Resistive Switching Mechanism of HfO₂ Based Resistance Random Access Memory Devices with Different Electrode Materials

This study investigated the impact of electrode materials on HfO₂-based RRAM devices. The research includes three types of electrode materials: (1) the electrodes with strong ability of oxygen reservoirs; (2) the electrode with poor ability of oxygen reservoirs; (3) the active electrode with injection ability. Through implementing different combinations of electrodes, three types of switching modes were obtained and the relative conduction mechanism was analyzed, as well as conduction model. Those studies may offer ways of using electrodes to control the resistive switching processes and fabricating the RRAM devices with good performance.

[Association between both maternal pre-pregnancy body mass index/gestational weight gain and overweight/obesity children at preschool stage]

Objective: To investigate the association of both maternal pre-pregnancy body mass index (BMI) and gestational weight gain (GWG) with childhood overweight and adiposity in preschool children. Methods: A total of 4 303 preschool children aged 3-5 years were enrolled in our study during June and November 2016 in Guangzhou. Children defined as overweight and obesity were according to the criteria of WHO while weight status during maternal pre-pregnancy was using the China Adult Reference. Gestational weight gain was defined according to the Institute of Medicine guidelines. Results: After adjusting the possible confounding factors, results from the logistic regression analysis showed that both maternal pre-pregnancy overweight and obesity would increase the risk for both childhood overweight and obesity (OR=1.820, 95%CI: 1.368-2.422). The analysis of covariance results also showed that both maternal overweight and obesity before pregnancy and excessive maternal weight gain during pregnancy increased the BMI Z-score in children. Maternal GWG over the recommended level were associated with both the childhood overweight and obesity (OR=1.296, 95%CI: 1.007-1.667). Joint associations of pre-pregnancy BMI and inappropriate GWG were also noticed in the study. Stratified analysis was conducted in three groups according to the pre-pregnancy BMI of the mothers. Result showed that there was no statistical difference in the risks of either overweight or obesity in children (P>0.05). However, when compared to mothers with adequate pre-pregnancy higher BMI and adequate GWG, under the combination of high pre-pregnancy BMI and excessive GWG, their adverse effects on childhood overweight and obesity were much higher (OR=1.574, 95%CI: 1.029-2.409). Conclusions: Both high pre-pregnancy BMI and inappropriate GWG were associated with greater BMI of their offspring. Pregnant women should follow the appropriate weight gain program and help their children to prevent from becoming obese.

[Effect of multimodal analgesia using periprostatic nerve block anesthesia combined with flurbiprofen in transperineal template-guided prostate biopsy]

Objective: To evaluate the effect of multimodal analgesia using periprostatic nerve block anesthesia (PNB) combined with flurbiprofen in patients undergoing transperineal template-guided prostate biopsy (TTPB). Methods: Totally 166 patients (aged (68.2±9.1) years, range: 47 to 81 years) who received TTPB from October 2017 to June 2018 at Department of Urology, Northern Jiangsu People's Hospital Affiliated to Yangzhou University were enrolled prospectively. All the patients were randomly divided into 2 groups. The observation group (n=79) was given flurbiprofen axetil 1 mg/kg intravenously for half an hour before operation and lidocaine was used for PNB before the biopsy. The control group (n=87) was given normal saline combined with PNB. A visual analog scale (VAS) and visual numeric scale (VNS) were used to assess the patients' pain and quantify their satisfaction at two time points: VAS-1 and VNS-1: during biopsy procedure, VAS-2 and VNS-2: 30 min after the procedure. The date were compared by t test, χ(2) test, Fisher exact test and two-way repeated measures anova analysis between the 2 groups. Results: The age, total prostate volume, serum prostate-specific antigen and the number of cores were comparable among the 2 groups (P>0.05). The VAS-1 scores of the control group and the observation group were 2.8±1.7, 1.9±1.2, respectively, and the VNS-1 were 3.1±0.7, 3.4±0.3, respectively. The VAS-1 were significantly lower in observation group than in control group (F=3.904, P=0.000). Conversely, the VNS-1 were higher in observation group (F=3.526, P=0.000). At 30-minute postoperative, the VAS-2 and VNS-2 were 0.7±0.4 and 3.7±0.2 in the control group, respectively. The VAS-2 and VNS-2 were 0.6±0.5 and 3.8±0.1 in the observation group, respectively. There were no significant differences in the pain scores or the satisfaction scores between the 2 groups (F=1.429, 2.825; P=0.136, 0.083). The incidence of overall complications was 26.4% (23/87) in the control group and 25.3% (20/79) in the observation group, with no statistical difference between the 2 groups (χ(2)=0.027, P=0.869). And the complications had no statistically significant difference among the 2 groups including hematuria, urinary retention, infection, hematospermia, vascular and neurological reactions, nausea, vomiting, dizziness, headache, and respiratory depression (P>0.05). Conclusion: The multimodal analgesia induced by PNB and flurbiprofen could effectively relieve the pain for patients who received TTPB.

Genetic analysis of STR markers on chromosome 21 in a Han population from southeast China

Short tandem repeats (STRs) are highly polymorphic sequences and have been extensively used as genetic markers in mapping studies, disease diagnosis, and human identity testing. In this study, 11 STR markers on chromosome 21, including D21S1432, D21S11, D21S1246, D21S1412, D21S1437, D21S1442, D21S2039, D21S1270, D21S1435, D21S1409, and D21S1446, were analyzed in 740 unrelated Han individuals from southeast China. A total of 132 alleles, ranging from 7-21 for each locus, were named according to the guidelines of the International Society for Forensic Haemogenetics. The distributions of allelic frequencies for the 11 STRs and population genetic parameters were determined. All 11 STR markers showed high polymorphism and heterogeneity in the southeast Han population, with polymorphism information content of 0.61-0.87, heterogeneity of 64.5-86.1%, and power of discrimination of 0.835-0.973. Among the 11 STR markers, D21S1412, D21S1270, D21S11, and D21S1442 showed relatively higher heterogeneity. Their combination was relatively informative and was used in a quantitative fluorescence-polymerase chain reaction assay to diagnose Down syndrome (trisomy 21) in a southeast Chinese Han population. The genetic information and population data for these 11 STRs may be used not only in quantitative fluorescence-polymerase chain reaction assays but also in forensic studies and other genetic tests.

