This study examined the effects of rehearsal on the neural substrates supporting episodic autobiographical and semantic memory. Stimuli were collected prospectively using audio recordings, thereby bringing under experimental control ecologically valid, naturalistic autobiographical stimuli. Participants documented both autobiographical and semantic stimuli over a period of 6–8 months, followed by a rehearsal manipulation during the 3 d preceding scanning. During functional magnetic resonance imaging scanning, participants were exposed to recordings that they were hearing for the first, second, or eighth time. Rehearsal increased the rated vividness with which information was remembered, particularly for autobiographical events. Neuroimaging findings revealed rehearsal-related suppression of activation in regions supporting episodic autobiographical and semantic memory. Episodic autobiographical and semantic memory produced distinctly different patterns of regional activation that held even after eight repe...

One of the most remarkable abilities of bilinguals is to produce and/or to perceive a switch from one language to the other without any apparent difficulty. However, several psycholinguistic studies indicate that producing, recognizing, and integrating a linguistic code different from the one in current use may entail a processing cost for the speaker/listener. Up to now, the underlying neural substrates of perceiving language switches are unknown. In the present study, we investigated the neural mechanisms of language switching during auditory perception in bilinguals. Event-related functional magnetic resonance imaging was performed in 12 early, highly proficient Italian/French bilinguals, who were more exposed to their second language. Subjects had to listen to narratives containing “switched passages” that could either respect (i.e., regular switches) or violate (i.e., irregular switches) the constituents of sentence structure. The results indicate that switching engages an extensive neural network, in...

The neurophysiological basis of practice-induced gray matter increase is unclear. To study the relationship of practice-induced gray matter changes and neural activation, we conducted a combined longitudinal functional and morphometric (voxel-based morphometry) magnetic resonance imaging (MRI) study on mirror reading. Compared with normal reading, mirror reading resulted in an activation of the dorsolateral occipital cortex, medial occipital cortex, superior parietal cortex, medial and dorsolateral prefrontal cortex, as well as anterior insula and cerebellum. Daily practice of 15 min for 2 weeks resulted in an increased performance of mirror reading. After correction for pure performance effects, we found a practice-related decrease of activation at the right superior parietal cortex and increase of activation at the right dorsal occipital cortex. The longitudinal voxel-based morphometry analysis yielded an increase of gray matter in the right dorsolateral occipital cortex that corresponded to the peak of ...

In human lateral temporal cortex, some regions show specific sensitivity to human motion. Here we examine whether such effects reflect a general biological–nonbiological organizational principle or a process specific to human–agent processing by comparing processing of human, animal, and tool motion in a functional magnetic resonance imaging (fMRI) experiment with healthy participants and a voxel-based lesion-symptom mapping (VLSM) study of patients with brain damage (77 stroke patients). The fMRI experiment revealed that in the lateral temporal cortex, the posterior superior temporal sulcus shows a preference for human and animal motion, whereas the middle part of the right superior temporal sulcus/gyrus (mSTS/STG) shows a preference for human and functional tool motion. VLSM analyses also revealed that damage to this right mSTS/STG region led to more severe impairment in the recognition of human and functional tool motion relative to animal motion, indicating the causal role of this brain area in human–a...

Saccadic latencies are influenced by what occurred during the previous trial. When the previous trial is an antisaccade, the latencies of both prosaccades and antisaccades are prolonged. The aim of this study was to identify neural correlates of this intertrial effect of antisaccades. Specifically, based on both monkey electrophysiology and human neuroimaging findings, we expected trials preceded by antisaccades to be associated with reduced frontal eye field (FEF) activity relative to those preceded by prosaccades. Twenty-one healthy participants performed pseudorandom sequences of prosaccade and antisaccade trials during functional magnetic resonance imaging (fMRI) with concurrent monitoring of eye position. We compared activity in trials preceded by an antisaccade with activity in trials preceded by a prosaccade. The primary result was that a previous antisaccade prolonged saccadic latency and reduced fMRI activity in the FEF and other regions. No regions showed increased activity. We interpret the redu...

