Bilateral Superior Colliculus Research Articles

Ultrastructure of ipsilateral and contralateral tectopulvinar projections in the mouse.

Visual pathways of the brain are organized into parallel channels that code different features of the external environment. In the current study, we investigated the anatomical organization of parallel pathways from the superior colliculus (SC) to the pulvinar nucleus in the mouse. Virus injections placed in the ipsilateral and contralateral SC to induce the expression of different fluorescent proteins define two pulvinar zones. The lateral pulvinar (Pl) receives ipsilateral SC input and the caudal medial pulvinar (Pcm) receives bilateral SC input. To examine the ultrastructure of these projections using transmission electron microscopy, we injected the SC with viruses to induce peroxidase expression within synaptic vesicles or mitochondria. We quantitatively compared the sizes of ipsilateral and contralateral tectopulvinar terminals and their postsynaptic dendrites, as well as the sizes of the overall population of synaptic terminals and their postsynaptic dendrites in the Pl and Pcm. Our ultrastructural analysis revealed that ipsilateral tectopulvinar terminals are significantly larger than contralateral tectopulvinar terminals. In particular, the ipsilateral tectopulvinar projection includes a subset of large terminals (≥ 1 μm2 ) that envelop dendritic protrusions of postsynaptic dendrites. We also found that both ipsilateral and contralateral tectopulvinar terminals are significantly larger than the overall population of synaptic terminals in both the Pl and Pcm. Thus, the ipsilateral tectopulvinar projection is structurally distinct from the bilateral tectopulvinar pathway, but both tectopulvinar channels may be considered the primary or "driving" input to the Pl and Pcm.

Hybrid auditory fMRI: In pursuit of increasing data acquisition while decreasing the impact of scanner noise

BackgroundTwo challenges in auditory fMRI include the loud scanner noise during sound presentation and slow data acquisition. Here, we introduce a new auditory imaging protocol, termed “hybrid”, that alleviates these obstacles. New methodWe designed a within-subject experiment (N = 14) wherein language-driven activity was measured by hybrid, interleaved silent (ISSS), and continuous multiband acquisition. To determine the advantage of noise attenuation during sound presentation, hybrid was compared to multiband. To identify the benefits of increased temporal resolution, hybrid was compared to ISSS. Data were evaluated by whole-brain univariate general linear modeling (GLM) and multivariate pattern analysis (MVPA). ResultsComparison with existing methods:•Hybrid vs. Multiband: in both GLM and MVPA, hybrid showed widespread activation throughout the language network including the left inferior frontal gyrus, bilateral superior temporal regions, thalamus, and inferior colliculus. By contrast, multiband showed activity mostly within the left frontotemporal cortices.•Hybrid vs. ISSS: in MVPA, hybrid yielded more activation than ISSS throughout the language network. However, in GLM, hybrid detected less activation than ISSS. Despite the reduction of activation, hybrid more specifically detected activity in the canonical language network compared to ISSS. ConclusionsOur data revealed that hybrid imaging restored neural activity in the canonical language network that was absent due to the loud noise or slow sampling in the conventional imaging protocols. With its noise-attenuated sound presentation windows and increased acquisition speed, the hybrid protocol is well-suited for auditory fMRI research tracking neural activity pertaining to fast, time-varying acoustic events.

Concurrent brain structural and functional alterations in patients with migraine without aura: an fMRI study

ObjectivesTo explore the possible concurrent brain functional and structural alterations in patients with migraine without aura (MwoA) patients compared to healthy subjects (HS).MethodsSeventy-two MwoA patients and forty-six HS were recruited. 3D-T1 and resting state fMRI data were collected during the interictal period for MwoA and HS. Voxel-based morphometry (VBM) for structure analysis and regional homogeneity (Reho) for fMRI analysis were applied. The VBM and Reho maps were overlapped to determine a possible brain region with concurrent functional and structural alteration in MwoA patients. Further analysis of resting state functional connectivity (FC) alteration was applied with this brain region as the seed.ResultsCompared with HS, MwoA patients showed decreased volume in the bilateral superior and inferior colliculus, periaqueductal gray matter (PAG), locus ceruleus, median raphe nuclei (MRN) and dorsal pons medulla junction. MwoA patients showed decreased Reho values in the middle occipital gyrus and inferior occipital gyrus, and increased Reho values in the MRN. Only a region in the MRN showed both structural and functional alteration in MwoA patients. Pearson correlation analysis showed that there was no association between volume or Reho values of the MRN and headache frequency, headache intensity, disease duration, self-rating anxiety scale or self-rating depression scale in MwoA patients. Resting state functional connectivity (FC) with the MRN as the seed showed that MwoA patients had increased FC between the MRN and PAG.ConclusionsMRN are involved in the pathophysiology of migraine during the interictal period. This study may help to better understand the migraine symptoms.Trial registrationNCT01152632. Registered 27 June 2010.

