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*

The purpose of this study was to investigate the influence of electrical stimulation of anterior cingulate cortex (ACC) on spontaneous activity of neurons in thalamic ventrobasal nucleus (VB). Experiments were performed on 12 male Sprague-Dawley rats weighing 250-310 g (4-5 months old). According to Paxinos and Watson's coordinate atlas of the rat, the frontal and parietal cortical areas were exposed by craniotomy, the recording electrodes were then inserted into the VB (P 2.4-4.1 mm, R 2.0-3.5 mm, H 5.2-6.8 mm) and the stimulating electrodes into the ACC (A 1.1-3.0 mm, R 0.0-1.0 mm, H 1.5-2.4 mm). Single-unit activities were recorded extracellularly in the VB by glass micropipettes (impedance 3-8 MOmega) filled with 0.5 mol/L sodium acetate solution containing saturated Fast Green. To study the effects of ACC activation on the spontaneous activities of VB cells, single electrical pulse (0.2 ms duration) was delivered to the ACC by a concentric bipolar stainless steel electrode (0.32 mm outer diameter). An effective ACC stimulation was determined for each VB neuron by gradually increasing the current intensity from 0.1 mA until either a significant change in the spontaneous activity of the VB neuron was observed, or the current intensity reached 0.4 mA. The results showed that ACC stimulation significantly suppressed the spontaneous activities in 12 out of 53 VB neurons (22.6%). (1) After the stimulation was delivered to ACC, the spontaneous activities of different VB neurons were totally suppressed for different time span. (2) There was obvious dose-effect relevance between ACC stimulation intensity and their inhibitory effect. The duration of complete inhibition was prolonged with the increases in the intensity and number of stimulation impulses in ACC. (3) The stimulation in the ACC depressed the spontaneous activities of VB neurons in different forms and this inhibition exhibited an accumulative effect. All these results indicate that the stimulation of ACC exerts an inhibitory influence on the spontaneous activities of VB neurons.
Animals ; Electric Stimulation ; Gyrus Cinguli ; physiology ; Male ; Neurons ; cytology ; Rats ; Rats, Sprague-Dawley ; Thalamic Nuclei ; cytology

Previous studies have indicated that the thalamic nucleus submedius (Sm) and the anterior pretectal nucleus (APtN) are involved in the descending modulation of nociception. The aim of the present study was to examine whether the opioid receptors in the Sm and APtN mediated the electroacupuncture (EA)-produced analgesia. The latency of tail flick (TF) reflex induced by radiant heat was used as an index of nociceptive response. The effects of microinjection of opioid receptor antagonist naloxone (1.0 microg, 0.5 ml) into Sm or APtN on the inhibition of the TF reflex induced by EA of "Zusanli" point (St. 36) with high- (5.0 mA) and low- (0.5 mA) intensity were examined in the lightly anesthetized rats. Sm microinjection of naloxone blocked the high- but not low-intensity EA-induced inhibition of the TF reflex. In contrast, naloxone applied to APtN blocked the low- but not high-intensity EA-induced inhibition. When naloxone applied to other brain regions adjacent to Sm or APtN, the EA-induced inhibition was not influenced under either high- or low-intensity condition. These results suggest that opioid receptors in Sm are involved in mediating the analgesia by high-intensity EA for exciting small (A-delta and C group) afferent fibers, while opioid receptors in APtN are involved in mediating the analgesia induced by low-intensity EA for only exciting large (A-beta) afferent fibers.
Acupuncture Analgesia ; Animals ; Electroacupuncture ; Naloxone ; pharmacology ; Narcotic Antagonists ; Nociceptors ; physiology ; Pain Measurement ; Rats ; Receptors, Opioid ; physiology ; Thalamic Nuclei ; physiology

