Lateralization of Spatial Learning in the Avian Hippocampal Formation.

The authors investigated lateralization of spatial learning within the avian hippocampal formation (HF). In Experiment 1, homing pigeons (Columba livia) with unilateral lesions of the right or left HF were trained to locate a goal in a square room containing local landmarks and global room cues. All groups learned the task. During probe trials, when landmarks were rotated or removed, intact pigeons and left HF-lesioned pigeons relied exclusively on global room cues to locate the food goal. Pigeons with right HF lesions were the only group to demonstrably use the landmarks. The results suggest that the right HF is preferentially involved in the representation of global environmental space, whereas only the left HF may be sensitive to local landmarks for navigation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

What Does a Pigeon (Columba livia) Brain Look Like During Homing? Selective Examination of ZENK Expression.

Lesion studies have shown that the avian hippocampus plays a crucial role in homing pigeon (Columba livia) navigation. Using the expression of the immediate early gene protein ZENK in intact pigeons, the authors found regional variation in hippocampal activation as a consequence of homing and, necessarily, the behavior and internal states that accompany it. Specifically, pigeons that homed displayed a significant increase in the number of ZENK-labeled cells in the lateral hippocampal formation compared with pigeons that did not home, whereas no difference was seen in the medial hippocampus. Significant changes in ZENK expression were also found in the medial striatum, which resembles the mammalian ventral striatum. The results identify portions of the hippocampal formation and the medial striatum as sites of plasticity associated with homing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Responses of pigeon (Columba livia) Wulst neurons during acquisition and reversal of a visual discrimination task.

The avian visual "Wulst" is a target of the ascending thalamofugal visual pathway. In pigeons (Columba livia), lesion damage to the Wulst has little effect on simple visual discriminations, but impairs performance on tasks such as reversal learning. We recorded the responses of single Wulst neurons as pigeons were trained on the acquisition and subsequent reversal of a visual discrimination. Of the 64 units recorded, 54 (84%) displayed a significant difference in firing rate between some component of the task and the intertrial interval that separated trials. More important, 14 units (22%) displayed a significant change in firing rate exclusively to the S+ and/or S- as learning progressed either during acquisition or reversal. The responses of these 14 neurons indicate that learning during initial acquisition was as likely to correlate with a change in firing rate as during reversal, and some neuronal responses could be characterized as representing reward properties together with visual stimulus features. As such, responses of pigeon Wulst neurons indicate a role in representing aspects of learning as much as the physical/perceptual properties of visual stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The avian hippocampus: Evidence for a role in the development of the homing pigeon navigational map.

Young homing pigeons were subjected to hippocampal lesion before being placed in their permanent loft to examine what effect such treatment may have on the development of their navigational map, which supports homing from distant unfamiliar locations. When later released from 3 distant unfamiliar locations, the hippocampal-lesioned pigeons were impaired in taking up a homeward bearing. The results identify a deficit in the acquisition of navigational ability after hippocampal ablation in homing pigeons. The results suggest a deficit in navigational map acquisition, but alternative interpretations cannot be excluded. The findings offer the first insight into the central neural structures involved in the acquisition of the pigeon navigational map. Further, the results identify the hippocampus as a structure critical for the regulation of navigational behavior that manifests itself in a natural setting. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Olfaction and the homing ability of pigeons in the southeastern United States

The importance of atmospheric odors for homing pigeon navigation was tested using birds from a loft located in Savannah, GA, in the southeastern United States. When released from a familiar training site, control pigeons and pigeons given intranasal injections of zinc sulfate to produce anosmia both displayed good homeward orientation and homed quickly. When released from three unfamiliar release sites, in contrast, control birds tended to orient southeast, while zinc sulfate-treated birds were more likely to fly northwest. More importantly, while the majority of control pigeons returned to the home loft, few of the zinc sulfate-treated birds returned. The good performance of both groups from the familiar site indicates that zinc sulfate treatment does not impair the general motor ability or motivation of homing pigeons. Therefore, the observed impairment in homing success of the zinc sulfate-treated pigeons from the unfamiliar locations presumably reflects an impaired ability to use atmospheric odors to navigate home. As such, the data support the hypothesis that successful homing pigeon navigation is based on the perception of atmospheric odors and that olfactory navigation is the primary mechanism used by pigeons over a broad range of geographic areas to approximate their relative position with respect to home from unfamiliar locations.     

