Abstract
Aging is typically associated with substantial declines in motor functioning as well as robust changes in the functional organization of brain networks. Previous research has investigated ...the link between these 2 age-varying factors but examinations were predominantly limited to the functional organization within motor-related brain networks. Little is known about the relationship between age-related behavioral impairments and changes in functional organization at the whole brain (i.e., multiple network) level. This knowledge gap is surprising given that the decreased segregation of brain networks (i.e., increased internetwork connectivity) can be considered a hallmark of the aging process. Accordingly, we investigated the association between declines in motor performance across the adult lifespan (20-75 years) and age-related modulations of functional connectivity within and between resting state networks. Results indicated that stronger internetwork resting state connectivity observed as a function of age was significantly related to worse motor performance. Moreover, performance had a significantly stronger association with the strength of internetwork as compared with intranetwork connectivity, including connectivity within motor networks. These findings suggest that age-related declines in motor performance may be attributed to a breakdown in the functional organization of large-scale brain networks rather than simply age-related connectivity changes within motor-related networks.
In humans, some evidence suggests that there are two different types of spindles during sleep, which differ by their scalp topography and possibly some aspects of their regulation. To test for the ...existence of two different spindle types, we characterized the activity associated with slow (11-13 Hz) and fast (13-15 Hz) spindles, identified as discrete events during non-rapid eye movement sleep, in non-sleep-deprived human volunteers, using simultaneous electroencephalography and functional MRI. An activation pattern common to both spindle types involved the thalami, paralimbic areas (anterior cingulate and insular cortices), and superior temporal gyri. No thalamic difference was detected in the direct comparison between slow and fast spindles although some thalamic areas were preferentially activated in relation to either spindle type. Beyond the common activation pattern, the increases in cortical activity differed significantly between the two spindle types. Slow spindles were associated with increased activity in the superior frontal gyrus. In contrast, fast spindles recruited a set of cortical regions involved in sensorimotor processing, as well as the mesial frontal cortex and hippocampus. The recruitment of partially segregated cortical networks for slow and fast spindles further supports the existence of two spindle types during human non-rapid eye movement sleep, with potentially different functional significance.
In addition to classical visual effects, light elicits nonvisual brain responses, which profoundly influence physiology and behavior. These effects are mediated in part by melanopsin-expressing ...light-sensitive ganglion cells that, in contrast to the classical photopic system that is maximally sensitive to green light (550 nm), is very sensitive to blue light (470–480 nm). At present, there is no evidence that blue light exposure is effective in modulating nonvisual brain activity related to complex cognitive tasks. Using functional magnetic resonance imaging, we show that, while participants perform an auditory working memory task, a short (18 min) daytime exposure to blue (470 nm) or green (550 nm) monochromatic light (3 × 1013 photons/cm2/s) differentially modulates regional brain responses. Blue light typically enhanced brain responses or at least prevented the decline otherwise observed following green light exposure in frontal and parietal cortices implicated in working memory, and in the thalamus involved in the modulation of cognition by arousal. Our results imply that monochromatic light can affect cognitive functions almost instantaneously and suggest that these effects are mediated by a melanopsin-based photoreceptor system.
Abstract
The functional interaction between hippocampo- and striato-cortical regions during motor sequence learning is essential to trigger optimal memory consolidation. Based on previous evidence ...from other memory domains that stress alters the balance between these systems, we investigated whether exposure to stress prior to motor learning modulates motor memory processes. Seventy-two healthy young individuals were exposed to a stressful or nonstressful control intervention prior to training on a motor sequence learning task in a magnetic resonance imaging (MRI) scanner. Consolidation was assessed with an MRI retest after a sleep episode. Behavioral results indicate that stress prior to learning did not influence motor performance. At the neural level, stress induced both a larger recruitment of sensorimotor regions and a greater disengagement of hippocampo-cortical networks during training. Brain-behavior regression analyses showed that while this stress-induced shift from (hippocampo-)fronto-parietal to motor networks was beneficial for initial performance, it was detrimental for consolidation. Our results provide the first experimental evidence that stress modulates the neural networks recruited during motor memory processing and therefore effectively unify concepts and mechanisms from diverse memory fields. Critically, our findings suggest that intersubject variability in brain responses to stress determines the impact of stress on motor learning and subsequent consolidation.
Aerobic exercise training (AET) has been shown to provide general health benefits, and to improve motor behaviours in particular, in individuals with Parkinson's disease (PD). However, the influence ...of AET on their motor learning capacities, as well as the change in neural substrates mediating this effect remains to be explored.
In the current study, we employed functional Magnetic Resonance Imaging (fMRI) to assess the effect of a 3-month AET program on the neural correlates of implicit motor sequence learning (MSL).
20 healthy controls (HC) and 19 early PD individuals participated in a supervised, high-intensity, stationary recumbent bike training program (3 times/week for 12 weeks). Exercise prescription started at 20 min (+ 5 min/week up to 40 min) based on participant's maximal aerobic power. Before and after the AET program, participants' brain was scanned while performing an implicit version of the serial reaction time task.
Brain data revealed pre-post MSL-related increases in functional activity in the hippocampus, striatum and cerebellum in PD patients, as well as in the striatum in HC individuals. Importantly, the functional brain changes in PD individuals correlated with changes in aerobic fitness: a positive relationship was found with increased activity in the hippocampus and striatum, while a negative relationship was observed with the cerebellar activity.
