Neuronal segmentation in cephalopod arms.

The prehensile arms of the cephalopod are among these animals most remarkable features, but the neural circuitry governing arm and sucker movements remains largely unknown. We studied the neuronal organization of the adult axial nerve cord (ANC) of Octopus bimaculoides with molecular and cellular methods. The ANCs, which lie in the center of every arm, are the largest neuronal structures in the octopus, containing four times as many neurons as found in the central brain. In transverse cross section, the cell body layer (CBL) of the ANC wraps around its neuropil (NP) with little apparent segregation of sensory and motor neurons or nerve exits. Strikingly, when studied in longitudinal sections, the ANC is segmented. ANC neuronal cell bodies form columns separated by septa, with 15 segments overlying each pair of suckers. The segments underlie a modular organization to the ANC neuropil: neuronal cell bodies within each segment send the bulk of their processes directly into the adjoining neuropil, with some reaching the contralateral side. In addition, some nerve processes branch upon entering the NP, forming short-range projections to neighboring segments and mid-range projections to the ANC segments of adjoining suckers. The septa between the segments are employed as ANC nerve exits and as channels for ANC vasculature. Cellular analysis establishes that adjoining septa issue nerves with distinct fiber trajectories, which across two segments (or three septa) fully innervate the arm musculature. Sucker nerves also use the septa, setting up a nerve fiber "suckerotopy" in the sucker-side of the ANC. Comparative anatomy suggests a strong link between segmentation and flexible sucker-laden arms. In the squid Doryteuthis pealeii, the arms and the sucker-rich club of the tentacles have segments, but the sucker-poor stalk of the tentacles does not. The neural modules described here provide a new template for understanding the motor control of octopus soft tissues. In addition, this finding represents the first demonstration of nervous system segmentation in a mollusc.

Neuronal segmentation in cephalopod arms.

The prehensile arms of the cephalopod are among these animals' most remarkable features, but little is known about the neural circuitry governing arm and sucker movements1,2. Here, we investigated the cellular and molecular organization of the arm nervous system, focusing on the massive axial nerve cords (ANCs) in the octopus arms which collectively harbor four times as many neurons as the central brain3. We found that the ANC is segmented. In transverse cross sections, the ANC cell body layer wraps around the neuropil with no apparent segregation of sensory and motor neurons. In longitudinal sections, however, ANC neurons form segments, setting up a modular organization to the adjoining ANC neuropil. The septa between each segment are, in contrast, neuron-poor but contain nerve exits, vasculature and abundant collagen. Surprisingly, nerves exiting from neighboring septa differ in their fiber trajectories indicating that multiple adjoining segments must cooperate to innervate the arm musculature fully. The nerves for each sucker also exit through septa and set up a spatial "suckerotopy" in the ANC. A strong link between ANC segmentation and flexible sucker-laden arms was confirmed by comparative study of squid arms and tentacles. The ANC segmental modules represent a new template for understanding the motor control of octopus soft tissues. They also provide the first example of nervous system segmentation in a mollusc4.

Toward an Understanding of Octopus Arm Motor Control.

Octopuses have the extraordinary ability to control eight prehensile arms with hundreds of suckers. With these highly flexible limbs, they engage in a wide variety of tasks, including hunting, grooming, and exploring their environment. The neural circuitry generating these movements engages every division of the octopus nervous system, from the nerve cords of the arms to the supraesophegeal brain. In this review, the current knowledge on the neural control of octopus arm movements is discussed, highlighting open questions and areas for further study.

Smooth pursuit eye movements to extraretinal motion signals: deficits in relatives of patients with schizophrenia.

BACKGROUND: Although mounting evidence supports the idea that smooth pursuit abnormality marks the genetic liability to schizophrenia, the precise ocular motor mechanism underlying the abnormality remains unknown. Based on recent findings in schizophrenia, we hypothesize that subtle deficits in the ability to hold online and/or use extraretinal motion information underlie the pursuit abnormality in vulnerable individuals. METHODS: The hypothesis was tested in 69 first-degree, biological relatives of probands with schizophrenia; 26 relatives had schizophrenia spectrum personalities (SSP). Subjects recruited from the community (n=71; 29 with SSP), without a known family history of psychosis, constituted the comparison groups. The traditional smooth pursuit gain measure, which is a ratio of smooth pursuit eye velocity in response to both retinal and extraretinal motion signals and the target velocity, was obtained. In addition, newly developed measures of predictive smooth pursuit (ie, in the presence of only extraretinal motion signals) were obtained. The latter measures were evaluated after the current retinal motion signals were made unavailable by briefly making the target invisible. RESULTS: Relatives, particularly those with SSP, showed significantly poorer predictive pursuit response to extraretinal motion signals (F(2,136)=6.51, P<.005), compared with the community subjects. However, the traditional smooth pursuit gain in response to both retinal and extraretinal motion signals was not different between groups. CONCLUSIONS: These results suggest that relatives of patients with schizophrenia, particularly those with SSP, have specific deficits in predictive pursuit based on only extraretinal motion signals. Normal smooth pursuit gain in response to both retinal and extraretinal motion signals is likely due to compensation based on retinal motion information. The latter suggests normal retinal motion processing and smooth pursuit motor output.

