Kelly M. Goedert

Neural Substrates of Response-based Sequence Learning using fMRI

Representation of sequential structure can occur with respect to the order of perceptual events or the order in which actions are linked. Neural correlates of sequence retrieval associated with the order of motor responses were identified in a variant of the serial reaction time task in which training occurred with a spatially incompatible mapping between stimuli and finger responses. After transfer to a spatially compatible version of the task, performance enhancements indicative of learning were only present in subjects required to make finger movements in the same order used during training. In contrast, a second group of subjects performed the compatible task using an identical sequence of stimuli (and different order of finger movements) as in training. They demonstrated no performance benefit, indicating that learning was response based. Analysis was restricted to subjects demonstrating low recall of the sequence structure to rule out effects of explicit awareness. The interaction of group (motor vs. perceptual transfer) with sequence retrieval (sequencing vs. rest) revealed significantly greater activation in the bilateral supplementary motor area, cingulate motor area, ventral premotor cortex, left caudate, and inferior parietal lobule for subjects in the motor group (illustrating successful sequence retrieval at the response level). Retrieval of sequential responses occurs within mesial motor areas and related motor planning areas.

Functional Assessment of Spatial Neglect: A Review of the Catherine Bergego Scale and an Introduction of the Kessler Foundation Neglect Assessment Process

Abstract Spatial neglect is a debilitating poststroke neurocognitive disorder associated with prolonged hospitalization and poor rehabilitation outcomes. The literature suggests a high prevalence of this disorder, but clinicians have difficulty reliably identifying affected survivors. This discrepancy may result from suboptimal use of validated neglect assessment procedures. In this article, we suggest use of a validated assessment tool that is sensitive to identification of neglect and its functional consequences – the Catherine Bergego Scale (CBS). We provide detailed item-by-item instructions for observation and scoring – the Kessler Foundation Neglect Assessment Process (KF-NAP). Rehabilitation researchers may be able to use the CBS via the KF-NAP to measure ecological outcomes and specific, separable perceptual-attentional and motor-exploratory spatial behaviors.

Psychometric Evaluation of Neglect Assessment Reveals Motor-Exploratory Predictor of Functional Disability in Acute-Stage Spatial Neglect

OBJECTIVE To determine the psychometric properties of 2 neglect measures, the Behavioral Inattention Test (BIT)-conventional and the Catherine Bergego Scale (CBS), in acute spatial neglect. Spatial neglect is a failure or slowness to respond, orient, or initiate action toward contralesional stimuli, associated with functional disability that impedes stroke recovery. Early identification of specific neglect deficits may identify patients likely to experience chronic disability. However, psychometric evaluation of assessments has focused on subacute/chronic populations. DESIGN Correlational/psychometric study. SETTING Inpatient rehabilitation hospital. PARTICIPANTS Screening identified 51 consecutive patients with a right-hemisphere stroke with left neglect (BIT score <129 or CBS score >11) tested an average of 22.3 days poststroke. INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES We obtained BIT, CBS, and Barthel Index assessments for each participant and clinical and laboratory measures of perceptual-attentional and motor-intentional deficits. RESULTS The BIT showed good reliability and loaded onto a single factor. Consistent with our theoretical prediction, principal components analysis of the CBS identified 2 underlying factors: Where perceptual-attentional items (CBS-PA) and embodied, motor-exploratory items (CBS-ME). The CBS-ME uniquely predicted deficits in activities of daily living (ADLs) assessed by using the Barthel Index, but did not predict clinical and laboratory assessments of motor-intentional bias. More severe neglect on the CBS-PA correlated with greater Where perceptual-attentional bias on clinical and laboratory tests, but did not uniquely predict deficits in ADLs. CONCLUSIONS Our results indicate that assessments of spatial neglect may be used to detect specific motor-exploratory deficits in spatial neglect. Obtaining CBS-ME scores routinely might improve the detection of acute-stage patients with spatial action deficits requiring increased assistance that may persist to the chronic stage.

Effects of prism adaptation on motor-intentional spatial bias in neglect.

Prism adaptation may alleviate some symptoms of spatial neglect. However, the mechanism through which this technique works is still unclear. This study investigated whether prism adaptation differentially affects dysfunction in perceptual-attentional ‘where’ bias versus motor-intentional ‘aiming’ bias. Five neglect patients performed a line bisection task in which lines were viewed under both normal and right–left reversed viewing conditions, allowing for the fractionation of ‘where’ and ‘aiming’ spatial bias components. After two consecutive days of prism adaptation, participants demonstrated a significant improvement in ‘aiming’ spatial bias, with no effect on ‘where’ spatial bias. These findings suggest that prism adaptation may primarily affect motor-intentional ‘aiming’ bias in poststroke spatial neglect patients.

Presence of Motor-Intentional Aiming Deficit Predicts Functional Improvement of Spatial Neglect With Prism Adaptation.

