Working memory in the chick: parallel and lateralized mechanisms for encoding of object- and position-specific information

Working memory of chicks was probed in a delayed-response task, with either object- or position-specific information available in order to locate a goal that had disappeared behind one of two screens in a test arena. When the position of the correct screen was the only available cue (i.e., the two screens were identical) binocular and monocular chicks could easily locate the goal, and the same occurred when the visual characteristics of the screens (no matter what their spatial position) were the only relevant information available and when object- and position-specific cues were both available and in agreement (i.e., the two screens were different and maintained fixed spatial locations). In contrast, when object- and position-specific cues were available but were put in conflict (the two screens were different and were swapped during the delay time) left-eyed and binocular chicks went to the correct position, whereas right-eyed chicks seemed to choose both the correct spatial position and the correct object cue to the same degree. When during the delay the correct screen was substituted by an entirely novel screen, no left-right asymmetry associated with response to novelty was observed; monocular chicks preferentially approached the novel screen in the correct position, whereas binocular chicks did not show any clear choice. The results suggest that both object- and position-specific information is available to the two cerebral hemispheres in working memory tasks; however, when a conflict between cues arises, the right hemisphere preferentially attends to position-specific cues, whereas the left hemisphere tends to attend to object-specific cues.