The extreme-male theory of autism spectrum disorders (ASD) contends that individuals with ASD have a “hyper-male?brain profile characterized behaviorally by increased “systematizing?and a decreased ability to “empathize?(Baron-Cohen, 2002). If the extreme-male theory is correct, one might expect to see evidence in brain structures that are known to be sexually dimorphic. The caudate nucleus has been shown to be smaller in males than females (Goldstein, 2001) and in the present study we utilized magnetic resonance images (MRI) to evaluate the volume of the caudate nucleus in males and females with ASD. The caudate nucleus was measured bilaterally in control males (n=13), control females (n=13), males with ASD (n=10) and a smaller group of females with ASD (n=3). When normalized to whole brain volumes, the average caudates of the ASD groups were always relatively smaller than the control groups. ANOVA done on the average caudate size from the control males, control females, and ASD males showed only modest d...

A special area, the marginal division (MrD), has been found at the caudomedial border of rat striatum in 1988 by Shu et al. It consists of fusiform neurons and is densely filled of many neuropeptide fibers and terminals. The MrD has been also identified in the neostriatum of cat, monkey and human brains. Learning and memory function of the MrD has been verified by Y-maze test in rats. In order to investigate the function of the MrD in human brain, functional magnetic resonance imaging (fMRI) of healthy volunteers tested with an auditory digital working memory task was performed. Highly active areas were observed in the prefrontal cortex and MrD with left sided predominance during performance of the task, but other parts of the neostriatum were not excited and the MrD was not activated in a control test of non-working memory. The results indicate that the MrD participate the auditory digital working memory of human brain. Clinical case investigation combining MRI and cognitive function analyses exhibited th...

fMRI based on gradient echo (GE) BOLD effect is the most widely used method for studying brain function non-invasively in vivo. It is not clear, however, whether the spatial specificity of GE-BOLD fMRI could provide a viable tool for the investigation of cortical micro-organization, and whether alternative fMRI modalities such as CBF fMRI could be more suitable than GE-BOLD fMRI for this goal. To address this question, we investigated the lateral point spread function (PSF) in the cat visual cortex (area 18) with GE-BOLD and CBF fMRI on the same cats. All experiments were performed at ultra-high magnetic field, 9.4 T. Four anesthetized cats (1.45 ~ 1.95 kg) were monocularly stimulated with sinusoidal wave gratings (0.15 cyc/deg, 2 Hz). Contiguous areas of the upper- and lower visual fields were alternately stimulated. The activation maps of GE-BOLD and CBF were analyzed, and the border between the areas activated by the stimulation of the upper and the lower visual fields was detected. Lateral PSFs of GE-B...

The left-hand advantage seen during tactile discrimination tasks suggests hemispheric-processing asymmetry, although its neural substrates are not well known. We used functional magnetic resonance imaging to evaluate the laterality of the neural substrates involved in tactile discrimination in 19 normal volunteers. Passive tactile discrimination tasks, along with appropriate control tasks, were performed with both the right and left hands to evaluate the effects of the hand used and hemispheric effects (i.e., laterality of the activation pattern). Regardless of the hand used, the right dorsolateral prefrontal cortex, posterior parietal cortex, pre-supplementary motor area, and rostral portion of the dorsal premotor cortex (PMdr) were activated asymmetrically during tactile discrimination. This confirms the previous finding of a right-sided asymmetry for tactile shape discrimination. Hand effects were found in the left caudal portion of PMd (PMdc) adjacent to the central sulcus, which showed prominent activ...

Dopamine agonists considered selective for D3>D2 receptor subtypes induce hypolocomotion at low doses, and hyperlocomotion at higher doses, in rats. The causative mechanism is unclear[1]. We used functional magnetic resonance imaging to determine brain regions responding to doses of quinelorane known to induce either hypo- or hyperlocomotion. Male Sprague-Dawley rats (n=5) were anaesthetised with α-chloralose (60mg/kg i.v., 30mg/kg/hr) and scanned using multi-echo gradient-echo imaging (TE=5,10&15ms; TR=460ms; 120 volumes in 2 hours). Quinelorane (3 or 30µg/kg, s.c.) or saline vehicle were randomly administered 30-60 minutes after scan initiation. Mean echo images were realigned, normalised to a rat brain template and analysed using a general linear model[2]. 30µg/kg quinelorane, which induces hyperlocomotion, caused significant signal increases within the caudate-putamen, nucleus accumbens and olfactory nuclei (T>4.3, p<0.05), suggesting hyperlocomotor responses are mediated by areas rich in either D2 rec...

