RESUMO
A number of different system identification techniques have been proposed to assess dynamic cerebral autoregulation in critically ill patients. From these methods, the response to a standard stepwise change in blood pressure can be estimated. Responses lacking physiological consistency are a common occurrence and could be the consequence of particular system identification procedures or, alternatively, caused by measurements with a poor signal-to-noise ratio. A multi-observer approach was adopted in this paper to classify cerebral blood flow velocity (CBFV) step responses to spontaneous changes in arterial blood pressure in a group of 43 neonates with a mean gestational age of 33.7 weeks (range 24-42 weeks) and a mean birthweight of 1,980 g (range 570-3,910 g). Three experienced observers independently analysed the estimated step responses in 191 recordings each lasting 100 s; for an autoregressive (ARX) model, 124 (65%) of the step responses were accepted by at least two of the three observers. Two other system identification methods, transfer function analysis and the moving average Wiener-Laguerre model, gave 90 (45%) and 98 (51%) acceptable responses, respectively. Only 54 epochs (28%) were accepted with all three methods. With 88 (46%) responses rejected by at least two methods, it can be concluded that signal quality was the main reason for nonphysiological step responses. To avoid the need for subjective visual selection, an automatic procedure for classifying step responses was implemented leading to sensitivities and specificities in the range 85-90%, with respect to the agreement with subjective evaluations. Objective selection of CBFV step responses is thus feasible and could also be adapted for other physiological measurement techniques relying on system identification methods.
Assuntos
Velocidade do Fluxo Sanguíneo/fisiologia , Pressão Sanguínea/fisiologia , Circulação Cerebrovascular/fisiologia , Homeostase , Humanos , Recém-Nascido , Análise de Regressão , Processamento de Sinais Assistido por Computador/instrumentaçãoRESUMO
Interpretation and quantification of cerebral blood flow autoregulation can be carreid out from step responses to arterial blood pressure changes estimated with various identification methods. However estimates usually need to be visually inspected to rejected some that are not physiologically acceptable...
Assuntos
Circulação Cerebrovascular , Encéfalo/irrigação sanguínea , Recém-Nascido , Pressão IntracranianaRESUMO
The incidence of gynaecologic cancers in women from Kingston and St Andrew for the period 1973-1997 were reviewed by analyzing data previously published by the Jamaica Cancer Registry. Gynaecologic cancer-related mortality statistics for the entire island for 1999 were compiled from data obtained from the Registrar General's Department (RGD) and the Statistical Institute of Jamaica (STATIN). Data were compared to gynaecologic cancer statistics for women from the United States of America for 1973-1997. A total of 2862 gynaecologic cancers were registered for the years 1973-1997, which represents 26.8 of all female cancers from Kingston and St Andrew. Cervical cancer accounted for 62 of these gynaecologic cancers. The 268 cancer-related deaths (168 due to cervical cancer) registered in Jamaican women for 1999 represent approximately 15 of all female cancer-related deaths. The present incidence (27.9 per 100,000) and mortality rate (15.8 per 100,000) of cervical cancer are much higher than that documented for American women--both African Americans and Caucasians--and signify the limited success, to date, of efforts to decrease the incidence and mortality of cervical cancer by the implementation of cervical cancer screening programmes. For the time period reviewed, an increase was noted in the incidence of cancer of the corpus uteri while decreases were recorded for the incidence of choriocarcinoma, ovarian cancer and cancers arising from the vulva, vagina and fallopian tube
Assuntos
Humanos , Feminino , Neoplasias dos Genitais Femininos/mortalidade , Análise de Sobrevida , Estados Unidos/epidemiologia , Fatores Etários , Incidência , Invasividade Neoplásica , Jamaica/epidemiologia , Neoplasias dos Genitais Femininos/patologia , Saúde da Mulher , Sistema de RegistrosRESUMO
The incidence of gynaecologic cancers in women from Kingston and St Andrew for the period 1973-1997 were reviewed by analyzing data previously published by the Jamaica Cancer Registry. Gynaecologic cancer-related mortality statistics for the entire island for 1999 were compiled from data obtained from the Registrar General's Department (RGD) and the Statistical Institute of Jamaica (STATIN). Data were compared to gynaecologic cancer statistics for women from the United States of America for 1973-1997. A total of 2862 gynaecologic cancers were registered for the years 1973-1997, which represents 26.8% of all female cancers from Kingston and St Andrew. Cervical cancer accounted for 62% of these gynaecologic cancers. The 268 cancer-related deaths (168 due to cervical cancer) registered in Jamaican women for 1999 represent approximately 15% of all female cancer-related deaths. The present incidence (27.9 per 100,000) and mortality rate (15.8 per 100,000) of cervical cancer are much higher than that documented for American women--both African Americans and Caucasians--and signify the limited success, to date, of efforts to decrease the incidence and mortality of cervical cancer by the implementation of cervical cancer screening programmes. For the time period reviewed, an increase was noted in the incidence of cancer of the corpus uteri while decreases were recorded for the incidence of choriocarcinoma, ovarian cancer and cancers arising from the vulva, vagina and fallopian tube.
