Imaging the Spatiotemporal Dynamics of Cognitive Processes at High Temporal Resolution

This letter presents a noninvasive imaging technique that captures the exact timing and locations of cortical activity sequences that are specific to a cognitive process. These precise spatiotemporal sequences can be detected in the human brain as specific time-position pattern associated with a cognitive task. They are consistent with direct measurements of population activity recorded in nonhuman primates, thus suggesting that specific time-position patterns associated with a cognitive task can be identified. This imaging technique is based on estimating the amplitude of cortical current dipoles from MEG recordings. Although the spatial resolution of these estimations is poor (approximately 2 cm), the temporal resolution is high (milliseconds). We show that within these cortical current dipoles, time points of cortical activation can be identified as brief amplitude undulations and that sequences of these transients repeat with millisecond accuracy, hence making it possible to treat the timing of these transients as point processes. We illustrate the feasibility of finding spatiotemporal templates specific to the cognitive processes associated with following the rhythm of drumbeats that involve the activation at multiple cortical and cerebellar loci. These templates evolve at an accuracy of a few milliseconds. This approach can thus pave the way for new perspectives on the relationships between brain dynamics and cognition.

Revealing instances of coordination among multiple cortical areas

Cognitive functions must involve interactions between several (perhaps many) cortical regions. The instances of such interactions may not be tightly time locked to any external cue. Thus averaging over repeated trials of brain activity or its spectrograms may miss these instances. Here, coordinated activity among multiple cortical locations is revealed in ongoing activity with millisecond accuracy without the need for averaging over time or frequencies. This is based on reconstructions of the cortical current dipole amplitudes at multiple points from MEG recordings. In these current dipole traces, instances of brief activity undulations (BAUs) are automatically detected and used to reveal where and when cortical points interact. The article shows that these BAUs truly represent the reorganization of activity at the cortex and are strongly connected to behavior.

Cleaning MEG artifacts using external cues

Using EEG, ECoG, MEG, and microelectrodes to record brain activity is prone to multiple artifacts. The main power line (mains line), video equipment, mechanical vibrations and activities outside the brain are the most common sources of artifacts. MEG amplitudes are low, and even small artifacts distort recordings. In this study, we show how these artifacts can be efficiently removed by recording external cues during MEG recordings. These external cues are subsequently used to register the precise times or spectra of the artifacts. The results indicate that these procedures preserve both the spectra and the time domain wave-shapes of the neuromagnetic signal, while successfully reducing the contribution of the artifacts to the target signals without reducing the rank of the data.

Sensitivity of global network dynamics to local parameters versus motif structure in a cortexlike neuronal model

In the field of network dynamics it has been suggested that statistical information of motifs, small subnetworks, can help in understanding global activity of the entire network. We present a counterexample where the relation between the stable synchronized activity modes and network connectivity was studied using the Hodgkin-Huxley brain dynamics model. Simulations indicate that small motifs of three nodes exhibit different synchronization modes depending on their local parameters such as delays, synaptic strength, and external drives. Thus the activity of a complex network composed of interconnected motifs cannot be extracted from the activity mode of each individual motif and is governed by local parameters. Finally, we exemplify how local dynamics ultimately enriches the ability of a network to generate diverse modes with a given motif structure.

Minimally important difference in diffuse systemic sclerosis: results from the D-penicillamine study

OBJECTIVE

To estimate minimally important differences (MIDs) in scores for the modified Rodnan Skin Score (mRSS) and Health Assessment Questionnaire-Disability Index (HAQ-DI) in a clinical trial on diffuse systemic sclerosis (SSc).

PARTICIPANTS AND METHODS

134 people participated in a 2-year, double-blind, randomised clinical trial comparing efficacy of low-dose and high-dose D-penicillamine in diffuse SSc. At 6, 12, 18 and 24 months, the investigator was asked to rate the change in the patient's health since entering the study: markedly worsened, moderately worsened, slightly worsened, unchanged, slightly improved, moderately improved or markedly improved. Patients who were rated as slightly improved were defined as the minimally changed subgroup and compared with patients rated as moderately or markedly improved.

RESULTS

The MID estimates for the mRSS improvement ranged from 3.2 to 5.3 (0.40-0.66 effect size) and for the HAQ-DI from 0.10 to 0.14 (0.15-0.21 effect size). Patients who were rated to improve more than slightly were found to improve by 6.9-14.2 (0.86-1.77 effect size) on the mRSS and 0.21-0.55 (0.32-0.83 effect size) on the HAQ-DI score.

CONCLUSION

MID estimates are provided for improvement in the mRSS and HAQ-DI scores, which can help in interpreting clinical trials on patients with SSc and be used for sample size calculation for future clinical trials on diffuse SSc.

On embedding synfire chains in a balanced network

We investigate the formation of synfire waves in a balanced network of integrate-and-fire neurons. The synaptic connectivity of this network embodies synfire chains within a sparse random connectivity. This network can exhibit global oscillations but can also operate in an asynchronous activity mode. We analyze the correlations of two neurons in a pool as convenient indicators for the state of the network. We find, using different models, that these indicators depend on a scaling variable. Beyond a critical point, strong correlations and large network oscillations are obtained. We looked for the conditions under which a synfire wave could be propagated on top of an otherwise asynchronous state of the network. This condition was found to be highly restrictive, requiring a large number of neurons for its implementation in our network. The results are based on analytic derivations and simulations.

Trial to trial variability in either stimulus or action causes apparent correlation and synchrony in neuronal activity

In this report we show that the observed inter-neuronal correlation reflects a superposition of correlations associated with the intrinsic correlation between neurons, and correlations associated with variability in the stimuli presented to, or the actions performed by, the subject. We argue that the effects of either stimulus or action variability on the observed correlation, though generally ignored, can be substantial. Specifically, we demonstrate how observed correlations are effected by trial to trial variability in either stimulus or action. In addition, assuming that all relevant stimuli and actions are known, we outline a method for eliminating their effects on the observed correlation. It is also shown that tuning of correlations to a stimulus or an action might be a direct consequence of variability in that stimulus or action, even in the absence of any modulation of direct inter-neuronal interaction. The effects of stimulus and action variability should therefore be carefully considered when designing and interpreting experiments involving multi-neuronal recordings.

