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1.
Nature ; 603(7902): 654-660, 2022 03.
Artigo em Inglês | MEDLINE | ID: mdl-35296861

RESUMO

Magnetic resonance imaging (MRI) has transformed our understanding of the human brain through well-replicated mapping of abilities to specific structures (for example, lesion studies) and functions1-3 (for example, task functional MRI (fMRI)). Mental health research and care have yet to realize similar advances from MRI. A primary challenge has been replicating associations between inter-individual differences in brain structure or function and complex cognitive or mental health phenotypes (brain-wide association studies (BWAS)). Such BWAS have typically relied on sample sizes appropriate for classical brain mapping4 (the median neuroimaging study sample size is about 25), but potentially too small for capturing reproducible brain-behavioural phenotype associations5,6. Here we used three of the largest neuroimaging datasets currently available-with a total sample size of around 50,000 individuals-to quantify BWAS effect sizes and reproducibility as a function of sample size. BWAS associations were smaller than previously thought, resulting in statistically underpowered studies, inflated effect sizes and replication failures at typical sample sizes. As sample sizes grew into the thousands, replication rates began to improve and effect size inflation decreased. More robust BWAS effects were detected for functional MRI (versus structural), cognitive tests (versus mental health questionnaires) and multivariate methods (versus univariate). Smaller than expected brain-phenotype associations and variability across population subsamples can explain widespread BWAS replication failures. In contrast to non-BWAS approaches with larger effects (for example, lesions, interventions and within-person), BWAS reproducibility requires samples with thousands of individuals.


Assuntos
Mapeamento Encefálico , Encéfalo , Imageamento por Ressonância Magnética , Mapeamento Encefálico/métodos , Cognição , Conjuntos de Dados como Assunto , Humanos , Imageamento por Ressonância Magnética/métodos , Neuroimagem , Fenótipo , Reprodutibilidade dos Testes
2.
Cereb Cortex ; 34(1)2024 01 14.
Artigo em Inglês | MEDLINE | ID: mdl-38059685

RESUMO

In the perinatal period, reward and cognitive systems begin trajectories, influencing later psychiatric risk. The basal ganglia is important for reward and cognitive processing but early development has not been fully characterized. To assess age-related development, we used a measure of basal ganglia physiology, specifically brain tissue iron, obtained from nT2* signal in resting-state functional magnetic resonance imaging (rsfMRI), associated with dopaminergic processing. We used data from the Developing Human Connectome Project (n = 464) to assess how moving from the prenatal to the postnatal environment affects rsfMRI nT2*, modeling gestational and postnatal age separately for basal ganglia subregions in linear models. We did not find associations with tissue iron and gestational age [range: 24.29-42.29] but found positive associations with postnatal age [range:0-17.14] in the pallidum and putamen, but not the caudate. We tested if there was an interaction between preterm birth and postnatal age, finding early preterm infants (GA < 35 wk) had higher iron levels and changed less over time. To assess multivariate change, we used support vector regression to predict age from voxel-wise-nT2* maps. We could predict postnatal but not gestational age when maps were residualized for the other age term. This provides evidence subregions differentially change with postnatal experience and preterm birth may disrupt trajectories.


Assuntos
Recém-Nascido Prematuro , Nascimento Prematuro , Lactente , Feminino , Recém-Nascido , Humanos , Imageamento por Ressonância Magnética , Nascimento Prematuro/patologia , Ferro , Gânglios da Base/diagnóstico por imagem , Encéfalo/diagnóstico por imagem
3.
Neuroimage ; 267: 119831, 2023 02 15.
Artigo em Inglês | MEDLINE | ID: mdl-36586541

RESUMO

Converging evidence from both human neuroimaging and animal studies has supported a model of mesolimbic processing underlying reward learning behaviors, based on the computation of reward prediction errors. However, competing evidence supports human dopamine signaling in the basal ganglia as also contributing to the generation of higher order learning heuristics. Here, we present data from a large (N = 81, 18-30yo), multi-modal neuroimaging study using simultaneously acquired task fMRI, affording temporal resolution of reward system function, and PET imaging with [11C]Raclopride (RAC), assessing striatal dopamine (DA) D2/3 receptor binding, during performance of a probabilistic reward learning task. Both fMRI activation and PET DA measures showed ventral striatum involvement for signaling rewards. However, greater DA release was uniquely associated with learning strategies (i.e., learning rates) that were more task-optimal within the best fitting reinforcement learning model. This DA response was associated with BOLD activation of a network of regions including anterior cingulate cortex, medial prefrontal cortex, thalamus and posterior parietal cortex, primarily during expectation, rather than prediction error, task epochs. Together, these data provide novel, human in vivo evidence that striatal dopaminergic signaling interacts with a network of cortical regions to generate task-optimal learning strategies, rather than representing reward outcomes in isolation.