Assuntos
Neoplasias dos Genitais Femininos/mortalidade , Fatores Etários , Feminino , Neoplasias dos Genitais Femininos/patologia , Humanos , Incidência , Jamaica/epidemiologia , Invasividade Neoplásica , Sistema de Registros , Análise de Sobrevida , Estados Unidos/epidemiologia , Saúde da MulherRESUMO
A total of 2697 cancer-related deaths were documented among Jamaicans for the year 1999, accounting for 17.7% of all deaths. Males accounted for 1466 and females for 1231. The age-adjusted cancer mortality rate was 171.7 per 100,000 for males, 122.0 per 100,000 for females and 140.5 per 100,000 for the total population. Leading cancer mortality sites for males were prostate, lung and stomach and in females, breast, cervix uteri and large bowel. Most deaths were recorded in the 55-64 and 65-74 year-age groups. Despite well-established cervical cancer screening programmes, the calculated mortality rate for cancer of the cervix uteri in Jamaican females (15.8 per 100,000) is approximately two and a half times that seen in African-American females.
Assuntos
Neoplasias/mortalidade , Adulto , Idoso , Feminino , Humanos , Jamaica/epidemiologia , Masculino , Pessoa de Meia-IdadeRESUMO
A total of 2697 cancer-related deaths were documented among Jamaicans for the year 1999, accounting for 17.7 of all deaths. Males accounted for 1466 and females for 1231. The age-adjusted cancer mortality rate was 171.7 per 100,000 for males, 122.0 per 100,000 for females and 140.5 per 100,000 for the total population. Leading cancer mortality sites for males were prostate, lung and stomach and in females, breast, cervix uteri and large bowel. Most deaths were recorded in the 55-64 and 65-74 year-age groups. Despite well-established cervical cancer screening programmes, the calculated mortality rate for cancer of the cervix uteri in Jamaican females (15.8 per 100,000) is approximately two and a half times that seen in African-American females.
Assuntos
Humanos , Masculino , Feminino , Adulto , Pessoa de Meia-Idade , Neoplasias , JamaicaRESUMO
Coherence between a pulse train representing periodic stimuli and the EEG has been used in the objective detection of steady-state evoked potentials. This work aimed to quantify the strength of the stimulus responses based on the statistics of coherence estimate between one random and one periodic signal, focusing on the confidence limits and power of significance tests in detecting responses. To detect the responses in 95% of cases, a signal-to-noise ratio of about -7.9 dB was required when using 48 windows (M) in the coherence estimation. The ratio, however, increased to -1.2 dB when M was 12. The results were tested in Monte Carlo simulations and applied to EEGs obtained from 14 subjects during visual stimulation. The method showed differences in the strength of responses at the stimulus frequency and its harmonics, as well as variations between individuals and over cortical regions. In contrast to those from the parietal and temporal regions, results for the occipital region gave confidence limits (with M = 12) that were above zero for all subjects, indicating statistically significant responses. The proposed technique extends the usefulness of coherence as a measure of stimulus responses and allows statistical analysis that could also be applied usefully in a range of other biological signals.
