Dynamic changes of resting state connectivity related to the acquisition of a lexico-semantic skill.

The brain undergoes adaptive changes during learning. Spontaneous neural activity has been proposed to play an important role in acquiring new information and/or improve the interaction of task related brain regions. A promising approach is the investigation of resting state functional connectivity (rs-fc) and resting state networks, which rely on the detection of interregional correlations of spontaneous BOLD fluctuations. Using Morse Code (MC) as a model to investigate neural correlates of lexico-semantic learning we sought to identify patterns in rs-fc that predict learning success and/or undergo dynamic changes during a 10-day training period. Thirty-five participants were trained to decode twelve letters of MC. Rs-fMRI data were collected before and after the training period and rs-fc analyses were performed using a group independent component analysis. Baseline connectivity between the language-network (LANG) and the anterior-salience-network (ASN) predicted learning success and learning was associated with an increase in LANG - ASN connectivity. Furthermore, a disconnection between the default mode network (DMN) and the ASN as well as the left fusiform gyrus, which is critically involved in MC deciphering, was observed. Our findings demonstrate that rs-fc can undergo behaviorally relevant changes within 10 training days, reflecting a learning dependent modulation of interference between task specific networks.

Distinct patterns of functional and structural neuroplasticity associated with learning Morse code.

Learning is based on neuroplasticity, i.e. on the capability of the brain to adapt to new experiences. Different mechanisms of neuroplasticity have been described, ranging from synaptic remodeling to changes in complex neural circuitry. To further study the relationship between changes in neural activity and changes in gray matter density associated with learning, we performed a combined longitudinal functional and morphometric magnetic resonance imaging (MRI) study on healthy volunteers who learned to decipher Morse code. We investigated 16 healthy subjects using functional MR imaging (fMRI) and voxel-based morphometry (VBM) before and after they had learned to decipher Morse code. The same set of Morse-code signals was presented to participants pre- and post-training. We found an increase in task-specific neural activity in brain regions known to be critically involved in language perception and memory, such as the inferior parietal cortex bilaterally and the medial parietal cortex during Morse code deciphering. Furthermore we found an increase in gray matter density in the left occipitotemporal region, extending into the fusiform gyrus. Anatomically neighboring sites of functional and structural neuroplasticity were revealed in the left occipitotemporal/inferior temporal cortex, but these regions only marginally overlapped. Implications of this morpho-functional dissociation for learning concepts are discussed.

Working memory performance is correlated with local brain morphology in the medial frontal and anterior cingulate cortex in fibromyalgia patients: structural correlates of pain-cognition interaction.

Fibromyalgia (FM) is a disorder of unknown aetiology, characterized by chronic widespread pain, stiffness and sleep disturbances. In addition, patients frequently complain of memory and attention deficits. Accumulating evidence suggests that FM is associated with CNS dysfunction and with an altered brain morphology. However, few studies have specifically investigated neuropsychological issues in patients suffering from FM. We therefore sought to determine whether neuropsychological deficits found in FM patients may be correlated with changes in local brain morphology specifically in the frontal, temporal or cingulate cortices. Twenty FM patients underwent extensive testing for potential neuropsychological deficits, which demonstrated significantly reduced working memory and impaired non-verbal long-term memory (limited to free recall condition) in comparison with normative data from age- and education-matched control groups. Voxel-based morphometry (VBM) was used to evaluate for potential correlations between test results and local brain morphology. Performance on non-verbal working memory was positively correlated with grey matter values in the left dorsolateral prefrontal cortex, whereas performance on verbal working memory (digit backward) was positively correlated with grey matter values in the supplementary motor cortex. On the other hand, pain scores were negatively correlated with grey matter values in the medial frontal gyrus. White matter analyses revealed comparable correlations for verbal working memory and pain scores in the medial frontal and prefrontal cortex and in the anterior cingulate cortex. Our data suggest that, in addition to chronic pain, FM patients suffer from neurocognitive deficits that correlate with local brain morphology in the frontal lobe and anterior cingulate gyrus, which may be interpreted to indicate structural correlates of pain-cognition interaction.

Striatal grey matter increase in patients suffering from fibromyalgia--a voxel-based morphometry study.

Fibromyalgia (FM), among other chronic pain syndromes, such as chronic tension type headache and atypical face pain, is classified as a so-called dysfunctional pain syndrome. Patients with fibromyalgia suffer from widespread, "deep" muscle pain and often report concomitant depressive episodes, fatigue and cognitive deficits. Clear evidence for structural abnormalities within the muscles or soft tissue of fibromyalgia patients is lacking. There is growing evidence that clinical pain in fibromyalgia has to be understood in terms of pathological activity of central structures involved in nociception. We applied MR-imaging and voxel-based morphometry, to determine whether fibromyalgia is associated with altered local brain morphology. We investigated 20 patients with the diagnosis of primary fibromyalgia and 22 healthy controls. VBM revealed a conspicuous pattern of altered brain morphology in the right superior temporal gyrus (decrease in grey matter), the left posterior thalamus (decrease in grey matter), in the left orbitofrontal cortex (increase in grey matter), left cerebellum (increase in grey matter) and in the striatum bilaterally (increase in grey matter). Our data suggest that fibromyalgia is associated with structural changes in the CNS of patients suffering from this chronic pain disorder. They might reflect either a consequence of chronic nociceptive input or they might be causative to the pathogenesis of fibromyalgia. The affected areas are known to be both, part of the somatosensory system and part of the motor system.