Assuntos
Dopamina , Motivação , Animais , Humanos , Dopamina/metabolismo , Imageamento por Ressonância Magnética/métodos , Corpo Estriado/fisiologia , Recompensa , Tomografia por Emissão de Pósitrons/métodos
5.
Psychol Med ; 52(12): 2299-2308, 2022 09.
Artigo em Inglês | MEDLINE | ID: mdl-33222723

RESUMO

BACKGROUND: Cognitive impairments, which contribute to the profound functional deficits observed in psychotic disorders, have found to be associated with abnormalities in trial-level cognitive control. However, neural tasks operate within the context of sustained cognitive states, which can be assessed with 'background connectivity' following the removal of task effects. To date, little is known about the integrity of brain processes supporting the maintenance of a cognitive state in individuals with psychotic disorders. Thus, here we examine background connectivity during executive processing in a cohort of participants with first-episode psychosis (FEP). METHODS: The following fMRI study examined background connectivity of the dorsolateral prefrontal cortex (DLPFC), during working memory engagement in a group of 43 patients with FEP, relative to 35 healthy controls (HC). Findings were also examined in relation to measures of executive function. RESULTS: The FEP group relative to HC showed significantly lower background DLPFC connectivity with bilateral superior parietal lobule (SPL) and left inferior parietal lobule. Background connectivity between DLPFC and SPL was also positively associated with overall cognition across all subjects and in our FEP group. In comparison, resting-state frontoparietal connectivity did not differ between groups and was not significantly associated with overall cognition, suggesting that psychosis-related alterations in executive networks only emerged during states of goal-oriented behavior. CONCLUSIONS: These results provide novel evidence indicating while frontoparietal connectivity at rest appears intact in psychosis, when engaged during a cognitive state, it is impaired possibly undermining cognitive control capacities in FEP.


Assuntos
Transtornos Psicóticos , Mapeamento Encefálico , Cognição , Humanos , Imageamento por Ressonância Magnética/métodos , Vias Neurais
6.
Int J Mol Sci ; 23(24)2022 Dec 13.
Artigo em Inglês | MEDLINE | ID: mdl-36555487

RESUMO

Converging lines of evidence suggest that an imbalance between excitation and inhibition is present in the dorsolateral prefrontal cortex (DLPFC) of schizophrenia (SCZ). Gamma-aminobutyric-acid (GABA) and, to a lesser extent, glutamate (Glu) abnormalities were reported in the DLPFC of SCZ patients, especially on the right hemisphere, by post-mortem studies. However, in vivo evidence of GABA, Glu, and Glu/GABA DLPFC abnormalities, particularly on the right side and the early stages of illness, is limited. In this preliminary study, we utilized 7-Tesla magnetic resonance spectroscopic imaging (MRSI) to investigate bilateral Glu/Creatine (Cre), GABA/Cre, and Glu/GABA in the DLPFC of sixteen first episode schizophrenia (FES), seventeen clinical high risk (CHR), and twenty-six healthy comparison (HC) subjects. FES and CHR had abnormal GABA/Cre and Glu/GABA in the right DLPFC (rDLPFC) compared with HC participants, while no differences were observed in the left DLPFC (lDLPFC) among the three groups. Furthermore, HC had higher Glu/GABA in rDLPFC compared to lDLPFC (R > L), whereas the opposite relationship (R < L) was observed in the DLPFC Glu/GABA of FES patients. Altogether, these findings indicate that GABA/Cre and Glu/GABA DLPFC alterations are present before illness manifestation and worsen in FES patients, thus representing a putative early pathophysiological biomarker for SCZ and related psychotic disorders.