Women's pursuit of personal goals in daily life with fibromyalgia: a value-expectancy analysis

Eighty-nine women with fibromyalgia completed the Life Orientation Test, identified health and social goals, and answered questions from the Goal Systems Assessment Battery (P. Karoly & L. Ruehlman, 1995) about their valuation of, and self-efficiency in attaining, each goal. For 30 days, they responded to palm-top computer interviews about their pain and fatigue and rated their goal effort, goal progress, and pain- and fatigue-related goal barriers. Goal barriers increased and goal efforts and progress decreased on days with greater pain and fatigue; goals valued more highly were pursued more effortfully and successfully; more optimistic individuals were less likely to perceive goal barriers and, on days that were more fatiguing than usual, were less likely to reduce their effort and to retreat from progress in achieving their health goal; and more pessimistic individuals perceived greater goal barriers on days that were less painful than usual.

Women's pursuit of personal goals in daily life with fibromyalgia: a value-expectancy analysis

Eighty-nine women with fibromyalgia completed the Life Orientation Test, identified health and social goals, and answered questions from the Goal Systems Assessment Battery (P. Karoly & L. Ruehlman, 1995) about their valuation of, and self-efficiency in attaining, each goal. For 30 days, they responded to palm-top computer interviews about their pain and fatigue and rated their goal effort, goal progress, and pain- and fatigue-related goal barriers. Goal barriers increased and goal efforts and progress decreased on days with greater pain and fatigue; goals valued more highly were pursued more effortfully and successfully; more optimistic individuals were less likely to perceive goal barriers and, on days that were more fatiguing than usual, were less likely to reduce their effort and to retreat from progress in achieving their health goal; and more pessimistic individuals perceived greater goal barriers on days that were less painful than usual.

Effects of the American College of Rheumatology systemic sclerosis trial guidelines on the nature of systemic sclerosis patients entering a clinical trial

OBJECTIVES

To compare the systemic sclerosis (SSc) patients entered into the d-penicillamine trial with SSc patients entered into previous controlled SSc trials. It was hypothesized that the d-penicillamine trial patients, who conformed to the American College of Rheumatology (ACR) guidelines for clinical trials in SSc were different from patients entered into previous trials.

METHODS

Patients entering a double-blind, randomized trial of low- vs high-dose d-penicillamine were described carefully and completely. Their characteristics were then compared with previously published data on SSc and its treatment.

RESULTS

One hundred and thirty-four patients had early [mean duration 9.5 (s.d. 4.2) months], diffuse [skin score 21 (8)] disease. Organ involvement in the patients was as follows: pulmonary 54%, cardiac 20%, joints 38%, muscular 20%. Thirty-three per cent had mild proteinuria and 13% were hypertensive when first seen. Compared with patients in most previous studies, these SSc patients had earlier disease and uniformly had diffuse disease. They had less muscular involvement, less dyspnoea, less abnormal pulmonary function and less cardiac and less renal involvement than patients in earlier studies.

CONCLUSIONS

The use of the new ACR guidelines for SSc trials may change the nature of patient populations entering future studies.

Detecting precise firing sequences in experimental data

A precise firing sequence (PFS) is defined here as a sequence of three spikes with fixed delays (up to some time accuracy Delta), that repeat excessively. This paper provides guidelines for detecting PFSs, verifying their significance through surrogate spike trains, and identifying existing PFSs. The method is based on constructing a three-fold correlation among spikes, estimating the expected shape of the correlation by smoothing, and detecting points for which the correlations significantly protrude above the expected correlation. Validation is achieved by generating surrogate spike trains in which the time of each of the real spikes is randomly jittered within a small time window. The method is extensively tested through application to simulated spike trains, and the results are illustrated with recordings of single units in the frontal cortex of behaving monkeys. Pitfalls which may cause false detection of PFSs, or loss of existing PFSs, include searching for PFSs in which the same neuron participates more than once, and attempting to produce a surrogate with some fixed statistical property.

The Disability Index of the Health Assessment Questionnaire is a predictor and correlate of outcome in the high-dose versus low-dose penicillamine in systemic sclerosis trial

OBJECTIVE

To explore the clinical implications of a score of > or =1.0 on the Disability Index of the Health Assessment Questionnaire (HAQ DI) at the first patient visit, and to examine the implications of improvement in HAQ DI score over 2 years in a cohort of systemic sclerosis (SSc) patients with diffuse cutaneous scleroderma.

METHODS

SSc skin and visceral involvement was assessed in 134 SSc patients with diffuse scleroderma (mean +/- SD disease duration of 10 +/- 4 months) when they entered a multicenter drug trial and again 2 years later. Mortality and the occurrence of scleroderma renal crisis were assessed for a mean +/- SD of 4.0 +/- 1.1 years. Logistic and linear regression analyses were used to examine the relationship of the baseline HAQ DI score to morbidity, mortality, and visceral involvement, as well as the relationship of changes in the HAQ DI score to changes in physical examination, laboratory, and functional variables over 2 years.

RESULTS

A baseline HAQ DI score of > or =1.0 was predictive of mortality (odds ratio 3.22, 95% confidence interval 1.097-9.468) over 4 years. Multivariate linear regression demonstrated that a model which included the erythrocyte sedimentation rate at baseline (P = 0.005) and changes at 2 years in the swollen joint count (P = 0.002), total skin score (P = 0.005), and white blood cell count (P = 0.005) best explained the change in HAQ DI score over 2 years (R2 = 0.528). The HAQ DI score and total skin score at baseline were highly correlated (correlation coefficient 0.368), as were changes in the HAQ DI score and the total skin score over 2 years (correlation coefficient 0.492). Although the HAQ DI score was heavily influenced by hand dysfunction at baseline and at 2 years, improvement (reduction) in the HAQ DI score over 2 years was related to factors other than hand dysfunction.

CONCLUSION

A baseline HAQ DI score of > or =1.0 predicted mortality over 4 years. Improvement in the HAQ DI score in these patients with diffuse scleroderma was associated with improvement in skin thickening, hand function, oral aperture, lung function, signs of arthritis, serum creatinine level, and the investigator's global assessment of improvement. The HAQ DI is a self-administered questionnaire that SSc patients can complete easily and rapidly and that gives the practicing physician important information about prognosis, patient status, and changes in disease course over time.

