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*

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