Residential Mobility within Guangzhou City, China, 1990-2010: Local Residents Versus Migrants

Drawing on residential history data from two household surveys conducted in Guangzhou in 2005 and 2010, this paper compares the pattern of intra-city residential moves of local residents and that of migrants. The findings show different trajectories of residential moves for the two groups. While migrants showed increasing mobility over time, residential moves of locals first rose until the early 2000s, then declined steadily afterward. Moreover, the determinants of residential moves of migrants differ from those of the local population. Also, whereas residential moves for the local population are subject to changing factors over time, drivers of relocation for migrants remain more or less stable.

Phase contribution of image potential on empty quantum well States in pb islands on the cu(111) surface

We use scanning tunneling spectroscopy to explore the quantum well states in the Pb islands grown on a Cu(111) surface. Our observation demonstrates that the empty quantum well states, whose energy levels lie beyond 1.2 eV above the Fermi level, are significantly affected by the image potential. As the quantum number increases, the energy separation between adjacent states is shrinking rather than widening, contrary to the prediction for a square potential well. By simply introducing a phase factor to reckon the effect of the image potential, the shrinking behavior of the energy separation can be reasonably explained with the phase accumulation model. The model also reveals that there exists a quantum regime above the Pb surface in which the image potential is vanished. Moreover, the quasi-image-potential state in the tunneling gap is quenched because of the existence of the quantum well states.

Manifestation of work function difference in high order Gundlach oscillation

Gundlach oscillation (or the standing-wave state) is a general phenomenon manifesting in the tunneling spectrum acquired from a metal surface using scanning tunneling spectroscopy. Previous studies relate the energy shift between peaks of the lowest-order Gundlach oscillation observed on the thin film and the metal substrate to the difference in their work functions. By observing Gundlach oscillations on Ag/Au(111), Ag/Cu(111), and Co/Cu(111) systems, we demonstrate that the work function difference is not the energy shift of the lowest order but the ones of higher order where a constant energy shift exhibits. Higher order Gundlach oscillations can thus be applied to determine the work function of thin metal films precisely.

Distinct NMDA and AMPA receptor-mediated responses in mouse and human Cajal-Retzius cells

This study examined glutamate-activated current responses of mouse and human Cajal-Retzius (C-R) cells. Thin cortical slices were prepared from the brains of mice 4-6 days after birth and from those of midgestational human fetuses. Both human and mouse C-R cells displayed glutamate-induced whole-cell current responses that were voltage-dependent and included an N-methyl-D-aspartate (NMDA) receptor-mediated component that was differentially sensitive to blockade by the NMDA receptor antagonists 2-amino-5-phosphonovaleric acid and ifenprodil. alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), a non-NMDA glutamate receptor agonist, induced current responses in human but not in mouse C-R cells. These results, taken together, lead us to conclude that human C-R cells express both NMDA and AMPA types of glutamate receptors very early during development of the cortex. In contrast, mouse C-R cells express only the NMDA type of glutamate receptor. Thus we demonstrate a species-dependent sensitivity of C-R cells to glutamate and postulate that this differential sensitivity may account in part for a species-dependent difference in the persistence of C-R cells during cortical development.

Relationship between ABO blood groups and carcinoma of esophagus and cardia in Chaoshan inhabitants of China

AIM

To study the relationship between ABO blood groups and carcinoma of esophagus and cardia in Chaoshan inhabitants of China, which is a unique Littoral high-risk area of esophageal carcinoma in China. The poor communication and transportation in the past has made Chaoshan a relatively closed area and kept its culture and custure of old China thousand years ago.

METHODS

Data on age, sex, ABO blood type and X-ray or pathological diagnose of the patients with carcinoma of esophagus or cardia were collected from the Tumor Hospital. First Affiliated Hospital, Second Affiliated Hospital of Shantou University Medical College; and the Central Hospital of Shantou and the Central Hospital of Jieyang. A total of 6685 patients with esophageal carcinoma (EC) and 2955 patients with cardiac cancer (CC) in Chaoshan district were retrospectively assessed for their association with ABO blood groups.

RESULTS

The distribution of ABO blood groups in patients with EC or CC was similar to the normal local population in Chaoshan. However, blood group B in male patients with CC and in the patients with carcinoma in the upper third esophagus was 2.3% and 4.7% higher than the corresponding controls. The relative risk B O was 1.1415 (P<0.05) and 1.2696 (P<0.05), respectively. No relationship was found between ABO blood groups and tumor differentiation.

CONCLUSION

ABO blood group B is associated with the incidence of CC in male individuals and carcinoma in the upper third esophagus. The distribution of ABO blood groups varies in the different geographical and ethnic groups. As a result, proper controls are very important for such studies.

Predicting the reactivity of proteins from their sequence alone: Kazal family of protein inhibitors of serine proteinases

An additivity-based sequence to reactivity algorithm for the interaction of members of the Kazal family of protein inhibitors with six selected serine proteinases is described. Ten consensus variable contact positions in the inhibitor were identified, and the 19 possible variants at each of these positions were expressed. The free energies of interaction of these variants and the wild type were measured. For an additive system, this data set allows for the calculation of all possible sequences, subject to some restrictions. The algorithm was extensively tested. It is exceptionally fast so that all possible sequences can be predicted. The strongest, the most specific possible, and the least specific inhibitors were designed, and an evolutionary problem was solved.

Ethanol modulates AMPA-induced current responses of primary somatosensory cortical neurons

This study examined the effect of ethanol on responses of primary somatosensory cortical neurons to AMPA. Thin (200-250 microns) brain slices were sectioned to include the primary somatosensory cortex of rats 6-15 days after birth. Visually-identified neurons were selected for whole-cell patch clamp recording and an eight-barrel drug pipet assembly was used to deliver test agents. Ethanol (5-100 mM) either positively or negatively modulated AMPA (100 microM)-induced current to varying degrees in approximately 70% of primary somatosensory cortical neurons. As revealed in layer V large pyramidal neurons, the outcome of an ethanol-induced modulation appeared to be age-dependent, the trend being one of potentiation in slices derived from younger rats (postnatal days 6-9) but one of attenuation in those derived from older animals (postnatal days 13-15). These findings indicate that ethanol at physiologically relevant concentrations modulates non-NMDA receptor-mediated responses of neurons in the rat primary somatosensory cortex.