Activity of pallidal and striatal tonically active neurons is correlated in mptp-treated monkeys but not in normal monkeys

The goal of this study is to assess the function of tonically active neurons (TANs) of the striatum and their malfunction in the parkinsonian state. We recorded multiple spike trains of striatal TANs and pallidal neurons, which are the main target of striatal projections. Recordings were performed in two vervet monkeys before and after the induction of tremulous parkinsonism by systemic injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine hydrochloride (MPTP). We then calculated cross-correlograms between TANs and pallidal neurons to evaluate the interactions between them. In the normal monkeys, only 1.3% (2/152) of the cross-correlograms displayed significant peaks, and 8.6% (13/152) displayed significant oscillations. After MPTP treatment, 42.8% (83/194) of the cross-correlograms displayed significant peaks or troughs, or both, and 58.8% (114/194) displayed significant 3-19 Hz periodic oscillations. The frequency content of the coherent oscillations matched the frequency content of the activity of individual TANs, but was only weakly related to that of individual pallidal cells. These results confirm the notion that in the normal state neurons in the basal ganglia tend to fire independently, whereas in the parkinsonian state they exhibit synchronized oscillatory activity. The low level of correlated activity in the normal state demonstrates that TANs have only a slight effect on pallidal activity during execution of familiar behavior. The high level of oscillatory correlated activity in the parkinsonian state further suggests that coherent oscillations of the whole basal ganglia circuitry underlie the clinical features of Parkinson's disease.

Skin thickness score as a predictor and correlate of outcome in systemic sclerosis: high-dose versus low-dose penicillamine trial

OBJECTIVE

To study the clinical implications of a skin thickness score > or =20 at first visit and of softening of sclerodermatous skin in a cohort of systemic sclerosis (SSc) patients with diffuse cutaneous scleroderma.

METHODS

Skin and visceral involvement were assessed in 134 SSc patients with diffuse scleroderma (mean +/- SD duration of SSc 10 +/- 4 months) as they entered a multicenter drug trial and again at 2 years of followup. Advent of mortality and scleroderma renal crisis (SRC) were assessed during a followup of 4.0 +/- 1.1 years (mean +/- SD). Logistic and linear regression were used to examine the relationship of baseline skin score to morbidity, mortality, and visceral involvement and the relationship of changes in skin score to changes in physical examination, laboratory, and functional variables over 2 years.

RESULTS

A baseline skin score > or =20 was associated with heart involvement at baseline (odds ratio [OR] 3.10, 95% confidence interval [95% CI] 1.25-7.70) and was predictive of mortality (OR 3.59, 95% CI 1.23-10.55) and SRC (OR 10.00, 95% CI 2.21-45.91) over 4 years. Multivariate linear regression demonstrated that a model with skin score at baseline (P = 0.0078) and changes in large joint contractures (P = 0.0072), tender joint counts (P = 0.0119), handspread (P = 0.0242), and Health Assessment Questionnaire disability index (HAQ-DI) (P = 0.0244) explained the change in skin score over 2 years (R2 = 0.567). Multivariate logistic regression demonstrated that the investigator's global assessment of improvement was best explained by a model with skin score and HAQ-DI (R2 = 0.455).

CONCLUSION

A baseline skin score > or =20 was associated with heart involvement at baseline and predicted mortality and SRC over the subsequent 4 years. Improvement in skin score in these patients with diffuse cutaneous scleroderma was associated with improvement in hand function, inflammatory indices, joint contractures, arthritis signs, overall functional ability, and the examining investigator's global assessment of improvement.

Correlates of the disability index of the health assessment questionnaire: a measure of functional impairment in systemic sclerosis

OBJECTIVE

To evaluate functional impairment in systemic sclerosis (SSc) patients with diffuse cutaneous scleroderma at the time of entry into a trial of a therapeutic intervention (D-penicillamine).

METHODS

The 20-item Disability Index of the Health Assessment Questionnaire (HAQ-DI) was administered to 134 patients as they entered a multicenter trial of high-dose versus low-dose D-penicillamine. All patients had diffuse SSc of < 18 months' duration. SSc patients who had severe organ system involvement and recent renal crisis and who were receiving prednisone > 10 mg/day were excluded from entry. Logistic regression modeling was used to examine the relationship of HAQ-DI scores to SSc skin and organ system involvement. Odds ratios (OR) and 95% confidence intervals (95% CI) were used to estimate effects.

RESULTS

The mean (+/-SD) HAQ-DI score at entry was 1.04 +/- 0.67. Fifty-three percent of patients had HAQ-DI scores > or = 1.0 (signifying moderate-to-severe functional impairment). Multivariate logistic regression demonstrated that impaired fist closure > or = 23 mm (OR 4.24, 95% CI 1.68-10.70), reduced handspread < or = 175 mm (OR 4.5, 95% CI 1.80-11.24), joint tenderness count > or = 1.0 (OR 2.93, 95% CI 1.16-7.40), age > or = 43 years (OR 2.44, 95% CI 1.01-5.95), platelet count > or = 330,000/mm3 (OR 2.30, 95% CI 0.96-5.57), and female sex (OR 2.43, 95% CI 0.77-7.73) were the most important correlates of HAQ-DI scores > or = 1.0.

CONCLUSION

Increased HAQ-DI scores at baseline were correlated with reduced fist closure, reduced hand-spread, elevated platelet count, presence of tender joints, older age, and female sex. The most important contributor to functional impairment was hand dysfunction. Even within the first 18 months after SSc onset, moderate-severe functional impairment (HAQ-DI scores > or = 1.0) was frequent (53%) in this group of diffuse SSc patients. In early diffuse SSc, the self-administered HAQ-DI is therefore a valuable assessment of function that correlates with objective physical and laboratory measures of SSc disease involvement. Abnormal HAQ-DI scores may support patient claims of functional impairment, help to focus physician attention on implementing measures to reduce functional impairment, and be useful in reflecting the disease course over time.

