Biomedical subjects

Valeria Anna Sovrano

Publications and source records attributed to Valeria Anna Sovrano.

13 recordsLinked to original sources

PubMed2006

Spatial reorientation: the effects of space size on the encoding of landmark and geometry information.

The effects of the size of the environment on animals' spatial reorientation was investigated. Domestic chicks were trained to find food in a corner of either a small or a large rectangular enclosure. A distinctive panel was located at each of the four corners of the enclosures. After removal of the panels, chicks tested in the small enclosure showed better retention of geometrical information than chicks tested in the large enclosure. In contrast, after changing the enclosure from a rectangular-shaped to a square-shaped one, chicks tested in the large enclosure showed better retention of landmark (panels) information than chicks tested in the small enclosure. No differences in the encoding of the overall arrangement of landmarks were apparent when chicks were tested for generalisation in an enclosure differing from that of training in size together with a transformation (affine transformation) that altered the geometric relations between the target and the shape of the environment. These findings suggest that primacy of geometric or landmark information in reorientation tasks depends on the size of the experimental space, likely reflecting a preferential use of the most reliable source of information available during visual exploration of the environment.

Animals↗

PubMed2006

How fish do geometry in large and in small spaces.

It has been shown that children and non-human animals seem to integrate geometric and featural information to different extents in order to reorient themselves in environments of different spatial scales. We trained fish (redtail splitfins, Xenotoca eiseni) to reorient to find a corner in a rectangular tank with a distinctive featural cue (a blue wall). Then we tested fish after displacement of the feature on another adjacent wall. In the large enclosure, fish chose the two corners with the feature, and also tended to choose among them the one that maintained the correct arrangement of the featural cue with respect to geometric sense (i.e. left-right position). In contrast, in the small enclosure, fish chose both the two corners with the features and the corner, without any feature, that maintained the correct metric arrangement of the walls with respect to geometric sense. Possible reasons for species differences in the use of geometric and non-geometric information are discussed.

Animals↗

PubMed2006

Dissecting the geometric module: a sense linkage for metric and landmark information in animals' spatial reorientation.

Disoriented children can use geometric information in combination with featural information to reorient themselves in large but not in small spaces; somewhat similar effects have been found in nonhuman animals. These results call for an explanation. We trained young chicks to reorient to find food in a corner of a small or a large rectangular room with a distinctive featural cue (a blue wall) -- a task similar to that used with children. Then we tested the chicks after displacement of the feature to an adjacent wall. In the large enclosure, chicks chose the corner that maintained the correct arrangement of the featural cue with respect to sense, whereas in the small enclosure, they chose the corner that maintained the correct metrical arrangement of the walls with respect to sense. On the basis of these findings, we propose a simple model that can explain the effects of room size on spatial reorientation.

Animals↗

PubMed2005

Lateralized fish perform better than nonlateralized fish in spatial reorientation tasks.

Lines of fish (Girardinus falcatus) obtained through selective breeding showing different degree and direction of behavioural lateralization in a variety of tasks were tested for their ability for spatial reorientation. In the first experiment, fish were required to reorient themselves after passive disorientation in a rectangular tank in the presence of a salient feature (a blue wall). Lateralized fish proved to be better than nonlateralized fish at using the geometric cues provided by the shape of the tank in order to disambiguate between corners with similar featural information. In the second experiment fish were tested in a square-shaped tank (in order to eliminate any geometric cues) in the presence of salient features (panels) located at the corners. Lateralized fish proved better than nonlateralized fish in using featural cues to reorient themselves. These findings suggest that lateralization may confer advantages in spatial reorientation based on the use of geometric and nongeometric cues.

Animals↗

PubMed2005

Reorientation by geometric and landmark information in environments of different size.

It has been found that disoriented children could use geometric information in combination with landmark information to reorient themselves in large but not in small experimental spaces. We tested domestic chicks in the same task and found that they were able to conjoin geometric and nongeometric (landmark) information to reorient themselves in both the large and the small space used. Moreover, chicks reoriented immediately when displaced from a large to a small experimental space and vice versa, suggesting that they used the relative metrics of the environment. However, when tested with a transformation (affine transformation) that alters the geometric relations between the target and the shape of the environment, chicks tended to make more errors based on geometric information when tested in the small than in the large space. These findings suggest that the reliance of the use of geometric information on the spatial scale of the environment is not restricted to the human species.

