title: Implicit cognition is impaired and dissociable in a head-injured group with executive deficits.
abstract: Implicit or non-conscious cognition is traditionally assumed to be robust to pathology but Gomez-Beldarrain et al. recently showed deficits on a single implicit task after head injury. Laboratory research suggests that implicit processes dissociate. This study therefore examined implicit cognition in 20 head-injured patients and age- and IQ-matched controls using a battery of four implicit cognition tasks: a serial reaction time task (SRT), mere exposure effect task, automatic stereotype activation and hidden co-variation detection. Patients were assessed on an extensive neuropsychological battery, and MRI scanned. Inclusion criteria included impairment on at least one measure of executive function. The patient group was impaired relative to the control group on all the implicit cognition tasks except automatic stereotype activation. Effect size analyses using the control mean and standard deviation for reference showed further dissociations across patients and across implicit tasks. Patients impaired on implicit tasks had more cognitive deficits overall than those unimpaired, and a larger dysexecutive self/other discrepancy (DEX) score suggesting greater behavioural problems. Performance on the SRT task correlated with a composite measure of executive function. Head injury thus produced heterogeneous impairments in the implicit acquisition of new information. Implicit activation of existing knowledge structures appeared intact. Impairments in implicit cognition and executive function may interact to produce dysfunctional behaviour after head injury. Future comparisons of implicit and explicit cognition should use several measures of each function, to ensure that they measure the latent variable of interest.
authors.affiliation: Department of Psychology, University of Sheffield, Western Bank, Sheffield S10 2TP, UK. l.barker@shu.ac.uk
authors.forename: L A
authors.initials: LA
authors.lastname: Barker
authors.forename: J
authors.initials: J
authors.lastname: Andrade
authors.forename: C A J
authors.initials: CA
authors.lastname: Romanowski
authors.forename: N
authors.initials: N
authors.lastname: Morton
authors.forename: A
authors.initials: A
authors.lastname: Wasti
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D016022:Case-Control Studies; D003072:Cognition Disorders / Q000209:etiology*; D006259:Craniocerebral Trauma / Q000150:complications / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007859:Learning Disabilities / Q000150:complications / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests / Q000706:statistics & numerical data; D011340:Problem Solving / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D012691:Serial Learning / Q000502:physiology