Sensory-motor transformation and motor planning in the primate frontal cortex

To examine the role of the frontal cortex in sensory-motor processing, we trained a Rhesus monkey to perform a behavioral task with alternations between localization (LOC) and non-localization (NL) paradigms. In the LOC block, the monkey had to remember the modality and location of two sequential cues. Two different GO signals instructed the monkey to touch the memorized location of either auditory or visual spatial cues (GO-AUD or GO-VIS, respectively). In the NL paradigm the monkey received the same stimuli, but was instructed to touch a fixed target, disregarding the location and modality of the spatial and GO signals. Reaction time was significantly longer after GO-AUD signals in the LOC mode compared to the reaction time following GO-VIS signals, or in the NL mode. We examined 961 neurons in the frontal cortex and 427 parietal neurons. A group of frontal task-related neurons (72/430; 16.7%) showed evoked activity both after the visual and the GO-AUD stimuli in the LOC mode. The units did not respond to the GO-VIS signal that instructed the monkey to move to the same location, or to the identical stimuli in the NL mode. No such neurons were found in the sampled areas of the parietal cortex. Our findings suggest that the monkey initially planned a default response towards the location of the visual stimulus and immediately updated his motor plans when instructed to touch the memorized location of the auditory stimulus. We suggest that frontal activity may also be related to such modifications of sensory-motor associations.

High-dose versus low-dose D-penicillamine in early diffuse systemic sclerosis: analysis of a two-year, double-blind, randomized, controlled clinical trial

OBJECTIVE

To test the hypothesis that systemic sclerosis (SSc) patients taking high-dose D-penicillamine (D-Pen) would have greater softening of skin, lower frequency of renal crisis, and better survival than patients taking low-dose D-Pen.

METHODS

Seventeen centers enrolled 134 SSc patients with early (< or =18 months) diffuse cutaneous scleroderma into a 2-year, double-blind, randomized comparison of high-dose D-Pen (750-1,000 mg/day) versus low-dose D-Pen (125 mg every other day). All 134 patients were followed up for a mean+/-SD of 4.0+/-1.1 years to assess the frequencies of new-onset scleroderma renal crisis (SRC) and mortality.

RESULTS

Sixty-eight patients completed 24 months of drug treatment. The course of the modified Rodnan skin thickness score in the 32 high-dose and the 36 low-dose D-Pen completers was not different at 24 months: the skin score dropped 4.8+/-10.3 (mean+/-SD) units in the high-dose group and 6.9+/-8.4 units in the low-dose group (P = 0.384 by t-test; favoring low-dose D-Pen) from 20.4+/-10.3 in the high-dose and 19.9+/-6.6 in the low-dose D-Pen group at study entry. The incidences of SRC and mortality were not different (P > 0.38 by Cox proportional hazards and by chi-square test) in the 66 high-dose patients (8 developed SRC and 8 died) compared with the 68 low-dose patients (10 developed SRC and 12 died). Of the 20 adverse event-related withdrawals, 80% occurred in the high-dose D-Pen group.

CONCLUSION

The course of the skin score and the frequencies of SRC and mortality in the high-dose D-Pen group were not different from those in the low-dose D-Pen group. Eighty percent of the adverse event-related withdrawals occurred in the high-dose D-Pen patients. Although this study cannot answer the question of whether low-dose D-Pen is effective, it does suggest that there is no advantage to using D-Pen in doses higher than 125 every other day.

Frontal cognitive impairments and saccadic deficits in low-dose MPTP-treated monkeys

There is considerable overlap between the cognitive deficits observed in humans with frontal lobe damage and those described in patients with Parkinson's disease. Similar frontal impairments have been found in the 1-methyl-4-phenyl-1,2,3, 6-tetrahydropyridine (MPTP) primate model of Parkinsonism. Here we provide quantitative documentation of the cognitive, oculomotor, and skeletomotor dysfunctions of monkeys trained on a frontal task and treated with low-doses (LD) of MPTP. Two rhesus monkeys were trained to perform a spatial delayed-response task with frequent alternations between two behavioral modes (GO and NO-GO). After control recordings, the monkeys were treated with one placebo and successive LD MPTP courses. Monkey C developed motor Parkinsonian signs after a fourth course of medium-dose (MD) MPTP and later was treated with combined dopaminergic therapy (CDoT). There were no gross motor changes after the LD MPTP courses, and the average movement time (MT) did not increase. However, reaction time (RT) increased significantly. Both RT and MT were further increased in the symptomatic state, under CDoT. Self-initiated saccades became hypometric after LD MPTP treatments and their frequency decreased. Visually triggered saccades were affected to a lesser extent by the LD MPTP treatments. All saccadic parameters declined further in the symptomatic state and improved partially during CDoT. The number of GO mode (no-response, location, and early release) errors increased after MPTP treatment. The monkeys made more perseverative errors while switching from the GO to the NO-GO mode. Saccadic eye movement patterns suggest that frontal deficits were involved in most observed errors. CDoT had a differential effect on the behavioral errors. It decreased omission errors but did not improve location errors or perseverative errors. Tyrosine hydroxylase immunohistochemistry showed moderate ( approximately 70-80%) reduction in the number of dopaminergic neurons in the substantia nigra pars compacta after MPTP treatment. These results show that cognitive and motor disorders can be dissociated in the LD MPTP model and that cognitive and oculomotor impairments develop before the onset of skeletal motor symptoms. The behavioral and saccadic deficits probably result from the marked reduction of dopaminergic neurons in the midbrain. We suggest that these behavioral changes result from modified neuronal activity in the frontal cortex.