Thermodynamic criterion for the conformation of P1 residues of substrates and of inhibitors in complexes with serine proteinases

Eglin c, turkey ovomucoid third domain, and bovine pancreatic trypsin inhibitor (Kunitz) are all standard mechanism, canonical protein inhibitors of serine proteinases. Each of the three belongs to a different inhibitor family. Therefore, all three have the same canonical conformation in their combining loops but differ in their scaffoldings. Eglin c (Leu45 at P1) binds to chymotrypsin much better than its Ala45 variant (the difference in standard free energy changes on binding is -5.00 kcal/mol). Similarly, turkey ovomucoid third domain (Leu18 at P1) binds to chymotrypsin much better than its Ala18 variant (the difference in standard free energy changes on binding is -4.70 kcal/mol). As these two differences are within the +/-400 cal/mol bandwidth (expected from the experimental error), one can conclude that the system is additive. On the basis that isoenergetic is isostructural, we expect that within both the P1 Ala pair and the P1 Leu pair, the conformation of the inhibitor's P1 side chain and of the enzyme's specificity pocket will be identical. This is confirmed, within the experimental error, by the available X-ray structures of complexes of bovine chymotrypsin Aalpha with eglin c () and with turkey ovomucoid third domain (). A comparison can also be made between the structures of P1 (Lys+)15 of bovine pancreatic trypsin inhibitor (Kunitz) ( and ) and of the P1 (Lys+)18 variant of turkey ovomucoid third domain (), both interacting with chymotrypsin. In this case, the conformation of the side chains is strikingly different. Bovine pancreatic trypsin inhibitor with (Lys+)15 at P1 binds to chymotrypsin more strongly than its Ala15 variant (the difference in standard free energy changes on binding is -1.90 kcal/mol). In contrast, turkey ovomucoid third domain variant with (Lys+)18 at P1 binds to chymotrypsin less strongly than its Ala18 variant (the difference in standard free energies of association is 0.95 kcal/mol). In this case, P1 Lys+ is neither isostructural nor isoenergetic. Thus, a thermodynamic criterion for whether the conformation of a P1 side chain in the complex matches that of an already determined one is at hand. Such a criterion may be useful in reducing the number of required X-ray crystallographic structure determinations. More importantly, the criterion can be applied to situations where direct determination of the structure is extremely difficult. Here, we apply it to determine the conformation of the Lys+ side chain in the transition state complex of a substrate with chymotrypsin. On the basis of kcat/KM measurements, the difference in free energies of activation for Suc-AAPX-pna when X is Lys+ and X is Ala is 1.29 kcal/mol. This is in good agreement with the corresponding difference for turkey ovomucoid third domain variants but in sharp contrast to the bovine pancreatic trypsin inhibitor (Kunitz) data. Therefore, we expect that in the transition state complex of this substrate with chymotrypsin, the P1 Lys+ side chain is deeply inserted into the enzyme's specificity pocket as it is in the (Lys+)18 turkey ovomucoid third domain complex with chymotrypsin.

Subcellular membrane impairment and application of phospholipase A2 inhibitors in endotoxic shock

The study aims at elucidating the mechanism involved in the cell dysfunction or impairment and the protective effects of phospholipase A2 (PLA2) inhibitors in endotoxin shock. Thirty-four rabbits were divided randomly into four groups: (1) normal control group (NC, n = 6), receiving saline intravenously; (2) endotoxin shock group (ES, n = 12), receiving 3 mg/kg of E. coli endotoxin; (3) chloroquine pretreated group (CQ, n = 8), receiving 3 mg/kg of chloroquine 3 min before endotoxin injection and (4) chlorpromazine pretreated group (CPZ, n = 8), receiving 0.3 mg/kg of chlorpromazine 30 min before endotoxin injection. Hepatic mitochondria were extracted either 8 h after commencement of the experiment or when the animals died for detecting PLA2 activity, membrane fluidity, membrane bound succinate dehydrogenate (SDH) and malondialdehyde (MDA). Mitochondria of the lung, heart and kidney were also used for detection of the membrane fluidity. It was revealed that the survival rate of 8 h was 100% (NC), 58% (ES), 87.5% (CQ) and 75% (CPZ), respectively. Mean arterial pressure (MAP) dropped soon after endotoxin injection and descended continuously afterwards in the ES group (P < 0.01). Fluorescence polarization, microviscosity and anisotrophy with a DPH probe were elevated above control levels (P < 0.01). SDH was decreased obviously following endotoxin infusion (P < 0.01). Chloroquine and chlorpromazine, serving as PLA2 inhibitors, could abate cellular dysfunction and increase survival rate. It is proposed that PLA2 plays a pivotal role in cellular injury in endotoxin shock. PLA2 inhibitor might serve as a useful adjunct in combating sepsis and shock.

Role of the basal forebrain cholinergic projection in somatosensory cortical plasticity

Trimming all but two whiskers in adult rats produces a predictable change in cortical cell-evoked responses characterized by increased responsiveness to the two intact whiskers and decreased responsiveness to the trimmed whiskers. This type of synaptic plasticity in rat somatic sensory cortex, called "whisker pairing plasticity," first appears in cells above and below the layer IV barrels. These are also the cortical layers that receive the densest cholinergic inputs from the nucleus basalis. The present study assesses whether the cholinergic inputs to cortex have a role in regulating whisker pairing plasticity. To do this, cholinergic basal forebrain fibers were eliminated using an immunotoxin specific for these fibers. A monoclonal antibody to the low-affinity nerve growth factor receptor 192 IgG, conjugated to the cytotoxin saporin, was injected into cortex to eliminate cholinergic fibers in the barrel field. The immunotoxin reduces acetylcholine esterase (AChE)-positive fibers in S1 cortex by >90% by 3 wk after injection. Sham-depleted animals in which either saporin alone or saporin unconjugated to 192 IgG is injected into the cortex produces no decrease in AChE-positive fibers in cortex. Sham-depleted animals show the expected plasticity in barrel column neurons. In contrast, no plasticity develops in the ACh-depleted, 7-day whisker-paired animals. These results support the conclusion that the basal forebrain cholinergic projection to cortex is an important facilitator of synaptic plasticity in mature cortex.

Influence of the superior colliculus on the primate blink reflex

In this study we used microstimulation to investigate the influence of the superior colliculus on the trigeminal blink reflex. We report that stimulation in the intermediate to deep layers of the tectum produced inhibition of reflex blinks at a latency of approximately 26 ms. We considered the hypothesis that the blink inhibition was mediated via the omnipause neurons (OPNs) of the eye movement control system in the brainstem. Our results show that the least effective sites for suppression were in the rostral colliculus. This is inconsistent with the prediction that OPNs should be maximally recruited from the rostral tectum near the "fixation zone." From these points and other considerations, we conclude that the reflex blink suppression from the superior colliculus is not directly mediated by the OPNs or the saccadic eye movement circuits.