Assuntos
Eletroencefalografia/métodos , Processamento de Sinais Assistido por Computador , Adolescente , Criança , Pré-Escolar , Humanos , Método de Monte Carlo , Estimulação Luminosa , Estatística como AssuntoRESUMO
In order to identify latent bioelectrical oscillators, 15 normal subjects (aged 9-17 years, 8 males, 7 females) were subjected to intermittent photic stimulation. The EEG amplitude spectra corresponding to the 11 fixed frequencies of stimulation presented (3-24 Hz) were combined to form "profiles" of the driving reaction in the right occipital area. The driving response varied with frequency, and was demonstrable in 70-100 percent of cases (using as criterion peak amplitudes 20 percent larger than those of the neighbors). The strongest responses were observed at the frequency closest to the alpha peak of the resting EEG. A secondary profile maximum was in the theta band. In 10 subjects, this maximum exceeded half the alpha peak (with an average of 72.4 percent of the alpha peak), while in the resting spectra, theta amplitudes were much lower than the alpha maxima. This responsiveness in theta activity seems to be characteristic of prepubertal and pubertal subjects. The profiles and resting EEG spectra showed a highly significant Pearson's correlation, with the peak in the theta band of the profiles being the main difference observed between them. The correlation coefficient was significantly correlated with the ratio of the maxima in the theta and alpha bands (R = -0.77, P<0.001). The correlation coefficient between profile and resting spectrum may be a useful indicator in screening methods used to reveal latent cerebral oscillators. Profiles for the second and third harmonics were correlated with those of the first harmonic (fundamental frequency), when considering the corresponding EEG frequencies. Peak frequencies in all three profiles were close to those of the individual's background alpha rhythm, and peak amplitudes in higher harmonics were not much lower than those of the fundamental frequency (mean values of 84 and 63 percent, for second and third harmonics, respectively)
Assuntos
Humanos , Masculino , Feminino , Criança , Adolescente , Estimulação Luminosa , Descanso , Eletroencefalografia , Lobo OccipitalRESUMO
In order to identify latent bioelectrical oscillators, 15 normal subjects (aged 9-17 years, 8 males, 7 females) were subjected to intermittent photic stimulation. The EEG amplitude spectra corresponding to the 11 fixed frequencies of stimulation presented (3-24 Hz) were combined to form "profiles" of the driving reaction in the right occipital area. The driving response varied with frequency, and was demonstrable in 70-100% of cases (using as criterion peak amplitudes 20% larger than those of the neighbors). The strongest responses were observed at the frequency closest to the alpha peak of the resting EEG. A secondary profile maximum was in the theta band. In 10 subjects, this maximum exceeded half the alpha peak (with an average of 72.4% of the alpha peak), while in the resting spectra, theta amplitudes were much lower than the alpha maxima. This responsiveness in theta activity seems to be characteristic of prepubertal and pubertal subjects. The profiles and resting EEG spectra showed a highly significant Pearson's correlation, with the peak in the theta band of the profiles being the main difference observed between them. The correlation coefficient was significantly correlated with the ratio of the maxima in the theta and alpha bands (R = -0.77, P<0.001). The correlation coefficient between profile and resting spectrum may be a useful indicator in screening methods used to reveal latent cerebral oscillators. Profiles for the second and third harmonics were correlated with those of the first harmonic (fundamental frequency), when considering the corresponding EEG frequencies. Peak frequencies in all three profiles were close to those of the individual's background alpha rhythm, and peak amplitudes in higher harmonics were not much lower than those of the fundamental frequency (mean values of 84 and 63%, for second and third harmonics, respectively).
Assuntos
Eletroencefalografia/métodos , Lobo Occipital/fisiologia , Estimulação Luminosa/métodos , Descanso/fisiologia , Adolescente , Criança , Feminino , Humanos , MasculinoRESUMO
A total of 4285 malignant neoplasms were recorded in Kingston and St. Andrew during the period 1993-1997, 2344 in females and 1941 in males. The crude incidence rate per 100,000 (CIR) for males was 121.6 and for females 129.2. Age standardized rates per 100,000 (ASR) were 156.7 and 176.7 for males and females respectively. In males, the leading sites for cancer were prostate (619 cases), bronchus (265 cases) and large bowel (144 cases) while in females the leading sites were breast (627 cases) cervix uteri (376 cases) and large bowel (204 cases). The crude and age standardized incidence rates have remained stable as compared to those for the previous five year period (1998-1992). The leading sites for both males and females have also been maintained in the same order but there was a marked increase in prostate cancer (ASR 56.4 versus 36). Invasive cervical cancer has shown no significant change in incidence (ASR 25.2 versus 26.3) but the rate for in-situ cancers has decreased (ASR 27.4 versus 43.8). The incidence of cancer of the female breast has remained relatively stable (ASR 43.2 versus 47.1). The trends exhibited by both prostate cancer and in-situ cervical cancer probably represent the influence of screening methods for prostate cancer and ablative management for low grade dysplastic lesions of the cervix uteri respectively.