Spatiotemporal structure of cortical activity: properties and behavioral relevance

The study was designed to reveal occurrences of precise firing sequences (PFSs) in cortical activity and to test their behavioral relevance. Two monkeys were trained to perform a delayed-response paradigm and to open puzzle boxes. Extracellular activity was recorded from neurons in premotor and prefrontal areas with an array of six microelectrodes. An algorithm was developed to detect PFSs, defined as a set of three spikes and two intervals with a precision of +/-1 ms repeating significantly more than expected by chance. The expected level of repetition was computed based on the firing rate and the pairwise correlation of the participating units, assuming a Poisson distribution of event counts. Accordingly, the search for PFSs was corrected for rate modulations. PFSs were found in 24/25 recording sessions. Most PFSs (76%) were composed of spikes of more than one unit but usually not more than two units (67%). The PFSs spanned hundreds of milliseconds, and the average interval between two events within the PFSs was 200 ms. No traces of periodic oscillations were found in the PFS intervals. The bins of the matrix that were defined as PFSs were isolated temporally: the spikes that generated PFSs were not associated with high-frequency bursts or rapid coherent rate fluctuations. A given PFS tended to be correlated with the animal's behavior. Furthermore, for 19% of the PFS pairs that shared the same unit composition, each member of the pair was associated with a different type of behavior. The PFSs often appeared in clusters that were associated with particular phases of the behavior. The firing rate of single units did not provide a full explanation for the timing and structure of these clusters. A reduced spike train (RST) was defined for each unit by taking all spikes of that unit that were part of any PFS. In 88% of the cases the degree of modulation of the RST was higher than that of the complete spike train. The results suggest that relevant information is carried by the fine temporal structure of cortical activity. A coding scheme that involves such temporal structures is rich and sufficiently flexible to facilitate a rapid organization of cortical neurons into functional groups. The results can be accounted for by the synfire chain model, which suggests that cortical activity is mediated by synchronous activation of neural groups in a reverberatory mode.

Fibromyalgia and women's pursuit of personal goals: a daily process analysis

For 30 days, 50 women with primary fibromyalgia syndrome reported daily progress and effort toward a health-fitness and a social-interpersonal goal and the extent to which their pain and fatigue hindered their accomplishment. They also carried palmtop computers to assess their sleep and their pain, fatigue, and positive and negative mood throughout the day. Analyses of the person-day data set showed that on days during which pain or fatigue increased from morning to evening, participants perceived their goal progress to be more attenuated by pain and fatigue. Unrestorative sleep the night before predicted the following day's effort and progress toward accomplishing health-fitness goals, but not social-interpersonal goals. Finally, participants who reported more progress toward social-interpersonal goals on a given day were more likely to evidence improvements in positive mood across the day, regardless of any changes in pain or fatigue that day.

Hebbian-like functional plasticity in the auditory cortex of the behaving monkey

In this study, the necessary conditions, including those related to behavior, for lasting modifications to occur in correlated activity ('functional plasticity') were examined in the behaving monkey. Previously, in-vitro studies of neuronal plasticity yielded important information about possible mechanisms of synaptic plasticity, but could not be used to test their functionality in the intact, behaving brain. In-vivo studies usually focused on analysis of the responsiveness of single cells, but did not examine interactions between pairs of neurons. In this study, we combined the two approaches. This was achieved by recording extracellularly and simultaneously the spike activity of several single cells in the auditory cortex of the behaving monkey. The efficacy of neuronal interactions was estimated by measuring the correlation between firing times of pairs of single neurons. Using acoustic stimuli, a version of cellular conditioning was applied when the monkey performed an auditory discrimination task and when it did not. We found that: (i) functional plasticity is a function of the change in correlation, and not of the correlation or covariance per se, and (ii) functional plasticity depends critically on behavior. During behavior, an increase in the correlation caused a short-lasting strengthening of the neuronal coupling efficacy, and a decrease caused a short-lasting weakening. These findings indicate that neuronal plasticity in the auditory cortex obeys a version of Hebb's associative rule under strong behavioral control, as predicted by Thorndike's "Law of Effect".

Fibromyalgia and women's pursuit of personal goals: a daily process analysis

For 30 days, 50 women with primary fibromyalgia syndrome reported daily progress and effort toward a health-fitness and a social-interpersonal goal and the extent to which their pain and fatigue hindered their accomplishment. They also carried palmtop computers to assess their sleep and their pain, fatigue, and positive and negative mood throughout the day. Analyses of the person-day data set showed that on days during which pain or fatigue increased from morning to evening, participants perceived their goal progress to be more attenuated by pain and fatigue. Unrestorative sleep the night before predicted the following day's effort and progress toward accomplishing health-fitness goals, but not social-interpersonal goals. Finally, participants who reported more progress toward social-interpersonal goals on a given day were more likely to evidence improvements in positive mood across the day, regardless of any changes in pain or fatigue that day.

Physiological aspects of information processing in the basal ganglia of normal and parkinsonian primates

There are two views as to the character of basal-ganglia processing - processing by segregated parallel circuits or by information sharing. To distinguish between these views, we studied the simultaneous activity of neurons in the output stage of the basal ganglia with cross-correlation techniques. The firing of neurons in the globus pallidus of normal monkeys is almost always uncorrelated. However, after dopamine depletion and induction of parkinsonism by treatment with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), oscillatory activity appeared and the firing of many neurons became correlated. We conclude that the normal dopaminergic system supports segregation of the functional subcircuits of the basal ganglia, and that a breakdown of this independent processing is a hallmark of Parkinson's disease.

Sequential daily relations of sleep, pain intensity, and attention to pain among women with fibromyalgia

Fifty women with fibromyalgia syndrome (FS) recorded their sleep quality, pain intensity, and attention to pain for 30 days, using palm-top computers programmed as electronic interviewers. They described their previous night's sleep quality within one-half hour of awakening each day, and at randomly selected times in the morning, afternoon, and evening rated their present pain in 14 regions and attention to pain during the last 30 min. We analyzed the 30-day aggregates cross-sectionally at the across-persons level and the pooled data set of 1500 person-days at the within-persons level after adjusting for between-persons variation and autocorrelation. Poorer sleepers tended to report significantly more pain. A night of poorer sleep was followed by a significantly more painful day, and a more painful day was followed by a night of poorer sleep. Pain attention and sleep were unrelated at the across-persons level of analysis. But there was a significant bi-directional within-person association between pain attention and sleep quality that was not explained by changes in pain intensity.