Analysis of the step response of the saccadic feedback: system behavior

We used prolonged stimulation of the monkey superior colliculus to elicit staircase eye movements. By changing the parameters of the stimulating current we were able to obtain movements with different dynamics. An increase in the current frequency resulted in the shortening of the intersaccadic interval and a decrease of the amplitudes in the staircase. In cases of high stimulation, after an initial saccade of fixed metrics, the eyes moved in an apparently smooth fashion. The movement was conjugate and in the same direction as the first saccade. By analyzing the velocity trace we found that the movement consisted of a chain of small saccades, each of which started before the previous one ended. We conducted a quantitative analysis of the staircase movements including the cases of apparently smooth movement of the eyes. We conclude that all of the movements elicited by prolonged SC stimulation were generated by the saccadic feedback circuitry. The dynamic profiles of the elicited movements changed continuously with the stimulating current parameters. On one end of the continuum we observed the classically, described staircase movements with individual movements separated in time. On the other end of the continuum we saw the apparent smooth movement as the limit case produced by high stimulation of the SC.

Lack of mutation in tumour-suppressor gene p53 in gestational trophoblastic tumours

The objectives of this study were to better our understanding of the carcinogenesis of gestational trophoblastic tumours and to investigate the possible presence of mutational alteration of the p53 tumour-suppressor gene in these tumours. Amplification-based direct DNA sequencing was performed on 14 hydatidiform moles, six invasive moles, eight choriocarcinomas and ten normal early placental tissues. No mutation in exons 5-8 was detected in any of these 38 tissue specimens. These results suggest that a mutation in p53 tumour suppressor either does not exist or is a very rare event in gestational trophoblastic tumours. The gestational trophoblastic tumours probably involve a tumour-suppressor gene other than p53 gene or may follow a completely different pathway to their malignant phenotype.

Human papillomavirus type 18 DNA in gestational trophoblastic tissues and choriocarcinomas

The objectives of our study were to better understand carcinogenesis of gestational trophoblastic tumors and to investigate the possible presence of human papillomavirus types 16 and 18 DNA sequences in these tumors. Amplification-based DNA methodology was used on 11 hydatidiform moles, 5 invasive moles, 8 choriocarcinomas and 9 normal early placental tissues. Human papillomavirus type 16 DNA was not found in any of these tissues. Although human papillomavirus type 18 DNA was also not found in the 9 normal placentas and 5 invasive moles, it was present in 2 of the 11 (18%) hydatidiform moles and in 4 of the 8 (50%) choriocarcinomas.

Receiver operating characteristic (ROC) analysis of neurons in the cat's lateral geniculate nucleus during tonic and burst response mode

Relay cells of the lateral geniculate nucleus respond to visual stimuli in one of two modes: burst and tonic. The burst mode depends on the activation of a voltage-dependent, Ca2+ conductance underlying the low threshold spike. This conductance is inactivated at depolarized membrane potentials, but when activated from hyperpolarized levels, it leads to a large, triangular, nearly all-or-none depolarization. Typically, riding its crest is a high-frequency barrage of action potentials. Low threshold spikes thus provide a nonlinear amplification allowing hyperpolarized relay neurons to respond to depolarizing inputs, including retinal EPSPs. In contrast, the tonic mode is characterized by a steady stream of unitary action potentials that more linearly reflects the visual stimulus. In this study, we tested possible differences in detection between response modes of 103 geniculate neurons by constructing receiver operating characteristic (ROC) curves for responses to visual stimuli (drifting sine-wave gratings and flashing spots). Detectability was determined from the ROC curves by computing the area under each curve, known as the ROC area. Most cells switched between modes during recording, evidently due to small shifts in membrane potential that affected the activation state of the low threshold spike. We found that the more often a cell responded in burst mode, the larger its ROC area. This was true for responses to optimal and nonoptimal visual stimuli, the latter including nonoptimal spatial frequencies and low stimulus contrasts. The larger ROC areas associated with burst mode were due to a reduced spontaneous activity and roughly equivalent level of visually evoked response when compared to tonic mode. We performed a within-cell analysis on a subset of 22 cells that switched modes during recording. Every cell, whether tested with a low contrast or high contrast visual stimulus exhibited a larger ROC area during its burst response mode than during its tonic mode. We conclude that burst responses better support signal detection than do tonic responses. Thus, burst responses, while less linear and perhaps less useful in providing a detailed analysis of visual stimuli, improve target detection. The tonic mode, with its more linear response, seems better suited for signal analysis rather than signal detection.

Latency variability of responses to visual stimuli in cells of the cat's lateral geniculate nucleus

We constructed average histograms from responses evoked by flashing stimuli and noted previously described variations in the shape of the response profile, particularly with respect to sharpness of the peak. To express this variable, we measured the half-rise latency, which is the latency from stimulus onset required to reach half the maximum response. A short half-rise latency, which is characteristic of nonlagged cells, is associated with a brisk response and sharp peak; a long half-rise latency, characteristic of lagged cells, is associated with a sluggish response and broad peak. Nonlagged cells were readily seen; we attempted to identify cells with long latencies as lagged, but we were unable to do so unambiguously due to failure to observe lagged properties other than latency. We thus refer to these latter cells as having "lagged-like" responses to indicate that we are not certain whether these are indeed lagged cells. In addition to the histograms, we analyzed the individual response trials that were summed to create each histogram, and we used spike density analysis to estimate the initial response latency to the flashing spot for each trial. We found that lagged-like responses were associated with more variability in initial response latency than were nonlagged responses. We then employed an alignment procedure to eliminate latency variation from individual trials; that is, responses during individual trials were shifted in time as needed so that each had a latency equal to the average latency of all trials. We used these "aligned" trials to create a second, "aligned" response histogram for each cell. The alignment procedure had little effect on nonlagged responses, because these were already well aligned due to consistent response latencies amongst trials. For lagged-like responses, however, the alignment made a dramatic difference. The aligned histograms looked very much like those for nonlagged responses: the responses appeared brisk, with a sharply rising peak that was fairly high in amplitude. We thus conclude that the slow build up to a relatively low peak of firing of the lagged-like response histogram is not an accurate reflection of responses on single trials. Instead, the sluggishness of lagged-like responses inferred from average response histograms results from temporal smearing due to latency variability amongst trials. We thus conclude that there is relatively little difference in briskness between nonlagged and lagged-like responses to single stimuli.

