While some of the ideas pursued in the
Active Perception Laboratory
have a long history,
their importance in visual perception has become apparent and susceptible
to precise experimental analysis only recently.
As researchers in the Active Perception Laboratory
approached these research questions, an important obstacle to testing theoretical
predictions was the incapability of precisely controlling retinal image motion
during natural fixation. Traditional systems came with major technical limitations.
For example, available techniques for retinal stabilization gave no access
to the quality of the manipulation, which critically depended on how the subject
executed complicated calibration procedures.
An important component of work in the Active Perception Laboratory
the development of new tools and techniques for better measuring eye movements
and manipulating visual input signals. Most notably, we have:
- Developed a general-purpose system for gaze-contingent control display,
which has opened the way to experiments not feasible with previous methods (Santini et al, 2007, read more).
- Implemented new techniques for localizing the line of sight, which provide a precision improvement
of more than one order of magnitude over standard methods (Poletti et al, 2013; supplemental material).
Use of these methods has led to a new understanding of the functions of ocular
- Developed a new system for recording microscopic head movements (Aytekin and Rucci, 2012). Use of this
system has shown that even small fixational head movements contribute significant depth information in the space nearby the observer.This system has been integrated with Virtual Reality googles.
- We are currently working on the development of two high-resolution eye-trackers, a video-based digital Dual Purkinje Image system, and a redesigned coil system
for high-precision head-free measurements.
The Active Perception Laboratory is equipped with extensive computational
and experimental facilities. Some of the tools present in the laboratory are listed below.
An ActiveTwo EEG with 64 active electrodes (Biosemi) with a Polhemus 3D digitizer for source localization. The EEG system is interfaced with EyeRIS, our system for gaze contingent display control.
is a binocular pan/tilt system specifically designed to replicate human eye movements.
Two mobile cameras, each with two degrees of freedom, are controlled by microprocessors with high spatial
and temporal resolutions. The spatial precision of movement is higher than 1 arcmin.
Cameras provide input to a high-performance frame grabber with real-time image processing capabilities.
Mr. T is the latest version of a humanoid platform, built as part of our
ongoing effort of coupling computational models of the brain with behaving automata.
Like J5, the head/eye system of this robot was designed to replicate the visual input signals
to the retina. This system is the result of trade-off considerations between velocity and precision,
in order to accurately replicate retinal image motion during fast macroscopic saccades and during
fixational eye movements.
Mr. T is equipped with two anthropomorphic arms, each with 5 degrees of freedom.
for Mr. T's birth photo gallery.
The Active Perception Laboratory possesses extensive psychophysical facilities, which include the following:
- A Binocular Generation 6 Dual Purkinje Image (DPI) eyetracker (by
Fourward Technologies), a device that allows measurement of eye movement with high spatial and temporal resolution.
- Dedicated video hardware for the generation and real-time manipulation of visual stimuli,
including a (VSG2/5 board
by Cambridge Research Systems).
- Dedicated computers and high-quality monitors for stimulus display.
- EyeRIS (Eye movement Real-time Integrated System), a in-house developed system for
gaze-contingent display control. This hardware and software system allows flexible real-time modification
of the stimulus according to subject's eye movements with refresh rates up to 200Hz.
page for details.
- A stimulus deflector, an optico-electronic device for retinal stabilization. This system uses a set of mirrors
to translate the image according to the subject's eye movements and maintain the stimulus at a fixed location on the retina.
Eye Coil system
A Revolving Field Monitor to record eye movements and head movements with high resolution.
Virtual reality googles
An Oculus VR (SDK1) for experiments involving a 3D virtual environment.
A PhaseSpace Motion Capture system for high resolution head-tracking.