Errors on the Trail Making Test Are Associated with Right Hemispheric Frontal Lobe Damage in Stroke Patients

Measures of performance on the Trail Making Test (TMT) are among the most popular neuropsychological assessment techniques. Completion time on TMT-A is considered to provide a measure of processing speed, whereas completion time on TMT-B is considered to constitute a behavioral measure of the ability to shift between cognitive sets (cognitive flexibility), commonly attributed to the frontal lobes. However, empirical evidence linking performance on the TMT-B to localized frontal lesions is mostly lacking. Here, we examined the association of frontal lesions following stroke with TMT-B performance measures (i.e., completion time and completion accuracy measures) using voxel-based lesion-behavior mapping, with a focus on right hemispheric frontal lobe lesions. Our results suggest that the number of errors, but not completion time on the TMT-B, is associated with right hemispheric frontal lesions. This finding contradicts common clinical practice-the use of completion time on the TMT-B to measure cognitive flexibility, and it underscores the need for additional research on the association between cognitive flexibility and the frontal lobes. Further work in a larger sample, including left frontal lobe damage and with more power to detect effects of right posterior brain injury, is necessary to determine whether our observation is specific for right frontal lesions

Temporal dynamics of selective attention and conflict resolution during cross-dimensional go-nogo decisions

<p>Abstract</p> <p>Background</p> <p>Decision-making is a fundamental capacity which is crucial to many higher-order psychological functions. We recorded event-related potentials (ERPs) during a visual target-identification task that required go-nogo choices. Targets were identified on the basis of cross-dimensional conjunctions of particular colors and forms. Color discriminability was manipulated in three conditions to determine the effects of color distinctiveness on component processes of decision-making.</p> <p>Results</p> <p>Target identification was accompanied by the emergence of prefrontal P2a and P3b. Selection negativity (SN) revealed that target-compatible features captured attention more than target-incompatible features, suggesting that intra-dimensional attentional capture was goal-contingent. No changes of cross-dimensional selection priorities were measurable when color discriminability was altered. Peak latencies of the color-related SN provided a chronometric measure of the duration of attention-related neural processing. ERPs recorded over the frontocentral scalp (N2c, P3a) revealed that color-overlap distractors, more than form-overlap distractors, required additional late selection. The need for additional response selection induced by color-overlap distractors was severely reduced when color discriminability decreased.</p> <p>Conclusion</p> <p>We propose a simple model of cross-dimensional perceptual decision-making. The temporal synchrony of separate color-related and form-related choices determines whether or not distractor processing includes post-perceptual stages. ERP measures contribute to a comprehensive explanation of the temporal dynamics of component processes of perceptual decision-making.</p

Performance on the Frontal Assessment Battery is sensitive to frontal lobe damage in stroke patients

Background: The Frontal Assessment Battery (FAB) is a brief battery of six neuropsychological tasks designed to assess frontal lobe function at bedside [Neurology 55:1621-1626, 2000]. The six FAB tasks explore cognitive and behavioral domains that are thought to be under the control of the frontal lobes, most notably conceptualization and abstract reasoning, lexical verbal fluency and mental flexibility, motor programming and executive control of action, self-regulation and resistance to interference, inhibitory control, and environmental autonomy. Methods: We examined the sensitivity of performance on the FAB to frontal lobe damage in right-hemisphere-damaged first-ever stroke patients based on voxel-based lesion-behavior mapping. Results: Voxel-based lesion-behavior mapping of FAB performance revealed that the integrity of the right anterior insula (BA13) is crucial for the FAB global composite score, for the FAB conceptualization score, as well as for the FAB inhibitory control score. Furthermore, the FAB conceptualization and mental flexibility scores were sensitive to damage of the right middle frontal gyrus (MFG; BA9). Finally, the FAB inhibitory control score was sensitive to damage of the right inferior frontal gyrus (IFG; BA44/45). Conclusions: These findings indicate that several FAB scores (including composite and item scores) provide valid measures of right hemispheric lateral frontal lobe dysfunction, specifically of focal lesions near the anterior insula, in the MFG and in the IFG

