Sensory constraints on birdsong syntax: neural responses to swamp sparrow songs with accelerated trill rates

► We consider that sensory constraints may shape the emergence of novel song syntax. ► Auditory activity of sensorimotor neurons follows trills presented at normal rates. ► Gaps in neural responses emerge when trills are presented at accelerated rates. ► The 'flickering' suggests a mechanism for the development of 'broken song syntax'.