Biomedical subjects

Ana Solodkin

Publications and source records attributed to Ana Solodkin.

9 recordsLinked to original sources

PubMed2006

Age-related connectivity changes in fMRI data from children listening to stories.

The way humans comprehend narrative speech plays an important part in human development and experience. A group of 313 children with ages 5-18 were subjected to a large-scale functional magnetic resonance imaging (fMRI) study in order to investigate the neural correlates of auditory narrative comprehension. The results were analyzed to investigate the age-related brain activity changes involved in the narrative language comprehension circuitry. We found age-related differences in brain activity which may either reflect changes in local neuroplasticity (of the regions involved) in the developing brain or a more global transformation of brain activity related to neuroplasticity. To investigate this issue, Structural Equation Modeling (SEM) was applied to the results obtained from a group independent component analysis (Schmithorst, V.J., Holland, S.K., et al., 2005. Cognitive modules utilized for narrative comprehension in children: a functional magnetic resonance imaging study. NeuroImage) and the age-related differences were examined in terms of changes in path coefficients between brain regions. The group Independent Component Analysis (ICA) had identified five bilateral task-related components comprising the primary auditory cortex, the mid-superior temporal gyrus, the most posterior aspect of the superior temporal gyrus, the hippocampus, the angular gyrus and the medial aspect of the parietal lobule (precuneus/posterior cingulate). Furthermore, a left-lateralized network (sixth component) was also identified comprising the inferior frontal gyrus (including Broca's area), the inferior parietal lobule, and the medial temporal gyrus. The components (brain regions) for the SEM were identified based on the ICA maps and the results are discussed in light of recent neuroimaging studies corroborating the functional segregation of Broca's and Wernicke's areas and the important role played by the right hemisphere in narrative comprehension. The classical Wernicke-Geschwind (WG) model for speech processing is expanded to a two-route model involving a direct route between Broca's and Wernicke's area and an indirect route involving the parietal lobe.

Adolescent↗

PubMed2006

Changes in the amplitude and timing of the hemodynamic response associated with prepulse inhibition of acoustic startle.

Disruption of the early stages of information processing in limbic brain circuits may underlie symptoms of severe neuropsychiatric disorders. Prepulse inhibition of acoustic startle (PPI) is diminished in many of these disorders and may reflect the disruption of this CNS function. PPI is associated with brain activity in many of the same regions in humans as it is in laboratory animals, suggesting that neuroimaging studies in humans may help localize deficits that can then be elucidated in animal models. In this article, we employed a rapid presentation event-related design during continuous EPI BOLD scanning to examine hemodynamic response functions (HRFs) associated with PPI. Fourteen healthy participants listened to 100 pulse alone and 100 prepulse combined with pulse (prepulse-pulse) trials. PPI is the normalized difference in the startle response to the two trial types. Following the prepulse-pulse trials, the amplitudes of the HRFs in auditory cortices and in the anterior insula were increased, while in the cerebellum, thalamus and anterior cingulate, they were decreased, relative to the pulse alone trials. In addition, the timing of the prepulse-pulse responses was delayed in the auditory cortices, anterior insula and cerebellum. Finally, PPI measured outside the scanner was predicted by the difference in BOLD responses between trial types in the anterior insula and in the cerebellum. The results suggest that prepulse inhibition, and by extension early stages of information processing, modulate both the amplitude as well as timing of neural activity.

Acoustic Stimulation↗

PubMed2006

Complex motor function in humans: validating and extending the postulates of Alexandr R. Luria.

OBJECTIVE: We used functional brain imaging to reevaluate Luria's postulates and to elaborate the neural circuitry underlying performance of complex motor tasks. BACKGROUND: The anatomic organization and physiologic functioning of the normal human motor system have great significance for understanding motor dysfunction and remediation in neurology. Working with victims of penetrating head injuries, noted Russian neuropsychologist Aleksandr R. Luria designed several tests of fine motor control to understand their difficulties with complex voluntary movements. This led to his postulates that such function involves the premotor cortices and their interaction with the parietal lobe. METHOD: Six healthy young adults performed the hand imitation, fist-scissors-gun, and piano key tasks during blood oxygen level-dependent functional magnetic resonance imaging at 3 T. RESULTS: All 3 tasks revealed activation of both premotor and parietal cortices. Furthermore, while hand Imitation relied more on the ventral premotor area and right parietal lobe, fist-scissors-gun and piano key relied more on the supplementary motor cortex. CONCLUSIONS: We postulate that differences in task-dependent activations across these tasks relate to degrees of sequential movement, pacing, and imitation. These results uphold Luria's original hypotheses, and extend that work by providing a further characterization of the motor areas involved in complex motor behaviors.

Adolescent↗

PubMed2006

Functions of the mirror neuron system: implications for neurorehabilitation.

Mirror neurons discharge during the execution of hand object-directed actions and during the observation of the same actions performed by other individuals. These neurons were first identified in the ventral premotor cortex (area F5) and later on in the inferior parietal lobule of monkey brain, thus constituting the mirror neuron system. More recently, mirror neurons for mouth object-directed actions have also been found in the monkey. Several pieces of experimental data demonstrate that a mirror neuron system devoted to hand, mouth, and foot actions is also present in humans. In the present paper we review the experimental evidence on the role of the mirror neuron system in action understanding, imitation learning of novel complex actions, and internal rehearsal (motor imagery) of actions. On the basis of features of the mirror neuron system and its role in action understanding and imitation, we discuss the possible use of action observation and imitation as an approach for systematic training in the rehabilitation of patients with motor impairment of the upper limb after stroke.

