No abstract

Representing the position of the objects independently from our own position is a fundamental cognitive ability. Here we investigated whether this ability depends on visual experience. Congenitally blind, late blind and blindfolded sighted participants haptically learnt a room-sized regularly shaped array of objects, and their spatial memory was tested to determine which spatial reference frame was used. Crucially, the use of an object-based reference frame requires representing the regular structure of the array. We found that blindfolded sighted and late blind participants, that is those with visual experience, showed a preferential use of the object-based or 'allocentric' reference frame. On the contrary, congenitally blind participants preferred a self-based, or egocentric, reference frame. This suggests that, due to its developmental effect on the multisensory brain areas involved in spatial cognition, visual experience is necessary to develop a preference for an object-based, allocentric reference frame.

No abstract

No abstract

Although a number of studies have been devoted to 2-D navigation, relatively little is known about how the brain encodes and recalls navigation in complex multifloored environments. Previous studies have proposed that humans preferentially memorize buildings by a set of horizontal 2-D representations. Yet this might stem from the fact that environments were also explored by floors. Here, we have investigated the effect of spatial learning on memory of a virtual multifloored building. Two groups of 28 participants watched a computer movie that showed either a route along floors one at a time or travel between floors by simulated lifts, consisting in both cases of a 2-D trajectory in the vertical plane. To test recognition, the participants viewed a camera movement that either replicated a segment of the learning route (familiar segment) or did not (novel segment-i.e., shortcuts). Overall, floor recognition was not reliably superior to column recognition, but learning along a floor route produced a better spatial memory performance than did learning along a column route. Moreover, the participants processed familiar segments more accurately than novel ones, not only after floor learning, but crucially, also after column learning, suggesting a key role of the observation mode on the exploitation of spatial memory.

Scene recognition has been found to be sensitive to the orientation of the scene with respect to the stationary observer. Recent studies have shown, however, that observer movement can compensate for changes in visual scene orientation, through a process of spatial updating. Here we investigated whether spatial updating in scene recognition is affected by the encoding or learning modality by examining whether observer movement can also compensate for orientation changes in haptic scene recognition. In experiment 1, we replicated previously reported effects of observer movement on visual scene recognition. In experiment 2, we used the same apparatus as in experiment 1 but here participants were required to learn and recognize the scenes using touch alone. We found a cost in recognition performance with changes in scene orientation relative to the stationary observer. However, when participants could move around the scene to recognize the new orientation, then this cost in recognition performance disappeared. Thus, we found that spatial updating applies to recognition in both the visual and haptic modalities, both of which intrinsically encode the spatial properties of a scene.

Previous studies reported that congenitally blind people possess superior verb-generation skills. Here we tested the impact of blindness on capacity and the fidelity of semantic memory by using a false memory paradigm. In the Deese-Roediger-McDermott paradigm, participants study lists of words that are all semantically related to a lure that is not presented. Subsequently, participants frequently recall the missing lure. We found that congenitally blind participants have enhanced memory performance for recalling the presented words and reduced false memories for the lure. The dissociation of memory capacity and fidelity provides further evidence for enhanced verbal ability in the blind, supported by their broader structural and functional brain reorganisation.

The sense of touch allows us to infer objects' physical properties, while the same input also produces affective sensations. These affective sensations are important for interpersonal relationships and personal well-being, which raises the possibility that tactile preferences are adapted to the characteristics of the skin. Previous studies examined how physical properties such as surface roughness and temperature influence affective sensations; however, little is known about the effect of compliance (physical correlate of softness) on pleasantness. Thus, we investigated the psychophysical link between softness and pleasantness. Pieces of human skin-like rubber with different compliances were pressed against participants' fingers. Two groups of participants numerically estimated the perceived magnitude of either pleasantness or softness. The perceived magnitude of pleasantness and softness both increased monotonically as a function of increasing object compliance, levelling off at around the end of the stimulus range. However, inter-subject variability was greater for pleasantness than for perceived softness, whereas the slope of the linear function fit to the magnitude estimates was steeper for softness than for pleasantness. These results indicate that object compliance is a critical physical determinant for pleasantness, whereas the effect of compliance on pleasantness was more variable among individuals than the effect on softness was.