Requirement of Prefrontal and Midbrain Regions for Rapid Executive Control of Behavior in the Rat

To study rapid sensorimotor remapping, we developed a method to train rats in a behavior in which subjects are cued, on each trial, to apply a sensorimotor association to orient either toward a visual target ("Pro") or away from it, toward its reverse ("Anti"). Multiple behavioral asymmetries suggested that Anti behavior is cognitively demanding while Pro is easier to learn and perform. This is consistent with a prominent hypothesis in the primate literature that Anti requires prefrontal cortex (PFC), whereas Pro could be mediated by midbrain superior colliculus (SC). Pharmacological inactivation of rat medial PFC supported its expected role in Anti. Remarkably, bilateral SC inactivation substantially impaired Anti while leaving Pro essentially intact. Moreover, SC inactivation eliminated the performance cost of switching from Anti to Pro tasks. Our results establish a rodent model of single-trial sensorimotor remapping and suggest a critical role for SC in the cognitively demanding Anti task.

Causal functional contributions and interactions in the attention network of the brain: an objective multi-perturbation analysis.

Spatial attention is a prime example for the distributed network functions of the brain. Lesion studies in animal models have been used to investigate intact attentional mechanisms as well as perspectives for rehabilitation in the injured brain. Here, we systematically analyzed behavioral data from cooling deactivation and permanent lesion experiments in the cat, where unilateral deactivation of the posterior parietal cortex (in the vicinity of the posterior middle suprasylvian cortex, pMS) or the superior colliculus (SC) cause a severe neglect in the contralateral hemifield. Counterintuitively, additional deactivation of structures in the opposite hemisphere reverses the deficit. Using such lesion data, we employed a game-theoretical approach, multi-perturbation Shapley value analysis (MSA), for inferring functional contributions and network interactions of bilateral pMS and SC from behavioral performance in visual attention studies. The approach provides an objective theoretical strategy for lesion inferences and allows a unique quantitative characterization of regional functional contributions and interactions on the basis of multi-perturbations. The quantitative analysis demonstrated that right posterior parietal cortex and superior colliculus made the strongest positive contributions to left-field orienting, while left brain regions had negative contributions, implying that their perturbation may reverse the effects of contralateral lesions or improve normal function. An analysis of functional modulations and interactions among the regions revealed redundant interactions (implying functional overlap) between regions within each hemisphere, and synergistic interactions between bilateral regions. To assess the reliability of the MSA method in the face of variable and incomplete input data, we performed a sensitivity analysis, investigating how much the contribution values of the four regions depended on the performance of specific configurations and on the prediction of unknown performances. The results suggest that the MSA approach is sensitive to categorical, but insensitive to gradual changes in the input data. Finally, we created a basic network model that was based on the known anatomical interactions among cortical-tectal regions and reproduced the experimentally observed behavior in visual orienting. We discuss the structural organization of the network model relative to the causal modulations identified by MSA, to aid a mechanistic understanding of the attention network of the brain.

Whole-body prepulse inhibition protocol to test sensorymotor gating mechanisms in monkeys.

Prepulse inhibition (PPI) is the decrease of startle reflex amplitude when a slight stimulus is previously generated. This paradigm may provide valuable information about sensorimotor gating functionality. Here we aimed at determining the inhibited and uninhibited startle response of capuchin monkeys (Sapajus spp.), and to evaluate the role of the superior colliculus in PPI. Capuchin monkeys were tested in a whole-body protocol, to determine the best startle amplitude and interstimuli interval. Additionally we tested two subjects with bilateral superior colliculus damage in this protocol. Results show that 115 dB auditory pulse has induced the best startle response. In contrast to reports in other species, no habituation to the auditory stimuli was observed here in capuchins. Also, startle reflex inhibition was optimal after 120 msec interstimuli interval. Finally, there was a downward tendency of percentage inhibition in superior colliculus-lesioned monkeys. Our data provides the possibility of further studies with whole-body protocol in capuchin monkeys and reinforces the importance of the superior colliculus in PPI.

