In birds, the entopallium is the primary telencephalic target of themajor visual ascending route called the tectofugal pathway. Oftenfunctionally compared to the primate geniculo-striate pathway andits subsequent telencephalic (cortical) regions, the latter processes visualinformation in a parallel fashion in terms of anatomy, physiology,and function. Little is known, however, about the exact mechanismof whether or how information is segregated or integrated inthe avian tectofugal pathway including the telencephalon. Testingfour pigeons, we examined whether or not color, form, and motioninformation is selectively processed by different portions of the entopallium.Each learned three distinct visual tasks requiring discriminationof different combinations of color, form and motion cues. Afterlearning and pre-lesion testing, two pigeons received lesions to theanterior portion of the entopallium and two received lesions to theposterior entopallium. During post-lesion testing the pigeons with anteriorlesions exhibited significant deficits in those tasks most dependenton color and form discrimination, but showed no deficit on atask that had involved discriminating among forms that were moving.Pigeons with posterior lesions showed a different pattern of deficits,exhibiting significant reductions in discriminating both movingand static forms, but little or no deficits in color discrimination.These divergent profiles of effects for each lesion suggest there is afunctional segregation of visual information processing in the pigeontelencephalon. This indicates a convergence between birds and primatesregarding the parallel processing and separation of informationwithin their phylogenetically distinct major visual pathways.
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