharmacological characterization, no cellular counterpart of this phenomenon has been reported.

Closed-loop processing

Closed-loop computation

Two classes of neuronal architectures dominate in the ongoing debate on the nature of computing by nervous systems. The first is a predominantly feedforward architecture, in which local interactions among neurons within each processing stage play a less influential role compared with the drive of the input to that stage. The second class is a recurrent network architecture, in which the local interactions among neighboring neurons dominate the dynamics of neuronal activity so that the input acts only to bias or seed the state of the network.

Fast feedback in active vibrissal touch

We studied the effects of touching an object on whisking in head-fixed rats. Simultaneous movements of whiskers C1, C2, and D1 were tracked bilaterally and their movements compared.

Motor-sensory adapation while perceiving object location

Tactile perception is obtained by coordinated motor-sensory processes. We studied the processes underlying the perception of object location in freely moving rats.

Modeling exploration via curiosity and novelty management

We analyzed exploratory behavioral data from two modalities: whisking and locomotion in rats and mice.

Muscle architecture serving active touch

The musculature of the rat mystacial pad was revealed by slicing the mystacial pad in four different planes, staining of mystacial pad slices for cytochrome oxidase, and tracking spatial organization of mystacial pad muscles in consecutive slices.

Human touch

Motor-sensory convergence in tactile perception

Perception involves motor closedloopcontrol of sensory organs. However, the dynamics underlying emergence of perception from motor-sensory interactions are not yet known.

Active temporal coding

While scanning a textured surface with fingers, tactile information is encoded both spatially, by differential activation of adjacent receptors, and temporally, by changes in receptor activation during movements of the fingers across the surface.

Human vision

Active vision

During natural viewing, the eyes are never still.  Even during fixation, miniature movements of the eyes move the retinal image across tens of foveal photoreceptors. Most theories of vision implicitly assume that the visual system ignores these movements and somehow overcomes the resulting smearing.

Functions of saccades and drifts

During natural viewing large saccades shift the visual gaze from one target to another every few hundreds of milliseconds. The role of microsaccades (MSs), small saccades that show up during long fixations, is still debated.

Synthetic Perception

Synthetic (robotic) vision

The SYCLOP perceiver

Our lab-developed robotic perceiver, the SYCLOP, is composed of an event-based camera (sensitive to luminance transitions in each pixel) that is installed on a mount with horizontal and vertical rotating motors, all integrated within a programmable closed loop system.