Early decrease of type 1 cannabinoid receptor binding and phosphodiesterase 10A activity in vivo in R6/2 Huntington mice

Several lines of evidence imply early alterations in endocannabinoid and phosphodiesterase 10A (PDE10A) signaling in Huntington disease (HD). Using [18F]MK-9470 and [18F]JNJ42259152 small-animal positron emission tomography (PET), we investigated for the first time cerebral changes in type 1 cannabinoid (CB1) receptor binding and PDE10A levels in vivo in presymptomatic, early symptomatic, and late symptomatic HD (R6/2) mice, in relation to glucose metabolism ([18F]FDG PET), brain morphology (magnetic resonance imaging) and motor function. Ten R6/2 and 16 wild-type (WT) mice were investigated at 3 different time points between the age of 4 and 13 weeks. Parametric CB1 receptor and PDE10A images were anatomically standardized to Paxinos space and analyzed voxelwise. Volumetric microMRI imaging was performed to assess HD pathology. In R6/2 mice, CB1 receptor binding was decreased in comparison with WT in a cluster comprising the bilateral caudate-putamen, globus pallidus, and thalamic nucleus at week 5 (−8.1% ± 2.6%, p = 1.7 × 10−5). Longitudinal follow-up showed further progressive decline compared with controls in a cluster comprising the bilateral hippocampus, caudate-putamen, globus pallidus, superior colliculus, thalamic nucleus, and cerebellum (late vs. presymptomatic age: −13.7% ± 3.1% for R6/2 and +1.5% ± 4.0% for WT, p = 1.9 × 10−5). In R6/2 mice, PDE10A binding potential also decreased over time to reach significance at early and late symptomatic HD (late vs. presymptomatic age: −79.1% ± 1.9% for R6/2 and +2.1% ± 2.7% for WT, p = 1.5 × 10−4). The observed changes in CB1 receptor and PDE10A binding were correlated to anomalies exhibited by R6/2 animals in motor function, whereas no correlation was found with magnetic resonance imaging-based striatal volume. Our findings point to early regional dysfunctions in endocannabinoid and PDE10A signaling, involving the caudate-putamen and lateral globus pallidus, which may play a role in the progression of the disease in R6/2 animals. PET quantification of in vivo CB1 and/or PDE10A binding may thus be useful early biomarkers for HD. Our results also provide evidence of subtle motor deficits at earlier stages than previously described.

眼球運動制御系における上丘間抑制性及び興奮性交連結合の性質について

The superior colliculus serves to orient an animal to a target in the opposite visual hemifield. Commissural connections between the bilateral superior colliculi (SCs) are known to help maintain visual fixation and suppress saccades. Sprague (1966) showed that after transection of the commissure between the SCs, cats that had been made blind by prior ablation of the occipitotemporal cortex once again visually oriented to objects in a hemifield. This outcome, called the Sprague effect, suggests that the commissural connection of the SC may play an important role in visual-orienting behavior, and may mediate mutual suppression between the two SCs to prevent competing responses in the opposite direction.Later electrophysiological studies confirmed the inhibitory nature of the commissural tectotectal projection. Our recent study, using intracellular recording combined with electrical stimulation of the SC, showed that tectoreticular neurons (TRNs) in the caudal ‘saccade zone’ mainly received monosynaptic inhibition from the contralateral rostral SC and mono- or disynaptic inhibition from its caudal part, whereas TRNs in the rostral SC received monosynaptic excitation from the contralateral rostral SC, and mono- or disynaptic inhibition from all rostrocaudal levels of the contralateral SC. This review summarizes the characteristic features of commissural inhibition and excitation between the two SCs on various output TRNs terminating on different kinds of interneurons in the horizontal saccade generator in the brainstem of the cat.

