If you have no existing image object in your axes, then you need to use image() to create the image object. imagesc() and imshow() call upon image() to create the image object.
If you have an existing image object, then you can change which image it shows by updating the CData property of the image object. For example,
im1 = image(rand(65,65));
pause(3);
set(im1, 'CData', rand(32, 96));
pause(3)
will draw an image, leave it for 3 seconds, and then update the image object with new data.
If the CData property associated with an image object is a scalar or a vector or is 2 dimensional, then the current colormap() will be used to determine the colors the image object is displayed with. If the CData property associated with the image object is a 3D matrix in which the third dimension is length 3 (an M x N x 3 array), then the CData will be interpreted as RGB color information and the colormap() will not be used for that image object.