GABA agonist-induced changes in motor, oculomotor, and attention measures correlate in schizophrenics with tardive dyskinesia.

Saccadic distractibility, Stroop color-word scores, and serial dyskinesia assessments were obtained on 10 schizophrenic patients with tardive dyskinesia during a pharmacologic challenge with placebo or 7 mg muscimol, a potent, direct-acting GABA agonist. Although no significant difference in the measures was evident between conditions, a significant correlation was found between GABA agonist-induced changes in saccadic distractibility and dyskinesia scores where no correlation existed between these measures on placebo. Improvement in saccadic distractibility was also correlated with reduction in attention performance, as measured by Stroop. These effects are not due to sedation. The correlation between dyskinesia and saccadic distractibility is consistent with a model of parallel motor and oculomotor cortico-striatal-thalamic circuits in humans. This work supports the hypothesis that a dysfunction in GABA-mediated neurotransmission may be the basis for tardive dyskinesia.

Psychiatric illnesses in families of subjects with schizophrenia-spectrum personality disorders: high morbidity risks for unspecified functional psychoses and schizophrenia.

OBJECTIVE: The authors determined morbidity risks for psychiatric illnesses in the families of probands with schizophrenia-spectrum personality disorders. METHOD: Subjects were recruited from the community through newspaper advertisements. Subjects were identified as having schizophrenia-spectrum personality disorders (N = 30) if they met at least three, four, or three DSM-III-R criteria for schizoid (N = 14), schizotypal (N = 20), and/or paranoid (N = 15) personality disorder, respectively. The comparison subjects had no psychiatric diagnoses (N = 8) or had other personality disorders (N = 12); none of the subjects in either group had any DSM-III-R axis I diagnosis. Trained interviewers collected family history information about the relatives of the two groups; the interviewers were blind to the probands' diagnoses. RESULTS: The risks for schizophrenia, other functional psychoses, and schizophrenia-spectrum personality disorders were significantly higher in the relatives of subjects with schizophrenia-spectrum personality disorders than in the families of the comparison subjects. CONCLUSIONS: The high rate of schizophrenia in the families of probands with schizophrenia-spectrum personality disorders is consistent with the previous findings of higher than normal rates of these personality disorders in the biological relatives of schizophrenic patients. The significance of the high rate of unspecified functional psychoses is unclear. Use of the family study method, by which valid differential diagnosis of psychoses is possible, is indicated. The results from the current study do not rule out the possibility that the schizophrenia-spectrum personality disorders are related to psychoses in general rather than specifically to schizophrenia.

Eye movements in spectrum personality disorders: comparison of community subjects and relatives of schizophrenic patients.

OBJECTIVE: The purpose of the current study was to test the specificity of an association between eye tracking abnormality and schizophrenia spectrum personality symptoms in the family members of schizophrenic patients. The studies of biological markers for genetic vulnerability to schizophrenia, which test an association between a biological measure and schizophrenia spectrum personality symptoms, are constrained, since these personality symptoms may lack the specificity for a schizophrenic phenotype. An association between a behavioral measure and these personality symptoms in general can easily be false (i.e., not related to schizophrenic vulnerability). In contrast, a strong deviant finding in the relatives of schizophrenic patients with spectrum personality symptoms, in the presence of a relatively normal finding in spectrum subjects without a known history of schizophrenia, makes the biobehavioral measure an interesting candidate for such investigations. METHOD: Seventy-five subjects recruited from the community who did not have a family history of psychosis completed the study (24 of the 75 had significant schizophrenia spectrum personality symptoms). Thirty-two first-degree relatives of schizophrenic patients (13 with spectrum symptoms) completed the study. Subjects were 18-45 years old and had no DSM-III-R axis I diagnosis. RESULTS: Qualitative smooth pursuit eye movement score was significantly worse in relatives with the spectrum symptoms than in spectrum subjects without a family history of schizophrenia and the nonspectrum relatives. Schizotypal and schizoid symptoms explained a significant amount of the variance in the eye tracking measure in the relatives (31% and 20%, respectively) but not in the community subjects (less than 2%). Relatives of schizophrenic patients with and without the spectrum symptoms had significantly longer antisaccade latency, in spite of comparable latency for visually guided saccades, than the community subjects. CONCLUSIONS: Smooth pursuit abnormality in subjects with schizophrenia spectrum personality disorders is specifically associated with a family history of schizophrenia.

