Presented by Lyndon Woytuck

Top-down gain control of the auditory space Top-down gain control of the auditory space map by gaze control circuitry in the barn owlmap by gaze control circuitry in the barn owl

Daniel E. Winkowski & Eric I. Knudsen

Background

● High-level circuits in the brain that control gaze are linked with the control of visual spatial attention

● Just before gaze is directed to a stimulus, both Psychophysical sensitivity and neural responsiveness that represent the stimulus increase dramatically

● This has been replicated by focal electrical microstimulation of gaze control centres (FEF) in monkeys

● Can the gaze control system modulate neuronal responsiveness

– in the AGF of avians?

– of other sensory modalities?

Design

● Microstimulation of AGF to stimulate auditory gaze response (without eye movement)

● Single electrode in optic tectum to measure auditory response SOUND + ST [stimulation]

● In half trials, ST preceded SOUND

Tuning Shift in OT due to AGF StimulationBest ITD response changed from -16us to -12us

AGF microstimulation suppressed response when stimulus ITD near best ITD for OT

Best ITD response at 55 aligned pair sites increased 33% ave. (range 28-105%)

Tuning width at half-max decreased 16%

References

● diracdelta.co.uk● http://www.pnas.org/content/105/2/401/F4.expansion.html● http://www.diracdelta.co.uk/science/source/i/n/interaural

%20level%20difference/source.html

Conclusion

● AGF activation increases response gain for ITDs represented in AGF site, while suppressing responses to auditory stimuli at other locations in space

● Top-down enhancement of the representation of auditory stimuli from stimulus location selection by gaze control circuitry

● Similar to the induced modulations of visual responses observed in monkeys (linked directly to spatial attention) and visual response modulation of animals trained to direct spatial attention

● Really linked to spatial attention? - behavioural tests● Underlying mechanisms?

Conclusion

● AGF activation increases response gain for ITDs represented in AGF site, while suppressing responses to auditory stimuli at other locations in space

● Top-down enhancement of the representation of auditory stimuli from stimulus location selection by gaze control circuitry

● Similar to the induced modulations of visual responses observed in monkeys (linked directly to spatial attention) and visual response modulation of animals trained to direct spatial attention

● Really linked to spatial attention? - behavioural tests● Underlying mechanisms?