Research Blog

Research Introduction and Some Published Research

Basal ganglia affect eye movements by modulating activity in other key nuclei, such as the superior colliculus in the midbrain (below), and the frontal eye field in the cortex.  As such, the cortex/basal ganglia/brainstem network in the brain is critical to influencing our behaviour.

These key brain regions for eye movement control contain neurons that are activated differently according to the behavioural condition.  This may contribute to our ability to flexibly tune our behaviour in the real world.

In the brain, neurons transmit information in pulses of electrical current ("spikes"). To visualize this, the electrical potential of single neurons in the brain can be recorded using a high-fidelity amplifier system. We can then calculate a binary "firing rate," which is simply the number of electrical spikes recorded per second, to represent information transfer in the brain.

We can correlate brain activity to a number of well-defined behavioural tasks, designed to emphasize or promote a particular action and/or type of processing in the brain:

For example, in the "pro-saccade" task (see below, BLUE), a subject must look toward a peripheral visual target.  Interestingly, in this task it has been shown that visual information (from the visual target) in the brain can be directly converted to a motor command to look toward the target.. without the need for a voluntary command.  To visualize this, imagine how you would behave if a cannon was fired behind you, right now.  We can reliably mimic this behaviour using this simple eye movement task in the lab.

In contrast, the "anti-saccade" task (see below, RED) is much more difficult.  Here, a subject must look 180 degrees away from a peripheral visual target when it is presented.  To do this, the subject must inhibit his or her reflex to look toward the visual target (see the "pro-saccade" task above).  We also use this ability in every-day behaviour.. any time when circumstances dictate that it is impolite or inadvisable to look at something.

Here is the activity of two sample populations of neurons in the superior colliculus, a critical structure for eye movement control.  As seen above, when a subject makes a fast eye movement ("saccade") toward a peripheral visual target (pro-saccade), neurons demonstrate higher activity than when a subject makes a saccade away from the peripheral visual target (anti-saccade). This is because 1) in the pro-saccade task, visual and motor activity are combining in the brain, 2) in the anti-saccade task, visual and motor signals are separated in the brain, and 3) we increase our brain inhibitory signals in the anti-saccade task to prevent an unwanted movement toward the visual target.