Assuntos
Neoplasias/epidemiologia , Sistema de Registros/estatística & dados numéricos , Adulto , Distribuição por Idade , Idoso , Neoplasias da Mama/epidemiologia , Feminino , Humanos , Incidência , Neoplasias Intestinais/epidemiologia , Jamaica/epidemiologia , Neoplasias Pulmonares/epidemiologia , Masculino , Pessoa de Meia-Idade , Neoplasias da Próstata/epidemiologia , Neoplasias do Colo do Útero/epidemiologiaRESUMO
The coherence function has been widely applied in quantifying the degree of synchronism between electroencephalogram (EEG) signals obtained from different brain regions. However, when applied to investigating synchronization resulting from rhythmic stimulation, misleading results can arise from the high correlation of background EEG activity. We, thus propose a modified measure, which emphasizes the synchronized stimulus responses and reduces the influence of the spontaneous EEG activity. Critical values for this estimator are derived and tested in Monte Carlo simulations. The effectiveness of the method is illustrated on data recorded from 12 young normal subjects during rhythmic photic stimulation.
Assuntos
Eletroencefalografia/métodos , Processamento de Sinais Assistido por Computador , Adolescente , Criança , Sincronização Cortical , Humanos , Método de Monte Carlo , Estimulação LuminosaRESUMO
Cross-correlation between cerebral blood flow (CBF) and background EEG activity can indicate the integrity of CBF control under changing metabolic demand. The difficulty of obtaining long, continuous recordings of good quality for both EEG and CBF signals in a clinical setting is overcome, in the present work, by an algorithm that allows the cross-correlation function (CCF) to be estimated when the signals are interrupted by segments of missing data. Methods are also presented to test the statistical significance of the CCF obtained in this way and to estimate the power of this test, both based on Monte Carlo simulations. The techniques are applied to the time-series given by the mean CBF velocity (recorded by transcranial Doppler) and the mean power of the EEG signal, obtained in 1 s intervals from nine sleeping neonates. The peak of the CCF is found to be low (< or = 0.35), but reached statistical significance (p < 0.05) in five of the nine subjects. The CCF further indicates a delay of 4-6s between changes in EEG and CBF velocity. The proposed signal-analysis methods prove effective and convenient and can be of wide use in dealing with the common problem of missing samples in biological signals.
Assuntos
Circulação Cerebrovascular/fisiologia , Eletroencefalografia , Processamento de Sinais Assistido por Computador , Velocidade do Fluxo Sanguíneo/fisiologia , Humanos , Recém-Nascido , Método de Monte Carlo , Ultrassonografia Doppler TranscranianaRESUMO
Several studies have attributed the prevalence of low back pain (LBP) in helicopter pilots mainly to poor posture in-flight and whole-body vibration, with the latter hypothesis particularly related to a cyclic response of the erector spine (ES) muscle to vibration. This work aims to determine if helicopter vibration and the pilot's normal posture during flight have significant effects on the electromyogram (EMG) of the ES muscle. The bilateral surface EMG of the ES muscle at the L3 level was collected in 10 young pilots before and during a short flight in UH-50 helicopters. The vibration was monitored by a triaxial accelerometer fixed to the pilots' seat. Prior to the flight, the EMG was recorded for relaxed seated and standing postures with 0 degrees (P0) and 35 degrees (P35) of trunk flexion. The effect of the posture during the flight was tested by comparing left and right EMG (normalized with respect to P35). The in-flight muscle stress was evaluated by histograms of EMG activity, and compared to P0 values. Only one pilot in ten showed significant (p<0.05) correlation between the vibration and the EMG over cycles of vibration, and no consistent causal effect was found. The pilots' posture did not show significant asymmetric muscular activity, and low EMG levels were observed during most of the duration of the flight. The results do not provide evidence that LBP in helicopter pilots is caused by ES muscle stress in the conditions studied.
