Like humans, animals that use acoustic stimuli to perceive their world ought to be able to parse the auditory scene into functionally significant sounds. The ability to do so ought to have significant adaptive value when, for example, an animal can identify the sounds of a predator among other natural noises. In earlier work it was shown that a species of songbird, the European starling, can identify excerpts of both its own song and songs from other avian species when the songs are mixed concurrently with other natural signals. In this experiment it is demonstrated that starlings can segregate two synthetic pure-tone sequences when the sequences differ in frequency. Taken together, the experiments show that at least one nonhuman species is capable of auditory scene analysis both for natural and for non-natural acoustic stimuli. This suggests in turn that auditory scene analysis may be a general perceptual process that occurs in many species that make use of acoustic information.

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Using lesions and infusions, the present study investigated the way in which and the extent to which the ventral hippocampus (vHIP) modulates amphetamine-induced hyperactivity in rats. Rats were lesioned (excitotoxic or sham) in the vHIP or were implanted with cannulae for subsequent infusions. A high dose (12.5 microg/microl) of N-methyl-D-aspartate (NMDA) was used to make excitotoxic lesions and a low dose (0.5 microg/microl) of NMDA to cause activation of the hippocampus. Lidocaine was used to inactivate the hippocampus. Lidocaine or a low dose of NMDA was infused into the vHIP in combination with either systemic injection or intra-accumbens infusions of amphetamine. The effects of these treatments on locomotor activity were measured by distance traveled in 10-min intervals for 40-60 min. Lesions and deactivation of the hippocampus attenuated amphetamine-induced hyperlocomotion, compared to the controls. Stimulation of the hippocampus augmented amphetamine-induced hyperlocomotion. The present findings provide evidence that the hippocampus exerts excitatory modulation on the expression of behavioral excitation produced by amphetamine, likely via the nucleus accumbens.