Spatial choices of macaque monkeys based on the visual representation of the response space: rotation of the stimuli.

In earlier experiments we have demonstrated that macaque monkeys (Macaca mulatta) are able to use abstract visual stimuli presented on a computer screen to make spatial choices in the real environment. In those experiments a touch board ("response space") was directly connected to the computer screen ("virtual space"). The goal of the present experiment was to find out whether macaque monkeys are able: (1) To make spatial choices in a response space which is completely separated from the screen where the stimuli (designed as representation of the response space) are presented. (2) To make spatial choices based on visual stimuli representing the configuration of the response space which are rotated with respect to this response space. The monkeys were trained to choose one of the nine "touch holes" on a transparent touch panel situated beside a computer monitor on which the visual stimuli were presented. The visual stimuli were designed as an abstract representation of the response space: the rewarded position was shown as a bright circle situated at a certain position in the rectangle representing the contours of the touch panel. At first, the monkeys were trained with non-rotated spatial stimuli. After this initial training, the visual stimuli were gradually rotated by 20 degrees in each step. In the last phase, the stimulus was suddenly rotated in the opposite direction by 60 degrees in one step. The results of the experiment suggest that the monkeys are able to use successfully abstract stimuli from one spatial frame for spatial choices in another frame. Effective use of the stimuli after their rotation suggested that the monkeys perceived the stimuli as a representation of the configuration of the touch holes in the real space, not only as different geometrical patterns without configuration information.