Evaluation of a partial optic nerve crush model in rats

This study was performed to determine whether a partial optic nerve crush (PONC) model in rats is effective and reliable for the study of optic nerve protection and regeneration. Bilateral superior colliculus (SC) retrograde 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate (DiI) labeling of retinal ganglion cells (RGCs; n=3) and unilateral SC retrograde labeling of RGCs (n=3) were performed in adult Sprague-Dawley (SD) rats and the results were compared with the bilateral and unilateral SC retrograde-labeled RGCs. Another 40 adult SD rats, three days after bilateral SC retrograde DiI labeling of RGCs underwent crushing with a non-invasive vascular clip (40 gram power) 1 mm behind the right optic nerve head for 5, 10 and 30 sec (n=10 each), and a sham-operated control group (n=10) was used as a control. The retinas of all 40 rats were flattened by four radial cuts, mounted vitreal side-up on gelatin-coated slides, and the number of labeled RGCs was counted in four distinct regions per retinal quadrant at three different eccentricities of 1/6, 3/6 and 5/6 of the retinal radius three days later. Bilateral SC retrograde DiI injection labeled the majority of normal RGCs, while unilateral SC injections only labeled a small part of the RGCs; the majority of RGCs were not labeled. In the mild crush (5 sec) injury group, the bilateral SC retrograde DiI injection labeled the majority of RGCs. The RGC densities at 1/6, 3/6 and 5/6 of the retinal radius showed no significant difference compared with the RGC densities at the corresponding region of the retinal radius in the sham-operated control group (P=0.734, 0.461, 0.273, respectively). In the moderate crush injury (10 sec) group, the number of labeled RGCs was significantly lower compared to that of the sham-operated control group, and the RGC densities at 1/6, 3/6, 5/6 of the retinal radius were significantly lower compared to the RGC densities at the corresponding retinal radius in the sham-operated control group (P<0.001). In the severe crush injury (30 sec) group the number of labeled RGCs was significantly decreased, and the labeled RGCs were not observed in the region at 5/6 of the retinal radius. The RGC densities at 1/6 and 3/6 of the retinal radius were significantly lower compared to the RGC densities at the corresponding retinal radius region in the sham-operated control group (P<0.001). Compared with the mild and severe optic nerve crush injury models, the moderate crush injury model is more suitable for the study of optic nerve damage and regeneration.

Cortico-subcortical visual, somatosensory, and motor activations for perceiving dynamic whole-body emotional expressions with and without striate cortex (V1)

Patients with striate cortex damage and clinical blindness retain the ability to process certain visual properties of stimuli that they are not aware of seeing. Here we investigated the neural correlates of residual visual perception for dynamic whole-body emotional actions. Angry and neutral emotional whole-body actions were presented in the intact and blind visual hemifield of a cortically blind patient with unilateral destruction of striate cortex. Comparisons of angry vs. neutral actions performed separately in the blind and intact visual hemifield showed in both cases increased activation in primary somatosensory, motor, and premotor cortices. Activations selective for intact hemifield presentation of angry compared with neutral actions were located subcortically in the right lateral geniculate nucleus and cortically in the superior temporal sulcus, prefrontal cortex, precuneus, and intraparietal sulcus. Activations specific for blind hemifield presentation of angry compared with neutral actions were found in the bilateral superior colliculus, pulvinar nucleus of the thalamus, amygdala, and right fusiform gyrus. Direct comparison of emotional modulation in the blind vs. intact visual hemifield revealed selective activity in the right superior colliculus and bilateral pulvinar for angry expressions, thereby showing a selective involvement of these subcortical structures in nonconscious visual emotion perception.

Neuroprotective effect of epigallocatechin-3-gallate on retinal ganglion cells in optic nerve crush rat model

Objective To investigate the neuroprotective effect of epigallocatechin-gallate (EGCG),the major catechin found in green tea, in an optic nerve crush (ONC) rat model. Methods Seventy-two Wistar rats were divided randomly into four groups: normal control, sham-operation+ EGCG, ONC+vehicle, and ONC+ EGCG groups. Animals were treated intraperitoneally and orally with either vehicle (normal saline) or EGCG (25 mg/kg, injected daily for up to five days, and orally 2 mg/kg daily afterwards). Two days after the first injection, an ONC injury using a micro optic nerve clipper was performed at approximately 2 mm from the optic nerve head for 60 seconds. Fluorogold was injected into bilateral superior colliculi five days before sacrifice and fluorescent gold labeled retinal ganglion cells (RGC)were counted under fluorescence microscopy on days seven, 14 and 28 after optic nerve crush. Meanwhile,the expression of neurofilament triplet L (NF-L) was measured by immunohistochemistry and Western blotting. Results In the ONC + vehicle group, a progressive loss of RGC was observed;however,compared with the ONC+vehicle group, RGC density was significantly higher on day seven (t=3. 216, P=0. 009), day 14 (t=2. 609, P=0. 026) and day 28 (t=2. 792, P=0. 019) , and a significant increase of theNF-L protein expression has been observed on days seven, 14 and 28 after optic nerve crush in the ONC+EGCG group. Conclusions EGCG has a protective effect to the bodies and axons of the RGC after optic nerve crush. Key words: Optic nerve injuries; Callic acid /therapeutic use; Retinal ganglion cells; Animal experimentation

