Temporal Discrimination of Sub- and Suprasecond Time Intervals: A Voxel-Based Lesion Mapping Analysis

We used voxel-based lesion-symptom mapping (VLSM) to determine which brain areas are necessary for discriminating time intervals above and below 1 s. VLSM compares behavioral scores of patients that have damage to a given voxel to those that do not on a voxel-by-voxel basis to determine which voxels are critical for the given behavior. Forty-seven subjects with unilateral hemispheric lesions performed a temporal discrimination task in which a standard stimulus was compared on each trial to a test stimulus. In different blocks of trials, standard stimuli were either 600 or 2000 ms. Behavioral measures included the point of subjective equality, a measure of accuracy, and the coefficient of variation, a measure of variability. Lesions of the right middle and inferior frontal gyri were associated with decrements in performance on both durations. In addition, lesions of the left temporal lobe and right precentral gyrus were associated exclusively with impaired performance for subsecond stimuli. In line with results from other studies, these data suggest that different circuits are necessary for timing intervals in these ranges, and that right frontal areas are particularly important to timing

Establishing the reliability and validity of the Zagazig Depression Scale in a UK student population: an online pilot study

Background: It is thought that depressive disorders will be the second leading cause of disability worldwide by 2020. Recently, there is a steady increase in the number of university students diagnosed and treated as depression patients. It can be assumed that depression is a serious mental health problem for university students because it affects all age groups of the students either younger or older equally. The current study aims to establish the reliability and validity of the Zagazig Depression scale in a UK sample. Methods: The study was a cross-sectional online survey. A sample of 133 out of 275 undergraduate students from a range of UK Universities in the academic year 2008-2009, aged 20.3 ± 6.3 years old were recruited. A modified back translated version of Zagazig Depression scale was used. In order to validate the Zagazig Depression scale, participants were asked to complete the Patient Health Questionnaire. Statistical analysis includes Kappa analysis, Cronbach's alpha, Spearman's correlation analysis, and Confirmatory Factor analysis. Results: Using the recommended cut-off of Zagazig Depression scale for possible minor depression it was found that 30.3% of the students have depression and higher percentage was identified according to the Patient Health Questionnaire (37.4%). Females were more depressed. The mean ZDS score was 8.3 ± 4.2. Rates of depression increase as students get older. The reliability of The ZDS was satisfactory (Cronbach's alpha was .894). For validity, ZDS score was strongly associated with PHQ, with no significant difference (p-value > 0.05), with strong positive correlation (r = +.8, p-value < 0.01). Conclusion: The strong, significant correlation between the PHQ and ZDS, along with high internal consistency of the ZDS as a whole provides evidence that ZDS is a reliable measure of depressive symptoms and is promising for the use of the translated ZDS in a large-scale cross-culture study

Semantic short-term memory and resolution of interference: Patient, ERP and fMRI data

Experiment 1 presents data from a patient with a semantic short-term memory deficit, patient ML, that indicate profound susceptibility to interference. For example, although this patient cannot reliably recall three items in a serial recall task, he paradoxically shows exaggerated effects of proactive interference in short-term memory. However, this patient's difficulty with interference appears to be limited to tasks involving verbal stimuli---other data show that patient ML performs normally on two nonverbal tasks that require resolution of interference. Experiment 2 attempted to identify ERP components related to proactive interference in one of the tasks administered in Experiment 1. This task, the recent negatives task, is a convenient measure of susceptibility to proactive interference. Moreover, Experiment 2 added an additional manipulation motivated by a unique effect discovered during the testing of patient ML (Hamilton, 2004), whereby the patient performed much better on the recent negatives task when repetition was minimized and the number of stimuli presented within the task were expanded. Two ERP components, a frontally distributed N400 effect and parietally distributed late positive component (LPC), were found to respond to the manipulation of recency and repetition. Experiment 3 and Experiment 4 examined a language comprehension paradigm known to differentiate between patients with semantic and phonological short-term memory deficits. This task requires detection of semantic anomalies in phrases in which multiple adjectives appear before or after a noun---multiple adjectives appearing before a noun are believed to place greater demands on semantic short-term memory relative to when adjectives appear after a noun. Thus, patients with semantic short-term memory deficits are especially poor at detecting anomalies in the before condition. Experiment 3 uses the parietally distributed N400 as an indirect measure of short-term memory demands to corroborate behavioral and patient data. Relative to the "after" condition, the "before" condition did elicit smaller N400s, consistent with the idea that integration of adjectives in the before condition differs from integration in the after condition. Experiment 4 uses a modification of the sentence anomaly task employed in Experiment 3 to identify brain areas engaged in short-term maintenance of semantic representations. It was hypothesized that the before condition would produce greater activation in the left inferior frontal gyrus, a region that has been related to short-term maintenance of semantic representations. Results from Experiment 4 are discussed in terms of the organization of maintenance and control processes important in semantic short-term memory. Finally, data from Experiments 1--4 are discussed in terms of their implications for theories of semantic short-term memory deficits and the associations of semantic short-term memory deficits with particular deficits of language comprehension and production