A behavioral assay to measure responsiveness of XXXX to changes in light intensities.

@entity64702 @entity71096 @entity735 @entity427 @entity3392
The optokinetic reflex (OKR) is a basic visual reflex exhibited by most vertebrates and plays an important role in stabilizing the eye relative to the visual scene. However, the OKR requires that an animal detect moving stripes and it is possible that fish that fail to exhibit an OKR may not be completely blind. One @entity3392 mutant, the @entity71096 ( @entity71096 ) has no OKR under any light conditions tested and was reported to be completely blind. Previously, we have shown that OFF-ganglion cell activity can be recorded in these mutants. To determine whether mutant fish with no OKR such as the @entity71096 mutant can detect simple light increments and decrements we developed the visual motor behavioral assay (VMR). In this assay, single @entity3392 larvae are placed in each well of a 96-well plate allowing the simultaneous monitoring of larvae using an automated video-tracking system. The locomotor responses of each larva to 30 minutes light ON and 30 minutes light OFF were recorded and quantified. WT fish have a brief spike of motor activity upon lights ON, known as the @entity427 response, followed by return to lower-than baseline activity, called a freeze. WT fish also sharply increase their locomotor activity immediately following lights OFF and only gradually (over several minutes) return to baseline locomotor activity. The @entity71096 mutants respond similarly to light OFF as WT fish, but exhibit a slight reduction in their average activity as compared to WT fish. Motor activity in response to light ON in @entity71096 mutants is delayed and sluggish. There is a slow rise time of the @entity71096 mutant response to light ON as compared to WT light ON response. The results indicate that @entity71096 fish are not completely blind. Because teleosts can detect light through non-retinal tissues, we confirmed that the immediate behavioral responses to light-intensity changes require intact eyes by using the chokh ( @entity64702 ) mutants, which completely lack eyes from the earliest stages of development. In our VMR assay, the @entity64702 mutants exhibit no @entity427 response to either light ON or OFF, showing that the @entity735 mediate this behavior. The VMR assay described here complements the well-established OKR assay, which does not test the ability of @entity3392 larvae to respond to changes in light intensities. Additionally, the automation of the VMR assay lends itself to high-throughput screening for defects in light-intensity driven visual responses.
