Assessing attention in zebrafish (Danio rerio) through a modified version of novel object recognition test using two I-pods.

Even if some learning and memory tasks have been applied to zebrafish, their attentional ability has not been fully evaluated. The aim of the present work was to evaluate sustained attention in zebrafish using the virtual object recognition test (VORT) recently applied by us to mice (2). Secondly, to validate this task nicotine and two non-selective cholinergic drugs, were given i.p. Swimming activity was monitored to evaluate motor function. Fish were individually evaluated in three phases. After habituation, fish were subjected to an acquisition phase (T1) where two identical 2D shapes (circle, square or triangle) were presented on two I-pods widescreen displays attached to the opposite walls of the water tank. After a delay (from 5 min to 96 hours) one shape was replaced by a new one (T2). To evaluate the possibility that moving 2D shapes increased the attention of zebrafish, specific movements were applied to the same geometrical shapes. Zebrafish were able to discriminate different stationary 2D shapes. Notably, the discrimination of shapes, previously not discriminated, increased when they were moving. Treatment with nicotine (0.02 mg/kg) improved discrimination for stationary shapes previously not discriminated while scopolamine (0.025 mg/kg for zebrafish) and mecamylamine (1 mg/kg) impaired episodic memory. Taken together, these findings demonstrate that it is possible to study sustained attention in zebrafish and open a new avenue to rapidly screen the efficacy of pharmacotherapies for cognitive disorders.