The muscarinic acetylcholine antagonist scopolamine impairs short-distance homing pigeon navigation

The present study employed intramuscular (i.m.) injections of the acetylcholine (ACh) receptor antagonist scopolamine hydrobromide (0.10 mg/kg) to investigate the possible involvement of ACh in naturally occurring spatial navigation in homing pigeons (Columba livia). Control pigeons receiving injections of saline or scopolamine methylbromide, an ACh antagonist that does not cross the blood-brain barrier, were oriented in a homeward direction when released from a location 8 km from home. In contrast, pigeons injected with scopolamine hydrobromide (0.10 mg/kg, i.m.) were less well oriented and took more time to return home from the same location. These results suggest that homing pigeon navigation is regulated, in part, by central cholinergic mechanisms.     

Spared feature-structure discrimination but diminished salience of environmental geometry in hippocampal-lesioned homing pigeons (Columba livia).

Homing pigeons (Columba livia) were trained to locate a goal in one corner of a rectangular arena by either its shape (geometry) or the left-right configuration of colored features located in each corner (feature structure). Control and hippocampal-lesioned pigeons learned at a similar rate, but the control birds made proportionally more geometric errors during acquisition. On conflict probe trials, the control birds preferred geometrically correct corners, whereas the hippocampal-lesioned birds displayed a greater preference for the correct corner defined by feature structure. On geometry-only probe trials, both groups demonstrated an ability to identify the goal location. Hippocampal lesions do not interfere with goal recognition by the feature structure of local cues but diminish the salience of arena shape. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The homing pigeon hippocampus and the development of landmark navigation

The temporo-spatial patterning of lectin-binding sites was examined by lectin histochemistry and quantitative methods in the microvasculature of the optic tectum of 9-, 14-, 20-day-old embryos and 30-day-old chickens. Horseradish peroxidase and colloidal-gold-labelled lectins were used for detection of beta-D-galactose (RCA-I, Ricinus communis agglutinin-I) and of N-acetylglucosamine and sialic residues (WGA, Wheat germ agglutinin) at light and electron microscopical levels. At the light microscopical level, RCA-I and WGA binding sites were detectable in the early embryonic capillaries in a diffuse staining pattern; in later embryonic stages and in adult animals, RCA-I labelling became located on the abluminal surface of the vessels, while WGA staining was detected on the luminal surface. Ultrastructurally, gold labelling for RCA-I was seen intracytoplasmically in endothelial cells in 9-day-old embryos. In 14-to 20-day-old embryos and in chickens, binding sites for RCA-I were detected in endothelial tight junctions and basement membranes. In contrast, labelling of the gold-coupled WGA lectin was distributed almost exclusively on the luminal endothelial surface already in early embryos. The results indicate that the endothelial cells of the optic tectum acquire functional polarity early in their development and that glycoconjugates containing beta-D-galactose residues are involved in the biochemical composition of the tight junctions and basement membrane, which are considered to be key structures in blood-brain barrier (BBB) differentiation.     

Goal recognition and hippocampal formation in the homing pigeon (Columba livia).

Stimulus control of food-site recognition and role of the hippocampal formation (HF) were investigated. Control and HF-lesioned pigeons were trained to find food located in a colored bowl, near a landmark beacon, in a constant room location. During later test trials, the sources of information were individually removed and/or disassociated. For all test trial types, HF-lesioned pigeons consistently chose bowls associated with one of the training stimuli. Controls were more sensitive to the changes introduced during the test trials; choosing like HF-lesioned pigeons on some test trials but choosing randomly on others. The data identify a critical role of the avian HF in learning the spatial relationship among environmental stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Paired-associate learning is unaffected by combined hippocampal and parahippocampal lesions in homing pigeons.

To examine whether the avian hippocampus-parahippocampus (HF) is necessary for nonspatial, paired-associate learning, as has been suggested for rodents, HF-lesioned and control homing pigeons were tested on a visual paired-associate learning task. Both groups learned equally well to discriminate trials that consisted of a stimulus preceded by its paired associate from trials that consisted of a stimulus preceded by stimuli from other paired associates (mispair trials), even when a mispair was experienced for the first time. The groups also learned equally well not to respond to 2 stimuli that were never rewarded. The results demonstrate that HF lesions do not impair nonspatial paired-associate learning in birds, suggesting that the role of HF in nonspatial cognition differs between birds and mammals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)