OBJECTIVE: There has been inconsistency about definition of the temporal stem despite of several descriptions demonstrating its microanatomy using fiber dissection and/or diffusion tensor tractography. This study was designed to clarify three dimensional configurations of the temporal stem. METHODS: The fronto-temporal regions of several formalin-fixed human cerebral hemispheres were dissected under an operating microscope using the fiber dissection technique. The consecutive coronal cuts of the dissected specimens were made to define the relationships of white matter tracts comprising the temporal stem and the subcortical gray matters (thalamus, caudate nucleus, amygdala) with inferior limiting (circular) sulcus of insula. RESULTS: The inferior limiting sulcus of insula, limen insulae, medial sylvian groove, and caudate nucleus/amygdala were more appropriate anatomical structures than the roof/dorso-lateral wall of the temporal horn and lateral geniculate body which were used to describe previously for delineating the temporal stem. The particular space located inside the line connecting the inferior limiting sulcus of insula, limen insulae, medial sylvian groove/amygdala, and tail of caudate nucleus could be documented. This space included the extreme capsule, uncinate fasciculus, inferior occipito-frontal fasciculus, anterior commissure, ansa peduncularis, and inferior thalamic peduncle including optic radiations, whereas the stria terminalis, cingulum, fimbria, and inferior longitudinal fiber of the temporal lobe were not passing through this space. Also, this continued posteriorly along the caudate nucleus and limiting sulcus of the insula. CONCLUSION: The temporal stem is white matter fibers passing through a particular space of the temporal lobe located inside the line connecting the inferior limiting sulcus of insula, limen insulae, medial sylvian groove/amygdala, and tail of caudate nucleus. The three dimensional configurations of the temporal stem are expected to give the very useful anatomical and surgical insights in the temporal lobe.
Animals ; Caudate Nucleus ; Cerebrum ; Diffusion ; Geniculate Bodies ; Horns ; Humans ; Temporal Lobe

70%-80% of our sensory input comes from vision. Light hit the retina at the back of our eyes and the visual information is relayed into the dorsal lateral geniculate nuclei (dLGN) and primary visual cortex (V1) thereafter, constituting the image-forming visual circuit. Molecular cues are one of the key factors to guide the wiring and refinement of the image-forming visual circuit during pre- and post-embryonic stages. Distinct molecular cues are involved in different developmental stages and nucleus, suggesting diverse guidance mechanisms. In this review, we summarize molecular guidance cues throughout the image-forming visual circuit, including chiasm determination, eye-specific segregation and refinement in the dLGN, and at last the reciprocal connections between the dLGN and V1.
Animals ; Geniculate Bodies ; metabolism ; Humans ; Visual Cortex ; metabolism ; Visual Pathways ; metabolism

Stimulus-specific adaptation (SSA), defined as a decrease in responses to a common stimulus that only partially generalizes to other rare stimuli, is a widespread phenomenon in the brain that is believed to be related to novelty detection. Although cross-modal sensory processing is also a widespread phenomenon, the interaction between the two phenomena is not well understood. In this study, the thalamic reticular nucleus (TRN), which is regarded as a hub of the attentional system that contains multi-modal neurons, was investigated. The results showed that SSA existed in an interactive oddball stimulation, which mimics stimulation changes from one modality to another. In the bimodal integration, SSA to bimodal stimulation was stronger than to visual stimulation alone but similar to auditory stimulation alone, which indicated a limited integrative effect. Collectively, the present results provide evidence for independent cross-modal processing in bimodal TRN neurons.
Acoustic Stimulation ; Animals ; Auditory Perception/physiology* ; Geniculate Bodies ; Rats ; Rats, Wistar ; Thalamic Nuclei/physiology*

To investigate the applicability of the Bartha strain of pseudorabies virus(PRV-Ba) as a neurotracer in the visual system, we performed immunohistochemical study of the rat brain after intravitreal injection of the PRV-Ba. Cholera toxin-horseradish peroxidase(CT-HRP), a well known neurotracer, was also injected into the vitreous cavity for comparison. After given survival time the brain was removed and processed immunohistochemical stain for PRV-Ba and neurohistochemical stain for CT-HRP. The CT-HRP positive reactions were observed almost contralaterally in optic chiasm, optic tract, suprachiasmatic nucleus(SCN), olivary pretectal nucleus(OPT), all three subdivision of lateral geniculate body, superficial gray layer and optic layer of superior colliculus and medial, lateral, dorsal terminal nucleus of accessory optic tract. PRV-Ba immunopositive reaction was observed in SCN and OPT, but not in nerve fiber system and dorsal lateral geniculate body. Also PRV-Ba positive cells were distributed mainly in intermediate layer and weakly distributed in superficial layer of the superior colliculus. This study suggests that PRV-Ba is not a useful neurotracer in studying the visual system of the rat.
Animals ; Brain ; Cholera ; Geniculate Bodies ; Herpesvirus 1, Suid* ; Intravitreal Injections ; Nerve Fibers ; Optic Chiasm ; Pseudorabies* ; Rats* ; Superior Colliculi ; Visual Pathways