Assuntos
Ácido Glutâmico , Esquizofrenia , Humanos , Córtex Pré-Frontal Dorsolateral , Esquizofrenia/diagnóstico por imagem , Córtex Pré-Frontal/diagnóstico por imagem , Imageamento por Ressonância Magnética , Ácido gama-Aminobutírico , Espectroscopia de Ressonância Magnética/métodos
7.
Cereb Cortex ; 30(3): 1548-1558, 2020 03 14.
Artigo em Inglês | MEDLINE | ID: mdl-31670797

RESUMO

Significant improvements in cognitive control occur from childhood through adolescence, supported by the maturation of prefrontal systems. However, less is known about the neural basis of refinements in cognitive control proceeding from adolescence to adulthood. Accumulating evidence indicates that integration between hippocampus (HPC) and prefrontal cortex (PFC) supports flexible cognition and has a protracted neural maturation. Using a longitudinal design (487 scans), we characterized developmental changes from 8 to 32 years of age in HPC-PFC functional connectivity at rest and its associations with cognitive development. Results indicated significant increases in functional connectivity between HPC and ventromedial PFC (vmPFC), but not dorsolateral PFC. Importantly, HPC-vmPFC connectivity exclusively predicted performance on the Stockings of Cambridge task, which probes problem solving and future planning. These data provide evidence that maturation of high-level cognition into adulthood is supported by increased functional integration across the HPC and vmPFC through adolescence.


Assuntos
Cognição/fisiologia , Hipocampo/crescimento & desenvolvimento , Vias Neurais/crescimento & desenvolvimento , Córtex Pré-Frontal/crescimento & desenvolvimento , Adolescente , Adulto , Mapeamento Encefálico , Criança , Feminino , Humanos , Imageamento por Ressonância Magnética/métodos , Masculino , Adulto Jovem
8.
Neuroimage ; 209: 116476, 2020 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-31875520

RESUMO

Adolescence is increasingly viewed as a sensitive period in the development of substance use disorders (SUDs). Neurodevelopmental 'dual-risk' theories suggest adolescent vulnerability to problematic substance use is driven by an overactive reward drive mediated by the striatum, and poor cognitive control mediated by the prefrontal cortex. To this end, there has been a growing number of neuroimaging studies examining cognitive and affective neural systems during adolescence for markers of vulnerability to problematic substance use. Here, we perform a coordinate-based meta-analysis on this emerging literature. Twenty-two task-based voxelwise fMRI studies with activation differences associated with substance use vulnerability, representative of approximately 1092 subjects, were identified through a systematic literature search (PubMed, Scopus) and coordinates of activation differences (N â€‹= â€‹190) were extracted. Adolescents were defined as 'at-risk' for problematic substance use based on a family history of SUD or through prospective prediction of substance use initiation or escalation. Multilevel kernel density analysis was used to identify the most consistent brain regions associated with adolescent substance use vulnerability. Across the included studies, substance use vulnerability was most reliably associated with activation differences in the striatum, where at-risk adolescents had hyper-activation in the dorsal subdivision (putamen). Follow-up analyses suggested striatal differences were driven by tasks sharing a motivational and/or reward component (e.g., monetary incentive) and common across subgroups of substance use risk (family history and prospective prediction studies). Analyses examining the role of psychiatric comorbidity revealed striatal activation differences were significantly more common in samples whose definition of substance use risk included cooccurring externalizing psychopathology. Furthermore, substance use risk meta-analytic results were no longer significant when excluding these studies, although this may reflect limitations in statistical power. No significant activation differences were observed in prefrontal cortex in any analysis. These results suggest striatal dysfunction, rather than prefrontal, may be a more primary neural feature of adolescent vulnerability to problematic substance use, possibly through a dimension of individual variability shared with externalizing psychopathology. However, our systematic literature search confirms this is still an emerging field. More studies, increased data sharing, and further quantitative integration are necessary for a comprehensive understanding of the neuroimaging markers of adolescent substance use risk.


