Biomedical subjects

Virginie Durier

Publications and source records attributed to Virginie Durier.

4 recordsLinked to original sources

PubMed2004

The binding and recall of snapshot memories in wood ants (Formica rufa L.).

Insects can locate spatial goals by means of 2-D retinotopic views of the surrounding landmarks, which they memorise from the vantage point of the goal. Wood ants acquire such snapshot memories while fixating conspicuous landmarks with frontal retina, and their snapshots extend horizontally at least 120 degrees into the periphery. Are spatially separate items within such an extended snapshot bound together so that a snapshot is recalled as a whole, or are its components recognised individually? We approached this question by training ants to find food midway between two upright black cylinders of different sizes and then examined where they searched when they were given two cylinders of the same size. If the ants know which cylinder replaces the small cylinder and which the large, they should search at a position where the two equal-sized cylinders subtend the same angles as do the training cylinders when viewed from the feeder. Ants conformed to this prediction under one condition, searching at a shorter distance from the substitute for the large cylinder than from the substitute for the small cylinder. But, under another condition, ants were unable to distinguish between the two equal-sized cylinders. Ants failed when white curtains completely surrounded the platform on which the cylinders were placed. They succeeded when one side of the platform had a patterned curtain. We suggest that ants take two snapshots at the feeding site, one when facing the small cylinder and one when facing the large cylinder, and that each snapshot includes the patterned curtain, if it is there. Ants will view the patterned curtain with the lateral retina of one eye when facing the small cylinder and with the lateral retina of the other eye when facing the large cylinder. Our data suggest that there may be associative links between these spatially separate components of the snapshot, which cause the memory of the small cylinder or the large cylinder to be recalled according to which eye sees the curtain. It seems that an extended snapshot not only enhances the accuracy of localisation but can also increase the reliability of snapshot recall, provided that the components of a snapshot are bound together.

Animals↗

PubMed2004

Switching destinations: memory change in wood ants.

We have studied the changing use of spatial memories in wood ants by charting how the ants' paths transform when ants are first trained to feed at one site and must then switch to another site. Because ants, which are trained to approach a single feeding site from a single starting point, are attracted directly to that goal when started from unfamiliar positions, we describe the ants' paths in terms of the use of two stored snapshots. Each snapshot consists of retinotopic views of the ants' surroundings acquired at one of the two feeding sites. When a snapshot is activated, it draws an ant to the related site from a wide range of directions. Here, we focus on routes that occur before ants have learnt to go directly from the start to the second site. The initial direction of the ant's path is then mostly aimed either at the first site or between the two sites. On 62.2% of all recorded paths, this segment is followed by an abrupt turn, after which the ant often aims directly at the second feeding site. The details of this behaviour suggest that, after the turn, control of the path switches from the snapshot recorded at the first feeding site (or some combination of the two snapshots) to the snapshot recorded at the second feeding site. We discuss different ways in which control might be transferred from one snapshot to the other.

Animals↗

PubMed2003

Snapshot memories and landmark guidance in wood ants.

Insects are thought to pinpoint a place by using memorized "snapshots," i.e., two-dimensional retinotopic views of the surrounding landmarks recorded when at the place (reviewed in ). Insects then reach the place by moving until their current view matches their snapshot. To determine when snapshots are recalled, and how differences between view and snapshot are translated into appropriate movements, we analyzed the approaches of wood ants to a feeding site that was located in the center of an array of two or three cylinders. In ants, contrary to flying hymenopterans, body orientation and direction of travel are collinear, so that an ant approaching an object always looks at it with frontal visual field. On their way to a food site, ants fixated and approached a cylinder predominantly when its angular size was smaller than when viewed from the food site. This finding implies that ants store snapshots at this place while fixating landmarks with frontal retina, so simplifying the later alignment of snapshots with their current view. It also means that ants recall snapshots well in advance of reaching the place. Although snapshots are centered on a landmark, we show that they extend at least 120 degrees into the periphery.

Animals↗

PubMed2003

Route learning by insects.

Ants and other insects often follow fixed routes from their nest to a foraging site. The shape of an ant's route is set, initially, by navigational strategies, such as path integration and the ant's innate responses to landmarks, which depend minimally on memory. With increasing experience, these early routes are stabilised through the learning of views of landmarks and of associated actions. The substitution of memory-based strategies makes an insect's route more robust and precise. The ability to select between different learnt routes might incur additional memory requirements to those needed for performing a route, and lead to the associative grouping of those memories that relate to a particular route.

Animals↗