Although prism adaptation has been shown to improve performance for the
left side of space in numerous aspects of neglect (see reviews by Pisella et al., 2006 and Redding and Wallace, 2006) and to increase awareness for the left side of non-face objects in neglect patients (as demonstrated in Sarri et al., 2006) it appears ineffective for lateral preference tasks, possibly irrespective of the type of stimulus used (as shown here for both chimeric face expressions and greyscale gradients). In fact Mattingley et al., 1994 and Mattingley et al., 2004) have shown that performance in these lateral preference tasks does not correlate with other classical tests of neglect (specifically not with cancellation or line bisection in their data) and can be present in patients with unilateral brain damage even in the absence of neglect
Selleck U0126 http://www.selleckchem.com/products/AC-220.html (see also Peers et al., 2005, and Habekost and Rostrup, 2006, for further demonstrations of similar spontaneous attentional lateral biases in patients with unilateral damage without clinical signs of neglect). Mattingley et al. (1994) reported that although patients’ ability to reorient attention contralesionally at will may recover relatively quickly, more subtle ipsilesional attention biases–as potentially measured by lateral preference tasks may be relatively persistent. Thus the lateral preference tasks may tap into a potentially distinct and dissociable deficit involving a ‘chronic’ bias towards the right, which might dissociate from a deficit in controlled shifts of attention towards the
contralesional side. In our own data here, five patients (AK, CO, DF, JA and TL) performed at ceiling level in the chimeric/non-chimeric face discrimination task even prior to prisms, implying that medroxyprogesterone these patients could to some degree still become aware of the left side of chimeric face tasks when encouraged by the task. Yet these cases all still showed a strong rightward bias when required to make preference judgements between otherwise equivalent mirror-reversed stimuli, potentially lending further support to the idea of a dissociable deficit underlying lateral preference tasks. Since rightward biases in lateral preference paradigms can be found even in patients with no other signs of clinical neglect and no frank deficits of perceptual awareness for the contralesional side (see Mattingley et al., 1994, Mattingley et al., 2004 and Habekost and Rostrup, 2006), this might imply that such spatial preferences need not reflect explicit awareness for the contralesional space per se. Instead the lateral preferences may provide a more indirect or implicit measure of any difference in ‘salience’ for the stimuli on either side (e.g., Mattingley et al., 2004). If so, this might be reconciled with prisms on the one hand having some impact on awareness for the contralesional side (as in Maravita et al., 2003 and Sarri et al.