Activation induced changes in GABA: functional MRS at 7 T with MEGA-sLASER

Functional magnetic resonance spectroscopy (fMRS) has been used to assess the dynamic metabolic responses of the brain to a physiological stimulus non-invasively. However, only limited information on the dynamic functional response of γ-aminobutyric acid (GABA), the primary inhibitory neurotransmitter in the brain, is available. We aimed to measure the activation-induced changes in GABA unambiguously using a spectral editing method, instead of the conventional direct detection techniques used in previous fMRS studies. The Mescher-Garwood-semi-localised by adiabatic selective refocusing (MEGA-sLASER) sequence was developed at 7 T to obtain the time course of GABA concentration without macromolecular contamination. A significant decrease (−12±5%) in the GABA to total creatine ratio (GABA/tCr) was observed in the motor cortex during a period of 10 minutes of hand-clenching, compared to an initial baseline level (GABA/tCr = 0.11±0.02) at rest. An increase in the Glx (glutamate and glutamine) to tCr ratio was also found, which is in agreement with previous findings. In contrast, no significant changes in NAA/tCr and tCr were detected. With consistent and highly efficient editing performance for GABA detection and the advantage of visually identifying GABA resonances in the spectra, MEGA-sLASER is demonstrated to be an effective method for studying of dynamic changes in GABA at 7 T

Influences of glutamine administration on response selection and sequence learning: a randomized-controlled trial

Article / Letter to editorCognitieve Psychologi

Influences of glutamine administration on response selection and sequence learning: a randomized-controlled trial

Article / Letter to editorCognitieve Psychologi

The pathobiology of psychomotor slowing in psychosis: altered cortical excitability and connectivity.

Psychomotor slowing is a frequent symptom of schizophrenia. Short-interval intracortical inhibition assessed by transcranial magnetic stimulation demonstrated inhibitory dysfunction in schizophrenia. The inhibitory deficit results from additional noise during information processing in the motor system in psychosis. Here, we tested whether cortical inhibitory dysfunction was linked to psychomotor slowing and motor network alterations. In this cross-sectional study, we included 60 patients with schizophrenia and psychomotor slowing determined by the Salpêtrière Retardation Rating Scale, 23 patients without slowing and 40 healthy control participants. We acquired single and double-pulse transcranial magnetic stimulation effects from the left primary motor cortex, resting-state functional connectivity and diffusion imaging on the same day. Groups were compared on resting motor threshold, amplitude of the motor evoked potentials, as well as short-interval intracortical inhibition. Regression analyses calculated the association between motor evoked potential amplitudes or cortical inhibition with seed-based resting-state functional connectivity from the left primary motor cortex and fractional anisotropy at whole brain level and within major motor tracts. In patients with schizophrenia and psychomotor slowing, we observed lower amplitudes of motor evoked potentials, while the short-interval intracortical inhibition/motor evoked potentials amplitude ratio was higher than in healthy controls, suggesting lower cortical inhibition in these patients. Patients without slowing also had lower amplitudes of motor evoked potentials. Across the combined patient sample, cortical inhibition deficits were linked to more motor coordination impairments. In patients with schizophrenia and psychomotor slowing, lower amplitudes of motor evoked potentials were associated with lower fractional anisotropy in motor tracts. Moreover, resting-state functional connectivity between the primary motor cortex, the anterior cingulate cortex and the cerebellum increased with stronger cortical inhibition. In contrast, in healthy controls and patients without slowing, stronger cortical inhibition was linked to lower resting-state functional connectivity between the left primary motor cortex and premotor or parietal cortices. Psychomotor slowing in psychosis is linked to less cortical inhibition and aberrant functional connectivity of the primary motor cortex. Higher neural noise in the motor system may drive psychomotor slowing and thus may become a treatment target

Influences of glutamine administration on response selection and sequence learning: a randomized-controlled trial

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Investigating age-related changes in motor cortex excitability underlying fine

There is an age-related decline in fine motor control. Functional changes in the primary motor cortex may help explain the age-related decline in fine motor control. Both facilitatory and inhibitory processes in the motor cortex are important for the execution of movement. The aims of the current study were to systematically and comprehensively investigate age-related changes in motor cortical facilitation and inhibition and to investigate the role of these processes in fine motor control. In healthy younger (n = 26) and older adults (n = 21), fine motor control was measured using the Purdue pegboard and a unimanual circle task. Paired-pulse transcranial magnetic stimulation (TMS) was used to measure short-interval intracortical facilitation (SICF) and short-interval intracortical inhibition (SICI) acting on an intrinsic hand muscle (important for fine motor control). Results show no difference in SICF between younger and older adults. When SICI was measured using TMS parameters corresponding to high levels of SICF, older adults showed less SICI than younger adults. When SICI was measured using TMS parameters corresponding to low levels of SICF, there was no difference in SICI between younger and older adults. Older adults showed a relationship between SICI and fine motor control, suggesting greater SICI results in better performance on fine motor control tests. Together findings suggest a complex interaction between the balance of facilitation and inhibition, and that this is affected by age and influences fine motor control. Keywords: aging, fine motor control, primary motor cortex, transcranial magnetic stimulation, short-interval intracortical facilitation, short-interval intracortical inhibitio

Developmental coordination disorder

Developmental coordination disorder is a neurodevelopmental disorder primarily characterised by motor coordination significantly below that expected for an individual’s age, in the absence of neurological or intellectual deficits (American Psychiatric Association, 2013). This poorer coordination has a significant negative impact on activities of daily living and individual well-being. While it is understood that the root cause of DCD likely lies in the development of the brain, there is presently no consensus into the precise nature of this neurological basis of the disorder. The aim of this chapter is to outline the current understanding of DCD from a developmental cognitive neuroscience perspective. It begins by briefly describing the presentation of DCD, before moving on to outline neuroscientific hypotheses and the evidence supporting them. The chapter concludes with an exploration of current issues in the field and potential future directions for research into the developmental cognitive neuroscience of DCD