Monday, January 26,  12:00 – 1:30 pm, in 489 Minor Hall

Graduate Student Seminar

presented by

Christina Gambacorta, PhD Candidate (Levi Lab)

An irreducible delay in manual and saccadic reaction time in amblyopia

It is well established that reaction times to stimuli are slower in the non-dominant eye of amblyopic observers (Mackensen, 1958; von Noorden, 1961). This delay, in both manual reaction times and in the initiation of a saccade, is highly correlated with the visual acuity of the amblyopic eye (Hamaski and Flynn, 1981). While an oculomotor origin for the delay has been largely ruled out (Ciuffreda et al, 1978; Ciuffreda et al, 1991; Niechwiej-Szwedo et al, 2010), it is possible this delay is sensory based, caused by a difference in effective stimulus strength of the targets between the two eyes.

Here, we measure saccadic and manual reaction times of normal and amblyopic observers to the abrupt appearance of a Gabor patch at 5 degrees to the left or right of fixation, varying the contrast of the patch. Even after adjusting for differences in effective stimulus strength, we find significant delays in both saccadic and manual response times while viewing with the amblyopic eye. This irreducible delay is greater in strabismic than in anisometropic amblyopes, and we speculate that it may be a consequence of an impaired ability to rapidly direct spatial attention with the amblyopic eye.

  and

Brent Parsons, PhD Candidate (Ivry Lab)

Temporal Constraints in Eye Movements
In order to survive we must continuously shift our gaze to bring prioritized regions of the world into central vision. The high-resolution fovea, and the saccadic eye movements it necessitates, imposes a fundamental bottleneck on the extraction and processing of visual information. To understand and model vision, therefore, we need to have some account of how gaze is allocated, both in terms of space and time. To date the majority of research on this topic has focused on the spatial rather than the temporal aspects of viewing behavior (Itti & Koch, 2001, Wolfe 2007). Such saliency models, based on low-level spatial properties of the external sensory input, make predictions about where to look in a scene but often fail to account for the temporal aspects of viewing behavior. Studies thus far have also generally ignored the tight temporal coupling between vision and action that is so fundamental to natural behavior. The experiments outlined in this presentation are designed to address these gaps in knowledge and provide behavioral and neural insight into the temporal constraints that guide the control of eye movements.

In order to survive we must continuously shift our gaze to bring prioritized regions of the world into central vision. The high-resolution fovea, and the saccadic eye movements it necessitates, imposes a fundamental bottleneck on the extraction and processing of visual information. To understand and model vision, therefore, we need to have some account of how gaze is allocated, both in terms of space and time. To date the majority of research on this topic has focused on the spatial rather than the temporal aspects of viewing behavior (Itti & Koch, 2001, Wolfe 2007). Such saliency models, based on low-level spatial properties of the external sensory input, make predictions about where to look in a scene but often fail to account for the temporal aspects of viewing behavior. Studies thus far have also generally ignored the tight temporal coupling between vision and action that is so fundamental to natural behavior. The experiments outlined in this presentation are designed to address these gaps in knowledge and provide behavioral and neural insight into the temporal constraints that guide the control of eye movements.

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