Simultaneously recorded single units in the frontal cortex go through sequences of discrete and stable states in monkeys performing a delayed localization task

To test whether spiking activity of six to eight simultaneously recorded neurons in the frontal cortex of a monkey can be characterized by a sequence of discrete and stable states, neuronal activity is analyzed by a hidden Markov model (HMM). Using the HMM method, we are able to detect distinct states of neuronal activity within which firing rates are approximately stationary. Transitions between states, as expressed by concomitant changes in the firing rates of several units, occur quite abruptly. The significance and consistency of the states are confirmed by comparison with simulated data. The detected states are specific to a monkey's response in a delayed localization task, allowing correct prediction of the response in approximately 90% of the trials. Similar predictive power is achieved by a model based simply on the response histograms (PSTH) of the units. The two models reach this predictive ability with different time courses: the PSTH model gains predictive power with a higher rate in the first second of the delay, and the HMM gains predictive power with higher rate in the next 3 sec. In this later period, conventional methods such as the PSTH cannot detect any firing rate modulations, but the HMM successfully captures transitions between distinct states that are specific to the monkey's behavioral response and occur at highly variable times from trial to trial. Our results suggest that neuronal activity in this later period is described best as transitions among distinct states that may reflect discrete steps in the monkey's mental processes.

Spatio-temporal firing patterns in the frontal cortex of behaving monkeys

Recording the activity of several neurons in parallel in the frontal cortex of behaving monkeys reveals that firing times of neurons can maintain +/- 1 ms accuracy even after delays of over 400 ms. The accurate firing structures were associated with behavior. Neural networks that can sustain such accuracy can learn 'learn' to bind with each other and thus may serve as building blocks for cognitive processes.

Patients with type IV Ehlers-Danlos syndrome may be predisposed to atlantoaxial subluxation

OBJECTIVE

To determine if atlantoaxial subluxation is a complication of Ehlers-Danlos Syndrome (EDS).

METHODS

Observational study of a selected cohort of patients with EDS attending a national meeting. Twenty-six patients with EDS (19 with type III; 3 with type IV; 1 each with types II and I; 2 with undefined subtypes) were radiologically evaluated. Lateral flexion-extension views of the cervical spine in each patient were read in blinded fashion by a radiologist and compared to unblinded interpretations made by a separate radiologist. Measurement was taken from the most inferior aspect of the anterior arch of C1 to the dens along a horizontal plane. The remainder of the radiograph was examined for abnormalities.

RESULTS

Two patients with EDS type IV had radiographic evidence of atlantoaxial subluxation (p = 0.013 Fisher's exact test). Evidence of horizontal translation between vertebral bodies below C2 was noted in 3 patients. Cervical arthrosis was present in 9.

CONCLUSIONS

Atlantoaxial subluxation may be a more common finding in persons with type IV EDS than previously thought. Examination of the cervical spine radiographically should be considered before administering general anesthesia to these patients.

Cortical activity flips among quasi-stationary states

Parallel recordings of spike trains of several single cortical neurons in behaving monkeys were analyzed as a hidden Markov process. The parallel spike trains were considered as a multivariate Poisson process whose vector firing rates change with time. As a consequence of this approach, the complete recording can be segmented into a sequence of a few statistically discriminated hidden states, whose dynamics are modeled as a first-order Markov chain. The biological validity and benefits of this approach were examined in several independent ways: (i) the statistical consistency of the segmentation and its correspondence to the behavior of the animals; (ii) direct measurement of the collective flips of activity, obtained by the model; and (iii) the relation between the segmentation and the pair-wise short-term cross-correlations between the recorded spike trains. Comparison with surrogate data was also carried out for each of the above examinations to assure their significance. Our results indicated the existence of well-separated states of activity, within which the firing rates were approximately stationary. With our present data we could reliably discriminate six to eight such states. The transitions between states were fast and were associated with concomitant changes of firing rates of several neurons. Different behavioral modes and stimuli were consistently reflected by different states of neural activity. Moreover, the pair-wise correlations between neurons varied considerably between the different states, supporting the hypothesis that these distinct states were brought about by the cooperative action of many neurons.

Dynamics of neuronal interactions in monkey cortex in relation to behavioural events

It is possible that brain cortical function is mediated by dynamic modulation of coherent firing in groups of neurons. Indeed, a correlation of firing between cortical neurons, seen following sensory stimuli or during motor behaviour, has been described. However, the time course of modifications of correlation in relation to behaviour was not evaluated systematically. Here we show that correlated firing between single neurons, recorded simultaneously in the frontal cortex of monkeys performing a behavioural task, evolves within a fraction of a second, and in systematic relation to behavioural events. Moreover, the dynamic patterns of correlation depend on the distance between neurons, and can emerge even without modulation of the firing rates. These findings support the notion that neurons can associate rapidly into a functional group in order to perform a computational task, at the same time becoming dissociated from concurrently activated competing groups. Thus, they call for a revision of prevailing models of neural coding that rely solely on single neuron firing rates.

Recurrent leukocytoclastic vasculitis as the initial manifestation of acute myelomonocytic leukemia

The association between cutaneous and systemic leukocytoclastic vasculitis and myeloproliferative and lymphoproliferative malignancies has been reported. We describe a patient who developed recurrent episodes of leukocytoclastic vasculitis 10 months before the diagnosis of acute myelomonocytic leukemia. To our knowledge, this is the first documented case of leukocytoclastic vasculitis presenting as the initial manifestation of acute myelomonocytic leukemia, a subtype of acute myelogenous leukemia.

A 2 year, open ended trial of methotrexate in systemic lupus erythematosus

OBJECTIVE

To investigate a possible role for methotrexate (MTX) in the treatment of patients with systemic lupus erythematosus (SLE) who require unacceptably high doses of glucocorticosteroids (GCS) for control of their disease.

METHODS

Twelve patients with SLE participated in this open ended prospective study. Patients with active renal or central nervous system (CNS) disease were excluded as were patients with liver disease. Serological variables, SLE disease activity index, joint count, and prednisone dose were serially evaluated. Data were analyzed using paired t test and contingency table analysis.

RESULTS

Arthritis was the major persistent problem in 7 patients: 1 patient had recurrent pleuropericarditis, 2 patients had refractory cutaneous lupus rashes and 2 had vasculitis. Three patients discontinued MTX because of side effects. The remaining 9 patients have been treated from 7-26 months. In 6 patients the GCS dose was reduced by an average of 42%. In 1 patient symptoms subsided and joint count was reduced without change in the GCS dose. GCS dosage was increased in 2 patients: 1 with recurrent serositis, 1 with persistent vasculitis. No apparent effect on anti-dsDNA antibodies, complement or erythrocyte sedimentation rate (ESR) was noted.

CONCLUSION

MTX appears to be useful in selected patients with SLE, especially those with persistent synovitis.