The present study was designed to investigate the function and mechanism of high-frequency stimulation (HFS) of the parafascicular nucleus (PF) used as a therapeutic approach for Parkinson's disease (PD). PD rat model was built by injecting 6-hydroxydopamine (6-OHDA) into the substartia nigra pars compacta of adult male Sprague-Dawley rats. Using the ethological methods, we examined the effect of electrical stimulation of PF on the apomorphine-induced rotational behavior in PD rats. Moreover, Electrophysiological recordings were made in rats to investigate the effects of electrical stimulation of PF on the neuronal activities of the subthalamic nucleus (STN) and the ventromedial nucleus (VM). Our results showed that one week after HFS (130 Hz, 0.4 mA, 5 s) of PF, there was significant improvement in apomorphine-induced rotational behavior in PD rats. HFS of PF caused an inhibition of the majority of neurons (84%) recorded in the STN in PD rats. The majority of cells recorded in the VM of the thalamus responded to the HFS with an increase in their unitary discharge activity (81%). These effects were in a frequency-dependent manner. Only stimulus frequencies above 50 Hz were effective. Furthermore, employing microelectrophoresis, we demonstrated that glutamatergic and GABAergic afferent nerve fibers converged on the same STN neurons. These results show that the HFS of PF induces a reduction of the excitatory glutamatergic output from the PF which in turn results in deactivation of STN neurons. The reduction in tonic inhibitory drive from the basal ganglia induces a disinhibition of activity in the VM, a motor thalamic nucleus. In conclusion, the results suggest that HFS of PF may produce a therapeutic effect in PD rats, which is mediated by the nuclei of PF, STN and VM.
Action Potentials ; physiology ; Animals ; Electric Stimulation ; Intralaminar Thalamic Nuclei ; physiopathology ; Male ; Neurons ; physiology ; Parkinson Disease ; physiopathology ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Subthalamic Nucleus ; physiopathology ; Ventral Thalamic Nuclei ; physiopathology

BACKGROUNDElectrical stimulation of the anterior nucleus of the thalamus (ANT) appears to be effective against seizures. In this study, we investigated changes in glucose metabolism during high-frequency stimulation of ANT in epileptic rats.

METHODSThree groups of rats were used: (1) a stimulation group (n = 12), (2) a sham stimulation group (n = 12) with seizures induced by stereotactic administration of kainic acid (KA), and (3) a control group (n = 12) with sham surgery. Concentric bipolar electrodes were stereotaxically implanted unilaterally in the ANT. High-frequency stimulation was performed in each group except the sham stimulation group. Microdialysis probes were lowered into the CA3 region of the hippocampus unilaterally but bilaterally in the stimulation group. The concentrations of glucose, lactate, and pyruvate in dialysate samples were determined by an ISCUS microdialysis analyzer.

RESULTSThe extracellular concentrations of lactate and lactate/pyruvate ratio (LPR) of epileptic rats were significantly higher than in control rats (P = 0.020, P = 0.001; respectively). However, no significant difference in the concentration of glucose and pyruvate was found between these groups (P > 0.05). Electrical stimulation of ANT induced decreases in lactate and LPR in the ipsilateral hippocampus (KA injected) of the stimulation group (P < 0.05), but it did not influence the glucose metabolism in the contralateral hippocampus (P > 0.05).

CONCLUSIONSThis study demonstrated that the glycolysis was inhibited in the ipsilateral hippocampus of epileptic rats during electrical ANT stimulation. These findings may provide useful information for better understanding the mechanism of ANT-deep brain stimulation.

Animals ; Anterior Thalamic Nuclei ; physiology ; Deep Brain Stimulation ; Epilepsy ; metabolism ; therapy ; Glucose ; metabolism ; Glycolysis ; Hippocampus ; metabolism ; Male ; Rats ; Rats, Wistar

BACKGROUNDAlthough thalamotomy could dramatically improve both parkinsonian resting tremor and essential tremor (ET), the mechanisms are obviously different. This study aimed to investigate the neuronal activities in the ventrolateral thalamus of Parkinson's disease (PD) and ET.