This study was for investigating relations between distributions of monoamines-norepinephrine, serotonin, and dopamine-on the visual system and their functions. Distributions of these monoamines in the lateral geniculate body, pulvinar, lateral posterior nucleus, and suprachiasmatic nucleus were investigated. Brain of a squirrel monkey was removed and frozen sectioned. Immunocytochemical study was performed for the tissue of the brain. Results showed that the anterior part of the lateral geniculate body contained more monoamines than the posterior part. More serotonins were distrbuted at the magnocellular part, and more dopamines were found at the parvocellular part. In pulvinar, more norepinephrines were distributed at the medial part, while serotonins were evenly distributed at all parts. In lateral posterior nucleus and suprachiasmatic nucleus, three kinds of monoamines were distributed with high density. Among the three, density of the serotonin showed the highest value. The lateral geniculate body relates with visual perception such as visual acuity, form and color perception, and stereopsis, while the pulvinar relates with visual functions, such as visual attention, sensory integration, and differentiation. Since norepinephrine and serotonine are distributed with high density in the pulvinar than in the lateral geniculate body those two monoamines are expected to playa major role for visual functions. Inferior part of the pulvinar relates with visual imagination, and the lateral posterior nucleus relates with integration of visual sensory. Relatively high distribution of dopamine in these two parts means that dopamine may playa major role for visual imagination and integration. As suprachiasmatic nucleus relates with controlling biorhythm, dense distribution of monoamines in suprachiasmatic nucleus implies that the monoamines may work for controlling biorhythm.
Brain ; Color Perception ; Depth Perception ; Dopamine ; Geniculate Bodies ; Imagination ; Lateral Thalamic Nuclei ; Norepinephrine ; Periodicity ; Pulvinar ; Saimiri* ; Sciuridae* ; Serotonin ; Suprachiasmatic Nucleus ; Visual Acuity ; Visual Perception

PURPOSE: Blind individuals who have photoreceptor loss are known to perceive phosphenes with electrical stimulation of their remaining retinal ganglion cells. We proposed that implantable lateral geniculate body (LGB) stimulus electrode arrays could be used to generate phosphene vision. We attempted to refine the basic reference of the electrical evoked potentials (EEPs) elicited by microelectrical stimulations of the optic nerve, optic tract and LGB of a domestic pig, and then compared it to visual evoked potentials (VEPs) elicited by short-flash stimuli. METHODS: For visual function measurement, VEPs in response to short-flash stimuli on the left eye of the domestic pig were assessed over the visual cortex at position Oz with the reference electrode at Fz. After anesthesia, linearly configured platinum wire electrodes were inserted into the optic nerve, optic track and LGB. To determine the optimal stimulus current, EEPs were recorded repeatedly with controlling the pulse and power. The threshold of current and charge density to elicit EEPs at 0.3 ms pulse duration was about ±10 microA. RESULTS: Our experimental results showed that visual cortex activity can be effectively evoked by stimulation of the optic nerve, optic tract and LGB using penetrating electrodes. The latency of P1 was more shortened as the electrical stimulation was closer to LGB. The EEPs of two-channel in the visual cortex demonstrated a similar pattern with stimulation of different spots of the stimulating electrodes. We found that the LGB-stimulated EEP pattern was very similar to the simultaneously generated VEP on the control side, although implicit time deferred. CONCLUSIONS: EEPs and VEPs derived from visual-system stimulation were compared. The LGB-stimulated EEP wave demonstrated a similar pattern to the VEP waveform except implicit time, indicating prosthetic-based electrical stimulation of the LGB could be utilized for the blind to perceive vision of phosphenes.
Animals ; Electric Stimulation ; Electrodes, Implanted ; Evoked Potentials, Visual/*physiology ; Geniculate Bodies/*physiology ; Male ; Optic Nerve/physiology ; Optic Tract/physiology ; Photic Stimulation ; Sus scrofa ; Visual Cortex/*physiology