Background. Spatial neglect is a debilitating disorder for which there is no agreed on course of rehabilitation. The lack of consensus on treatment may result from systematic differences in the syndromes characteristics, with spatial cognitive deficits potentially affecting perceptual-attentional “Where” or motor-intentional “Aiming” spatial processing. Heterogeneity of response to treatment might be explained by different treatment impacts on these dissociated deficits: prism adaptation, for example, might reduce Aiming deficits without affecting Where spatial deficits. Objective. Here, we tested the hypothesis that classifying patients by their profile of Where-versus-Aiming spatial deficit would predict response to prism adaptation and specifically that patients with Aiming bias would have better recovery than those with isolated Where bias. Methods. We classified the spatial errors of 24 subacute right stroke survivors with left spatial neglect as (1) isolated Where bias, (2) isolated Aiming bias, or (3) both. Participants then completed 2 weeks of prism adaptation treatment. They also completed the Behavioral Inattention Test and Catherine Bergego Scale (CBS) tests of neglect recovery weekly for 6 weeks. Results. As hypothesized, participants with only Aiming deficits improved on the CBS, whereas those with only Where deficits did not improve. Participants with both deficits demonstrated intermediate improvement. Conclusion. These results support behavioral classification of spatial neglect patients as a potential valuable tool for assigning targeted, effective early rehabilitation.

Nonnormative discounting: There is more to cue interaction effects than controlling for alternative causes

Several experiments on human causal reasoning have demonstrated “discounting”-that the presence of a strong alternative cause may decrease the perceived efficacy of a moderate target cause. Some, but not all, of these effects have been shown to be attributable to subjects’ use of conditional rather than unconditional contingencies (i.e., subjects control for alternative causes). We review experimental results that do not conform to the conditionalizing contingency account of causal judgment. In four experiments, we demonstrate that there is “nonnormative discounting” above what is accounted for by conditionalization, that discounting may depend on the nature of the question put to the subjects, and that discounting can be affected by motivation. We conclude that because nonnormative discounting occurs for summary presentations as well as trial-by-trial presentations of information and because nonnormative discounting depends on motivation, it is not a necessary result of cue competition during the contingency learning process.

Integrity of medial temporal structures may predict better improvement of spatial neglect with prism adaptation treatment

Prism adaptation treatment (PAT) is a promising rehabilitative method for functional recovery in persons with spatial neglect. Previous research suggests that PAT improves motor-intentional “aiming” deficits that frequently occur with frontal lesions. To test whether presence of frontal lesions predicted better improvement of spatial neglect after PAT, the current study evaluated neglect-specific improvement in functional activities (assessment with the Catherine Bergego Scale) over time in 21 right-brain-damaged stroke survivors with left-sided spatial neglect. The results demonstrated that neglect patients’ functional activities improved after two weeks of PAT and continued improving for four weeks. Such functional improvement did not occur equally in all of the participants: Neglect patients with lesions involving the frontal cortex (n = 13) experienced significantly better functional improvement than did those without frontal lesions (n = 8). More importantly, voxel-based lesion-behavior mapping (VLBM) revealed that in comparison to the group of patients without frontal lesions, the frontal-lesioned neglect patients had intact regions in the medial temporal areas, the superior temporal areas, and the inferior longitudinal fasciculus. The medial cortical and subcortical areas in the temporal lobe were especially distinguished in the “frontal lesion” group. The findings suggest that the integrity of medial temporal structures may play an important role in supporting functional improvement after PAT.

Spacing practice sessions across days earlier rather than later in training improves performance of a visuomotor skill

Our goal was to determine whether the extent of off-line performance improvements on a visuomotor task depends on the amount of practice individuals experience prior to a 24-h between-session break. Subjects completed ten trials of a mirror-tracing task over two days. On Day 1, subjects experienced either one, three or seven trials. Twenty-four hours later subjects completed the remainder of the ten trials. Despite experiencing an equivalent number of total training trials, subjects experiencing the 24-h delay after one or three trials demonstrated off-line performance improvements, but those experiencing the delay after seven trials did not. Furthermore, the one- and three-trial groups reached a superior level of performance by the end of training relative to the seven-trial group.

The role of taxonomies in the study of human memory.

The idea that memory is not unitary but is instead composed of multiple systems has a long history and has been debated with particular vigor in the last 20 years. Nevertheless, whether or not there are multiple memory systems remains unsettled. In this article, we suggest that psychologists wishing to classify memory can learn from biological systematics, the discipline that creates taxonomies of species. In so doing, we suggest that psychologists have made two assumptions in classifying memory: that features of memory are perfectly correlated, and that there is a straightforward mapping between taxonomy and theory. We argue that these assumptions are likely to be incorrect, but we also argue that there is a place for taxonomy in the study of memory. Taxonomies of memory are organizational schemes for data—they are descriptive, not explanatory-and so can inspire theory, although they cannot serve as theories themselves.

Discounting and Conditionalization: Dissociable Cognitive Processes in Human Causal Inference

When people are asked to judge the strengths of two potential causes of an effect, they often demonstrate discounting—devaluing the strength of a target cause when it is judged in the presence of a strong (relative to a weak) alternative cause. Devaluing the target cause sometimes results from conditionalization—holding alternative causes constant while evaluating the target cause. Yet discounting not attributable to conditionalization also occurs. We sought to dissociate conditionalization and discounting (beyond that accounted for by conditionalization) by having subjects perform either a spatial or a verbal working memory task while learning a causal relation. Conditionalization was disrupted by the verbal task but not the spatial task; however, discounting was disrupted by the spatial task but not the verbal task. Conditionalization and discounting are therefore cognitively dissociable processes in human causal inference.