Alpha-delta sleep in patients with a chief complaint of chronic fatigue

Our prospective, standardized cohort study was designed to assess the presence of alpha wave intrusions during non-rapid eye movement sleep (alpha-delta sleep) and its relationship to fibromyalgia, major depression, and chronic fatigue syndrome (CFS) in patients with a chief complaint of chronic fatigue. The study group comprised 30 consecutive patients seen at a university hospital referral clinic for evaluation of chronic fatigue. All patients had nocturnal polysomnography, dolorimetric tender point assessment for fibromyalgia, a comprehensive history, physical, and laboratory evaluation, and a structured psychiatric interview. Alpha-delta sleep was identified in 8 of the 30 patients (26%), major depression in 20 (67%), CFS in 15 (50%), and fibromyalgia in 4 (13%). Ten of the 30 patients (33%) had a primary sleep disorder (sleep apnea, periodic limb movements, or narcolepsy). Alpha-delta sleep was not significantly correlated with fibromyalgia, CFS, major depression, or primary sleep disorders, but was significantly more common among patients who had chronic fatigue without major depression. We conclude that primary sleep disorders are relatively common among patients with chronic fatigue and must be diligently sought and treated. Alpha-delta sleep is not a marker of fibromyalgia or CFS, but may contribute to the illness of nondepressed patients with these conditions.

Population responses to multifrequency sounds in the cat auditory cortex: one- and two-parameter families of sounds

Population responses to multi-frequency sounds were recorded in primary auditory cortex of anesthetized cats. The sounds consisted of single-tone stimuli; two-tone stimuli; and nine-tone stimuli, with the tones evenly spaced on a linear frequency scale. The stimuli were presented through a sealed, calibrated sound delivery system. Single units, cluster activity (CA) and the short-time mean absolute value of the envelope of the neural signal (MABS) were recorded extracellularly from six microelectrodes simultaneously. The CA and MABS were interpreted as measures of the activity of large populations of neurons, in contrast with the single unit activity which is presumably recorded from single neurons. The responses of the MABS signal to simple stimuli were generally similar to those of the CA, but were more stable statistically. Thus, the MABS is better suited for studying the activity of populations of neurons. The responses to tones near the best frequency were strongly influenced by a second tone, even when the second tone was outside the single-tone response area. These influences could be both facilitatory and suppressory. They could not be predicted from the responses to single tones. The responses to the nine-tone stimuli could be explained qualitatively by the responses to the two-tone stimuli. It is concluded that the population responses in primary auditory cortex are shaped by the contributions of the individual frequencies appearing in the stimulus and by the interactions between pairs of frequencies. Interactions between stimulus components are therefore a necessary component of any attempt to explain the processing of complex sounds in the auditory cortex. They may play a role in a global representation of the stimulus spectrum in the primary auditory cortex. The presence of higher-order interactions cannot be excluded by the results presented here.

In search of the best stimulus: an optimization procedure for finding efficient stimuli in the cat auditory cortex

Units in the auditory cortex of cats respond to a large variety of stimuli: pure tones, AM- and FM-modulated signals, clicks, wideband noise, natural sounds, and more. However, no single family of sounds was found to be optimal (in the sense that oriented lines are optimal in the visual cortex). The search for optimal complex sounds is hard because of the high dimensionality of the space of interesting sounds. In an effort to overcome this problem, an automatic search procedure for finding efficient stimuli in high-dimensional sound spaces was developed. This procedure chooses the stimuli to be presented according to the responses to past stimuli, trying to increase the strength of the response. The results of applying this method to recordings of population activity in the primary auditory cortex of cats are described. The search was applied to single tones, two-tone stimuli, four-tone stimuli and to a two-dimensional subset of nine-tone stimuli, parametrized by the center frequency and the fixed difference between adjacent frequencies. The method was able to find efficient stimuli, and its performance improved with the dimension of the sound spaces. Efficient stimuli, found in different optimization runs using population activity recorded from the same electrode, often shared similar frequencies and pairs of frequencies, and tended to evoke similar levels of activity. This result indicates that a global analysis of the location of spectral peaks is performed at the level of the auditory cortex.

Population responses to multifrequency sounds in the cat auditory cortex: four-tone complexes

Population responses to two-tone and four-tone sounds were recorded in primary auditory cortex of anesthetized cats. The stimuli were delivered through a sealed, calibrated sound delivery system. The envelope of the neural signal (short time mean absolute value, MABS) was recorded extracellularly from six microelectrodes simultaneously. A new method was developed to describe the responses to the four-tone complexes. The responses were represented as sums of contributions of different orders. The first order contributions described the effect of the single frequencies appearing in the stimulus. The second order contributions described the modulatory effect of the pairs of frequencies. Higher order contributions could in principle be computed. This paper concentrates on the mean onset responses. The extent to which the first and second order contributions described the onset responses was assessed in two ways. First, the actual responses to two-tone stimuli were compared with those predicted using the contributions computed from the four-tone stimuli. Second, the residual variance in the responses, after the subtraction of the first and second order contributions, was computed and compared with the variability in the responses to repetitions of the same stimulus. The first type of analysis showed good quantitative agreement between the predicted and the measured two-tone responses. The second type of analysis showed that the first and second order contributions were often sufficient to predict the responses to four-tone stimuli up to the level of the variability in the responses to repetitions of a single stimulus. In conjunction with the results of the companion paper (Nelken et al., 1994a) it is concluded that the onset responses to multifrequency sounds are shaped mainly by the single frequency content of the sound and by two-tone interactions, and that higher order interactions contribute much less to the responses. It follows that single-tone effects and two-tone interactions are necessary and sufficient to explain the mean population onset responses to the four-tone stimuli. More information can be coded in the temporal evolution of the responses.