We investigated the electrophysiological and morphological characteristics of the neurons in the ventral partition of medial geniculate body (MGBv) in the rat during postnatal development (postnatal day 3-30, P3-30) with whole-cell patch clamp recording and intracellular labeling technique. The results are as follows: (1) There was an increase in the negativity of the resting membrane potential, a decrease in the input resistance and the time constant of the MGBv neurons of rats during the postnatal development; the amplitude, threshold and duration of the action potentials were also different on different postnatal days; (2) During the postnatal development, the changes in voltage-dependent ion channels dramatically influenced the waveform of action potential in the MGBv neurons. Application of 4-AP, a K(+)-channel blocker, reduced the amplitude and prolonged the durations of the action potentials in P6 neurons, and inactivated the neurons at the end of the pulse in P16 rats. Application of CdCl2 to block the voltage-dependent Ca(2+)-channel decreased the amplitude and increased the duration of the action potential in P16 rats; (3) Biocytin staining revealed that immature MGBv cell had smaller somata and short, simple dendritic aborization. During postnatal development, the matured neurons had oval somata and 3-4 primary dendrities that radiated irregularly and projected outside the section; spines also appeared on the dendrites of the mature neurons. These results reveal that the morphologic and electrophysiological properties are not matured during early postnatal development, and that the electrophysiological and morphological features of the developing MGBv neurons are interrelated.
Action Potentials ; Animals ; Electrophysiology ; Female ; Geniculate Bodies ; growth & development ; physiology ; Ion Channel Gating ; Male ; Membrane Potentials ; Neurons ; cytology ; physiology ; Patch-Clamp Techniques ; Rats ; Rats, Wistar

OBJECTIVETo investigate the changes of lateral geniculate body (LGB) in the normal aging brain using quantitative susceptibility mapping (QSM) technique.

METHODSMagnetic resonance (MR) phase and magnitude images were acquired from enhanced gradient echo T2 star weighted angiography sequence with 16 echoes on 3.0T MR system using the head coil with 32 channels. Morphology Enabled Dipole Inversion (MEDI) method was applied for QSM, and the susceptibility value of LGB was measured by region of interest (ROI) drawn manually on three orthogonal planes.

RESULTSLGB of the middle-aged group had a higher susceptibility value (0.16±0.05 ppm) than that of the youth group (0.12±0.05 ppm) and elderly group (0.13±0.03 ppm) (all P<0.05). Partial correlation analysis demonstrated that there was significantly positive correlation between susceptibility value and age in the youth group (r=0.71, P<0.05).

CONCLUSIONLGB could clearly be identified on QSM in the brain in vivo.

Adult ; Aged ; Brain Mapping ; methods ; Female ; Geniculate Bodies ; physiology ; Humans ; Magnetic Resonance Imaging ; methods ; Male ; Middle Aged ; Reference Values ; Young Adult

PURPOSE: To investigate the effect of dark rearing immediately after birth on the maturation of the visual relay neurons in the lateral geniculate nucleus. METHODS: Fifty neonatal rats were used. Neonates of the control groups were raised under a normal light/dark cycle. Neonates of the experiment groups were dark reared and isolated from light during the entire experimental period, then exposed to the sun light for 1 hour before sacrifice. RESULTS: In the control groups, the neurons in the dorsal lateral geniculate nucleus developed normally at each age tested. In the experiment groups, the cytoplasm of the large neurons in the dorsal lateral geniculate nucleus of 2-week-old rats contained small vesicles, and the cytoplasm of the large neurons of 4-week-old rats was converted into a vacuole-like space. Moreover, c-Fos immunoreactivity of the large neurons in the dorsal lateral geniculate nucleus in the experiment groups was significantly increased compared to that of the control groups. CONCLUSIONS: We suppose that the maturation of the neurons in the lateral geniculate nucleus might be influenced by light stimulation during the critical period. Furthermore, c-Fos could be a marker of the functional activity of the visual relay neurons of the lateral geniculate nucleus in albino rats.
Animals ; Animals, Newborn ; Critical Period (Psychology) ; *Dark Adaptation ; Geniculate Bodies/*metabolism ; Immunohistochemistry ; *Light ; Neurons/*metabolism ; Proto-Oncogene Proteins c-fos/*metabolism ; Rats ; Rats, Sprague-Dawley

In neurosurgical procedures that may cause visual impairment in the intraoperative period, the monitoring of flash visual evoked potential (VEP) is clinically used to evaluate visual function. Patients are unconscious during surgery under general anesthesia, making flash VEP monitoring useful as it can objectively evaluate visual function. The flash stimulus input to the retina is transmitted to the optic nerve, optic chiasm, optic tract, lateral geniculate body, optic radiation (geniculocalcarine tract), and visual cortical area, and the VEP waveform is recorded from the occipital region. Intraoperative flash VEP monitoring allows detection of dysfunction arising anywhere in the optic pathway, from the retina to the visual cortex. Particularly important steps to obtain reproducible intraoperative flash VEP waveforms under general anesthesia are total intravenous anesthesia with propofol, use of retinal flash stimulation devices using high-intensity light-emitting diodes, and a combination of electroretinography to confirm that the flash stimulus has reached the retina. Relatively major postoperative visual impairment can be detected by intraoperative decreases in the flash VEP amplitude.
Anesthesia, General* ; Anesthesia, Intravenous ; Electroretinography ; Evoked Potentials, Visual* ; Geniculate Bodies ; Humans ; Intraoperative Period ; Monitoring, Intraoperative* ; Neurosurgical Procedures ; Occipital Lobe ; Optic Chiasm ; Optic Nerve ; Optic Tract ; Propofol ; Retina ; Retinaldehyde ; Vision Disorders ; Visual Cortex