A área de transição amígdalo-piriforme (APir) está situada na confluência dos córtices piriforme, periamigdalóide e entorrinal lateral (ENTl). Com técnicas de rastreamento retrógrado foi observado que as principais aferências da APir se originam do bulbo olfativo, dos córtices piriforme, insular disgranular e agranular posterior, perirrinal, da formação hipocampal e da amígdala. Outras estruturas como o núcleo da banda diagonal de Broca, o pálido ventral, a substância inominada sublenticular, o tálamo da linha média, o núcleo dorsal da rafe, o locus coeruleus e a área parabraquial são fontes de aferências mais modestas a esta área de transição. A APir e o ENTl diferem no que diz respeito à origem de suas aferências mesocorticais, amigdalianas e talâmicas. Assim, a APir está em condições de integrar informações olfativas, gustativas, interoceptivas gerais e polissensoriais complexas e, através de suas projeções para a amígdala expandida, striatum ventral e formação hipocampal, influenciar a expressão de comportamentos motivados.

The amygdalo-piriform transition area (APir) lies at the junction of the piriform, periamygdaloid and entorhinal cortices. The afferent connections of this olfactory district were studied with retrograde tracing methods using the cholera toxin B subunit and Fluoro-Gold as tracers. Our retrograde experiments showed that the main input sources to APir derive from the olfactory bulb, mesocortical and allocortical areas including the dysgranular insular, posterior part of the agranular insular, piriform, lateral entorhinal and perirhinal cortices, temporal field CA1 of Ammon horn, ventral subiculum, as well as the endopiriform nucleus and the amygdaloid complex (anterior basomedial, posterior basolateral and anterior, posterolateral, posteromedial cortical nuclei). Several other structures among which the diagonal band, ventral pallidum, sublenticular substantia inominatta, midline thalamic nuclei, dorsal raphe nucleus, locus coeruleus and parabrachial area provide more modest inputs to APir. Our results suggest in addition that projections from mesocortical areas, hippocampal formation and the posterior basolateral amygdaloid nucleus to APir are topographically organized. Fluoro-Gold injections in the ventrolateral entorhinal cortex indicate that the afferent connections of this district differ in many regards from the afferent connections of APir. Cortical and amygdaloid inputs suggest tha APir is chiefly involved in the processing of olfactory, gustatory, visceral and somesthesic information, whereas the ventrolateral entorhinal cortex seems to be more crucially related with visual and auditory processes. APir is also less densely projected upon by midline thalamic nuclei than the lateral entorhinal cortex. Taken as a whole our results suggest that APir is in position to relay highly integrated olfactory, gustatory, interoceptive and somesthesic information to the extended amygdala, ventral striatum and ventral subiculum, and as such modulate the expression of motivated and emotional behavior.