Discriminatory approach to auditory stimuli in Guinea fowl (Numida meleagris) after hyperstriatal/hippocampal brain...

Guinea fowl were trained to approach, feed and retreat from a food dish after hearing a species-specific food-trill. An ethogram including approach, search, locomotion and tension behaviour was recorded before and after operation for a training and a test regime of variations of the natural calls and other sounds. Experimental groups consisted of shamcontrols and birds with lesions in the hyperstriatum/hippocampus anterior and posterior to the anterior commissure. Both the 'anterior' and 'posterior' groups showed impaired recognition of the stimulus variations as shown by increases of approach by the posterior group and of search behaviour by both lesion groups. The long approach of the posterior group was followed by a long period of arousal (high tension). This was more quickly habituated in the anterior group (search behaviour changed to low tension). It is hypothesised that in the anterior group, where activation is followed by a disengagement, there may have been changes in thresholds for matching learned specifications with new sensory input. The more generalised approach responses of the posterior group may show an impairment of the rules for the selection of input.