A review of the evidence for a disengage de®cit following parietal lobe damage Bruno J.W. Losier a , Raymond M. Klein b, * a Department of Psychology, Cape Breton Regional Hospital, Sydney, Nova Scotia, B1P 1P3, Canada b Department of Psychology, Dalhousie University, Halifax, Nova Scotia, B3H 4J1, Canada Received 11 January 1999; revised 9 June 2000; accepted 10 August 2000 Abstract We review the literature on response times to ipsilesional and contralesional targets following spatial precues in patients with damage involving the left- and right-parietal lobes with the aim of appraising the `disengage de®cit' reported initially by Posner and colleagues (Posner MI, Cohen A, Rafal RD. Neural systems control of spatial orienting. Proceedings of the Royal Society of London, B 1982;298:187±98). The data of individual subjects from a sub-sample of studies were submitted to analyses of variance, and data from all studies meeting our selection criteria were submitted to meta-analytic procedures (Hunter JE, Schmidt FL. Methods of meta- analysis: correcting error and bias in research. Newberg Park: Sagge Publications, 1990). Findings from both types of analysis conducted on data from patients with right-hemisphere lesions indicate that: (1) the disengage de®cit phenomenon is robust following peripheral cues, but not following central cues; (2) the disengage de®cit is large at shorter cue-target stimulus onset asynchronies (SOAs), and decreases as SOA increases; (3) the disengage de®cit is larger in patients with a diagnosis of hemispatial neglect; and (4) although the magnitude of the disengage de®cit appears to increase with increases in lesion size, multilobar vs unilobar involvement did not signi®cantly alter the pattern of the disengage de®cit. We also show that responses to validly cued targets in the contralesional hemispace were signi®cantly slower than for validly cued targets in ipsilesional hemispace. Similar, but usually smaller, effects were observed in patients with homologous left-hemisphere damage. The implications of these results for current models of the role of the parietal lobes in attentional orienting are discussed. q 2001 Elsevier Science Ltd. All rights reserved. Keywords: Parietal lobe; Visual attention; Disengage de®cit; Exogenous covert orienting; Endogenous covert orienting; Meta-analysis 1. Background A century has passed since the ®rst description of visuos- patial neglect following posterior hemispheric damage [23], and, although progress has been achieved in the interim, an understanding of the underlying mechanism of neglect has been elusive. In the last two decades, stimulated by beha- vioral paradigms developed within cognitive psychology, the focus of attempts to understand visuospatial neglect has shifted from purely sensori-motor (e.g. [13]) to cogni- tive de®cits, including those involving the representation of space [5], the link between representations of space and actions [51,52], and attention (e.g. [21,28,44]). Our focus in this review is on the extinction-like reaction time (RT) pattern often seen in variants of an attentional cuing para- digm. This pattern has been interpreted in an attentional framework, within which it has been attributed to a de®cit in disengaging attention (see below). Although this pattern might be interpreted within other [5,51,52] frameworks (albeit with debatable differences in explanatory ef®ciency), we will use the term `disengage de®cit' in this review. One of the most fruitful and widely-used attention-orient- ing protocols is the visual orienting paradigm developed by Posner [42,45], which is the focus of this review. In a proto- typical implementation of this paradigm, central or periph- eral cues are presented prior to a peripheral target requiring a simple detection response. Central cues (e.g. arrows) usually inform the subject where the target is likely to appear, whereas peripheral cues (e.g. luminance increase) may or may not be informative. Following the cue, at a variable interval, a target appears in the cued location (i.e. valid trial) or in an uncued location (i.e. invalid trial). The subject is instructed to press a button in response to the detection of the target, while maintaining ®xation on a centrally located stimulus (i.e. covert attentional orienting). Neuroscience and Biobehavioral Reviews 25 (2001) 1±13 PERGAMON NEUROSCIENCE AND BIOBEHAVIORAL REVIEWS 0149-7634/01/$ - see front matter q 2001 Elsevier Science Ltd. All rights reserved. PII: S0149-7634(00)00046-4 www.elsevier.com/locate/neubiorev * Corresponding author. Tel.: 11-902-494-3417; fax: 11-902-494-6585. E-mail address: klein@or.psychology.dal.ca (R.M. Klein).