Knowledge about the neuronal dynamics and the projectome are both essential for understanding how the neuronal network functions in concert. However, it remains challenging to obtain the neural activity and the brain-wide projectome for the same neurons, especially for neurons in subcortical brain regions. Here, by combining in vivo microscopy and high-definition fluorescence micro-optical sectioning tomography, we have developed strategies for mapping the brain-wide projectome of functionally relevant neurons in the somatosensory cortex, the dorsal hippocampus, and the substantia nigra pars compacta. More importantly, we also developed a strategy to achieve acquiring the neural dynamic and brain-wide projectome of the molecularly defined neuronal subtype. The strategies developed in this study solved the essential problem of linking brain-wide projectome to neuronal dynamics for neurons in subcortical structures and provided valuable approaches for understanding how the brain is functionally organized via intricate connectivity patterns.
Animals ; Neurons/physiology* ; Mice ; Brain/physiology* ; Mice, Inbred C57BL ; Somatosensory Cortex/physiology* ; Neural Pathways/physiology* ; Hippocampus/physiology* ; Mice, Transgenic ; Male ; Brain Mapping ; Nerve Net/physiology* ; Substantia Nigra/physiology* ; Tomography, Optical/methods*

Synaptic plasticity of barrel cortex is one of the most widely studied topics in neuroscience in recent years. The primary somatosensory cortex of the rodent has a good topology character,which provides an ideal experimental model for plasticity study. This system displays very strong experience-dependent plasticity both during development and in adulthood. The changes of sensory cortex's neural circuit can induce experience-dependent plasticity. In the synaptic level,thalamocortical synapse is considered to be the main location of plasticity. In the circuit level,both synapses from layer 4 to layer 2/3 and those within layer 2/3 are also the necessary parts of achieving synaptic plasticity in primary somatosensory cortex. The GABAergic inhibitory circuit may be involved in this plasticity of S1, but the exact mechanism remains unknown.
Animals ; Neural Pathways ; physiology ; Neuronal Plasticity ; Somatosensory Cortex ; physiology ; Synapses ; physiology ; Thalamus ; physiology ; Vibrissae ; physiology

BACKGROUNDLocalization of sensory cortical areas during the operation is essential to preserve the sensory function. Intraoperative direct electrostimulation under awake anesthesia is the golden standard but time-consuming. We applied 3T high field blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI) to identify the relationship between glioma and cortical sensory areas preoperatively and to guide intraoperative direct electrostimulation for quick and precise localization.

METHODSFive glioma patients with sensory cortex involvement by or next to the lesion had preoperative BOLD fMRI to determine the spatial relationship of cortical sensory areas to the tumours. Bilateral hand opposite movement was performed by these patients for fMRI. Precentral and postcentral gyri were identified by electrical stimulation during the operation. Karnofsky Performance Status scores of the patients' pre- and postoperative and the role of BOLD fMRI were evaluated.

RESULTSThe cortical sensory areas were all activated in five glioma patients involving postcentral gyrus areas by BOLD fMRI with bilateral hand opposite movement. The detected activation areas corresponded with the results from cortical electrical stimulation.

CONCLUSIONSThe relationship between cortical sensory areas and tumour can be accurately shown by BOLD fMRI before operation. And the information used to make the tumour resection could obtain good clinical results.

Adult ; Female ; Glioma ; blood ; pathology ; Humans ; Magnetic Resonance Imaging ; methods ; Male ; Middle Aged ; Oxygen ; blood ; Somatosensory Cortex ; physiology ; Young Adult

OBJECTIVETo investigate the change of behavior, as well as the plasticity of somatosensory cortex after whisker trimming.

METHODSSD rats were divided into 4 groups. Group A is the normal control group; group B: bilateral vibrissotomy on the second postnatal day; group C: unilateral right vibrissotomy on the second postnatal day; group D: right unilateral whisker trimmed during 1-5 days after birth, and leave untreated after the 5th postnatal day. Their body weight, length of the left D2 whiskers was measured on the 30th postnatal day. At the same time, the changes of their behavior (including the slit-detection test, the home exploring behavior and thigmotaxis test) were also recorded on the 30th postnatal day. Cytochrome oxydase histochemistry (CO reaction)was applied to study the development and arrangement of barrel cortex.

RESULTSIn the slit-detection test, control rats could find and get into the right slit very quickly. The rats in group B could get into the slit only if their noses touched the slit. The rats in group C couldn't identify the slit by right face, but if they turned their body and touched the slit with the left whiskers, they could get into the slit very quickly. The behavior of rats in group D was similar to that in group C. The time spent for finding out the right slit of the rats in group A, B, C was obviously longer than that of group A (P < 0.01, P < 0.05, P < 0.01). In the exploring behavior and thigmotaxis test, the time for left thigmotaxis, right thigmotaxis and total thigmotaxis of rats in group B was longer than that of control animals. The time for right thigmotaxis of group C was significantly shorter than that of group A (P < 0.05). Both the weight of the rats and the length of left D2 whiskers of rats in all the four groups had no significant difference. CO reaction showed that the barrels became smaller, the septum was not clear, the arrangement of the barrels was not tidy in the mice whose right whiskers were trimmed from 2-30 days after birth.