Cellular bases for the control of retinogeniculate signal transmission

The dorsal lateral geniculate nucleus (LGN) is the major thalamic relay for retinal signals en route to cortex. However, LGN cells operate as more than just a simple relay of their retinal inputs. Rather, they function as a variable gate, determining what, when, and how much retinal information gets passed to visual cortex. Two factors that are key to this control are the innervation patterns and electrophysiological membrane properties of geniculate cells. This paper discusses three active membrane properties and the manner in which they modulate the transfer of retinal signals to cortex. They are the low threshold calcium (Ca2+) conductance, a transient potassium (K+) conductance, and NMDA receptor-mediated excitatory postsynaptic potentials (EPSPs). The low-threshold Ca2+ conductance transforms a geniculate cell from a state of single spike activity to one of bursting discharge, the potassium current leads to a delay in membrane depolarization to reach spike threshold, and NMDA receptor activity modulates EPSP amplitude and duration near spike threshold. Additionally, we consider how nonretinal inputs, such as the ascending cholinergic pathway from the brainstem parabrachial region and the descending pathway from layer VI of visual cortex, influence the expression of these membrane properties through their control of membrane potential.

[The effects of the estradiol control delivery patch in the treatment of 176 cases of ovarian failure]

The effects of the estradiol control delivery patch made in China on the main manifestation in the 176 cases of ovarian failure patient were evaluated with the improvement of their symptoms, the changes of serum levels of LH, FSH, E2, the vaginal exfoliated cytologic maturation index (MI) and the histological alteration of endometrium. The results indicated that the six main symptoms including hectic fever, sweating, vaginal dry and hard-going, dizziness, emotioned lability and insomnia were improved significantly and progressively with prolongation of the treatment. The effective rates were 97.9%, 97.5%, 93.7%, 77.0%, 76.2%, 75.0% respectively form hectic fever to insomnia. The inhibitory effects on serum LH, FSH levels occurred on the 10th day of the treatment. The MI increased within whole course and the serum estradiol level elevated slightly and stably. There were no significant endometrial proliferation caused by the patch.

The brain-stem parabrachial region controls mode of response to visual stimulation of neurons in the cat's lateral geniculate nucleus

We recorded the responses of neurons from the cat's lateral geniculate nucleus to drifting sine-wave grating stimuli both before and during electrical stimulation of the parabrachial region of the midbrain. The parabrachial region provides a mostly cholinergic input to the lateral geniculate nucleus, and our goal was to study its effect on responses of geniculate cells to visual stimulation. Geniculate neurons respond to visual stimuli in one of two modes. At relatively hyperpolarized membrane potentials, low threshold (LT) Ca2+ spikes are activated, leading to high-frequency burst discharges (burst mode). At more depolarized levels, the low threshold Ca2+ spike is inactivated, permitting a more tonic response (relay or tonic mode). During our intracellular recordings of geniculate cells, we found that, at initially hyperpolarized membrane potentials, LT spiking in response to visual stimulation was pronounced, but that parabrachial activation abolished this LT spiking and associated burst discharges. Coupled with the elimination of LT spiking, parabrachial activation also led to a progressive increase in tonic responsiveness. Parabrachial activation thus effectively switched the responses to visual stimulation of geniculate neurons from the burst to relay mode. Accompanying this switch was a gradual depolarization of resting membrane potential by about 5-10 mV and a reduction in the hyperpolarization that normally occurs in response to the inhibitory phase of the visual stimulus. Presumably, the membrane depolarization was sufficient to inactivate the LT spikes. We were able to extend and confirm our intracellular observations on the effects of parabrachial activation to a sample of cells recorded extracellularly. This was made possible by adopting empirically determined criteria to distinguish LT bursts from tonic responses solely on the basis of the temporal pattern of action potentials. During parabrachial activation, every cell responded only in the relay mode, an effect that corresponds to our intracellular observations. We quantified the effects of parabrachial activation on various response measures. The fundamental Fourier response amplitude (F1) was calculated separately for the total response, the tonic response component, and the LT burst component. Parabrachial activation resulted in an increased F1 amplitude for the total response. This increase was due to an increase in the tonic response component. For a subset of cells showing epochs of LT bursting, parabrachial activation concurrently reduced LT bursting and increased the amplitude of the tonic response. Parabrachial activation, by eliminating LT bursting, also caused cells to respond with more linearity.(ABSTRACT TRUNCATED AT 400 WORDS)

[Determination of tumor necrosis factor from peripheral blood cells in patients with ovarian cancer]

The production of tumor necrosis factor (TNF) induced by LPS in the peripheral blood mononuclear cells from the patients with malignant and benign ovarian tumors were determined. Decreased production of TNF were observed in the patients with malignant ovarian tumor. In the advanced cases, TNF were lower than that in the early ones, which may indicate the progression of the tumors. These findings suggested that the TNF may be a useful indicator to diagnose the malignant tumors and prognosticate the tumors' developing.

Thalamic afferents of the rat barrel cortex: a light- and electron-microscopic study using Phaseolus vulgaris leucoagglutinin as an anterograde tracer

Anterograde tracers, Phaseolus vulgaris leucoagglutinin (PHA-L) and horseradish peroxidase (HRP), were used to study the thalamocortical afferents of the posteromedial barrel subfield (PMBSF) in rat primary somatosensory cortex (SI) at both light- and electron-microscopic levels. The PMBSF, also known as the barrel cortex, can be subdivided into barrel and interbarrel areas on the basis of cytoarchitectonic characteristics. Restricted injections confined to either the ventroposterior medial (VPM) or the rostral part of the posterior (Pom) nucleus allowed us to study and compare their projection patterns to the barrel cortex. We found that the interbarrel area receives inputs exclusively from the Pom, whereas the barrel area receives inputs from both the Pom and VPM. The laminar distributions of these two projections are largely segregated. After an injection of PHA-L or HRP into the VPM, labeled bouton-like swellings are found in layer VI and in layers IV through I of the barrel area, with the highest concentration in layer IV. On the other hand, after an injection of PHA-L or HRP into the Pom, labeled bouton-like swellings are distributed from upper layer V to layer I of the interbarrel area, as well as in layers V and I of the barrel area. Ultrastructural analysis showed that labeled bouton-like swellings of the VPM and the Pom pathways make synaptic contacts onto cortical neurons, and that these contacts are asymmetrical. Therefore, the VPM and the Pom projections are complementary to each other in the barrel cortex, and together they provide thalamic inputs to most layers of both the barrel and interbarrel areas. The differential patterns of terminations of the VPM and the Pom projections in the barrel cortex suggest that they may be involved in different types of cortical processing. Furthermore, our present findings may provide the anatomical basis for two parallel thalamocortical pathways, which previous physiological studies have indicated are each concerned with particular submodalities of somatic information.