Spontaneous dyskinesia in subjects with schizophrenia spectrum personality.

OBJECTIVE: The study of spontaneous dyskinesia in schizophrenia is confounded by the widespread use of neuroleptics. The authors hypothesized that spontaneous dyskinesia would be present in subjects with schizophrenia spectrum personality (schizoid, paranoid, or schizotypal). They also tested the hypothesis that dyskinetic-like movements would increase after repeated dextroamphetamine challenge to the dopaminergic system. METHOD: Dyskinetic-like movements were assessed in 34 spectrum subjects and 22 normal subjects; nine subjects from each group were administered both placebo and repeated dextroamphetamine challenges. RESULTS: Spectrum subjects had more dyskinetic-like movements than normal subjects. Spontaneous dyskinesia was present in 12% of the spectrum subjects but was not seen in the normal subjects. Subjects with schizotypal personality had more dyskinetic-like movements than subjects with schizoid personality or normal subjects. Dyskinesia was present in 24% of the schizotypal subjects but not in the other groups. Dyskinetic movement scores correlated with positive symptom scores. With repeated amphetamine challenge, normal subjects showed a pattern of behavioral sensitization (an increase in dyskinetic-like movements), but spectrum subjects showed an abnormal response (fewer dyskinetic-like movements). CONCLUSIONS: Dyskinesia and dyskinetic-like movements are more common in subjects with schizophrenia spectrum personality (primarily schizotypal) than in normal subjects and are related to positive symptoms. A failure of normal behavioral sensitization mechanisms after dextroamphetamine challenge is seen in subjects with schizophrenia spectrum personality.

Saccadic eye movement abnormalities in relatives of patients with schizophrenia.

Recent studies note abnormalities in saccadic eye movements of relatives of patients with schizophrenia. The current study examined which aspects of the saccadic system are affected, whether these saccadic abnormalities are associated with schizophrenia spectrum personality symptoms (SSP), and whether such an association is dependent on a family history of schizophrenia. Furthermore, the study examined what proportion of relatives have the saccadic abnormality(ies). Fifty-five first-degree relatives with no DSM-III-R Axis I diagnosis participated in the study. Twenty-one of these relatives experienced SSP symptoms and 34 had no Axis II diagnosis. Sixty-two subjects with no Axis I diagnosis were recruited from the community. Twenty-five experienced SSP symptoms and 37 had no Axis II diagnosis. Prosaccades (saccades toward the target) and antisaccades (saccades made in the opposite direction of the target jump) were examined. Relatives, particularly those with SSP, had difficulties with the antisaccade task as suggested by higher error rates and longer antisaccade latency. Prosaccades were not different in relatives compared to the community subjects, although the effects of field were different in the two groups on some measures. The antisaccade latency was 'abnormal' in only a small proportion (1.6%) of community subjects compared to 14.9% of all relatives (35.3% of SSP relatives and 3.3% of non-SSP relatives). Relatives of patients with schizophrenia have deficits in aspects of the saccadic system involved in generating internally driven saccades and inhibition of unwanted saccades. These deficits implicate frontal ocular motor neuronal circuitry involving frontal cortical and basal ganglia areas. These deficits are associated with SSP symptoms, but not in the absence of a blood relationship to schizophrenia. The relatively high prevalence rate of the abnormality in at-risk subjects may have relevance for use of these measures in linkage analysis.

Covert visual attention in schizophrenia spectrum personality disordered subjects: visuospatial cuing and alerting effects.

A recent study observed lateralized deficit in the disengagement of covert visual attention in schizophrenic patients. Subsequent attempts to replicate this finding have had mixed results. Differences in the neuroleptic treatment or other secondary factors associated with schizophrenia are some of the possible reasons for these inconsistent findings. In this study, we examined the ability to shift covert visual attention in neuroleptic-naive, schizophrenia spectrum personality disordered (SSPD; n = 35) subjects and normal controls (n = 34) under a variety of spatial cuing and alerting conditions. We hypothesized that SSPD subjects would have difficulty with disengagement of covert visual attention from an invalidly cued left visual field when the target appeared in the right visual field in comparison to the normal subjects. As predicted, schizophrenia spectrum personality disordered subjects had significantly longer latencies for the right visual field invalid targets than normals (p = .014). Under the remaining cue conditions, spectrum subjects performed normally. Consequently, the cost of left visual field invalid cueing for the right visual field target was significantly higher in spectrum personality subjects than in normals. The cost for the invalid right visual field cue and the benefits of valid cue in both fields were very similar in the two groups. The findings of an asymmetrical deficit in the disengagement and shift of covert visual attention in schizophrenia spectrum subjects are similar to the one's observed in patients with unilateral left hemisphere lesions.