Estrogen has been reported to enhance cocaine sensitization in the female rat, suggesting that brain circuits mediating the rewarding and addictive properties of cocaine are affected by the gonadal steroid. The present study used functional magnetic resonance imaging (fMRI) to investigate the effect of repeated cocaine administration on blood-oxygen-level-dependent (BOLD) signal changes in fully conscious female rats without and with estrogen. Rats were ovariectomized and given subcutaneous Silastic implants without (OVX) or with estradiol benzoate (OVX+EB). Upon recovery, rats were given an i.p. cocaine injection (1 mg/kg) on 7 consecutive days. Functional MRI was performed during injections on days 1 and 7. MR Images were acquired using a 4.7T/40-cm (Oxford magnet Technology, Oxford, UK) horizontal magnet interfaced to a Paravision console (Bruker Medical Instruments, MA, USA). Anatomical data sets were acquired using a fast spin echo (RARE) sequence, (TR=2.5s; TE=56ms; field of view= 3.5x3.5cm; data mat...

Previous research in humans has explored the relationship between volumetric measurements of the hippocampus and amygdala, the degree of volumetric asymmetry of these structures, and various cognitive and psychiatric symptoms. The present study provides the first systematic analysis using meta-analytic procedures of the normal population parameters of hippocampal and amygdala volumetric asymmetry as well as absolute intrahemispheric volumes in healthy adult individuals. A literature review resulted in a representative sample of 62 studies (N = 2,364 participants) providing volumetric information for the left and right hippocampi and 38 studies (N = 1,569 participants) providing volumetric information for the left and right amygdala. Results revealed that, in humans, the hippocampus is a statistically reliable asymmetrical structure in normal adults, with a relative larger right hemisphere volume (effect size Dh = 0.19, p < 0.001). The amygdala, however, was not found to be reliably asymmetrical. Additional...

Studies of patients with focal brain injury indicate that smell perception involves caudal orbitofrontal and medial temporal cortices, but a more precise functional organization has not been characterized. In addition, although it is believed that odors are potent triggers of emotion, support for an anatomical association is scant. We sought to define the neural substrates of human olfactory information processing and determine how these are modulated by affective properties of odors. We used event-related functional magnetic resonance imaging (fMRI) in an olfactory version of a classical conditioning paradigm, whereby neutral faces were paired with pleasant, neutral, or unpleasant odors, under 50% reinforcement. By comparing paired (odor/face) and unpaired (face only) conditions, odor-evoked neural activations could be isolated specifically. In primary olfactory (piriform) cortex, spatially and temporally dissociable responses were identified along a rostrocaudal axis. A nonhabituating response in posteri...

A novel procedure to measure the volume of gray and white matter in each lobe of the cerebral hemispheres was developed. Semi-automatic segmentation and volumetry is performed using high-resolution MR image sets. While previous techniques relied on manual tracing or segmentation in Talairach space, this procedure uses anatomical landmarks combined with region growing to improve reliability and to reduce analysis time. The procedure was implemented as a MATLAB toolbox. First, the skull was removed from the MRI volume before brain stem and cerebellum were separated as previously published. On the resulting volume comprising hemispheres and diencephalon, a novel iterated 3D region growing algorithm was applied to determine GM/WM intensity thresholds. This algorithm uses the derivative of the function between threshold and voxel count to determine optimal threshold values. It thereby minimizes subjective rater influence. The hemispheres were then warped to Talairach space. Lobar boundaries derived from the Tal...

The purpose of this report was to investigate the changes in brain tissue properties between in vivo and post mortem stage by using magnetic resonance imaging with a combination of T2, proton density (PD) and apparent diffusion coefficient (ADC) maps. Male Sprague rats, normal animals n=4, and one group n=3 with a pan-necrotic focal lesion in the sensori-motor cortex. The rats were recorded in a MR-scanner before, immediately after, 1h after death and in vitro after 2 d in formalin. The MRI-recordings were performed on a 4.7 T Bruker Biospec Avance 47/40 spectrometer. A double-echo RARE sequence was used. Seven contiguous coronal slices with regions of interest from Cortex, Thalamus and Striatum were chosen. Determination of T2 was made by multi-slice multi-echo MSME protocol. Determination of the ADC was made by conventional spin echo experiment. A PD increase of 12% in parallell with a decrease of 39% in T2-values was observed between 1 h after death to, in vitro, after 2 d in formalin. A decrease in ADC...