Causal Contributions of the SMA to Alertness and Consciousness Interactions.

Phasic alertness facilitates conscious perception through a fronto-striatal network, including the supplementary motor area (SMA). The functioning of the ventral attentional network has been related to the alerting system, overlapping with the ventral branch of the superior longitudinal fasciculus (SLF III). In this study, we use repetitive transcranial magnetic stimulation (rTMS) and a conscious detection task with near-threshold stimuli that could be preceded by an alerting tone to explore the causal implication of the SMA in the relationship between phasic alertness and conscious perception. Complementary to SMA stimulation, a sham and an active condition (left inferior parietal lobe; IPL) were included. Deterministic tractography was used to isolate the right and left SLF III. Behaviorally, the alerting tone enhanced conscious perception and confidence ratings. rTMS over the SMA reduced the alerting effect on the percentage of perceived stimuli while rTMS over the left IPL produced no modulations, demonstrating a region-specific effect. Additionally, a correlation between the rTMS effect and the integrity of the right SLF III was found. Our results highlight the causal implication of a frontal region, the SMA, in the relationship between phasic alertness and conscious perception, which is related to the white matter microstructure of the SLF III.

Perinatal post-mortem magnetic resonance imaging (MRI) of the central nervous system (CNS): a pictorial review.

Central nervous system (CNS) abnormalities cause approximately 32-37.7% of terminations of pregnancy (TOP). Autopsy is currently the gold standard for assessing dead foetuses and stillborn. However, it has limitations and is sometimes subject to parental rejection. Recent studies have described post-mortem foetal magnetic resonance imaging (MRI) as an alternative and even complementary to autopsy for CNS assessment. Radiologists now play a key role in the evaluation of perinatal deaths. Assessment of foetal CNS abnormalities is difficult, and interpretation of foetal studies requires familiarisation with normal and abnormal findings in post-mortem MRI studies as well as the strengths and limitations of the imaging studies. The purpose of this pictorial review is to report our experience in the post-mortem MRI evaluation of the CNS system, including a description of the protocol used, normal CNS findings related to post-mortem status, abnormal CNS findings in our sample, and the correlation of these findings with histopathological results.

Locoregional CT staging of colon cancer: does a learning curve exist?

PURPOSE: To evaluate the learning curve for locoreginal staging of colon cancer in radiologist trainees. METHODS: Eighty-eight cases of colon cancer CT were included in this retrospective study. Four senior radiology residents staged the CTs according to TNM classification. Two out of four radiologists received feedback after reading every 20 cases. Radiologic staging was compared with pathologic staging and the learning curve, diagnostic performance, reader confidence and reading time were evaluated and compared between the two groups (feedback vs. no feedback). Generalized estimating equations logistic regression, QICu statistic, ANOVA and t test/Mann-Whitney test were utilized. RESULTS: Radiologists demonstrated a significant increase in their performance to distinguish between ≤ T2 and ≥ T3 and reached an inflection point at 38 cases, with a significant association with increased number of cases reviewed (P < 0.001). Sensitivity (P < 0.001), specificity (P = 0.030) and NPV (P = 0.002) demonstrated significant associations with increased experience. The overall reader's confidence was significantly higher in the group which received feedback (P < 0.001). There was no significant improvement in performance nor in reader's confidence for N staging (N0 vs. ≥ N1) for all readers. Reading time decreased with experience and showed a significant negative association with experience (P < 0.001). CONCLUSION: Diagnostic performance of senior radiology trainees in differentiating between T2 and T3 colon cancer on CTs improved with increased experience. In contrast, evaluation of lymph node involvement did not improve with more experience. Feedback had no significant effect on improvement of diagnostic performances.