Assuntos
Medicina Aeroespacial , Dor Lombar/etiologia , Região Lombossacral/fisiopatologia , Músculo Esquelético/fisiologia , Doenças Profissionais/etiologia , Adulto , Aeronaves , Fenômenos Biomecânicos , Eletromiografia , Humanos , Dor Lombar/fisiopatologia , Militares , Movimento , Postura , Estresse Mecânico , Vibração/efeitos adversosRESUMO
A total of 4285 malignant neoplasms were recorded in Kingston and St. Andrew during the period 1993-1997, 2344 in females and 1941 in males. The crude incidence rate per 100,000 (CIR) for males was 121.6 and for females 129.2. Age standardized rates per 100,000 (ASR) were 156.7 and 176.7 for males and females respectively. In males, the leading sites for cancer were prostate (619 cases), bronchus (265 cases) and large bowel (144 cases) while in females the leading sites were breast (627 cases) cervix uteri (376 cases) and large bowel (204 cases). The crude and age standardized incidence rates have remained stable as compared to those for the previous five year period (1998-1992). The leading sites for both males and females have also been maintained in the same order but there was a marked increase in prostate cancer (ASR 56.4 versus 36). Invasive cervical cancer has shown no significant change in incidence (ASR 25.2 versus 26.3) but the rate for in-situ cancers has decreased (ASR 27.4 versus 43.8). The incidence of cancer of the female breast has remained relatively stable (ASR 43.2 versus 47.1). The trends exhibited by both prostate cancer and in-situ cervical cancer probably represent the influence of screening methods for prostate cancer and ablative management for low grade dysplastic lesions of the cervix uteri respectively.
Assuntos
Adulto , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Sistema de Registros , Neoplasias , Neoplasias da Mama , Neoplasias do Colo do Útero , Incidência , Neoplasias Intestinais , Jamaica , Neoplasias Pulmonares , Distribuição por Idade , Neoplasias da Próstata/epidemiologiaRESUMO
A total of 4285 malignant neoplasms were recorded in Kingston and St. Andrew during the period 1993-1997. 2344 in females and 1941 in males. The crude incidence rate per 100,000 (CIR) for males was 121.6 and for females 129.2. Age standardized rates per 100,0000 (ASR) were 156.7 and 176.7 for males and females respectively. In males, the leading sites for cancer were prostate (619 cases), bronchus (265 cases) and large bowel (144 cases) while in females the leading sites were breast (627 cases) cervix uteri (376 cases) and large bowel (204 cases). The crude and age standardized incidence rates have remained stable as compared to those for the previous five year period (1988-1992). The leading sites for both males and females have also been maintained in the same order but there was a marked increase in prostate cancer (ASR 56.4 versus 36). Invasive cervial cancer has shown no significant change in incidence (ASR 25.2 versus 26.3) but the rate for in-situ cancers has decreased (ASR 27.4 versus 43.8). The incidence of cancer of the female breast has remained relatively stable (ASR 43.2 versus 47.1). The trends exhibited by both prostate cancer and in-situ cervical cancer probably represent the influence of screening methods for prostate cancer and ablative management for low grade dysplastic lesions of the cervix uteri respectively.(Au)
Assuntos
Adulto , Criança , Pré-Escolar , Lactente , Pessoa de Meia-Idade , Idoso , Feminino , Humanos , Masculino , Recém-Nascido , Adolescente , Neoplasias/epidemiologia , Jamaica/epidemiologia , Neoplasias da Próstata/epidemiologia , Neoplasias Brônquicas/epidemiologia , Neoplasias do Colo do Útero/epidemiologia , Neoplasias da Mama/epidemiologia , Coleta de Dados , Incidência , Neoplasias Intestinais/epidemiologia , Neoplasias Pulmonares/epidemiologia , Sistema de Registros/estatística & dados numéricosRESUMO
A triagem auditiva, especialmente de recém nascidos (RN) que apresentem fatores de risco, tem sido recomendada por diversas entidades internacionais. O exame de potencial evocado auditivo de tronco cerebral (BERA - Brainstem Evoked Responses Audiometry) é atualmente considerado como referência para detecção do limiar auditivo em RNs, embora seja um procedimento demorado e de interpretação subjetiva. Para detecção objetiva da resposta auditiva em crianças foram aplicadas duas técnicas que utilizam a Transformada de Fourier: o CSM (Component Synchrony Meadure) e o MSC (Magnitude Squared Coherence). Sinais EEG de 32 crianças foram adquiridos durante BERA com estimulação por clicks a 20 Hz. Colheram-se ao todo 73 sinais EEG, cada um abrangendo 1024 estímulos de 85 dBHL. Destes 73 sinais, a interpretação clínica dos potenciais evocados indicou haver resposta (audição intacta) em 55. Um critério heurístico de detecção de resposta baseado em um conjunto de harmônicos da freqüência de estimulação (20 a 900 Hz) resultou em sensibilidade de 93 por cento e especificidade de 78 por cento para o MSC, e 98 por cento e 72 por cento para o CSM, respectivamente. Como o desempenho na detecção da surdez (resultado negativo) é o desejado, MSC seria mais adequado à detecção de resposta auditiva no EEG de crianças e recém-nascidos.