Neural mechanisms of saccadic eye movements: common ground with the vestibular system

The superior colliculus (SC) plays an important role in controlling eye and head movements. The neural organization of the pathways from the SC to motoneurons in the horizontal oculomotor system has been well analyzed, but the neural mechanisms in the vertical saccade have not yet been analyzed in detail. This article reviews the current state of knowledge of the neural mechanisms of the horizontal and vertical saccadic eye movement system, and shows that they have common features: both systems contain excitatory and inhibitory burst neurons which receive inputs from the SC and directly project to motoneurons. Our recent study showed the presence of commissural inhibition between the upper and lower fields of motor map of the bilateral SCs. This reciprocal inhibition between the medial upward saccade area in one SC and the lateral downward saccade area in the other SC is very similar to that in the vestibular system. This similarity of the patterns of reciprocal inhibition in the SC system and the semicircular canal system implies that the SC output system may use the coordinate system based on the semicircular canals.

Histological observation of RGCs and optic nerve injury in acute ocular hypertension rats.

To explore the injury of retinal ganglion cells (RGCs) and optic nerves in acute ocular hypertension (OHT) rats. We retrogradely labeled RGCs and optic nerves of Sprague-Dawley rats by injecting 20g/L fluorogold (FG) into bilateral superior colliculi. Twenty-four hours after the injection, the right eyes were performed physiological saline anterior chamber perfusion with intraocular pressure maintained at 100mmHg for 60 minutes, while the contralateral eyes were performed sham procedure as control group without elevation of the saline bottle. Retinal hematoxylin and eosin (HE) sections, retinal whole mounts and frozen sections were made 14 days later to observe the morphology and survival of RGCs. Frozen sections and transmission electron microscopy were utilized to investigate the histological manifestations of optic nerves at the same time. A larger number of RGCs presented in control group. It had an average density of 1995±125/mm(2) and distributed uniformly, while RGCs in OHT eyes reduced significantly to 1505±43/mm(2) compared with control group (P<0.05). The optic nerves in control group showed stronger and more uniform fluorescence on the frozen sections, and the auxiliary fibers as well as myelin sheaths were in even and intact organization by transmission electron microscopy. However, exiguous fluorescence signals, vesicular dissociation and disintegration of myelin sheaths were found in OHT group. The present study suggested that fluorogold retrograde tracing is a feasible, convenient method for quantitative and qualitative study of neuronal populations and axonal injury in acute ocular hypertension rats.

FMRI evidence of neural abnormalities in the subcortical face processing system in ASD

Recent evidence suggests that a rapid, automatic face detection system is supported by subcortical structures including the amygdala, pulvinar, and superior colliculus. Early-emerging abnormalities in these structures may be related to reduced social orienting in children with autism, and subsequently, to aberrant development of cortical circuits involved in face processing. Our objective was to determine whether functional abnormalities in the subcortical face processing system are present in adults with autism spectrum disorders (ASD) during supraliminal fearful face processing. Participants included twenty-eight individuals with ASD and 25 controls group-matched on age, IQ, and behavioral performance. The ASD group met diagnostic criteria on the ADI-R, ADOS-G, and DSM-IV. Both the ASD and control groups showed significant activation in bilateral fusiform gyri. The control group exhibited additional significant responses in the right amygdala, right pulvinar, and bilateral superior colliculi. In the direct group comparison, the controls showed significantly greater activation in the left amygdala, bilateral fusiform gyrus, right pulvinar, and bilateral superior colliculi. No brain region showed significantly greater activation in the ASD group compared to the controls. Thus, basic rapid face identification mechanisms appear to be functional in ASD. However, individuals with ASD failed to engage the subcortical brain regions involved in face detection and automatic emotional face processing, suggesting a core mechanism for impaired socioemotional processing in ASD. Neural abnormalities in this system may contribute to early-emerging deficits in social orienting and attention, the putative precursors to abnormalities in social cognition and cortical face processing specialization.