CONCLUSIONDeafferentation doesn't change the body weight and length of the whiskers left. But the stimulation of whiskers is important for rodent especially in thigmotaxis and exploring behavior. Deafferentation can also induce the plastic change of barrel cortex.

Animals ; Animals, Newborn ; Cerebral Cortex ; physiology ; Male ; Neuronal Plasticity ; Physical Stimulation ; Rats ; Rats, Sprague-Dawley ; Somatosensory Cortex ; physiology ; Vibrissae

While the activation of primary somatosensory (SI) cortex during pain perception is consistently reported in functional imaging studies on normal subjects and chronic pain patients, the specific roles of SI, particularly the subregions within SI, in the processing of sensory aspects of pain are still largely unknown. Using optical imaging of intrinsic signal (OIS) and single unit electrophysiology, we studied cortical activation patterns within SI cortex (among Brodmann areas 3a, 3b and 1) and signal amplitude changes to various intensities of non-nociceptive, thermal nociceptive and mechanical nociceptive stimulation of individual distal finerpads in anesthetized squirrel monkeys. We have demonstrated that areas 3a and 1 are preferentially involved in the processing of nociceptive information while areas 3b and 1 are preferentially activated in the processing of non-nociceptive (touch) information. Nociceptive activations of individual fingerpad were organized topographically suggesting that nociceptive topographic map exits in areas 3a and 1. Signal amplitude was enhanced to increasing intensity of mechanical nociceptive stimuli in areas 3a, 3b and 1. Within area 1, nociceptive response co-localizes with the non-nociceptive response. Therefore, we hypothesize that nocicepitve information is area-specifically represented within SI cortex, in which nociceptive inputs are preferentially represented in areas 3a and 1 while non-nociceptive inputs are preferentially represented in areas 3b and 1.
Animals ; Brain Mapping ; Nociception ; physiology ; Pain ; Saimiri ; Somatosensory Cortex ; physiology ; Touch

Neural network plasticity is fundamental for learning and memory. Its abnormal change underlies some neural diseases. Measurement of the plasticity of cortex can help understand the mechanism of plasticity, and provide a quantitative way to observe the neural process of natural aging and neurodegenerative diseases, which may lead to a new approach for evaluation of anti-aging drugs and new medical treatments for neurodegenerative diseases. In this study, a systematic method was established based on whisker pairing (WP) experiment to measure the network plasticity in the barrel cortex in rat. WP experiment is a classical experiment to study the effect of innocuous bias of the flow of sensory activity from the whiskers for certain periods in awake and behaving rats on the receptive field organization in S1 barrel cortex neurons. In the experiment, one pair of adjacent whiskers D2 and D3 remained intact while others were being trimmed throughout a certain period. After that, receptive fields of single cells in the contralateral barrel were analyzed by post-stimulus time histogram after certain days of WP and compared with the controls. In the control group, response magnitudes to surrounding whiskers D1 and D3 deflection were not significantly different. However, after WP, a bias occurred in response to paired surrounding whisker D3 relative to the opposite trimmed surrounding whisker D1. In this study, by comparing the bias degree in rats in different groups after WP, a quantitative method was established to compare cortical plasticity. Example of corical plasticity comparison between adolescent and mature rats was employed in this paper to illustrate our method. The key techniques of this method such as the identification of D2 barrels, supragranular (L2-3) and barrel layer (L4) in real-time were described in details. The feasibility of this approach was further verified by compendious report of results and our previous study regarding cortical plasticity comparison between adolescent and mature rats.
Animals ; Neuronal Plasticity ; Rats ; Somatosensory Cortex ; physiology ; Vibrissae

This experiment was carried out to analyze the time-frequency feature of rabbit cortical somatosensory evoked potential (SEP). Rabbit was narcotized and subjected to craniotomy. SEP was from sensory and motor cortex. Stimulation was continuing many times and signal was sampled at 3 800 Hz. The peak latency of each waveform was measured. Power spectrum of SEP was analyzed. The time-frequency feature of single-trial was compared with that of average SEP. It was found that the variability of single-trial SEP latency enlarges with time in a stimulation period. The spectrum of SEP includes three main frequency spectrum packages. The technique of summation makes a lot of signal aberration such as waveform confluence, new waveform emerging and after-discharging components dismissing.
Animals ; Cerebral Cortex ; physiology ; Electric Stimulation ; Evoked Potentials, Somatosensory ; physiology ; Female ; Fourier Analysis ; Male ; Rabbits ; Signal Processing, Computer-Assisted

