Windows to the soul – Eye tracking and the brain

As a researcher or clinician, you need to analyze how we process visual information in different situations. Eye tracking improves the effectiveness and verifiability of studies by filtering out trials where the subjects failed to see the stimulus, or to comply with the task. It can also improve the efficiency of many studies, since there is less statistical noise, leading to fewer subjects needed and thus faster results. In certain studies, eye tracking aids in filtering out those parts of the recording where eye movements created artifacts in the signal, which streamlines the analysis.

SMI Eye Tracking can also be connected with leading partner solutions, e.g. biometric systems (EEG, NIRS, GSR, HR) for a broad range of applications.

SMI provides various eye tracking solutions in the neurosciences where the camera can be head or desk-mounted, or use a Hi-Speed camera mounted in a chin-rest, or even an fMRI or MEG compatible camera. SMI systems are available with portable, high-speed and remote options. They are suitable for a wide range of research areas, including:

  • fMRI
  • MEG
  • EEG
  • Pupillometry
  • Neuro-ophthalmology
  • Neuro-degenerative diseases

Clinical research demands efficiency, such that time-consuming and complex processes are automated, while new equipment is fully compatible and thus easily and quickly integrated. Eye tracking systems need to ensure accurate measurements, integrate powerful analysis functions, and maximize patient comfort.

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Case Studies

Use of Eye Trackers combined with fMRI while studying brain functions

The Laboratory of Brain and Cognition at the National Institute of Mental Health, Bethesda, USA, is studying the brain functions involved in perceptual decision making. The researchers want to find out how the decision is subsequently transformed into a motor action and whether or not the decision is represented at an abstract level.

To address this issue, the researchers used fMRI to monitor changes in brain activity while human subjects discriminated the direction of motion in random-dot visual stimuli that varied in coherence and responded with either button presses or saccadic eye movements. The researchers hypothesized that areas representing decision variables should respond more to high- than to low-coherence stimuli independent of the motor system used to express a decision. Eye movements were recorded from the right eye by using the iView X™ MRI-SV eye-tracking system that was integrated into the goggle-based fiber optic projection system from Avotec Inc.

Overview Case Studies

Eyetracking in the fMRI scanner to present and track visual stimuli

The MRC Institute of Hearing Research is studying the brain networks involved in covert spatial orienting of attention across visual and auditory modalities using an fMRI scanner in the Sir Peter Mansfield Magnetic Resonance Centre at the University of Nottingham, UK.

Participants are tested in an fMRI scanner in order to measure which brain areas are activated by shifts in attention. However, saccadic eye movements can activate the same brain areas so it is essential that participants maintain fixation throughout the experiment.

The IHR uses the iView X™ MRI-SV to monitor eye movements in the scanner, and to present visual stimuli to the participant. The iView X™ RED remote system is also used to run the same experiments outside the scanner. An Ethernet link synchronizes eye-movement data with fMRI data and stimulus presentation, and BeGaze is used to automatically detect when participants move their eyes so as to ensure these subjects are removed from fMRI analysis.