METHODSThirty-six patients (PD: 20, ET: 16) were studied. Microelectrode recordings in the ventral oral posterior (Vop) and the ventral intermediate nucleus (Vim) of thalamus was performed on these patients who underwent thalamotomy. Electromyography (EMG) was recorded simultaneously on the contralateral limbs to surgery. Single unit analysis and the interspike intervals (ISIs) were measured for each neuronal type. ISI histogram and auto-correlograms were constructed to estimate the pattern of neuronal firing. Mann-Whitney test and Kruskal-Wallis (K-W) test were used to compare the mean spontaneous firing rate (MSFR) of neurons of PD and ET patients.

RESULTSThree hundred and twenty-three neurons were obtained from 20 PD trajectories, including 151 (46.7%) tremor related neuronal activity, 74 neurons (22.9%) with tonic firing, and 98 (30.4%) neurons with irregular discharge. One hundred and eighty-seven neurons were identified from 16 ET trajectories including 46 (24.6%) tremor-related neuronal activity, 77 (41.2%) neurons with tonic firing, and 64 neurons (34.2%) with irregular discharge. The analysis of MSFR of neurons with tonic firing was 26.7 (3.4 - 68.3) Hz (n = 74) and that of neurons with irregular discharge (n = 98) was 13.9 (3.0 - 58.1) Hz in PD; whereas MSFR of neurons with tonic firing (n = 77) was 48.8 (19.0 - 135.5) Hz and that of neurons with irregular discharge (n = 64) was 26.3 (8.7 - 84.7) Hz in ET. There were significant differences in the MSFR of two types of neuron for PD and ET (K-W test, both P < 0.05). Significant differences in the MSFR of neuron were also obtained from Vop and Vim of PD and ET (16.3 Hz vs. 34.8 Hz, 28.0 Hz vs. 49.9 Hz) (K-W test, both P < 0.05), respectively.

CONCLUSIONIn consistent with recent findings, the decreased MSFR of neurons observed in the Vop is likely to be involved in PD whereas the increased MSFR of neurons seen in the Vim may be a cause of ET.

Essential Tremor ; physiopathology ; Female ; Humans ; Male ; Middle Aged ; Neurons ; physiology ; Parkinson Disease ; physiopathology ; Retrospective Studies ; Ventral Thalamic Nuclei ; physiopathology

BACKGROUNDIt has been proposed that parkinsonian motor signs result from hyperactivity in the output nucleus of the basal ganglia, which suppress the motor thalamus and cortical areas. This study aimed to explore the neuronal activity in the globus pallidus internus (GPi) and the ventrolateral thalamic nuclear group (ventral oral posterior/ventral intermediate, Vop/Vim) in patients with Parkinson's disease (PD).

METHODSTwenty patients with PD who underwent neurosurgery were studied. Microelectrode recording was performed in the GPi (n = 10) and the Vop/Vim (n = 10) intraoperatively. Electromyography (EMG) contralateral to the surgery was simultaneously performed. Single unit analysis was carried out. The interspike intervals (ISI) and coefficient of variation (CV) of ISI were calculated. Histograms of ISI were constructed. A unified Parkinson's disease rating scale (UPDRS) was used to assess the clinical outcome of surgery.

RESULTSThree hundred and sixty-three neurons were obtained from 20 trajectories. Of 175 GPi neurons, there were 15.4% with tremor frequency, 69.2% with tonic firing, and 15.4% with irregular discharge. Of 188 thalamic neurons, there were 46.8% with tremor frequency, 22.9% with tonic firing, and 30.3% with irregular discharge. The numbers of three patterns of neuron in GPi and Vop/Vim were significantly different (P < 0.001). ISI analysis revealed that mean firing rate of the three patterns of GPi neurons was (80.9 +/- 63.9) Hz (n = 78), which was higher than similar neurons with 62.9 Hz in a normal primate. For the Vop/Vim group, ISI revealed that mean firing rate of the three patterns of neurons (n = 95) was (23.2 +/- 17.1) Hz which was lower than similar neurons with 30 Hz in the motor thalamus of normal primates. UPDRS indicated that the clinical outcome of pallidotomy was (64.3 +/- 29.5)%, (83.4 +/- 19.1)% and (63.4 +/- 36.3)%, and clinical outcome of thalamotomy was (92.2 +/- 12.9)%, (68.0 +/- 25.2)% and (44.3 +/- 27.2)% for tremor, rigidity and bradykinesia, respectively. A significant difference of tremor and rigidity was found between GPi and Vop/Vim (P < 0.05).