Differences in cortical activation during smooth pursuit and saccadic eye movements following cerebellar lesions.

Current evidence supports the proposal that the cerebellum mediates the activity of other brain areas involved in the control of eye movements. Most of the evidence so far has concentrated on the vermis and flocculi as the cerebellar agents of oculomotor control. But there is also evidence for an involvement of the cerebellar hemispheres in eye movement control. Straube et al. (Ann Neurol 42:891-898, 1997) showed that lateral hemispheric lesions affect initiation of smooth pursuit (SPEM) and saccadic eye movements. Ron and Robinson (J Neurophysiol 36:1004-1022, 1973) evoked smooth pursuit and saccadic eye movements by electrical stimulation of crus I and II, as well as in the dentate nuclei of the monkey. Functional MRI studies also provide evidence that the cerebellar hemispheres play a significant role in SPEM and saccadic eye movements. To clarify the role of the cerebral hemispheres in eye movement control we compared the eye movement related blood oxygen level dependent (BOLD) responses of 12 patients with cerebellar lesions due to stroke with those of an aged-matched healthy control group. Six patients showed oculomotor abnormalities such as dysmetric saccades or saccadic SPEM during the experiment. The paradigm consisted of alternating blocks of fixation, visually guided saccades and visually guided SPEM. A nonparametric random-effects group analysis showed a degraded pattern of activation in the patient group during the performance of SPEM and saccadic eye movements in posterior parietal areas putatively containing the parietal eye fields.

Impaired working-memory after cerebellar infarcts paralleled by changes in BOLD signal of a cortico-cerebellar circuit.

A considerable body of evidence supports the notion that cerebellar lesions lead to neuropsychological deficits, including impairments in working-memory, executive tasks and verbal fluency. Studies employing functional magnetic resonance imaging (fMRI) and anatomical tracing in primates provide evidence for a cortico-cerebellar circuitry as the functional substrate of working-memory. The present fMRI study explores the activation pattern during an n-back working-memory task in patients with an isolated cerebellar infarct. To determine each patient's cognitive impairment, neuropsychological tests of working-memory and attention were carried out. We conducted fMRI in nine patients and nine healthy age-matched controls while they performed a 2-back task in a blocked-design. In both groups we found bilateral activations in a widespread cortico-cerebellar network, consisting of the ventrolateral prefrontal cortex (BA 44, 45), dorsolateral prefrontal cortex (BA 9, 46), parietal cortex (BA 7, 40), pre-supplementary motor area (BA 6) anterior cingulate (BA 32). Relative to healthy controls, patients with isolated cerebellar infarcts demonstrated significantly more pronounced BOLD-activations in the precuneus and the angular gyrus during the 2-back task. The significant increase in activation in the posterior parietal areas of the cerebellar patients could be attributed to a compensatory recruitment to maintain task performance. We conclude that cerebellar lesions affect remote cortical regions that are part of a putative cortico-cerebellar network.

Cognitive changes after epilepsy surgery in the posterior cortex.

OBJECTIVE: The relationship between the posterior cortex and cognitive functions is still a relatively open field. There are no studies on populations in which functions of posterior structures were examined by a standardised neuropsychological examination before and after posterior resections. Changes in cognitive performance are regularly observed after epilepsy surgery in the temporal lobe. However, information about neuropsychological impairments after resections in the posterior cortex is poor, owing to the relatively low proportion of cortical resections in this area. METHODS: We retrospectively studied changes in cognition in the neuropsychological data of 28 patients prior to and 6 months after posterior cortical resections. RESULTS: Cognition significantly showed differences in performance intelligence quotient compared with verbal intelligence quotient. Post-operative verbal intelligence consistently increased, whereas performance intelligence decreased. There was no effect regarding the lesion side, continuation of seizures, or reduction of visual field after surgery. Epilepsy surgery in this area did not lead to significant differences in general intelligence after surgery. CONCLUSION: Functions of posterior areas could be described by standardised neuropsychological measures. Posterior regions contribute to explicit attentional and visuoconstructional abilities. Epilepsy surgery in the posterior cortex bears no risk for substantial decline in general cognition although some discrete impairment in performance intelligence may occur.

Language lateralization by Wada test and fMRI in 100 patients with epilepsy.

Comparing the determination of language dominance using fMRI with results of the Wada test in 100 patients with different localization-related epilepsies, the authors found 91% concordance between both tests. The overall rate of false categorization by fMRI was 9%, ranging from 3% in left-sided temporal lobe epilepsy (TLE) to 25% in left-sided extratemporal epilepsy. Language fMRI might reduce the necessity of the Wada test for language lateralization, especially in TLE.