Assuntos
Comportamento do Adolescente , Corpo Estriado , Função Executiva , Neuroimagem Funcional , Transtornos Relacionados ao Uso de Substâncias , Adolescente , Comportamento do Adolescente/fisiologia , Corpo Estriado/diagnóstico por imagem , Corpo Estriado/fisiopatologia , Função Executiva/fisiologia , Humanos , Transtornos Relacionados ao Uso de Substâncias/diagnóstico por imagem , Transtornos Relacionados ao Uso de Substâncias/epidemiologia , Transtornos Relacionados ao Uso de Substâncias/fisiopatologia
9.
Hum Brain Mapp ; 41(15): 4187-4199, 2020 10 15.
Artigo em Inglês | MEDLINE | ID: mdl-32652852

RESUMO

Pioneering studies have shown that individual correlation measures from resting-state functional magnetic resonance imaging studies can identify another scan from that same individual. This method is known as "connectotyping" or functional connectome "fingerprinting." We analyzed a unique dataset of 12-30 years old (N = 140) individuals who had two distinct resting state scans on the same day and again 12-18 months later to assess the sensitivity and specificity of fingerprinting accuracy across different time scales (same day, ~1.5 years apart) and developmental periods (youths, adults). Sensitivity and specificity to identify one's own scan was high (average AUC = 0.94), although it was significantly higher in the same day (average AUC = 0.97) than 1.5-years later (average AUC = 0.91). Accuracy in youths (average AUC = 0.93) was not significantly different from adults (average AUC = 0.96). Multiple statistical methods revealed select connections from the Frontoparietal, Default, and Dorsal Attention networks enhanced the ability to identify an individual. Identification of these features generalized across datasets and improved fingerprinting accuracy in a longitudinal replication data set (N = 208). These results provide a framework for understanding the sensitivity and specificity of fingerprinting accuracy in adolescents and adults at multiple time scales. Importantly, distinct features of one's "fingerprint" contribute to one's uniqueness, suggesting that cognitive and default networks play a primary role in the individualization of one's connectome.


Assuntos
Encéfalo/fisiologia , Conectoma , Rede de Modo Padrão/fisiologia , Desenvolvimento Humano/fisiologia , Rede Nervosa/fisiologia , Adolescente , Adulto , Encéfalo/diagnóstico por imagem , Criança , Conectoma/normas , Rede de Modo Padrão/diagnóstico por imagem , Feminino , Humanos , Individualidade , Estudos Longitudinais , Imageamento por Ressonância Magnética , Masculino , Rede Nervosa/diagnóstico por imagem , Sensibilidade e Especificidade , Adulto Jovem
10.
Exp Brain Res ; 237(10): 2665-2673, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31396645

RESUMO

Detection of 3D object-motion trajectories depends on the integration of two distinct visual cues: translational displacement and looming. Electrophysiological studies have identified distinct neuronal populations, whose activity depends on the precise motion cues present in the stimulus. This distinction, however, has been less clear in humans, and it is confounded by differences in the behavioral task being performed. We analyzed whole-brain fMRI, while subjects performed a common time-to-arrival task for objects moving along three trajectories: moving directly towards the observer (collision course), with trajectories parallel to the line of sight (passage course), and with trajectories perpendicular to the line of sight (gap closure). We found that there was substantial overlap in the pattern of activation associated with each of the three tasks, with differences among conditions limited to the human motion area (hMT+), which showed greater activation extent in the gap closure condition than for either collision or passage courses. These results support a common substrate for temporal judgments of an object's time-to-arrival, wherein the special cases of object motion directly toward, or perpendicular to, the observer represent two extremes within the broader continuum of 3D passage trajectories relative to the observer.


Assuntos
Sinais (Psicologia) , Percepção de Movimento/fisiologia , Análise e Desempenho de Tarefas , Córtex Visual/fisiologia , Feminino , Humanos , Julgamento/fisiologia , Masculino , Movimento (Física) , Estimulação Luminosa/métodos
11.
Exp Brain Res ; 237(9): 2137-2143, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31201472