Rheology of complex fluids by particle image velocimetry in microchannels

International audienceThe rheology of complex fluids has been the subject of attention for decades, partly in relation to its relevance for many processing or commercial applications.1 Recent studies have pointed out that many reported nonlinear behaviors may be related to the heterogeneous nature of the flow, which can adopt various forms, from simple steady “shear banding”2 to more complex spatiotemporal organizations.3 This has triggered the development of experimental methods to probe flow and structural heterogeneities (birefringence,4 NMR,5 neutrons,6 light scattering,7 and ultrasound8), as well as theoretical effort.In this letter we propose a complementary experimental method to access directly relevant information in this context. We flow the fluid in transparent microchannels of controlled geometry and measure in a spatially resolved way the motion of tracers embedded in that fluid. The resulting velocity profiles allow us to measure directly the nonlinear rheology of such fluids, with simultaneous information as to the occurrence of heterogeneities or wall slip. After a presentation of our setup (Fig. 1) and experimental procedure, we demonstrate here the power of our method by quantifying the bulk nonlinear rheology of model shear-thinning polymer solutions. We then comment on the observation of wall slip and point out perspectives for studies of more complex fluids

Temporal dynamics of selective attention and conflict resolution during cross-dimensional go-nogo decisions-4

<p><b>Copyright information:</b></p><p>Taken from "Temporal dynamics of selective attention and conflict resolution during cross-dimensional go-nogo decisions"</p><p>http://www.biomedcentral.com/1471-2202/8/68</p><p>BMC Neuroscience 2007;8():68-68.</p><p>Published online 17 Aug 2007</p><p>PMCID:PMC2045106.</p><p></p>ering (see Methods) at posterior electrodes (P7, O1, O2, P8)

Temporal dynamics of selective attention and conflict resolution during cross-dimensional go-nogo decisions-0

<p><b>Copyright information:</b></p><p>Taken from "Temporal dynamics of selective attention and conflict resolution during cross-dimensional go-nogo decisions"</p><p>http://www.biomedcentral.com/1471-2202/8/68</p><p>BMC Neuroscience 2007;8():68-68.</p><p>Published online 17 Aug 2007</p><p>PMCID:PMC2045106.</p><p></p>ue ellipse is the form-overlap distractor, C-F+, and the blue rectangle serves as standard distractor, C-F-. () When the blue ellipse is the target, C+F+, the blue rectangle is the color-overlap distractor, C+F-, the red ellipse is the form-overlap distractor, C-F+, and the red rectangle serves as standard distractor, C-F-. () When the red rectangle is the target, C+F+, the red ellipse is the color-overlap distractor, C+F-, the blue rectangle is the form-overlap distractor, C-F+, and the blue ellipse serves as standard distractor, C-F-. () When the blue rectangle is the target, C+F+, the blue ellipse is the color-overlap distractor, C+F-, the red rectangle is the form-overlap distractor, C-F+, and the red ellipse serves as standard distractor, C-F-

Errors on the Trail Making Test Are Associated with Right Hemispheric Frontal Lobe Damage in Stroke Patients

Measures of performance on the Trail Making Test (TMT) are among the most popular neuropsychological assessment techniques. Completion time on TMT-A is considered to provide a measure of processing speed, whereas completion time on TMT-B is considered to constitute a behavioral measure of the ability to shift between cognitive sets (cognitive flexibility), commonly attributed to the frontal lobes. However, empirical evidence linking performance on the TMT-B to localized frontal lesions is mostly lacking. Here, we examined the association of frontal lesions following stroke with TMT-B performance measures (i.e., completion time and completion accuracy measures) using voxel-based lesion-behavior mapping, with a focus on right hemispheric frontal lobe lesions. Our results suggest that the number of errors, but not completion time on the TMT-B, is associated with right hemispheric frontal lesions. This finding contradicts common clinical practice—the use of completion time on the TMT-B to measure cognitive flexibility, and it underscores the need for additional research on the association between cognitive flexibility and the frontal lobes. Further work in a larger sample, including left frontal lobe damage and with more power to detect effects of right posterior brain injury, is necessary to determine whether our observation is specific for right frontal lesions