F brain ehavior relationships in birds will not be restricted to visual systems.The auditory technique

F brain ehavior relationships in birds will not be restricted to visual systems.The auditory technique has also been examined, in particular in owls because of their remarkable sound localization capacity, one of a kind morphological specializations, and rather sophisticated, adaptive neural circuitry (Schwartzkopff and Winter, Payne, Knudsen et al Knudsen, Takahashi et al Whitchurch and Takahashi, Takahashi,).A rather special function that sets some owls apart from other individuals with respect to sound localization could be the presence of vertically asymmetrical ears, which has evolved independently several occasions in owls (Norberg, , ).This vertical ear asymmetry is especially critical for localizing sounds in elevation.To localize sound, neurons inside the external nucleus with the inferior colliculus (ICx) from the midbrain are tuned to auditory space, but these neurons differ PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/21531787 in their receptive SANT-1 Biological Activity fields involving asymmetrically and symmetrically eared owls.In owls with vertically asymmetrical ears, these neurons have receptive fields which are restricted in each elevation and azimuth, whereas in owls with vertically symmetrical ears, they’re restricted only in azimuth (Knudsen et al Knudsen and Konishi, a,b; Sensible et al Volman and Konishi,).The tuning of both elevation and azimuth enables asymmetrically eared owls to accurately capture prey in complete darkness based solely on acoustic cues whereas symmetrically eared owls cannot (Payne,).In barn owls, the azimuthal and elevationalLack of Hypertrophy in the Tectofugal PathwayDespite the truth that the tectofugal pathway (TeO, nRt, E; see Figures A) is regarded because the “main” visual pathway and is definitely the major supply of visual input for the avian brain, there is relatively little variation in the relative size on the pathway as a complete or each and every in the brain regions that comprise this pathway (Iwaniuk et al).All three structures, TeO, nRt, and E, were somewhat smaller sized in owls, parrots, and waterfowl (Figures D).Although not included in Iwaniuk et al Martin et al. discovered that the kiwi (Apteryx mantelli) has an even smaller sized TeO and likely represents a case of tectofugal hypotrophy.This may not reflect a reduction in the tectofugal regions per se, but rather an expansion of other regions and pathways.Waterfowl, parrots and owls all have an enlarged telencephalon (Portmann, Iwaniuk and Hurd,), but have enlarged regions inside the telencephalon apart from the E.The apparently smaller tectofugal pathway may well thus be a outcome of an enlarged telencephalon in these groups.At the other finish of the spectrum, no species appeared to possess a hypertrophied tectofugal pathway.The isthmal nuclei (Imc, Ipc, Slu), which are closely associated with the tectofugal pathway, scaled with unfavorable allometry relative to brain size, but had isometric (i.e ) relationshipsFrontiers in Neuroscience www.frontiersin.orgAugust Volume ArticleWylie et al.Evolution of sensory systems in birdsFIGURE Variation within the size of structures inside the tectofugal pathway.(A) Show Nissl stained sections highlighting the significant nuclei with the tectofugal pathway the optic tectum (TeO) (A), the nucleus rotundus (nRt) (B) as well as the Entopallium (E) (C).The sections in (A,B) are from an Eastern Yellow Robin (E.australis) whereas that in (C) is from a Shortbilled Dowitcher (L.griseus).GLv, ventral leaflet on the lateral geniculate nucleus; GP, globus pallidus; HA, hyperpalliumapicale; Imc, nucleus isthmi magnocellularis; Ipc, nucleus isthmi parvocellularis; LM, nucleus lentiformis mesenceph.