Assuntos
Audiometria de Resposta Evocada , Testes Auditivos , Potenciais Evocados Auditivos do Tronco Encefálico , Triagem NeonatalRESUMO
Techniques for objective response detection aim to identify the presence of evoked potentials based purely on statistical principles. They have been shown to be potentially more sensitive than the conventional approach of subjective evaluation by experienced clinicians and could be of great clinical use. Three such techniques to detect changes in an electroencephalogram (EEG) synchronous with the stimuli, namely, magnitude-squared coherence (MSC), the phase-synchrony measure (PSM) and the spectral F test (SFT) were applied to EEG signals of 12 normal subjects under conventional somatosensory pulse stimulation to the tibial nerve. The SFT, which uses only the power spectrum, showed the poorest performance, while the PSM, based only on the phase spectrum, gave results almost as good as those of the MSC, which uses both phase and power spectra. With the latter two techniques, stimulus responses were evident in the frequency range of 20-80 Hz in all subjects after 200 stimuli (5 Hz stimulus frequency), whereas for visual recognition at least 500 stimuli are usually applied. Based on these results and on simulations, the phase-based techniques appear promising for the automated detection and monitoring of somatosensory evoked potentials.
Assuntos
Eletroencefalografia , Potenciais Somatossensoriais Evocados/fisiologia , Monitorização Fisiológica , Análise Numérica Assistida por Computador , Processamento de Sinais Assistido por Computador , Adulto , Artefatos , Análise de Fourier , Humanos , Distribuição Normal , Variações Dependentes do Observador , Sensibilidade e Especificidade , Detecção de Sinal Psicológico , Nervo Tibial/fisiologiaRESUMO
Ecosystems are capital assets: When properly managed, they yield a flow of vital goods and services. Relative to other forms of capital, however, ecosystems are poorly understood, scarcely monitored, and--in many important cases--undergoing rapid degradation. The process of economic valuation could greatly improve stewardship. This potential is now being realized with innovative financial instruments and institutional arrangements.
Assuntos
Conservação dos Recursos Naturais/economia , Ecossistema , Austrália , Comércio , Costa Rica , Indústrias , Investimentos em SaúdeRESUMO
Theoretical considerations predict that amplification of expressed gene transcripts by reverse transcription-PCR using arbitrarily chosen primers will result in the preferential amplification of the central portion of the transcript. Systematic, high-throughput sequencing of such products would result in an expressed sequence tag (EST) database consisting of central, generally coding regions of expressed genes. Such a database would add significant value to existing public EST databases, which consist mostly of sequences derived from the extremities of cDNAs, and facilitate the construction of contigs of transcript sequences. We tested our predictions, creating a database of 10,000 sequences from human breast tumors. The data confirmed the central distribution of the sequences, the significant normalization of the sequence population, the frequent extension of contigs composed of existing human ESTs, and the identification of a series of potentially important homologues of known genes. This approach should make a significant contribution to the early identification of important human genes, the deciphering of the draft human genome sequence currently being compiled, and the shotgun sequencing of the human transcriptome.
Assuntos
Transcrição Gênica , Animais , Neoplasias da Mama/genética , DNA Complementar , Bases de Dados Factuais , Etiquetas de Sequências Expressas , Humanos , Dados de Sequência Molecular , Fases de Leitura Aberta , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
This is a longitudinal study of the postnatal development of lateralized rotational behavior. Hamsters (n = 75) were tested for spontaneous rotational behavior in cylindrical arenas, from P2 (P1 = day of birth) to P60. A daily laterality index was calculated for each animal, of which the averages and standard deviations were used to follow the animals' lateralized behavior. A strong variability between and within animals appeared throughout development, with a tendency to the right side in most animals, which declined after the first postnatal week. No oscillatory cycles were identified. To study patterns of development, the series were divided into four periods and the animals were separated into five groups. The laterality indexes of all four periods were significantly different between the groups. A total of 79% of the animals showed consistent behavior along development: either a preference to one side (20% left, 26% right), or no preference at all (33%). The remaining animals changed preference during development. Only a few animals remained strongly lateralized throughout the 60 days, most of them showing a slight, non-significant preference after P10. Results suggest an ontogenetic decrease in lateralization of this behavior that could in part be explained by the maturation of an interhemispheric regulatory system.