Validity of near infrared body composition analysis in children and adolescents.

The purpose of this study was to evaluate the validity and reliability of the Futrex 5000A near infrared (NIR) spectrophotometer for the assessment of body composition in children and adolescents. Forty-eight subjects (24 boys and 24 girls) with a mean age of 12.7 +/- 2.7 yr underwent three methods of body composition testing: NIR, densitometry by hydrostatic weighing (HYDRO), and skinfold anthropometry (SKF). Percent body fat (%BF) and fat free mass (FFM) derived from the Lohman's age-adjusted Siri equation served as the criterion. Within session test-retest reliability was determined for the NIR device for all subjects and between-week reliability was evaluated for all test methods in 14 subjects. Based on the excellent within- and between-session reliability (ICC ranged from 0.907-0.999), the system offers the potential of obtaining longitudinal data in growth and development studies. However, the significant mean differences, moderate correlations with the criterion (r = 0.62-0.71) and inflated standard errors of estimate (SEE = 4.9-5.5% BF, 2.2-2.9 kg FFM) and total prediction errors (TE = 5.5-8.0% BF, 2.7-3.7 kg FFM) indicate that refinement of prediction equations is needed to establish the measurement validity. Continued research with expanded populations is needed to further demonstrate and evaluate the utility of this device.

Cross-validation of the Slaughter skinfold equations for children and adolescents.

Prior to sexual maturation, children and adolescents have more water and less bone mineral content than adults, resulting in less dense fat-free body mass (FFM). This suggests that previously established adult skinfold/density equations are inappropriate for use with children and adolescents for the prediction of body fatness (%BF) and FFM. To overcome this problem, Slaughter and colleagues have introduced new skinfold (SKF) equations that take into account the changing density of FFM in children and adolescents as they mature. The purpose of our study was to cross-validate a select set of the Slaughter SKF equations by comparing them with a criterion measurement (Lohman's Siri age-adjusted body density equation) in 122 subjects ranging in sexual maturation from pre- to post-pubescent and ranging in age from 8-17. Our cross-validation found very high intraclass (reliability) correlations (ICCs = 0.98-0.99) and high validity correlations (rs = 0.79-0.99). The standard errors of the estimate for %BF ranged from 3.5-4.6% and total errors for %BF ranged from 3.6-4.6%. The Slaughter equation using tricep and calf SKF for females was significantly different (P < 0.05) from the criterion measure in its prediction of %BF. In males, there was an interaction between the SKF equation and subject maturation level. The data indicate that the Slaughter SKF equations hold promise for estimating body composition in children and adolescents but are still in need of refinement.

Psychosis proneness scales in schizophrenia spectrum personality disorders: familial vs. nonfamilial samples.

The authors evaluated the extent of overlap between DSM-III-R schizophrenia spectrum personality diagnoses (SSPD) and the Psychosis Proneness Scales of Chapman and his associates. The subjects were recruited from the family members of schizophrenic patients ("familial" subjects; n = 45) and members of the community with negative family histories for schizophrenia ("nonfamilial" subjects; n = 60). Clinical interviews were performed to obtain DSM-III-R Axis I and II diagnoses. In 105 individuals with no Axis I diagnosis, the five Chapman Scales were administered. The results suggest that the nonfamilial subjects with diagnoses of SSPD (n = 24) scored significantly higher on the Chapman Scales of Magical Ideation, Perceptual Aberration, and Impulsive Nonconformity compared with the familial SSPD subjects and the other non-SSPD groups. The familial SSPD subjects (n = 17) scored significantly higher than the nonfamilial, non-SSPD groups on the Physical Anhedonia Scale. Scores on the Social Anhedonia Scale were highest in the SSPD subjects, but only scores for the nonfamilial SSPD subjects were statistically different from those for the other non-SSPD groups. The data were reanalyzed by first dividing the scores from the Chapman Scales into high and low scores based on different cutoff points. Sensitivities, specificities, and predictive powers of the "high" Chapman scores for SSPD diagnoses were then calculated. These were done because the Chapman Scales are often used to identify individuals with schizophrenia-related personality disorders on the basis of scores that exceed arbitrary cutoff points. The results suggest that the Chapman Scales (other than the Physical Anhedonia Scale) and DSM-III-R criteria identified mostly the same subjects, when only nonfamilial subjects were considered (with sensitivities and specificities of about 0.70). However, the overlap between these two constructs was poor when only schizophrenia spectrum subjects recruited from the family members of schizophrenic patients were considered.