Animals↗

PubMed2004

Animals' use of landmarks and metric information to reorient: effects of the size of the experimental space.

Disoriented children could use geometric information in combination with landmark information to reorient themselves in large but not in small experimental spaces. We tested fish in the same task and found that they were able to conjoin geometric and non-geometric (landmark) information to reorient themselves in both the large and the small space used. Moreover, fish proved able to reorient immediately when dislocated from a large to a small experimental space and vice versa, suggesting that they encoded the relative rather than the absolute metrics of the environment. However, fish tended to make relatively more errors based on geometric information when transfer occurred from a small to a large space, and to make relatively more errors based on landmark information when transfer occurred from a large to a small space. The hypothesis is discussed that organisms are prepared to use only distant featural information as landmarks.

Animals↗

PubMed2004

Visual lateralization in response to familiar and unfamiliar stimuli in fish.

Left- and right-monocular viewing during inspection of their own mirror-image was measured in fish (Xenopoecilus sarasinorum) that had been kept for 20 days in a tank with a mirror or in a tank in which conspecifics were visible behind a transparent glass partition. Results revealed a preferential use of the monocular visual field of the left eye in both conditions. The asymmetry was stronger during the first 5 min of observation and tended to fade slightly thereafter. In a second experiment left- and right-monocular viewing was measured in presence of artificial stimuli. Fish were kept for 20 days in a tank with either horizontal or vertical stripes positioned along one wall and then tested for eye use in a tank with a familiar (same orientation) or an unfamiliar (different orientation) pattern of stripes. Fish showed a preferential use of the monocular field of the left eye when presented with the familiar pattern and a slight preferential use of the right eye with the unfamiliar pattern. The former bias was stronger in the first minutes of test, after which it tended first to reverse and then to fade away; the latter bias, in contrast, appeared only after some minutes of observation. It is argued that the preferential use of the monocular visual field of the left eye (mainly serving structures located to the right side of the encephalon) is probably part of a more general specialization to establish identity, i.e. that an apparently familiar stimulus is indeed identical with one previously experienced. Preferential use of the monocular field of the right eye, in contrast, is argued to be associated with visual control of response.

Animals↗

PubMed2004

Separate geometric and non-geometric modules for spatial reorientation: evidence from a lopsided animal brain.

Research has proved that disoriented children and nonhuman animals can reorient themselves using geometric and nongeometric features of the environment, showing conjoined use of both types of information to different degree depending on species and developmental level. Little is known of the neurobiological bases of these spatial reorientation processes. Here we take advantage of the neuroanatomical peculiarities of the visual system of birds (showing segregation of information between the two sides of the brain to a considerable degree) to investigate the way in which geometric and nongeometric information is encoded and used by the left and right hemispheres. Domestic chicks were trained binocularly in an environment with a distinctive geometry (a rectangular cage) with panels at the corners providing nongeometric cues. Between trials, chicks were passively disoriented to disable dead reckoning. When tested after removal of the panels, left-eyed chicks, but not right-eyed chicks, reoriented using the residual information provided by the geometry of the cage. When tested after removal of geometric information (i.e., in a square-shaped cage), both right- and left-eyed chicks reoriented using the residual nongeometric information provided by the panels. When trained binocularly with only geometric information, at test, left-eyed chicks reoriented better than right-eyed chicks. Finally, when geometric and nongeometric cues provided contradictory information, left-eyed chicks showed more reliance on geometric cues, whereas right-eyed chicks showed more reliance on nongeometric cues. The results suggest separate mechanisms for dealing with spatial reorientation problems, with the right hemisphere taking charge of large-scale geometry of the environment and with both hemispheres taking charge of local, nongeometric cues when available in isolation, but with a predominance of the left hemisphere when competition between geometric and non-geometric information occurs.

Animals↗

PubMed2003

Temporal pattern of social aggregation in tadpoles and its influence on the measurement of lateralised response to social stimuli.