The modulation of ACh on delayed rectifier-like potassium currents (I(K)) was studied in freshly dissociated cerebral cortical neurons using the whole-cell patch-clamp technique. Wistar rats between 10- and 14-day old of both sexes were used. After rats were decapitated, their brains were quickly removed, iced, and then manually cut into 400 mum slices. Slices were then incubated for 0.5 h at 32 degrees C in a buffered artificial cerebrospinal fluid (ACSF) bubbled with 95% O2, 5% CO2. Slices were then removed into buffered ACSF containing protease (0.5 mg/ml) at 32 degrees C. After 30 min of enzyme digestion, tissue was rinsed three times in the buffered saline. Then the enzyme-treated slices were mechanically dissociated with a graded series of fire-polished Pasteur pipettes. The cell suspension was then plated into a 35 mm dish and placed on the stage of a Olympus inverted microscope. For whole-cell recordings of currents, standard voltage-clamp techniques were used. Neurons were held at -80 mV, and the I(K) was evoked by 2 000 ms depolarizing voltage commands to potential between -40 mV and +60 mV in 10 mV steps applied at a frequency of 0.5 Hz. It was found that the inhibitory effect of ACh (0.1, 1, 10, 100 mumol/L) on I(K) was dose-dependent. It was also found that ACh affected the activation process of I(K) significantly, i.e., the activation curve of I(K) was characterized by half-activation potential of (-41.8+/-9.7) mV and a slope factor of (30.7+/-7.2) mV in the cortical neurons and they were changed to (-122.4+/-38.6) mV and (42.4+/-7.0) mV, respectively, after giving ACh (10 mumol/L). Tubocurarine (100 mumol/L) antagonized the inhibitory effect of ACh on I(K), and the drop of currents varied from the control value of (36.5+/-7..8)% to (16.9+/-13.8)% (n=8, P<0.01). 4-DAMP (10 mumol/L) blocked the inhibitory effect of ACh on I(K), and the currents reduced from the control value of (36.5+/-7.8)% to (26.8+/-4.7) % (n=6, P<0.05). Pirenzepin did not antagonize the inhibition of ACh on I(K) (n=7, P>0.05). Chelerythrine (20 mumol/L) blocked the inhibitory effect of ACh on I(K) and the currents reduced from the control value of (36.5+/-7.8)% to (11.7+/-17.3)% (n=6, P<0.05). On the contrary, PDBu (10 mumol/L) strengthened the inhibition of ACh on I(K) and the drop of currents changed from the control value of (36.5+/-7.8)% to (59.2+/-14.0)% (n=5, P<0.05). PDBu abolished the antagonism of chelerythrine on ACh in cortical neurons. It is suggested that the ACh-induced depolarization of neurons in the cortex is attributed to the inhibition of I(K) that is most likely evoked by the activation of nicotinic ACh receptors and muscarinic M3 receptor via protein kinase C (PKC) signal transduction pathway.
Acetylcholine ; physiology ; Animals ; Cell Separation ; Delayed Rectifier Potassium Channels ; antagonists & inhibitors ; Female ; Male ; Neurons ; metabolism ; physiology ; Patch-Clamp Techniques ; Protein Kinase C ; metabolism ; physiology ; Rats ; Rats, Wistar ; Receptor, Muscarinic M3 ; metabolism ; Receptors, Nicotinic ; metabolism ; Signal Transduction ; physiology ; Somatosensory Cortex ; cytology ; physiology

AIMTo investigate the effect of 5-hydroxytryptamine (5-HT) on spontaneous unit discharges of primary somatosensory cortex (SI-SUD) and the role of 5-HT1A receptor in 5-HT inhibitory effect on SI-SUD in rat.

METHODSThe SI-SUD was recorded before and during microiontophoresis of 5-HT and 8-OH-DPAT (the selective agonist for 5-HT1A receptor. The changes of mean of interspike interval (MISI) of SI-SUD were analysed and handled with the statistics.

RESULTS(1) Effects of 5-HT on SI-SUD may be inhibitory (48/96), excitatory (26/96) or non-responsive (22/96), and the major effect is inhibitory. (2) In 20 of 5-HT inhibited units, 17 are also inhibited with microiontophoresis of 8-OH-DPAT, but 3 have no obvious response to 8-OH-DPAT.

CONCLUSIONThe major effect of 5-HT on SI-SUD is inhibitory. In majority of 5-HT inhibited units, 5-HT1A receptor may be existence, which may involve in the inhibition of 5-HT on SI-SUD.

8-Hydroxy-2-(di-n-propylamino)tetralin ; pharmacology ; Animals ; Female ; Male ; Rats ; Rats, Wistar ; Receptors, Serotonin ; drug effects ; physiology ; Serotonin ; physiology ; Somatosensory Cortex ; drug effects ; physiology

Adult ; Aged ; Aging ; physiology ; Evoked Potentials, Somatosensory ; physiology ; High-Frequency Ventilation ; Humans ; Middle Aged ; Somatosensory Cortex ; physiology