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John H. Reynolds

 

John H. Reynolds

John H. Reynolds

Associate Professor
Systems Neurobiology Laboratory

"The long-range goal of our laboratory is to understand the neural mechanisms of selective visual attention at the level of the individual neuron and the cortical circuit, and to relate these to perception and conscious awareness."

Every kid knows that moms have "eyes in the back of their heads." We are adept at fixing our gaze on one object while independently directing attention to others. John Reynolds and his team are beginning to tease apart the complex brain networks that enable humans and other higher mammals to achieve this feat. In their latest study, animals learned how to play a sophisticated video game, which challenged their visual attention-focusing skills. During the game, the researchers recorded electrical activity from individual neurons in the part of the visual cortex that has been implicated in mediating visual attention. These neurons change their firing rate when a stimulus appears within their "receptive field"—a window encompassing a small part of the visual field.

Reynolds and his team found that neurons typically responded more strongly when attention was directed to the stimulus in their receptive fields. Upon closer inspection, however, the researchers noticed that different neurons produced different shaped electrical spikes: "broad spikes" and "narrow spikes." Other researchers had previously identified two different types of neurons that produce these two waveforms. The most common neuron type, called a pyramidal cell, produces broad spikes and transmits signals between different brain areas. The other class, a fast-spike interneuron, evokes narrow spikes and is involved in local computations.

After sorting the neurons by waveform, the researchers observed that attention had different effects on the two different types of neurons. The narrow-spiking cells typically fired more frequently when the tracked object was attended than when it was unattended. Broadspiking cells, on the other hand, were less influenced by attention. Some fired faster, while others fired more slowly when attention was directed to the stimulus in the receptive field, making it the first study ever to show functional differences across different classes of neurons in the cortex while a specific task was performed.

This research provides a novel and important understanding of how the different components of the cortical "circuit" mediate attention. This is a significant step forward in understanding the neural mechanisms that fail in neurological diseases where attention is impaired.

Lab Photo

Left to right:
John Reynolds, John Curtis, Emily Anderson, Tamara Berdyyeva, Jaclyn Reyes, Catherine Williams, Jude Mitchell

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John H. Reynolds

Faculty

John H. Reynolds

John H. Reynolds

Associate Professor
Systems Neurobiology Laboratory

The long-range goal of our laboratory is to understand the neural mechanisms of selective visual attention at the level of the individual neuron and the cortical circuit, and to relate these to perception and conscious awareness. We take as our starting point the observation that the brain is limited in the amount of visual information it can process at any moment in time. For instance, when people are asked to identify the objects in a briefly presented scene, they become less accurate as the number of objects increases. This inability to process more than a few objects at a time reflects the limited capacity of some stage (or stages) of sensory processing, decision-making, or behavioral control. Somewhere between stimulating the retina and generating a behavioral response, objects compete with one another to pass through this computational bottleneck. We seek to understand this selection process using a combination of visual psychophysics, neurophysiology, and computational neural modeling.

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