RESUMO

Global auditory-spatial orienting cues help the detection of weak visual stimuli, but it is not clear whether crossmodal attention cues also enhance the resolution of visuospatial discrimination. Here, we hypothesized that if anywhere, crossmodal modulations of visual localization should emerge in the periphery where the receptive fields are large. Subjects were presented with trials where a Visual Target, defined by a cluster of low-luminance dots, was shown for 220 ms at 25°-35° eccentricity in either the left or right hemifield. The Visual Target was either Uncued or it was presented 250 ms after a crossmodal Auditory Cue that was simulated either from the same or the opposite hemifield than the Visual Target location. After a whole-screen visual mask displayed for 800 ms, a pair of vertical Reference Bars was presented ipsilateral to the Visual Target. In a two-alternative forced choice task, subjects were asked to determine which of these two bars was closer to the center of the Visual Target. When the Auditory Cue and Visual Target were hemispatially incongruent, the speed and accuracy of visual localization performance was significantly impaired. However, hemispatially congruent Auditory Cues did not improve the localization of Visual Targets when compared to the Uncued condition. Further analyses suggested that the crossmodal Auditory Cues decreased the sensitivity (d') of the Visual Target localization without affecting post-perceptual decision biases. Our results suggest that in the visual periphery, the detrimental effect of hemispatially incongruent Auditory Cues is far greater than the benefit produced by hemispatially congruent cues. Our working hypothesis for future studies is that auditory-spatial attention cues suppress irrelevant visual locations in a global fashion, without modulating the local visual precision at relevant sites.


Assuntos
Atenção/fisiologia , Percepção Auditiva/fisiologia , Percepção Espacial/fisiologia , Campos Visuais/fisiologia , Percepção Visual/fisiologia , Adulto , Sinais (Psicologia) , Retroalimentação Sensorial/fisiologia , Feminino , Humanos , Masculino , Adulto Jovem
12.
Neuroimage ; 169: 496-509, 2018 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-29253654

RESUMO

Given prior reports of adverse effects of cannabis use on working memory, an executive function with a protracted developmental course during adolescence, we examined associations between developmental patterns of cannabis use and adult working memory (WM) processes. Seventy-five adults with longitudinal assessments of cannabis use (60 with reported use, 15 with no reported use) and prenatal drug exposure assessment completed a spatial WM task during fMRI at age 28. All subjects passed a multi-drug urine screen on the day of testing and denied recreational drug use in the past week. A fast event-related design with partial trials was used to separate the BOLD response associated with encoding, maintenance, and retrieval periods of the WM task. Behavioral results showed that subjects who began using cannabis earlier in adolescence had longer reaction times (RT) than those with later initiation. Cannabis age of onset was further associated with reduced posterior parietal cortex (PPC) encoding BOLD activation, which significantly mediated age of onset WM RT associations. However, cannabis age of onset brain-behavior associations did not differ between groups with a single reported use and those with repeated use, suggesting age of onset effects may reflect substance use risk characteristics rather than a developmentally-timed cannabis exposure effect. Within repeated cannabis users, greater levels of total cannabis use were associated with performance-related increases in dorsolateral prefrontal cortex (DLPFC) activation during maintenance. This pattern of significant results remained unchanged with inclusion of demographic and prenatal measures as covariates. Surprisingly, however, at the group level, cannabis users generally performed better than participants who reported never using cannabis (faster RT, higher accuracy). We extend previous investigations by identifying that WM associations with cannabis age of onset may be primary to PPC stimulus encoding activity, while the amount of cannabis use is associated with DLPFC maintenance processes. Poorer performance of participants who reported never using cannabis and the consistency of cannabis age of onset associations across single and repeated users limit interpretation of direct developmental effects of cannabis on WM in adulthood.


Assuntos
Comportamento do Adolescente/fisiologia , Função Executiva/fisiologia , Neuroimagem Funcional/métodos , Uso da Maconha , Memória de Curto Prazo/fisiologia , Lobo Parietal/fisiologia , Córtex Pré-Frontal/fisiologia , Desempenho Psicomotor/fisiologia , Tempo de Reação/fisiologia , Adolescente , Adulto , Feminino , Humanos , Estudos Longitudinais , Imageamento por Ressonância Magnética , Masculino , Uso da Maconha/efeitos adversos , Lobo Parietal/diagnóstico por imagem , Córtex Pré-Frontal/diagnóstico por imagem , Memória Espacial/fisiologia , Adulto Jovem
13.
Cereb Cortex ; 26(5): 2167-77, 2016 May.
Artigo em Inglês | MEDLINE | ID: mdl-25814508

