Neglect as a deficit determined by an imbalance between multiple spatial representations

Abstract

A previous study on neglect suggested that at least two hand parameters are crucial in producing an amelioration of neglect: the hand (left or right) and the spatial position of the hand (left or right). The improvement observed in perceiving left targets when the left hand acts in the left space can be due either to proprioceptive or to visual cuing. The stimulated left hand located in the left space may act as a powerful visual cue for the enhancement of the left visuo-spatial representation, in the same way as any other visual stimulus presented in the periphery of the visual field. Alternatively, it may be that the perceived hand location (due to the activation of the proprioceptive system) acts as an attentional field able to enhance the representation of the left space. In order to disentangle these two hypotheses, in the present study a naming task was executed by a group of neglect patients and by a control group. The subjects had to name all the objects depicted on a sheet of paper which were reflected on a mirror that inverted right and left space. While doing the naming performance, the subjects passively moved either the right or the left hand, in the left or right space. Stimuli and hand were reflected in the mirror that inverted right and left space and direct view of the stimuli and of the stimulated hand was prevented by a board. The results show that patients were more accurate at naming stimuli reflected in the left side of the mirror when the left hand was located and moved on the left side. In this condition, however, the left hand was seen in the right side of the mirror. It is therefore clear that the better performance was not due to visuo-spatial cuing but to a proprioceptive cuing effect. The results are discussed in terms of the relevance of personal and peripersonal spatial activation in the modulation of extrapersonal visual neglect. The coactivation of different spatial representations seems to be very influential on stimulus coding, thus confirming that spatial awareness is strictly related to the joint activity of multiple brain maps.

Patterns of spontaneous recovery of neglect and associated disorders in acute right brain-damaged patients

“…In agreement with the contribution provided by sensorimotor information for space representation, several studies showed that contralesional motor and proprioceptive stimulation ameliorates neglect. [77][78][79] Some parietal areas (BA 5,7,39,40) were also critically associated with neglect, as previously reported. 2 46 Thus, the present study does not support a privileged role being played by temporal lesions in the genesis of acute 3 or chronic neglect.…”

Hemispheric asymmetry: Looking for a novel signature of the modulation of spatial attention in multisensory processing

“…In this condition, crossmodal extinction of the tactile stimulus on left hand remained. Taken together, these results suggest that the patient’s peripersonal spatial frame was hand-centered, and therefore crossmodal extinction was not induced by a visual stimulus presented far from the right hand, and not influenced by the hands’ locations in terms of the external space frame (di Pellegrino et al., 1997; Làdavas, Berti, Ruozzi, & Barboni, 1997; Làdavas et al., 1998). However, a later study demonstrated that crossmodal extinction was modulated by the manipulation of an external spatial frame: In Kennett, Rorden, Husain, and Driver’s (2010) study, a tactile stimulus on the left hand was extinguished when an LED light was presented near the right hand; however, crossmodal extinction was eliminated when the patient turned her head toward the left, leading to the tactile stimulus on the left hand now spatially to overlap the LED in the right hemispace.…”

The effect of hand movements on numerical bisection judgments in early blind and sighted individuals

“…For instance, Reed et al (2006) found that visual target detection near the hand was facilitated relative to detection away from the hand. Moreover, symptoms related to neglect syndrome (due to right-parietal lesions) have been shown to be reduced by left-hand movements in left space, but not by left hand-movements in right space (Gainotti, Perri & Cappa, 2002; Làdavas, Berti, Ruozzi & Barboni, 1997; Robertson & North, 1992, 1993). This dichotomy illustrates the predominance of attentional orienting towards the hemispace where the hand is moved (in terms of body-centered coordinates) as opposed to the hand’s anatomical location (i.e.…”

“…on the left or right). Importantly, these effects do not seem to depend on visual feedback, but rather rely mainly on proprioceptive cues (Làdavas et al, 1997). In this view, we hypothesized that a judgment bias towards the hemispace in which the hand was moved would lead to a corresponding bias in the simultaneously activated spatial representation (i.e., the mental number line) (see Cattaneo, Fantino, Silvanto, Vallar, & Vecchi, 2011).…”