Animals↗

PubMed2005

Pathology of the insular cortex in Alzheimer disease depends on cortical architecture.

The insular cortex plays important roles in a variety of regulatory mechanisms ranging from visceral control and sensation to covert judgments regarding inner well-being. The dementia of Alzheimer disease (AD) often includes behavioral dyscontrol and visceral dysfunction not observed in other diseases affecting cognition. This could be related to autonomic instability and to loss of the sense of self, and pathologic changes within the insula may play essential roles. The pattern of insular pathology of 17 patients with AD was examined and the severity of pathology was compared with that of the entorhinal cortex (EC), a region involved early in AD with reciprocal connections to the insula. Thioflavin S staining and Alz-50 immunostaining revealed that the insula carries a heavy burden of pathology in AD. Neurofibrillary tangles (NFTs) were largely confined to the deep layers of the cortex, whereas neuritic plaques (NPs) were distributed throughout the cellular layers and subcortical white matter. The density of NFTs, but not NPs, was highly correlated with the degree of EC pathology. However, NFTs were not seen in the insula until EC pathology reached a relatively advanced level. The density of insular NFTs varied according to architectonic type, with agranular cortex most affected, dysgranular cortex less affected, and granular cortex least affected. Thus, the insula is often involved in AD, and some of the behavioral abnormalities in AD may reflect insular pathology.

Aged↗

PubMed2004

Fine modulation in network activation during motor execution and motor imagery.

Motor imagery, the 'mental rehearsal of motor acts without overt movements', involves either a visual representation (visual imagery, VI) or mental simulation of movement, associated with a kinesthetic feeling (kinetic imagery, KI). Previous brain imaging work suggests that patterns of brain activation differ when comparing execution (E) with either type of imagery but the functional connectivity of the participating networks has not been studied. Using functional magnetic resonance imaging (fMRI) and structural equation modeling, this study elucidates the inter-relationships among the relevant areas for each of the three motor behaviors. Our results suggest that networks underlying these behaviors are not identical, despite the extensive overlap between E and KI. Inputs to M1, which are facilitatory during E, have the opposite effect during KI, suggesting a physiological mechanism whereby the system prevents overt movements. Finally, this study highlights the role of the connection of superior parietal lobule to the supplementary motor area in both types of motor imagery.

Adult↗

PubMed2002

Functional lateralization of the human premotor cortex during sequential movements.

A neurological truism is that each side of the brain controls movements on the opposite side of the body. Yet some left hemisphere brain lesions cause bilateral impairment of complex motor function and/or ideomotor apraxia. We report that the left dorsal premotor cortex of normal right-handed people plays a fundamental role in sequential movement of both right and left hands. Subjects performed sequential finger movements during functional magnetic resonance imaging of the motor cortices. In right-handed subjects, the volume of activated dorsal premotor cortex showed a left hemispheric predominance during hand movements. We suggest that the observed left premotor dominance contributes to the lateralization found in lesion studies.

Adult↗

PubMedDate not supplied

On the road to automatic: dynamic aspects in the development of expertise.

One of the important steps on the road to becoming expert in a motor skill occurs when the individual can perform the movements in a seemingly effortless and automatic fashion. The authors review two lines of investigations, namely, fMRI and mathematically guided studies of the dynamics of skill acquisition, that suggest that this road to automatic involves two steps: (1) an increasing reliance on the self-regulatory aspects of the motor task, and (2) a minimization of the role of mechanisms based on intentionally directed corrective movements. The interplay between these two mechanisms implies that, at a given skill level, performance decreases whenever intention intervenes. The observation that psychological factors may be as important as mechanical repetition for the development of expertise has important implications for the design of neurorehabilitative strategies.

Humans↗

PubMedDate not supplied

Cortical plasticity during three-week motor skill learning.

The authors studied motor behavior and primary motor (M1) and somatosensory (S1) cortical representations of movement during hand motor skill acquisition over 3 weeks. During four functional MRI sessions 1 week apart, subjects performed simple movements of single fingers and wrist, and a sequential movement of the middle three fingers, contrasted with rest. Half of the subjects practiced the sequential movement, whereas the other half practiced a gross motor task (squeezing a sponge). In both groups, motor performance gradually improved both on the practiced sequence and also on unrelated tests of general hand performance. Similarly, gradual expansion of active M1 and S1 areas was observed with the practiced sequence and with the unpracticed single-finger and wrist movements. Motor practice enhanced overlaps and sharing of cortex (significantly more so in the fine-skill group), preserving somatotopy and the overall extent of the hand representations. Even a limited amount of practice on a complex task can thus lead to both specific and nonspecific improvements in behavior and to expansion of M1 and S1 movement representations. Finally, the extent of active M1 and S1 was significantly correlated with out-of-scanner performance on sequential finger movement and may reflect the current motor ability of the individual.

Adult↗