RESUMO

Paired-pulse transcranial magnetic stimulation (TMS) of the human motor cortex results in consecutive facilitatory motor-evoked potential (MEP) peaks in surface electromyography in intact humans. Here, we tested the effect of an incomplete cervical spinal cord injury (SCI) on early (first) and late (second and third) MEP peaks in a resting intrinsic finger muscle. We found that all peaks had decreased amplitude in SCI subjects compared with controls. The second and third peaks were delayed with the third peak also showing an increased duration. The delay of the third peak was smaller than that seen in controls at lower stimulation intensity, suggesting lesser influence of decreased corticospinal inputs. A mathematical model showed that after SCI the third peak aberrantly contributed to spinal motoneurone recruitment, regardless on the motor unit threshold tested. Temporal and spatial aspects of the late peaks correlated with MEP size and hand motor output. Thus, early and late TMS-induced MEP peaks undergo distinct modulation after SCI, with the third peak likely reflecting a decreased ability to summate descending volleys at the spinal level. We argue that the later corticospinal inputs on the spinal cord might be crucial for recruitment of motoneurones after human SCI.


Assuntos
Potencial Evocado Motor , Córtex Motor/fisiopatologia , Neurônios Motores/fisiologia , Tratos Piramidais/fisiopatologia , Traumatismos da Medula Espinal/fisiopatologia , Feminino , Dedos/inervação , Dedos/fisiologia , Humanos , Masculino , Pessoa de Meia-Idade , Modelos Neurológicos , Contração Muscular , Músculo Esquelético/inervação , Músculo Esquelético/fisiopatologia , Estimulação Magnética Transcraniana/métodos
14.
J Neurophysiol ; 115(1): 157-67, 2016 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-26467518

RESUMO

Cervical spinal cord injury (SCI) in humans typically damages both sides of the spinal cord, resulting in asymmetric functional impairments in the arms. Despite this well-accepted notion and the growing emphasis on the use of bimanual training strategies, how movement of one arm affects the motion of the contralateral arm after SCI remains unknown. Using kinematics and multichannel electromyographic (EMG) recordings we studied unilateral and bilateral reach-to-grasp movements to a small and a large cylinder in individuals with asymmetric arm impairments due to cervical SCI and age-matched control subjects. We found that the stronger arm of SCI subjects showed movement durations longer than control subjects during bilateral compared with unilateral trials. Specifically, movement duration was prolonged when opening and closing the hand when reaching for a large and a small object, respectively, accompanied by deficient activation of finger flexor and extensor muscles. In subjects with SCI interlimb coordination was reduced compared with control subjects, and individuals with lesser coordination between hands were those who showed prolonged times to open the hand. Although the weaker arm showed movement durations during bilateral compared with unilateral trials that were proportional to controls, the stronger arm was excessively delayed during bilateral reaching. Altogether, our findings demonstrate that during bilateral reach-to-grasp movements the more impaired arm has detrimental effects on hand opening and closing of the less impaired arm and that they are related, at least in part, to deficient control of EMG activity of hand muscles. We suggest that hand opening might provide a time to drive bimanual coordination adjustments after human SCI.


Assuntos
Lateralidade Funcional , Movimento , Traumatismos da Medula Espinal/fisiopatologia , Adulto , Idoso , Braço/fisiologia , Estudos de Casos e Controles , Feminino , Força da Mão , Humanos , Masculino , Pessoa de Meia-Idade , Músculo Esquelético/fisiologia
15.
Med Sci Monit ; 22: 1782-91, 2016 May 27.
Artigo em Inglês | MEDLINE | ID: mdl-27231114

RESUMO

BACKGROUND Understanding the dynamics of our surrounding environments is a task usually attributed to the detection of motion based on changes in luminance across space. Yet a number of other cues, both dynamic and static, have been shown to provide useful information about how we are moving and how objects around us move. One such cue, based on changes in spatial frequency, or scale, over time has been shown to be useful in conveying motion in depth even in the absence of a coherent, motion-defined flow field (optic flow). MATERIAL AND METHODS 16 right handed healthy observers (ages 18-28) participated in the behavioral experiments described in this study. Using analytical behavioral methods we investigate the functional specificity of this cue by measuring the ability of observers to perform tasks of heading (direction of self-motion) and 3D trajectory discrimination on the basis of scale changes and optic flow. RESULTS Statistical analyses of performance on the test-experiments in comparison to the control experiments suggests that while scale changes may be involved in the detection of heading, they are not correctly integrated with translational motion and, thus, do not provide a correct discrimination of 3D object trajectories. CONCLUSIONS These results have the important implication for the type of visual guided navigation that can be done by an observer blind to optic flow. Scale change is an important alternative cue for self-motion.