Spatiotemporal firing patterns in the frontal cortex of behaving monkeys

1. Activity of up to 10 single units was recorded in parallel from frontal areas of behaving monkeys. 2. Spatiotemporal firing patterns were revealed by a method that detects all excessively repeating patterns regardless of their complexity or single-unit composition. 3. Excess of repeating patterns was found in 30-60% of the cases examined when timing jitter of 1-3 ms was allowed. 4. An independent test refuted the hypothesis that these patterns represented chance events. 5. In a given behavioral condition there were usually many different patterns, each repeating several times, and not one (or a few) pattern repeating many times. 6. In 13 out of 20 cases, when a single unit elevated its firing rate in association with an external event beyond 40/s, most of the spikes within that period were associated with excessively repeating spatiotemporal patterns. 7. Of 157 types of patterns whose excess was most marked, 107 were composed of spikes from one single unit, 45 of the patterns contained spikes from two single units, and only one was composed of spikes from three different single units. 8. These properties suggest that the patterns were generated by reverberations in a synfire mode within self-exciting cell assemblies.

Dependence of cortical plasticity on correlated activity of single neurons and on behavioral context

It has not been possible to analyze the cellular mechanisms underlying learning in behaving mammals because of the difficulties in recording intracellularly from awake animals. Therefore, in the present study of neuronal plasticity in behaving monkeys, the net effect of a single neuron on another neuron (the "functional connection") was evaluated by cross-correlating the times of firing of the two neurons. When two neurons were induced to fire together within a short time window, the functional connection between them was potentiated, and when simultaneous firing was prevented, the connection was depressed. These modifications were strongly dependent on the behavioral context of the stimuli that induced them. The results indicate that changes in the temporal contingency between neurons are often necessary, but not sufficient, for cortical plasticity in the adult monkey: behavioral relevance is required.

Evaluation of Social Security disability in claimants with rheumatic disease

We compared the Social Security Administration's (SSA) judgment of disability with uninvolved rheumatologists' evaluations of ability to work. With the cooperation of the SSA, 52 new disability claimants who alleged rheumatoid arthritis, osteoarthritis, or systemic lupus erythematosus were identified at the beginning of their claim. At the same time that their claim was being formally reviewed, they had a standardized examination by an independent rheumatologist who was not involved with their care, and they had a standardized test of observed performance. Rheumatologists' judgments of ability to work were compared with the SSA judgments. Rheumatologist and SSA judgments were in agreement for 35 of the 52 claimants (67%). All 11 claimants who met or equaled the SSA medical evaluation criteria were judged work-disabled by the rheumatologist. Of 27 judged able to work by the SSA, the rheumatologist judged 11 to be unable. Agreement between the SSA judgment of residual functional capacity and observed performance was no more than would be expected by chance. Most SSA judgments agree with a clinician's evaluation but a standardized physical evaluation by a rheumatologist and performance-based tests appear to add important information.

Evidence for spatiotemporal firing patterns within the auditory thalamus of the cat

Multiple spike trains were recorded in the auditory thalamus of cats. Each unit was studied before, during and after cooling of the ipsilateral primary auditory cortex, during spontaneous activity and acoustically evoked activity. The search for spatiotemporal firing patterns provided evidence that excess of patterns does exist and that the acoustical stimulation increased their number. Cortical cooling did not affect the probability of finding the firing pattern.

Does the acetyl group of aspirin contribute to the antiinflammatory efficacy of salicylic acid in the treatment of rheumatoid arthritis?

In a multicenter, double-blind, parallel-group study, 233 patients with classical or definite RA who demonstrated disease flare during a prestudy washout period were randomized to 12 weeks of treatment with either the nonacetylated salicylate, salsalate (salicylsalicylic acid), or aspirin. Of the 150 patients who completed the study, 83 received salsalate and 67 were treated with aspirin. Doses of the two drugs were calculated to provide equal amounts of bioavailable salicylic acid. The efficacy of salsalate and aspirin, as measured by all the usual variables, was equivalent but aspirin-treated patients had a higher incidence of severe gastrointestinal problems. Thus, this study demonstrated that the acetyl group of aspirin does not enhance the anti-inflammatory efficacy of salicylic acid in RA.

The American College of Rheumatology 1990 Criteria for the Classification of Fibromyalgia. Report of the Multicenter Criteria Committee

To develop criteria for the classification of fibromyalgia, we studied 558 consecutive patients: 293 patients with fibromyalgia and 265 control patients. Interviews and examinations were performed by trained, blinded assessors. Control patients for the group with primary fibromyalgia were matched for age and sex, and limited to patients with disorders that could be confused with primary fibromyalgia. Control patients for the group with secondary-concomitant fibromyalgia were matched for age, sex, and concomitant rheumatic disorders. Widespread pain (axial plus upper and lower segment plus left- and right-sided pain) was found in 97.6% of all patients with fibromyalgia and in 69.1% of all control patients. The combination of widespread pain and mild or greater tenderness in greater than or equal to 11 of 18 tender point sites yielded a sensitivity of 88.4% and a specificity of 81.1%. Primary fibromyalgia patients and secondary-concomitant fibromyalgia patients did not differ statistically in any major study variable, and the criteria performed equally well in patients with and those without concomitant rheumatic conditions. The newly proposed criteria for the classification of fibromyalgia are 1) widespread pain in combination with 2) tenderness at 11 or more of the 18 specific tender point sites. No exclusions are made for the presence of concomitant radiographic or laboratory abnormalities. At the diagnostic or classification level, the distinction between primary fibromyalgia and secondary-concomitant fibromyalgia (as defined in the text) is abandoned.

Methods used by urban, low-income minorities to care for their arthritis

The purpose of this study is to describe the current treatment methods minorities use and believe are effective in relieving the pain and discomfort of arthritis. One hundred sixty subjects from two urban, low-income minority communities reported to case finders that they had some form of arthritis. Subsequently they were interviewed and examined by a rheumatologist. Sixty-six percent were black, and 34% were Hispanic. The study found that 83% had some type of rheumatic disease. Differences existed between the black and Hispanic samples in age, rheumatic disease distribution, and methods of care. The majority of black respondents were older, with a frequent diagnoses of osteoarthritis, compared to the Hispanics, who reported fibrositis as their dominant rheumatic problem. An array of conventional and nonconventional therapies were used by both groups to care for their arthritis. Prayer (92%), equipment (70%), and heat (33%) were reported as "most helpful" for the blacks. Hispanics reported prayer (50%), heat (40%), and topical ointments as "most helpful." In order to communicate and provide optimal care to patients from divergent cultural backgrounds, it is important to understand both likenesses and differences, and to be sensitive to the patient's belief system and health care practices.