Neuroprotective effects of Epigallocatechin-3-gallate (EGCG) in optic nerve crush model in rats

Epigallocatechin-3-gallate (EGCG), the major catechin found in green tea, is a powerful antioxidant and has anti-inflammatory with neuroprotective potential. This study aims to investigate the neuroprotective effects of EGCG in an optic nerve crush (ONC) model in rats. Seventy-two Wistar rats were randomly divided into four groups: normal control (group A), sham operation + EGCG (group B), ONC + vehicle (group C), and ONC + EGCG (group D). The rats were treated intraperitoneally and orally with either vehicle or EGCG (25 mg/kg, injected daily for 5 days and 2 mg/kg orally daily afterwards). Two days after the first injection, an ONC injury was performed by using a micro optic nerve clipper with 40 g power at approximately 2 mm from the optic nerve head for 60 s. Fluorogold was injected into the bilateral superior colliculi 5 days before sacrifice and fluorescent gold-labelled retinal ganglion cells (RGCs) were counted under fluorescence microscopy on days 7, 14 and 28 after ONC. The expression of Neurofilament triplet L (NF-L) was measured via immunohistochemical and Western blotting analysis. In group C, a progressive loss of RGCs was observed after ONC. In contrast, the density of RGCs was significantly higher in group D ( p = 0.009, independent samples t-test) on day 7 after ONC, and statistical differences were obtained on days 14 and 28 ( p = 0.026 and p = 0.019, respectively, independent samples t-test). The results of immunohistochemical and Western blotting analysis showed significantly higher NF-L protein expression in group D in comparison with group C on days 7, 14 and 28 after ONC. These findings suggest that there are protective effects of EGCG on RGCs after ONC, indicating EGCG might be a potential therapeutic agent for optic nerve diseases.

Neuroprotective effect on retinal ganglion cells by transpupillary laser irradiation of the optic nerve head

This study demonstrates that subthreshold transpupillary thermotherapy (TTT) laser irradiation on optic nerve head protects retinal ganglion cells (RGCs) in an optic nerve crush (ONC) model. TTT was performed in right eyes with an 810-nm diode laser aimed at the center of the optic nerve head, using the following protocol: power 60 mW, duration 60 s, spot size 500 μm. Fluoro-Gold was injected into bilateral superior colliculi 5 days before sacrifice and fluorescent gold labeled RGCs were counted under fluorescence microscopy. In the ONC group, a progressive loss of RGCs was observed; however, in comparison with the ONC group, RGCs density was significantly higher ( P = 0.001, independent samples t-test) at day 7 postoperative and only borderline significances were obtained at days 14 and 28 postoperative ( P = 0.044 and P = 0.045, respectively, independent samples t-test) in ONC + TTT group, which implies the potential neuroprotective role of TTT. This protective effect seems to be heat shock proteins (HSPs) related, because intraperitoneal Quercetin (an inhibitor of HSPs, 4 mg/kg/day for 7 days) could completely abolish this protective effect at days 7, 14 and 28 postoperative ( P = 0.012, P = 0.002, and P = 0.000, respectively, independent samples t-test). Minimal collateral damage of TTT on optic nerve head tissue, peripapillary RGCs and the myelin sheath of the optic nerve were observed under transmission electron microscopy. These findings suggested that subthreshold TTT might be a safe and practical approach to protect RGCs. The underlying mechanisms may involve TTT-induced HSPs in RGCs.

Neural processing of asynchronous audiovisual speech perception

The temporal synchrony of auditory and visual signals is known to affect the perception of an external event, yet it is unclear what neural mechanisms underlie the influence of temporal synchrony on perception. Using parametrically varied levels of stimulus asynchrony in combination with BOLD fMRI, we identified two anatomically distinct subregions of multisensory superior temporal cortex (mSTC) that showed qualitatively distinct BOLD activation patterns. A synchrony-defined subregion of mSTC (synchronous>asynchronous) responded only when auditory and visual stimuli were synchronous, whereas a bimodal subregion of mSTC (auditory>baseline and visual>baseline) showed significant activation to all presentations, but showed monotonically increasing activation with increasing levels of asynchrony. The presence of two distinct activation patterns suggests that the two subregions of mSTC may rely on different neural mechanisms to integrate audiovisual sensory signals. An additional whole-brain analysis revealed a network of regions responding more with synchronous than asynchronous speech, including right mSTC, and bilateral superior colliculus, fusiform gyrus, lateral occipital cortex, and extrastriate visual cortex. The spatial location of individual mSTC ROIs was much more variable in the left than right hemisphere, suggesting that individual differences may contribute to the right lateralization of mSTC in a group SPM. These findings suggest that bilateral mSTC is composed of distinct multisensory subregions that integrate audiovisual speech signals through qualitatively different mechanisms, and may be differentially sensitive to stimulus properties including, but not limited to, temporal synchrony.