Immunoreactivity for GAD and three peptides in somatosensory cortex and thalamus of the raccoon

Immunocytochemical methods were used to determine the distributions of glutamic acid decarboxylase (GAD), vasoactive intestinal polypeptide (VIP), cholecystokinin (CCK), and somatostatin (SOM) in the primary somatosensory cortex and somatosensory thalamus of adult raccoons. The cortex showed extensive immunoreactivity for GAD, revealing a large population of GABAergic neurons. GAD-labeled cells were numerous in all cortical layers, but were most concentrated in laminae II-IV. The cells were nonpyramidal and of varying morphology, typically with somata of small or medium size. GAD-immunoreactive puncta, presumably synaptic terminals, were widespread and often appeared to end on both GAD-negative and GAD-positive neurons. Immunoreactivity for the peptides was much less extensive than that for GAD, with the number of labeled neurons for VIP > CCK > SOM. Peptidergic cells were preferentially located in the upper and middle cortical layers, especially laminae II and III. The cells were nonpyramidal, often bitufted or bipolar in morphology, and small to medium in size. Their processes formed diffuse plexuses of fibers with terminal-like varicosities that occasionally surrounded nonpeptidergic neurons. The thalamus showed a clearly differentiated pattern of immunoreactivity for GAD, but little or no labeling for the three peptides. Nuclei adjoining the ventral posterior lateral (VPL)/ventral posterior medial (VPM) complex--including the reticular nucleus--contained many GAD-positive neurons and fibers. In contrast, the VPL and VPM nuclei displayed considerably less GAD immunoreactivity, somewhat surprising given the raccoon's highly developed somatosensory system. However, the ventral posterior inferior (VPI) nucleus revealed rather dense GAD labeling, perhaps related to a specialized role in sensory information processing. Thus, the primary somatosensory cortex of the raccoon showed patterns of immunoreactivity for GAD and peptides that were similar to those of other species; the somatosensory thalamus revealed a distinctive profile of GAD immunoreactivity, with labeling that was light to moderate in the VPL/VPM complex and relatively extensive in VPL.

Effects of membrane voltage on receptive field properties of lateral geniculate neurons in the cat: contributions of the low-threshold Ca2+ conductance

1. Thalamic relay cells, including those of the lateral geniculate nucleus, display a low-threshold spike (LT spike), which is a large depolarization due to an increased Ca2+ conductance. Typically riding the crest of each LT spike is a burst of from two to seven action potentials, which we refer to as the LT burst. The LT spike is voltage dependent, because if the cell's resting membrane potential is more depolarized than roughly -60 mV, the LT spike is inactivated, but if more hyperpolarized, the spike is deinactivated and can be activated by a depolarization, such as from an afferent excitatory postsynaptic potential (EPSP). Thalamic relay cells thus display two response modes: a relay or tonic mode, when the cell is depolarized and LT spikes are inactivated, leading to tonic firing of action potentials; and a burst mode, when the cell is hyperpolarized and tends to respond with LT spikes and their associated bursts of action potentials. 2. We were interested in the contribution of the LT spike on the transmission of visually evoked signals through geniculate relay cells to visual cortex. We recorded intracellularly from geniculate cells in an anesthetized, paralyzed, in vivo cat preparation to study the effects of membrane voltage, and thus the presence or absence of LT spikes, on responses to drifting sine-wave gratings. We monitored the visually evoked responses of 14 geniculate neurons (6 X, 7 Y, and 1 unclassified) at different membrane potentials at which LT spikes were inactivated or deinactivated. 3. Changing membrane voltage during visual stimulation switched the response mode of every cell between the relay and burst modes. In the burst mode, LT spikes occurred in phase with the visual stimulus and not at rhythmic intervals uncorrelated to visual stimuli. To any given stimulus cycle, the cell responded usually with an LT burst or a tonic response, and rarely was more than one LT burst evoked by a stimulus cycle. Occasionally a single cycle evoked both an LT burst and tonic response, but always the LT burst occurred first. 4. The spatial tuning characteristics of the cells did not differ dramatically as a function of membrane potential, because the tuning of the LT bursts was quite similar to that of the tonic response component. Although we did not obtain complete temporal tuning properties, we did note that hyperpolarized cells responded reliably with LT bursts at several temporal frequencies. 5. A consistent difference was seen between the LT burst and tonic response components in terms of response linearity.(ABSTRACT TRUNCATED AT 400 WORDS)

Relative contributions of burst and tonic responses to the receptive field properties of lateral geniculate neurons in the cat

1. In an anesthetized, paralyzed in vivo preparation, we recorded extracellular responses of 61 geniculate neurons (2 W, 25 X, 33 Y, and 1 mixed) to drifting sine-wave gratings of various spatial frequency, temporal frequency, and contrast. Our goal was to study the differential contributions to these visual responses of bursting caused by voltage dependent, low-threshold (LT) Ca2+ spikes and of purely tonic responses unrelated to LT spikes. Cells responding with LT spikes are said to be in the burst firing mode and those responding in a purely tonic fashion to be in the relay or tonic firing mode. We separated the total visual response into LT burst and tonic components by use of the empirical criteria set forth in our intracellular study described in the previous paper (Lu et al. 1992). A response component was considered to be an LT burst if its action potentials displayed interspike intervals < or = 4 ms and if the first spike in the burst episode occurred after a silent period of > or = 100 ms (or > or = 50 ms when the neuron responds to visual stimuli at temporal rates > or = 8 Hz). All other activity is considered to be part of the tonic response. 2. In addition to LT bursts, we recognized another type of burst response, the high-threshold (HT) burst. These also have clusters of action potentials with interspike intervals < or = 4 ms. However, HT bursts, unlike LT bursts, lack a preburst silent period. HT bursts are part of the tonic response component and merely reflect the gradual decrease in interspike intervals that occurs as the cell becomes more depolarized and thus more responsive. Thus interspike interval is a necessary but insufficient criterion to identify LT bursts. 3. Visually evoked LT bursts were recorded among W, X, and Y cells. When evoked, LT bursts occurred in phase with drifting sine-wave grating stimuli at a rate never exceeding one per stimulus cycle. In response to individual cycles of the visual stimulus, LT bursts could comprise the total response, a tonic component could comprise the total response, or an LT burst and tonic component could be mixed. When a stimulus evoked a mixture of LT bursts and tonic response components, LT bursts were always the first response. 4. Of the 61 cells tested with grating stimuli, 47 exhibited LT bursts and 14 did not. Those that did exhibited varying amounts of burstiness.(ABSTRACT TRUNCATED AT 400 WORDS)