Assuntos
Percepção de Movimento/fisiologia , Fluxo Óptico/fisiologia , Adolescente , Adulto , Sinais (Psicologia) , Feminino , Voluntários Saudáveis , Humanos , Masculino , Movimento (Física) , Estimulação Luminosa , Visão Ocular/fisiologia , Adulto Jovem
16.
J Cogn Neurosci ; 26(6): 1266-82, 2014 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-24345177

RESUMO

We studied patient JS, who had a right occipital infarct that encroached on visual areas V1, V2v, and VP. When tested psychophysically, he was very impaired at detecting the direction of motion in random dot displays where a variable proportion of dots moving in one direction (signal) were embedded in masking motion noise (noise dots). The impairment on this motion coherence task was especially marked when the display was presented to the upper left (affected) visual quadrant, contralateral to his lesion. However, with extensive training, by 11 months his threshold fell to the level of healthy participants. Training on the motion coherence task generalized to another motion task, the motion discontinuity task, on which he had to detect the presence of an edge that was defined by the difference in the direction of the coherently moving dots (signal) within the display. He was much better at this task at 8 than 3 months, and this improvement was associated with an increase in the activation of the human MT complex (hMT(+)) and in the kinetic occipital region as shown by repeated fMRI scans. We also used fMRI to perform retinotopic mapping at 3, 8, and 11 months after the infarct. We quantified the retinotopy and areal shifts by measuring the distances between the center of mass of functionally defined areas, computed in spherical surface-based coordinates. The functionally defined retinotopic areas V1, V2v, V2d, and VP were initially smaller in the lesioned right hemisphere, but they increased in size between 3 and 11 months. This change was not found in the normal, left hemisphere of the patient or in either hemispheres of the healthy control participants. We were interested in whether practice on the motion coherence task promoted the changes in the retinotopic maps. We compared the results for patient JS with those from another patient (PF) who had a comparable lesion but had not been given such practice. We found similar changes in the maps in the lesioned hemisphere of PF. However, PF was only scanned at 3 and 7 months, and the biggest shifts in patient JS were found between 8 and 11 months. Thus, it is important to carry out a prospective study with a trained and untrained group so as to determine whether the patterns of reorganization that we have observed can be further promoted by training.


Assuntos
Infarto Cerebral/fisiopatologia , Plasticidade Neuronal , Lobo Occipital/fisiopatologia , Vias Visuais/fisiopatologia , Percepção Visual/fisiologia , Adulto , Mapeamento Encefálico , Infarto Cerebral/patologia , Infarto Cerebral/terapia , Humanos , Masculino , Lobo Occipital/patologia , Estimulação Luminosa , Psicofísica , Retina/patologia , Retina/fisiopatologia , Vias Visuais/patologia , Adulto Jovem
17.
Med Sci Monit ; 20: 1024-42, 2014 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-24947491

RESUMO

BACKGROUND: We compared the functional brain connectivity produced during resting-state in which subjects were not actively engaged in a task with that produced while they actively performed a visual motion task (task-state). MATERIAL AND METHODS: In this paper we employed graph-theoretical measures and network statistics in novel ways to compare, in the same group of human subjects, functional brain connectivity during resting-state fMRI with brain connectivity during performance of a high level visual task. We performed a whole-brain connectivity analysis to compare network statistics in resting and task states among anatomically defined Brodmann areas to investigate how brain networks spanning the cortex changed when subjects were engaged in task performance. RESULTS: In the resting state, we found strong connectivity among the posterior cingulate cortex (PCC), precuneus, medial prefrontal cortex (MPFC), lateral parietal cortex, and hippocampal formation, consistent with previous reports of the default mode network (DMN). The connections among these areas were strengthened while subjects actively performed an event-related visual motion task, indicating a continued and strong engagement of the DMN during task processing. Regional measures such as degree (number of connections) and betweenness centrality (number of shortest paths), showed that task performance induces stronger inter-regional connections, leading to a denser processing network, but that this does not imply a more efficient system as shown by the integration measures such as path length and global efficiency, and from global measures such as small-worldness. CONCLUSIONS: In spite of the maintenance of connectivity and the "hub-like" behavior of areas, our results suggest that the network paths may be rerouted when performing the task condition.