CONCLUSIONSDifferent changes in neuronal firing rate and the pattern in GPi and Vop/Vim are likely responsible for parkinsonian motor signs. The results support the view that abnormal neuronal activity in GPi and Vop/Vim are involved in the pathophysiology of parkinsonism.

Adult ; Aged ; Female ; Globus Pallidus ; physiopathology ; Humans ; Male ; Middle Aged ; Neurons ; physiology ; Parkinson Disease ; physiopathology ; Ventral Thalamic Nuclei ; physiopathology

Adult ; Deep Brain Stimulation ; Dystonia ; etiology ; therapy ; Female ; Globus Pallidus ; physiology ; Humans ; Receptors, Dopamine D1 ; physiology ; Subthalamic Nucleus ; physiology ; Ventral Thalamic Nuclei ; physiology

OBJECTIVETo determine whether the convergences of tactile information also occur at thalamic ventroposterolateral nucleus in rats, we investigated the properties of tactile responses of the thalamic ventroposterolateral nucleus in rats.

METHODSUnit responses were recorded extracellularly from thalamic ventroposterolateral nucleus in anesthetized rats.

RESULTSAmong 156 neurons examined, 140 neurons (89.7%) had the single, continual and small receptive fields, and 16 neurons (10.3%) had two discrete receptive fields. Some neurons?exhibited different responses to the same intensity stimulation which delivered to different points in their receptive fields. In addition, 4.5% neurons (n = 7) responded only to locomotive stimulation but?not to a punctiform tactile stimulation.

CONCLUSIONThe majority of neurons in ventroposterolateral nucleus of rats have the spatial, temporal and submodal characteristics of cutaneous receptors, while the minority of neurons exhibit the responses of interaction of different peripheral receptors. Therefore, it is concluded that there are convergences of tactile information at the ventroposterolateral nucleus of rats.

Animals ; Male ; Neural Pathways ; cytology ; physiology ; Neurons ; cytology ; physiology ; Physical Stimulation ; Rats ; Rats, Sprague-Dawley ; Skin ; innervation ; Thalamic Nuclei ; cytology ; physiology ; Touch

The purpose of the present work was to study the effect of acute tetanization of the right caudate putamen nucleus (ATRC) on single neuronal interspike intervals (ISIs) in both laterodorsal thalamic nuclei (LDi), and electroencephalogram (EEG) wave interpeak intervals (IPIs) in both hippocampi (HPCi). Experiments were performed on 21 male Sprague-Dawley rats weighing 150~250 g. The seizures were induced by the ATRC (60 Hz, 2 s, 0.4~0.6 mA). Quadruple recordings were simultaneously carried out: two for single unit recordings from both LDi, and two for EEG recordings from both HPCi. The ATRC induced: (1) An interactive epileptic electrical network reconstructed in bilateral HPCi, which was driven by primary afterdischarges of single LD neuron. (2) A symmetric mirror-like ISI spot distribution of the LD neuronal firing before and after tetanus. (3) Gradually prolonged LD neuronal discharge intermittence was coherent with synchronous hippocampal EEG activities on the contralateral side. (4) Single LD neuronal spikes were phase- and time-locked to 20~25 Hz gamma oscillations in contralateral HPC. It suggests a particular temporal code patterning of single LD neuronal firing and its relationships to hippocampal EEG wave code in time series, the latter implies the LD neuronal encoding mechanisms of ATRC-induced epileptic electrical network in bilateral HPCi.
Action Potentials ; physiology ; Animals ; Caudate Nucleus ; physiology ; Electric Stimulation ; methods ; Electroencephalography ; Epilepsy ; etiology ; physiopathology ; Hippocampus ; physiology ; Lateral Thalamic Nuclei ; physiology ; Male ; Nerve Net ; physiology ; Neurons ; physiology ; Rats ; Rats, Sprague-Dawley ; Reaction Time ; physiology