Anatomical Organization of the Blind's Brain: Combined VBM and DTI Analysis.

Purpose: To explore the whole brain grey and white matter organization in a large cohort of congenital blindness (CB) individuals compared to normal-sight (NS) controls using Diffusion Tensor Imaging (DTI) and tractography (DTT). Materials and Methods: Thirteen CB and thirteen NS were scanned in this experiment. T1WI, T2WI, and DTI (61 directions; b=1200 s/mm) were acquired on a Siemens 3T scanner. T1 and T2 images were segmented using the VBM5 toolbox in SPM5. DARTEL was used for high dimensional inter-subject registration. The diffusion tensor was fitted using the RESTORE algorithm. VBM5 was used for voxel-based analysis for comparing the group differences of gray matter, white matter and FA values. Probabilistic tractography (20 streamlines) implemented in FSL was used to generate anatomical connectivity maps (ACM) using a brain mask as seed ROI. DTIstudio was used for DTT to display the fiber tracts related to the visual pathway, in which two regions of interest (ROI) were defined on the coronal plain for both sides: one covered the whole occipital lobe at middle level of occipital lobe and the other covered the inferior fronto-occipital fasciculus (IFO) at the level through middle corpus callosum. Results: All structures belonging to the visual system showed significant volume reductions. All components of the retino-geniculo-striate system including optic nerve, chiasm, lateral geniculate nucleus, optic radiations and visual cortex were reduced. Especially, the volume of the bilateral superior colliculi was decreased (see Fig.1). In the Non-visual areas changes were observed in the posterior hippocampus and parts of the frontal and temporal lobes. All structures belonging to the visual system showed significant reductions of anatomical connectivity (see Fig.2). Most of the NS, 11 of 13, showed the fiber tracts going through the both ROIs. On the contrary, only 2 of 13 CB demonstrated the similar fiber tracts (see Fig.3). Conclusion: We show for the first time large reductions in the midbrain visual structures. The tractography results of CB were consistent with our VBM results. Our VBM data however did not confirm the enlargement of the fronto-occipital and the supra-longitudinal fasciculi previously reported. Fig.1 Group Comparison for the White Matter between the subjects with NS and CB, FDR correction with p<0.005. All structures belonging to the visual system showed significant volume reductions, including optic chiasm, lateral geniculate bodies and primary and secondary visual area (green arrowheads). Especially, the volume reduction was found in both superior colliculi (blue arrow).

Human Amygdala Responses to Fearful Eyes

Fearfulfacial expressions evoke increased neural responses in human amygdala. We used event-related fMRI to investigate whether eye or mouth components of a fearful face are critical in evoking this increased amygdala activity. In addition to prototypical fearful (FF) and neutral (NN) faces, subjects viewed two types of chimerical face: fearful eyes combined with a neutral mouth (FN), and neutral eyes combined with a fearful mouth (NF). FF faces evoked specific responses in left anterior amygdala. FN faces evoked responses in bilateral posterior amygdala and superior colliculus. Responses in right amygdala, superior colliculus, and pulvinar exhibited significant time × condition interactions with respect to faces with fearful eyes (FF, FN) vs neutral eyes (NF, NN). These data indicate that fearful eyes alone are sufficient to evoke increased amygdala activity. In addition, however, left amygdala displayed discriminatory responses to fearful eyes in different configural contexts (i.e., in FF and FN faces). These results suggest, therefore, that human amygdala responds to both feature-specific and configural aspects of fearful facial expressions.

Accommodation and convergence palsy caused by lesions in the bilateral rostral superior colliculus

PURPOSE: To report a patient who developed accommodation and convergence palsy caused by lesions in the bilateral rostral superior colliculus. DESIGN: Observational case report. METHODS: A 30-year-old right-handed man experienced sudden onset of diplopia and blurred vision at near vision RESULTS: The patient showed accommodation and convergence palsy. Magnetic resonance imaging revealed lesions located in the bilateral rostral superior colliculus. CONCLUSION: These findings suggest that the rostral superior colliculus is involved in the control of accommodation and vergence eye movements.