Assuntos
Mapeamento Encefálico/métodos , Encéfalo/fisiologia , Simulação por Computador , Imageamento por Ressonância Magnética/métodos , Rede Nervosa/fisiologia , Descanso/fisiologia , Análise e Desempenho de Tarefas , Feminino , Humanos , Masculino , Estimulação Luminosa , Adulto Jovem
18.
Curr Opin Behav Sci ; 582024 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-38826569

RESUMO

Cognitive flexibility exhibits dynamic changes throughout development, with different forms of flexibility showing dissociable developmental trajectories. In this review, we propose that an adolescent-specific mode of flexibility in the face of changing environmental contingencies supports the emergence of adolescent-to-adult gains in cognitive shifting efficiency. We first describe how cognitive shifting abilities monotonically improve from childhood to adulthood, accompanied by increases in brain state flexibility, neural variability, and excitatory/inhibitory balance. We next summarize evidence supporting the existence of a dopamine-driven, adolescent peak in flexible behavior that results in reward seeking, undirected exploration, and environmental sampling. We propose a neurodevelopmental framework that relates these adolescent behaviors to the refinement of neural phenotypes relevant to mature cognitive flexibility, and thus highlight the importance of the adolescent period in fostering healthy neurocognitive trajectories.

19.
Dev Cogn Neurosci ; 66: 101373, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38574406

RESUMO

Adolescence has been hypothesized to be a critical period for the development of human association cortex and higher-order cognition. A defining feature of critical period development is a shift in the excitation: inhibition (E/I) balance of neural circuitry, however how changes in E/I may enhance cortical circuit function to support maturational improvements in cognitive capacities is not known. Harnessing ultra-high field 7 T MR spectroscopy and EEG in a large, longitudinal cohort of youth (N = 164, ages 10-32 years old, 347 neuroimaging sessions), we delineate biologically specific associations between age-related changes in excitatory glutamate and inhibitory GABA neurotransmitters and EEG-derived measures of aperiodic neural activity reflective of E/I balance in prefrontal association cortex. Specifically, we find that developmental increases in E/I balance reflected in glutamate:GABA balance are linked to changes in E/I balance assessed by the suppression of prefrontal aperiodic activity, which in turn facilitates robust improvements in working memory. These findings indicate a role for E/I-engendered changes in prefrontal signaling mechanisms in the maturation of cognitive maintenance. More broadly, this multi-modal imaging study provides evidence that human association cortex undergoes physiological changes consistent with critical period plasticity during adolescence.

20.
Nat Commun ; 14(1): 6922, 2023 10 30.
Artigo em Inglês | MEDLINE | ID: mdl-37903830

RESUMO

Theories of human neurobehavioral development suggest executive functions mature from childhood through adolescence, underlying adolescent risk-taking and the emergence of psychopathology. Investigations with relatively small datasets or narrow subsets of measures have identified general executive function development, but the specific maturational timing and independence of potential executive function subcomponents remain unknown. Integrating four independent datasets (N = 10,766; 8-35 years old) with twenty-three measures from seventeen tasks, we provide a precise charting, multi-assessment investigation, and replication of executive function development from adolescence to adulthood. Across assessments and datasets, executive functions follow a canonical non-linear trajectory, with rapid and statistically significant development in late childhood to mid-adolescence (10-15 years old), before stabilizing to adult-levels in late adolescence (18-20 years old). Age effects are well captured by domain-general processes that generate reproducible developmental templates across assessments and datasets. Results provide a canonical trajectory of executive function maturation that demarcates the boundaries of adolescence and can be integrated into future studies.


Assuntos
Desenvolvimento Infantil , Função Executiva , Adulto , Humanos , Criança , Adolescente , Adulto Jovem , Desenvolvimento do Adolescente , Psicopatologia
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