The Maryland Psychiatric Research Center scale and the characterization of involuntary movements.

The Maryland Psychiatric Research Center involuntary movement scale (MPRC scale) has been used in the evaluation of 1107 patients referred for drug-induced movement disorders. The scale has increased discrimination of body area and severity compared to other scales. Validity was examined using principal component analyses, pharmacologic response studies and associations with AIMS, global judgement and motor diagnosis. Reliability was examined using Cronbach's alpha, intraclass correlation coefficient (ICC) between raters and test-retest measurements. The prevalence of dyskinetic and parkinsonian signs at several levels of severity are reported. Total dyskinesia was strongly correlated with AIMS score, r = 0.97. Inter-rater reliability was 0.81-0.90 for total dyskinesia score. Receiver Operating Characteristic (ROC) analysis shows a total dyskinesia score of 4 or above to predict tardive dyskinesia, consistent with RDC-TD criteria. Hand dyskinesia showed a high prevalence comparable to that of oral dyskinesias. The MPRC scale is a valid, sensitive and reliable instrument for the rating of neuroleptic-induced dyskinetic and parkinsonian syndromes and may offer advantages over other scales in neurophysiologic research and brain imaging with its ease of use, uniform structure and greater discrimination of anatomic place and severity in the rating of involuntary movements.

Cardiorespiratory responses of healthy subjects to calisthenics performed on land versus in water.

This study evaluated the oxygen consumption (VO2) and heart rate response curves for standardized upper- and lower-extremity exercise on land and in water. Forty healthy subjects performed one upper-extremity and one lower-extremity exercise at three selected cadences on land and in water. Steady-state heart rate was determined by electrocardiographic radiotelemetry and expressed as a percentage of age-predicted maximal heart rate (% APMHR). Percentage of age-predicted maximal heart rate was used as the criterion measure of relative exercise intensity. Oxygen consumption was determined by the open-circuit method. Results indicated systematic increases in VO2 from 2 to 9 metabolic equivalents (METs) (1 MET = 3.5 mL O2.kg-1.min-1) and % APMHR from 45% to 73% with increased cadence. The VO2 responses were highest during water exercise, whereas % APMHR was greater during land exercise. Based on the magnitude of the responses, water calisthenics appear to be of sufficient intensity to elicit training adaptations. Training studies are needed to document these changes.

Cross-validation of bioelectrical impedance analysis of body composition in children and adolescents.

BACKGROUND AND PURPOSE: The reliability and validity of measurements obtained with two bioelectrical impedance analyzers (BIAs), an RJL Systems model BIA-103 and a Berkeley Medical Research BMR-2000, were investigated using the manufacturers' prediction equations for the assessment of fat-free mass (FFM) (in kilograms) in children and adolescents. SUBJECTS: Forty-seven healthy children and adolescents (23 male, 24 female), ranging in age from 8 to 20 years (mean = 12.1, SD = 2.3), participated. METHODS: In the context of a repeated-measures design, the data were analyzed according to gender and maturation (Tanner staging). Hydrostatic weighing (HYDRO) and Lohman's Siri age-adjusted body density prediction equation served as the criteria for validating the BIA-obtained measurements. RESULTS: High intraclass correlation coefficients (ICC > or = .987) demonstrated good test-retest (between-week) measurement reliability for HYDRO and both BIA methods. Between-method (HYDRO versus BIA) correlation coefficients were high for both boys and girls (r > or = .97). The standard errors of estimate (SEEs) for FFM were slightly larger for boys than for girls and were consistently smaller for the RJL system than for the BMR system (RJL SEE = 1.8 kg for boys, 1.3 kg for girls; BMR SEE = 2.4 kg for boys, 1.9 kg for girls). The coefficients of determination were high for both BIA methods (r2 > or = .929). Total prediction errors (TEs) for FFM showed similar between-method trends (RJL TE = 2.1 kg for boys, 1.5 kg for girls; BMR TE = 4.4 kg for boys, 1.9 kg for girls). DISCUSSION AND CONCLUSION: This study demonstrated that the RJL BIA with the manufacturer's prediction equations can be used to reliably and accurately assess FFM in 8- to 20-year-old children and adolescents. The prediction of FFM by the BMR system was acceptable for girls, but significant overprediction of FFM for boys was noted.