Tadpoles of several species have been proven to prefer using the left hemifield during fixation of their own mirror images. The lateral bias typically emerges some minutes after the placement of the animals in the test apparatus. Here we checked whether such a temporal pattern was associated with lateralisation per se, or rather reflected temporal variations in social aggregation. We tested the temporal changes in tadpoles' movements directed towards conspecifics and other parts of the environment. We found that the propensity to move to make social aggregation only appears after about 5 min following placement in a novel environment and this corresponded quite well with the appearance of lateralisation, when tadpoles showed a higher probability of approaching a conspecific appearing on their left hemifield rather than on their right hemifield. These findings confirm, using natural conspecifics, evidence that in tadpoles, the left hemifield is better at detecting and directing approach responses to social stimuli.

Animals↗

PubMed2003

Modularity as a fish (Xenotoca eiseni) views it: conjoining geometric and nongeometric information for spatial reorientation.

When disoriented in a closed rectangular tank, fish (Xenotoca eiseni) reoriented in accord with the large-scale shape of the environment, but they were also able to conjoin geometric information with nongeometric properties such as the color of a wall or the features provided by panels located at the corners of the tank. Fish encoded geometric information even when featural information sufficed to solve the spatial task. When tested after transformations that altered the original arrangement of the panels, fish were more affected by those transformations that modified the geometric relationship between the target and the shape of the environment. Finally, fish appeared unable to use nongeometric information provided by distant panels. These findings show that a reorientation mechanism based on geometry is widespread among vertebrates, though the joint use of geometric and nongeometric cues by fish suggest that the degree of information encapsulation of the mechanism varies considerably between species.

Animals↗

PubMed2003

Visual lateralisation in quails (Coturnix coturnix).

Two-week-old quails (Coturnix coturnix) were trained to discriminate food grains scattered randomly on a background of small pebbles of similar size adhering to the floor and differing from the grains in texture and hue ("pebble floor task"). Quails tested binocularly or with only their right eye in use showed less pecking to the pebbles and more pecking to the grains than quails tested with only their left eye in use. Adult quails in contrast did not show lateralisation. These findings add to previous evidence for visual lateralisation in birds in the pebble floor task suggesting that neural structures fed by the right eye, mainly located to the left hemisphere, are better suited to rapid visual categorisation of food objects. Like other galliformes species such as the domestic chick (Gallus gallus), but unlike non-galliformes species such as the pigeon, behavioural lateralisation in the pebble floor task may be associated with transitory anatomical asymmetries in the thalamofugal visual pathway.

Journal Article↗

PubMed2002

Frogs and toads in front of a mirror: lateralisation of response to social stimuli in tadpoles of five anuran species.

Tadpoles of five anuran species were tested for preferences in the use of the eyes during inspection of their own visual image in a mirror. When tested in a tank with several small mirrors, tadpoles of five different species (Bufo bufo, Bufo viridis, Rana temporaria, Rana esculenta, Bombina variegata) preferentially approached and positioned themselves with the mirror located on their left side, thus looking at the image with the monocular field of their left eye. Similar results were obtained with tadpoles of R. temporaria tested in a simple task in which they had to choose approaching one or other of two large mirrors located on their left and right side. Control experiment showed that the behavioural asymmetry was not due to motor preferences and that it was independent of morphological asymmetries in the positions of the spiracles. This is the first demonstration of a functional visual lateralisation among juvenile amphibia before metamorphosis.

Animals↗

PubMed2002

Modularity and spatial reorientation in a simple mind: encoding of geometric and nongeometric properties of a spatial environment by fish.

When disoriented in environments with distinctive geometry, such as a closed rectangular arena, human infants and adult rats reorient in accord with the large-scale shape of the environment, but not in accord with nongeometric properties such as the colour of a wall. Human adults, however, conjoined geometric and nongeometric information to reorient themselves, which has led to the suggestion that spatial processing tends to become more flexible over development and evolution. We here show that fish tested in the same tasks perform like human adults and surpass rats and human infants. These findings suggest that the ability to make use of geometry for spatial reorientation is an ancient evolutionary tract and that flexibility and accessibility to multiple sources of information to reorient in space is more a matter of ecological adaptations than phylogenetic distance from humans.

Animals↗