[Effects of combination chemotherapy of ovarian cancer in vitro]

To investigate the effects of combination chemotherapy on ovarian cancer in vitro, we observed the sensitivity of tumors to different drugs by incorporation assay of tritium thymidine (3H-TdR). The results revealed that the drugs and their sensitive degrees varied from tumor to tumor. Whether the combination of the drugs is synergism or sometimes only enhances toxicity depends on the difference of individuals. We suggest that in vitro anti-cancer drug sensitivity test could be applied in selection or determination of chemotherapy protocol.

[Effect of levonorgestrel intrauterine device on human endometrial estrogen and progesterone receptors]

Estrogen and progesterone cytoplasmic receptors (ER, PgR) were determined by radiochemical DCC technique in the endometria of 16 normal women at before child bearing age and 6 to 9 months after LNG IUD insertion. The study showed that both ER and PgR were reduced significantly after LNG IUD insertion (P less than 0.01). The decrease of ER and PgR might play an important role in gland reduction and endometrial atrophy. It may be one mechanism of the contraceptive effect and the cause of anemia or spotting between menstruation during the course of LNG IUD insertion.

Intracellular and extracellular in vivo recording of different response modes for relay cells of the cat's lateral geniculate nucleus

Prior studies of thalamic neurons have demonstrated that they exhibit at least two response modes: a relay mode and a burst mode. During the relay mode, sensory information is faithfully relayed to cortex; during the burst mode, which is caused by a voltage-dependent Ca2+ conductance, this relay of sensory information is interrupted. We began in vivo studies of these response modes in neurons from the lateral geniculate nucleus of anesthetized, paralyzed cats. Each of the 9 X and 10 Y cells we recorded intracellularly displayed voltage-dependent, low threshold spikes that were presumably the Ca2+ spikes described from in vitro recording. These spikes were triangular in waveform and typically had 2-7 fast action potentials (interspike intervals of 1.2-4 ms) riding its crest. Furthermore, the cell's membrane had to be hyperpolarized to de-inactivate the low threshold spike before a depolarization could then activate it. We could activate these low threshold spikes in Y cells from EPSPs, whether spontaneous or evoked from activation of the optic chiasm. However, in only one of the X cells could we activate low threshold spikes from chiasm shock; in the remainder, we could activate low threshold spikes only via depolarizing current pulses, possibly because the EPSPs of these X cells were too small to activate these spikes. We also used extracellular recording to study spontaneous activity and responses to chiasm shock from 114 geniculate neurons and, as a control, 57 optic tract axons. We concentrated on periods of bursty responsiveness signifying the burst mode. We define a burst as 2-7 action potentials with interspike intervals less than or equal to 4 ms, and the bursts are separated by greater than 100 ms; from our intracellular recording, we know that such bursts signify low threshold spikes. We found that, during extracellular recording, 20 of the 39 X cells and each of the 75 Y cells displayed evidence of the burst response mode, although burst periods were rare in X cells. Electrical activation of the optic chiasm greatly enhanced the burstiness of Y cells for periods of 500 ms or more. We also electrically stimulated the parabrachial region of the midbrain, which provides a mostly cholinergic innervation to the lateral geniculate nucleus. Although parabrachial activation by itself had no detectable effect on Y cell response modes, prior parabrachial activation prevented the enhanced burstiness caused by chiasm stimulation. This parabrachial effect lasted for roughly 500 ms after stimulation.(ABSTRACT TRUNCATED AT 400 WORDS)

[In vitro drug-resistance decrease of ovarian cancer cells]

A chemosensitivity test for ovarian cancer using tritiated thymidine incorporation assay was carried out. A dose-response relationship was observed for cis-platinum and an 5-fold increase of concentration converted the drug resistant tumor into a drug-sensitive one. Verapamil was found to enhance the cytotoxic effect of vincristine against ovarian cancer cells. It is suggested that combination of vincristine with verapamil may be helpful in treating some vincristine-resistant cases.

N-methyl-D-aspartate receptors contribute to excitatory postsynaptic potentials of cat lateral geniculate neurons recorded in thalamic slices

Neurons of the cat's dorsal lateral geniculate nucleus were recorded intracellularly to study the contribution of N-methyl-D-aspartate (NMDA) receptors to excitatory postsynaptic potentials (EPSPs) and low-threshold calcium spikes. EPSPs were evoked by stimulation of retinogeniculate axons in the optic tract and/or corticogeniculate axons in the optic radiations; EPSPs from both sources were similar. These EPSPs had one or two components, and the second component had several characteristics of NMDA receptor-mediated events. For example, EPSP amplitude decreased when neurons were hyperpolarized and increased when stimulus frequency was increased; these EPSPs could also be blocked reversibly by application of the selective NMDA receptor antagonist DL-2-amino-5-phosphonovaleric acid (APV). We also studied the influence of NMDA receptors on low-threshold calcium spikes, which are large, voltage- and calcium-dependent depolarizations that are often accompanied by high-frequency action potential discharge. APV blocked synaptically activated low-threshold calcium spikes, but APV had no effect on low-threshold calcium spikes that were elicited by current injection. Therefore, APV does not appear to have a direct effect on the T-type calcium channel that is involved in generation of low-threshold calcium spikes. The voltage and frequency dependence of the NMDA receptor-mediated component of the EPSPs, as well as its ability to trigger low-threshold calcium spikes, provide for complex signal processing in the lateral geniculate nucleus.