Mice over-expressing the mutant human G93A-SOD1 (Superoxide Dismutase 1) are widely used as an animal model for amyotrophic lateral sclerosis (ALS). ALS is characterized by a progressive degeneration of motor neurons in the motor cortex, brainstem and spinal cord. The underlying mechanisms for the selective cell death of motor neurons are still uncertain. To study factors that cause selective neuron degeneration or therapeutical approaches to delay the progression of the disease, a method is required to monitor the state of motor neurons under in vivo conditions. Using a Bruker Biospec 47/20 NMR scanner (4.7 T) we measured the signal intensities of motor nuclei within the brainstem of G93A-SOD1 mice and non-transgenic litter controls at days 50, 90, 112, and 130. T2-weighted MR-imaging performed at day 130 revealed a clear signal intensity enhancement compared to surrounding tissue in various motor nuclei within the brainstem, such as the hypoglossal nucleus (Nc. Nv XII), nucleus ambiguus (Nc. Nv IX, X), t...

Animal studies have established that the gonadal hormones estradiol and progesterone exert multiple effects in the central nervous system. The hippocampus seems to be particularly responsive to those hormones in its function and structure. The possible relevance of these effects for memory in older postmenopausal women is still debated. Studies in relatively young women have documented that estradiol improves verbal memory. Studies in older women in contrast have resulted in an inconclusive picture. In addition, the possible interaction of estradiol and progesterone has rarely been investigated. In this double blind experiment 51 hysterectomized women (age 58-75 years) were randomly assigned to one of three treatment groups: 1) Placebo, 2) Estradiol (2 mg estradiol valerate), or 3) Estradiol/Progesterone (2 mg estradiol valerate/100 mg micronized progesterone). Neuropsychological testing and structural MRI were conducted at baseline and after 4 (cognitive tests only) and 24 weeks of treatment. Verbal and v...

Constraints from functional magnetic resonance imaging (fMRI) were used to identify the sources of the visual P300 event-related potential (ERP). Healthy subjects performed a visual three-stimulus oddball paradigm with a difficult discrimination task while fMRI and high-density ERP data were acquired in separate sessions. This paradigm allowed us to differentiate the P3b component of the P300, which has been implicated in the detection of rare events in general (target and distractor), from the P3a component, which is mainly evoked by distractor events. The fMRI-constrained source model explained >99% of the variance of the scalp ERP for both components. The P3b was mainly produced by parietal and inferior temporal areas, whereas frontal areas and the insula contributed mainly to the P3a. This source model reveals that both higher visual and supramodal association areas contribute to the visual P3b and that the P3a has a strong frontal contribution, which is compatible with its more anterior distribution o...

Amphetamine (AMPH) is known to internalize the dopamine transporter protein (DAT) and subsequently releases massive amount of dopamine (DA). However, the degree of the released DA acting on the post-synaptic D1 versus D2 receptors is not clear. Controlling the amount of DA release by challenging rats with different doses of AMPH, we were able to probe the roles of the D1 and D2 receptors by measuring the regional cerebral blood volume (rCBV) response using pharmacological MRI (phMRI). Methods – Sprague-Dawley rats were used in this study. rCBV response to acute AMPH challenge were acquired using IRON method with conventional gradient echo sequence (TR/TE: 305ms/6ms) in a 9.4T Bruker scanner. Four groups of Sprague-Dawley rats were challenged with different AMPH doses (iv): 0.25mg/kg (n=8), 0.5mg/kg (n=6), 1.0mg/kg (n=6), and 3.0mg/kg (n=7). Results – There was a dose-dependent rCBV response to the AMPH challenge in the brain. AMPH of 3mg/kg and 1mg/kg induced significant rCBV increases in the caudate/putam...

We have previously reported in vivo µMRI detection of plaques following intra-carotid injection of Gd-DTPA-Aß1-40 in AD model mice. However, Aß1-40 is toxic and can potentially seed amyloid plaque growth. In the present study we developed non-toxic, Aß homologous probes, which can detect early amyloid plaques in vivo. Furthermore, we examined the MRI scans using voxel-based analysis, to allow for un-biased qualitation. µMRI was performed in AD Tg mice and wild-type controls prior to injection and following intra-carotid and intravenous injection with gadolinium-DTPA-K6Aß1-30. Imaging scans were realigned, spatially normalized to match the shape of a standard template MRI image in stereotactic space, smoothed and examined for statistical differences using statistical parametric mapping (SPM, version 2002) . Large plaques were detected in vivo prior to injection of contrast agent. Using Perl's staining these large plaques contained extensive iron deposits. Following injection, the contrast of these plaques w...