Patients with bipolar disorder show a selective deficit in the episodic simulation of future events.

A substantial body of evidence suggests that autobiographical recollection and simulation of future happenings activate a shared neural network. Many of the neural regions implicated in this network are affected in patients with bipolar disorder (BD), showing altered metabolic functioning and/or structural volume abnormalities. Studies of autobiographical recall in BD reveal overgeneralization, where autobiographical memory comprises primarily factual or repeated information as opposed to details specific in time and in place and definitive of re-experiencing. To date, no study has examined whether these deficits extend to future event simulation. We examined the ability of patients with BD and controls to imagine positive, negative and neutral future events using a modified version of the Autobiographical Interview (Levine, Svoboda, Hay, Winocur, & Moscovitch, 2002) that allowed for separation of episodic and non-episodic details. Patients were selectively impaired in imagining future positive, negative, and neutral episodic details; simulation of non-episodic details was equivalent across groups.

Optimization of 3D MP-RAGE for neonatal brain imaging at 3.0 T.

Three-dimensional (3D) magnetic resonance imaging (MRI) has shown great potential for studying the impact of prematurity and pathology on brain development. We have investigated the potential of optimized T1-weighted 3D magnetization-prepared rapid gradient-echo imaging (MP-RAGE) for obtaining contrast between white matter (WM) and gray matter (GM) in neonates at 3 T. Using numerical simulations, we predicted that the inversion time (TI) for obtaining strongest contrast at 3 T is approximately 2 s for neonates, whereas for adults, this value is approximately 1.3 s. The optimal neonatal TI value was found to be insensitive to reasonable variations of the assumed T1 relaxation times. The maximum theoretical contrast for neonates was found to be approximately one third of that for adults. Using the optimized TI values, MP-RAGE images were obtained from seven neonates and seven adults at 3 T, and the contrast-to-noise ratio (CNR) was measured for WM versus five GM regions. Compared to adults, neonates exhibited lower CNR between cortical GM and WM and showed a different pattern of regional variation in CNR. These results emphasize the importance of sequence optimization specifically for neonates and demonstrate the challenge in obtaining strong contrast in neonatal brain with T1-weighted 3D imaging.

Neonatal brain: regional variability of in vivo MR imaging relaxation rates at 3.0 T--initial experience.

PURPOSE: To retrospectively investigate regional in vivo magnetic resonance (MR) imaging transverse and longitudinal relaxation rates at 3.0 T in neonatal brain, the relationship between these rates, and their potential use for gray matter (GM) versus white matter (WM) tissue discrimination. MATERIALS AND METHODS: Informed parental consent for performance of imaging procedures was obtained in each infant. Informed consent for retrospective image analysis was not required; ethics approval was obtained from institutional review board. At 3.0 T, R1 and R2 were measured in brain regions (frontal WM, posterior WM, periventricular WM, frontal GM, posterior GM, basal ganglia, and thalamus) in 13 infants with suspected neurologic abnormality (two term, 11 preterm). Maps of R1 and R2 were acquired with T1 by multiple readout pulses and segmented spin-echo echo-planar imaging sequences, respectively. Accuracy of R1 and R2 map acquisition methods was tested in phantoms by comparing them with inversion-recovery and spin-echo sequences, respectively. Statistical analysis included linear regression analysis to determine relationship between R1 and R2 and Wilcoxon signed rank test to investigate the potential for discrimination between GM and WM. RESULTS: In phantoms, R1 values measured with T1 by multiple readout pulses sequence were 3%-8% lower than those measured with inversion recovery sequence, and R2 values measured with segmented echo-planar sequence were 1%-8% lower than those measured with spin-echo sequence. A strong correlation of 0.944 (P < .001) between R1 and R2 in neonatal brain was observed. For R2, relative differences between GM and WM were larger than were those for R1 (z = -2.366, P < .05). For frontal GM and frontal WM, (R2(GM) - R2(WM))/R2(WM) yielded 0.8 +/- 0.2 (mean +/- standard deviation) and (R1(GM) - R1(WM))/R1(WM) yielded 0.3 +/- 0.09. CONCLUSION: Results at 3.0 T indicate that R1 decreases with increasing field strength, while R2 values are similar to those reported at lower field strengths. For neonates, R2 image contrast may be more advantageous than R1 image contrast for differentiation between GM and WM.

Uncomplicated intraventricular hemorrhage is followed by reduced cortical volume at near-term age.

BACKGROUND: Intraventricular hemorrhage (IVH) is the most common brain injury among premature infants. Neonates with IVH are at greater risk of impaired neurodevelopmental outcomes, compared with those without IVH. IVH causes destruction of the germinal matrix and glial precursor cells, with possible effects on cortical development. OBJECTIVE: To investigate cortical development after uncomplicated IVH (with no parenchymal involvement and no posthemorrhagic hydrocephalus). We hypothesized that uncomplicated IVH would be followed by reduced cortical volume among premature infants at near-term age. METHODS: A prospective cohort study was conducted, with preset selection criteria. Infants with small-for-gestational age birth weight, congenital abnormalities or brain malformations, metabolic disorders, recurrent sepsis, or necrotizing enterocolitis were excluded. Also, infants with posthemorrhagic hydrocephalus, parenchymal involvement of hemorrhage, cystic periventricular leukomalacia, or persistent ventriculomegaly were excluded, on the basis of routine serial ultrasonographic assessments. Three-dimensional images were acquired for 23 infants at near-term age, with 3-T magnetic resonance imaging and a magnetization-prepared rapid gradient echo sequence. Image analysis and segmentation of the cerebrum in different tissue types were based on signal contrast and anatomic localization. The cortical gray matter (CGM), subcortical gray matter, white matter, and intraventricular cerebrospinal fluid volumes of 12 infants with uncomplicated IVH were compared with those of 11 infants without IVH, using multivariate analysis of variance. RESULTS: The multivariate analysis of variance for the regional brain volumes in the 2 groups indicated significance (Wilks' lambda = 0.546). The CGM volume was significantly reduced in the IVH group (no-IVH group: 122 +/- 12.9 mL; IVH group: 102 +/- 14.6 mL; F = 13.218). This finding remained significant after testing for possible confounding factors and adjustment for size differences between the infants (F = 9.415). There was no difference in the volumes of subcortical gray matter, white matter, and cerebrospinal fluid. CONCLUSIONS: This is the first study to document impaired cortical development after uncomplicated IVH. The impairment was demonstrated by a 16% reduction in cerebral CGM volume at near-term age. The finding supports concerns regarding possible glial precursor cell loss after germinal matrix IVH, but its clinical significance is still unclear. The alteration in brain development demonstrated in this report supports closer neurodevelopmental follow-up monitoring of preterm infants with uncomplicated IVH.