Immunoreactivity to calcitonin gene-related peptide in the superior olivary complex and cochlea of cat and rat

In both cat and rat, the cells of origin, axons, and terminals of the lateral olivocochlear system exhibit immunoreactivity to antisera to calcitonin gene-related peptide (CGRP). In the cat, immunoreactive neurons in the brainstem are located in the hilus of the lateral superior olivary nucleus and around its margins. In the rat, immunoreactive neurons are located within the lateral superior olivary nucleus proper. In both species, immunoreactivity in the cochlear duct is limited to the region beneath the inner hair cells. Immunoreactive axons in the cochlear nucleus could not be traced to their source but may arise as collaterals of the lateral olivocochlear system. No other components of the brainstem auditory system react to any extent with the antisera.

Glutamic acid decarboxylase and somatostatin immunoreactivities in rat visual cortex

Antibodies to glutamic acid decarboxylase (GAD) and somatostatin (SS) were used to determine the laminar distribution and morphology of GAD- and SS-immunoreactive neurons and terminals in rat visual cortex. The present study demonstrates that GAD-immunoreactive neurons constitute several morphologically distinct subclasses of neurons in rat visual cortex. These subclasses of neurons can be distinguished by differences in soma size, soma shape, dendritic branching patterns, axonal arborizations, and location in the neuropil. GAD-immunoreactive neurons are found throughout all layers of visual cortex. They have nonpyramidal morphology and constitute roughly 15% of the total neuronal population. The laminar pattern of GAD-immunoreactive puncta is uneven, with a prominent band of terminals in layer IV. Numerous large GAD-positive puncta surround the somata and proximal dendrites of pyramidal cells in layers II, III, and V. SS-immunoreactive neurons constitute a less numerous and more restricted population of nonpyramidal neurons. Their somata are located mainly in layers II, III, V, and VI. Very few, if any, SS-immunoreactive neurons are found in layers I and IV. SS-immunoreactive terminals are arranged along vertical and diagonal collateral branches that have a beaded appearance. Finally, many neurons in the supra- and infragranular layers and in the white matter are immunoreactive to both glutamic acid decarboxylase and somatostatin. This coexistence of immunoreactivity to both GAD and SS may characterize a broad subclass of cortical nonpyramidal neurons.

Glutamate decarboxylase immunoreactivity in the intermediate grey layer of the superior colliculus in the cat

Recent evidence suggests that gamma-aminobutyrate has a profound influence on the activity of premotor neurons in the intermediate grey layer of the superior colliculus. In the present study an antibody to glutamate decarboxylase, the synthesizing enzyme for gamma-aminobutyrate, was used to identify and characterize the structures in the intermediate grey layer of the cat that use gamma-aminobutyrate as a transmitter. The material was examined with both the light and electron microscope. Glutamate decarboxylase immunoreactivity was confined, for the most part, to axon terminals. Glutamate decarboxylase positive terminals almost completely cover the soma and proximal dendrites of the large neurons that are characteristic of this layer. Other glutamate decarboxylase positive terminals contact smaller, presumably more distal dendrites. By combining the glutamate decarboxylase immunocytochemistry with the retrograde transport of horseradish peroxidase in single animals, it was demonstrated that the cells of origin of the major descending efferent pathway from the intermediate grey layer, the predorsal bundle, are heavily contacted by glutamate decarboxylase immunoreactive terminals.

Glutamic acid decarboxylase immunoreactivity in layer IV of barrel cortex of rat and mouse

The morphology and distribution of neurons and terminals that are immunoreactive to glutamic acid decarboxylase (GAD) were investigated in barrel cortex of the rat and mouse. The morphology of the GAD-immunoreactive neurons located in layer IV of the barrel field resembles that of the large, smooth stellate neurons described previously in Golgi studies. Most of the somas of GAD-positive neurons are located along the sides of the barrels. They constitute about 13 to 15% of the total neuronal population in layer IV. The spatial distribution of GAD-positive terminals in layer IV is similar to the distribution of GAD-positive somas. Very few GAD-positive neurons and terminals are found in the septal regions. This unique distribution of GAD immunoreactivity in the barrel cortex may serve as a model to study cortical inhibitory mechanisms.

Excitability of auditory neurons in the dorsal and ventral cochlear nuclei of DBA/2 and C57BL/6 mice

Extracellular response properties were studied in neurons of the dorsal and ventral divisions of the cochlear nucleus (DCN and VCN, respectively) of DBA/2 (DBA) and C57BL/6 (C57) mice. Mice of the former inbred strain show susceptibility to audiogenic seizures and have severe high frequency hearing loss when young; mice of the latter strain do not. Whereas afterdischarges had been readily observed in the inferior colliculus of DBA mice in a previous study, they were never observed in the cochlear nucleus. The incidence of nonmonotonic intensity functions, the slopes of intensity functions, and the incidence of inhibition in response areas indicated that inhibition was diminished in the DCN of DBA mice. However, in the VCN, these response properties did not differ between the two strains. There appeared to be an "amplification" of excitability (i.e., attenuation of inhibition) from VCN to DCN to inferior colliculus in DBA mice.

Abnormal tonotopic organization in the ventral cochlear nucleus of the hearing-impaired DBA/2 mouse

The representation of sound frequency by auditory neurons (tonotopic organization) was evaluated in the ventral cochlear nucleus (VCN) of DBA/2 mice, a strain with impaired sensitivity to the highest and lowest frequencies heard by normal mice. Tuning curves were obtained from multiple-unit activity (MUA) and compared with those of C57 mice, which do not have severe hearing loss. Tuning curves in the C57 VCN displayed the dorsoventral progression from high- to low-frequency sensitivity that is typical of mammals. By contrast, tuning curves of DBA mice varied little as a function of dorsoventral location, and most MUA thresholds were lowest for frequencies within a narrow range (about 12-16 kHz). Thus, normal tonotopic organization is absent in the DBA mouse's VCN. In addition, because of the consistently low thresholds for 12-16 kHz tones in DBA MUA, mean thresholds for these frequencies are lower than those of C57 MUA in the dorsal and ventral portions of the VCN.

Noise-induced hearing loss can alter neural coding and increase excitability in the central nervous system

Responses of auditory neurons in the inferior colliculi of mice were studied longitudinally before and shortly after each animal was exposed to intense noise. Noise exposure caused expected losses in auditory sensitivity, but in 31 percent of the neurons studied, unexpected alterations of temporal patterns of action potentials were observed: certain suprathreshold stimuli that had evoked only transient "onset" responses or inhibition of spontaneous discharges prior to noise exposure came to elicit sustained excitation after exposure. Thus, noise-induced hearing loss can be associated with increases in neural responsivity and alterations of normal neural coding processes.