Research Profile
June 2009
Principal Investigators: Ed Callaway, John Reynolds
Co-Investigators: Stephani Otte, Andrea Hasenstaub, Takuma Mori, Emily Anderson
Functional Consequences of the Attentional Enhancement of Gamma Oscillatory Activity
Isn’t it a wonder that in spite of nearly overwhelming quantities of information bombarding our sensory systems every minute of the day, we are able to reduce, condense, amalgamate it into a manageable flow and to focus on only what relates to whatever is our current task? And the big question is how do we selectively attend to one aspect of our environment and back-burner the rest?
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For starters there’s mounting evidence from both primate and human studies suggesting:
• That cortical neurons are able to synchronize their activity, producing brain rhythms at different frequencies.
• That these brain rhythms, particularly in the gamma frequency range (30-80 Hz), are instrumental in our selective attention.
• That disruption of gamma rhythms is a key marker for such serious cognitive and attentional maladies as bipolar disorder, schizophrenia and attention deficit hyperactivity disorder (ADHD).
It’s true that basic mechanisms underlying gamma frequency synchronization have been found to be the same in many species. What has not been understood is the way that the synchronization of these neurons affects their targets. How do changes, such as attentional enhancement in gamma activity, interact with small circuits or single cells to control input processing? And just what is it that makes these changes happen?
Now, taking advantage of the similarities across different species, a team of Salk Institute researchers that includes electrophysiologists, engineers, systems biologists and virologists is utilizing their Kavli Foundation award to study the functional and physiological consequences of gamma frequency spike synchronization of neurons in transgenic mice.
Making use of innovative genetic, viral and computational techniques, the collaborators aim to better understand the biological underpinnings of selection and attention. Using a real-time neuron/computer hybrid system to introduce controllable conductances into neurons, as well as targeted recordings of specific neuronal types, they have determined the differing ways that different types of neurons respond to gamma frequency synchronized inputs.
These techniques have led the group to discover systematic differences in the way distinct neuron types respond to changes in gamma frequency oscillatory synchrony and how changes in this synchrony change the neurons’ processing of input. Further, they have identified specific electrical properties that account for the differences.
Interestingly, during cortical activity these properties can quickly change, suggesting that the cortex may indeed make moment-to-moment adjustments in filtering input to fit moment-to-moment changes in functional needs --- such as what input to process and what to ignore.
Currently the team is creating viral tools to change the way that cells integrate gamma frequency inputs and to affect the emergence of gamma oscillations. Through this work they hope to uncover the role of these oscillations in attentional selection, in the long term potentially leading to treatments for attentional disorders in humans.
