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Fig. 2 Gabra1−/− fish undergo evident generalized seizures upon light. A, Distance swam over 8 hours in the dark (left) or light (right) by 5 weeks postfertilization (wpf) gabra1+/− or −/− juveniles revealed significant hypoactivity of gabra1−/− compared to their heterozygous siblings (sib) in both light (t test, P < 0.03) and dark cycles (t test, P < 0.003). B, Measurements of the distance swam per 30‐second period after light was turned on revealed a strong increase of 5.5 wpf gabra1−/− motility just after light was turned on and followed by a period of immobility. C, Video frames of juvenile (5‐6 wpf) gabra1+/+ (top), +/− (middle), and −/− (bottom) siblings upon light exposure. Immediately after light, gabra1−/− fish underwent a first tonic‐like phase characterized by arching of the body (arrows), uncontrolled twitching (as seen with the red tracks), and loss of posture (arrowheads). After this first phase, which lasted a few seconds, gabra1−/− fish underwent a second, clonic‐like phase, during which they underwent rapid and uncontrolled movements, fast muscle contractions, and whole‐body convulsions leading to a whirlpool swimming pattern (tracks in red). Lastly, after about 1 minute of seizure, they entered a third, postictal phase, during which they stayed immobile and breathed heavily for 3‐10 minutes. D, E, Maximum acceleration upon light of 4 days postfertilization (dpf) gabra1 embryos (n = 96) showing an increased startle response to light of gabra1−/− specifically. Tracks of 3 seconds following light exposure show a stereotyped pattern of +/+ (left), +/− (middle), and −/− (right) light response