Biomedical subjects

Tim Curran

Publications and source records attributed to Tim Curran.

24 records · Page 2Linked to original sources

PubMed2003

Differentiating amodal familiarity from modality-specific memory processes: an ERP study.

Distinct event-related potential effects have been related to familiarity and recollection processes underlying recognition memory. Familiarity has been conceptualized as similar either to perceptual priming mechanisms supporting implicit memory or to amodal global-matching processes that should show little sensitivity to perceptual variables. The present experiment manipulated the study modality of words (auditory, visual) that were visually tested for recognition memory. The mid-frontal (300-500 ms) old/new effect often attributed to familiarity was not affected by study modality, so it appears related to an amodal familiarity process. An earlier (176-260 ms) fronto-polar old/new effect was perceptually specific in that it was observed only following visual study. The parietal old/new effect (400-800 ms), often attributed to recollection, was similar following both visual and auditory study. Temporal-spatial PCA clarified the separability of these effects.

Acoustic Stimulation↗

PubMed2003

Differentiating location- and distance-based processes in memory for time: an ERP study.

Memory for the time of events may benefit from reconstructive, location-based, and distance-based processes, but these processes are difficult to dissociate with behavioral methods. Neuropsychological research has emphasized the contribution of prefrontal brain mechanisms to memory for time but has not clearly differentiated location- from distance-based processing. The present experiment recorded event-related brain potentials (ERPs) while subjects completed two different temporal memory tests, designed to emphasize either location- or distance-based processing. The subjects' reports of location-based versus distance-based strategies and the reaction time pattern validated our experimental manipulation. Late (800-1,800 msec) frontal ERP effects were related to location-based processing. The results provide support for a two-process theory of memory for time and suggest that frontal memory mechanisms are specifically related to reconstructive, location-based processing.

Distance Perception↗

PubMed2002

A defense of the subordinate-level expertise account for the N170 component.

A recent paper in this journal reports two event-related potential (ERP) experiments interpreted as supporting the domain specificity of the visual mechanisms implicated in processing faces (Cognition 83 (2002) 1). The authors argue that because a large neurophysiological response to faces (N170) is less influenced by the task than the response to objects, and because the response for human faces extends to ape faces (for which we are not expert), we should reject the hypothesis that the face-sensitivity reflected by the N170 can be accounted for by the subordinate-level expertise model of object recognition (Nature Neuroscience 3 (2000) 764). In this commentary, we question this conclusion based on some of our own ERP work on expert object recognition as well as the work of others.

Brain Mapping↗

PubMed2002

A study of parallel implicit and explicit information processing in patients with obsessive-compulsive disorder.

OBJECTIVE: This study examined implicit sequence learning in patients with obsessive-compulsive disorder (OCD) under dual-task conditions. Frontal-striatal networks support implicit learning and are implicated in the pathophysiology of OCD. Neuroimaging data suggest that during implicit learning, OCD patients use neural systems normally active during explicit learning to compensate for striatal dysfunction. METHOD: The authors examined implicit sequence learning in 25 OCD patients and 25 healthy comparison subjects using a dual-task paradigm, with subjects simultaneously engaged in an explicit memory task and an implicit learning task. They predicted that implicit learning in OCD subjects would be disrupted because concurrent explicit information-processing demands would prevent use of compensatory processes. RESULTS: OCD patients failed to show evidence of implicit learning and exhibited a significant deficit in comparison with healthy subjects. CONCLUSIONS: These results are consistent with the hypothesis that concurrent explicit and implicit information-processing demands interfere with implicit learning in OCD patients.

Attention↗

PubMed2002

An electrophysiological comparison of visual categorization and recognition memory.

Object categorization emphasizes the similarities that bind exemplars into categories, whereas recognition memory emphasizes the specific identification of previously encountered exemplars. Mathematical modeling has highlighted similarities in the computational requirements of these tasks, but neuropsychological research has suggested that categorization and recognition may depend on separate brain systems. Following training with families of novel visual shapes (blobs), event-related brain potentials (ERPs) were recorded during both categorization and recognition tasks. ERPs related to early visual processing (N1, 156-200 msec) were sensitive to category membership. Middle latency ERPs (FN400 effects, 300-500 msec) were sensitive to both category membership and old/new differences. Later ERPs (parietal effects, 400-800 msec) were primarily affected by old/new differences. Thus, there was a temporal transition so that earlier processes were more sensitive to categorical discrimination and later processes were more sensitive to recognition-related discrimination. Aspects of these results are consistent with both mathematical modeling and neuropsychological perspectives.

Adult↗

PubMed2001

Implicit learning revealed by the method of opposition.

Complex information, such as that required for motor skills, can be learned implicitly, without awareness. Much debate has centered on the appropriate methods for proving that implicit learning is not influenced by explicit awareness. A recent study by Destrebecqz and Cleeremans has provided compelling evidence for implicit sequence learning without awareness by using the 'method of opposition'.

Journal Article↗