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Our exhibit at the Royal Society Summer Science Exhibition (1-7 July 2019), will bring the topic of ‘Breathing with your Brain’ to life!
Neuroanatomical correlates of working memory performance in Neurofibromatosis 1.
INTRODUCTION: Neurofibromatosis 1 (NF1) is a single-gene disorder associated with cognitive impairments, particularly with deficits in working memory. Prior research indicates that brain structure is affected in NF1, but it is unclear how these changes relate to aspects of cognition. METHODS: 29 adolescents aged 11-17 years were compared to age and sex-matched controls. NF1 subjects were assessed using detailed multimodal measurements of working memory at baseline followed by a 3T MR scan. A voxel-based morphometry approach was used to estimate the total and regional gray matter(GM) volumetric differences between the NF1 and control groups. The working memory metrics were subjected to a principal component analysis (PCA) approach. RESULTS: The NF1 groups showed increased gray matter volumes in the thalamus, corpus striatum, dorsal midbrain and cerebellum bilaterally in the NF1 group as compared to controls. Principal component analysis on the working memory metrics in the NF1 group yielded three independent factors reflecting high memory load, low memory load and auditory working memory. Correlation analyses revealed that increased volume of posterior cingulate cortex, a key component of the default mode network (DMN) was significantly associated with poorer performance on low working memory load tasks. CONCLUSION: These results are consistent with prior work showing larger subcortical brain volumes in the NF1 cohort. The strong association between posterior cingulate cortex volume and performance on low memory load conditions supports hypotheses of deficient DMN structural development, which in turn may contribute to the cognitive impairments in NF1.
The dynamics of cortical GABA in human motor learning
The ability to learn novel motor skills is both a central part of our daily lives and can provide a model for rehabilitation after a stroke. However, there are still fundamental gaps in our understanding of the physiological mechanisms that underpin human motor plasticity. The acquisition of new motor skills is dependent on changes in local circuitry within the primary motor cortex (M1). This reorganisation has been hypothesised to be facilitated by a decrease in local inhibition via modulation of the neurotransmitter GABA, but this link has not been conclusively demonstrated in humans. Here, we used 7T MR Spectroscopy to investigate the dynamics of GABA concentrations in human M1 during the learning of an explicit, serial reaction time task. We observed a significant reduction in GABA concentration during motor learning that was not seen in an equivalent motor task lacking a learnable sequence, nor during a passive resting task of the same duration. No change in glutamate was observed in any group. Furthermore, baseline M1 GABA was strongly predictive of the degree of subsequent learning, such that greater inhibition was associated with poorer subsequent learning. This result suggests that higher levels of cortical inhibition may present a barrier that must be surmounted in order achieve an increase in M1 excitability, and hence encoding of a new motor skill. These results provide strong support for the mechanistic role of GABAergic inhibition in motor plasticity, raising questions regarding the link between population variability in motor learning and GABA metabolism in the brain.Funding informationJ.K.:Wellcome Trust Sir Henry Wellcome Postdoctoral Fellowship (204696/Z/16/Z). C.J.S.: Wellcome Trust/Royal Society Henry Dale Fellowships (102584/Z/13/Z).
Motor learning shapes temporal activity in human sensorimotor cortex
AbstractAlthough neuroimaging techniques have provided vital insights into the anatomical regions involved in motor learning, the underlying changes in temporal dynamics are not well understood. Using magnetoencephalography and Hidden Markov Modelling to model the dynamics of neural oscillations on data-adaptive time-scales, we detected specific changes in movement-related sensorimotor β-activity during practice of a self-paced sequential visuo-motor task. The behaviourally-relevant neural signature generalised to another motor task, emphasising the centrality of β-activity in motor plasticity.
Sleep loss disrupts the neural signature of successful learning
AbstractSleep supports memory consolidation as well as next-day learning. The influential “Active Systems” account of offline consolidation suggests that sleep-associated memory processing paves the way for new learning, but empirical evidence in support of this idea is scarce. Using a within-subjects (n = 30), crossover design, we assessed behavioral and electrophysiological indices of episodic encoding after a night of sleep or total sleep deprivation in healthy adults (aged 18–25 years) and investigated whether behavioral performance was predicted by the overnight consolidation of episodic associations from the previous day. Sleep supported memory consolidation and next-day learning as compared to sleep deprivation. However, the magnitude of this sleep-associated consolidation benefit did not significantly predict the ability to form novel memories after sleep. Interestingly, sleep deprivation prompted a qualitative change in the neural signature of encoding: Whereas 12–20 Hz beta desynchronization—an established marker of successful encoding—was observed after sleep, sleep deprivation disrupted beta desynchrony during successful learning. Taken together, these findings suggest that effective learning depends on sleep but not necessarily on sleep-associated consolidation.
Sleep Preserves Physiological Arousal in Emotional Memory
AbstractTraumatic experiences are associated with increased emotional arousal. Overnight consolidation strengthens the episodic content of emotional memories, but it is still unclear how sleep influences the associated arousal response. To investigate this question, we compared the effects of sleep and wake on psychophysiological and subjective reactivity during emotional memory retrieval. Participants provided affective ratings for negative and neutral images while heart rate deceleration (HRD) and skin conductance responses (SCRs) were monitored. Following a 12-hour delay of sleep or wakefulness, participants completed an image recognition task where HRD, SCRs and affective ratings were recorded again. HRD responses to previously-encoded (“old”) negative images were preserved after sleep but diminished after wakefulness. No between-group difference in HRD was observed for novel negative images at recognition, indicating that the effects of sleep for old images were not driven by a generalised overnight increase in visceral activity, or circadian factors. No significant effects of sleep were observed for SCRs or subjective ratings. Our data suggest that cardiac arousal experienced at the time of encoding is sensitive to plasticity-promoting processes during sleep in a similar manner to episodic aspects of emotional memory.