Our results reveal, for the first time, that exercise training produces functional changes in known motor learning related brain structures that are consistent with improved behavioural performance observed in PD patients. As such, AET can be a valuable non-pharmacological intervention to promote, not only physical fitness in early PD, but also better motor learning capacity useful in day-to-day activities through increased plasticity in motor related structures.
The specific neural processes underlying vicarious pain perception are not fully understood. In this functional imaging study, 20 participants viewed pain-evoking or neutral images displaying either ...sensory or emotional-communicative information. The pain images displayed nociceptive agents applied to the hand or the foot (sensory information) or facial expressions of pain (emotional-communicative information) and were matched with their neutral counterparts. Combining pain-evoking and neutral images showed that body limbs elicited greater activity in sensory motor regions, whereas midline frontal and parietal cortices and the amygdala responded more strongly to faces. The pain-evoking images elicited greater activity than their neutral counterparts in the bilateral inferior frontal gyrus (IFG), the left inferior parietal lobule (IPL) and the bilateral extrastriate body area. However, greater pain-related activity was observed in the rostral IPL when images depicted a hand or foot compared to a facial expression of pain, suggesting a more specific involvement in the coding of somato-motor information. Posterior probability maps enabling Bayesian inferences further showed that the anterior IFG (BA 45 and 47) was the only region showing no intrinsic probability of activation by the neutral images, consistent with a role in the extraction of the meaning of pain-related visual cues. Finally, inter-individual empathy traits correlated with responses in the supracallosal mid/anterior cingulate cortex and the anterior insula when pain-evoking images of body limbs or facial expressions were presented, suggesting that these regions regulated the observer's affective-motivational response independent from the channels from which vicarious pain is perceived.
► In this functional imaging study, we looked at how pain is perceived by others. ► We showed images displaying either sensory or emotional-communicative information. ► The inferior frontal gyrus responded specifically to the pain in the images. ► The inferior parietal lobule coded most strongly to the painful sensory information.
One of the most consistently activated regions during verbal short-term memory (STM) tasks is the left intraparietal sulcus (IPS). However, its precise role remains a matter of debate. While some ...authors consider the IPS to be a specific store for serial order information, other data suggest that it serves a more general function of attentional focalization. In the current fMRI experiment, we investigated these two hypotheses by presenting different verbal STM conditions that probed recognition for word identity or word order and by assessing functional connectivity of the left IPS with distant brain areas. If the IPS has a role of attentional focalization, then it should be involved in both order and item conditions, but it should be connected to different brain regions, depending on the neural substrates involved in processing the different types of information (order versus phonological/orthographic) to be remembered in the item and order STM conditions. We observed that the left IPS was activated in both order and item STM conditions but for different reasons: during order STM, the left IPS was functionally connected to serial/temporal order processing areas in the right IPS, premotor and cerebellar cortices, while during item STM, the left IPS was connected to phonological and orthographic processing areas in the superior temporal and fusiform gyri. Our data support a position considering that the left IPS acts as an attentional modulator of distant neural networks which themselves are specialized in processing order or language representations. More generally, they strengthen attention-based accounts of verbal STM.
Introduction Motor sequence learning refers to the process by which simple, stereotyped movement elements come to be performed effortlessly as a unitary sequence through multiple sessions of ...practice. Numerous studies have convincingly demonstrated that sleep (at night and daytime) plays a critical role in the consolidation of motor sequence learning. Yet there is no consensus regarding the sleep stages implicated in the consolidation of various motor skills. Mounting evidence indicates that stage 2 sleep and spindle activity in particular, are critical for motor memory consolidation to occur, but most of those studies are only correlational in nature. In this study, we probed a possible causal role of stage 2 sleep in motor memory consolidation using an olfactory stimulation/motor sequence learning (MSL) conditioning protocol. Materials and methods We conditioned a first group of participants ( n = 26) with a rose-like odor during learning of a sequence of finger movements, and re-exposed them to the odor during stage 2 sleep (ST2). A second group ( n = 26) was conditioned with the same odor while doing the MSL task and was re-exposed during REM sleep (REM). Finally, a third group ( n = 22) was not conditioned with the odor during the MSL task, but was exposed to it during stage 2 sleep (CTL). All subjects were re-tested in the morning 2 h after waking up. Performance was assessed by comparing the mean time to complete the four first blocs of retest to the four last blocs of training. Results Analysis of gains in performance revealed a significant interaction between the experimental manipulation and participant’s gender ((F(2,68) = 5.10, p = .01). Gains were significantly higher for men than women in the ST2 group ( p = .01). Also, results demonstrated that men in the ST2 group showed greater gains in performance than those in the CTL ( p = .01), but not the REM group ( p = .73). Men’s performance in REM group showed no significant difference to CTL group ( p = .20). Conclusion These findings not only show that it is possible to potentiate the consolidation of a motor memory trace during sleep but also strongly support the proposal that the association between stage 2 sleep and motor memory consolidation is critical. However, in regards to our results we can’t designate that effect to be specific to stage 2 sleep. Gender differences could be cause by several factors as (1) familiarity to the odor, (2) hormonal fluctuations (Genzel, 2012) or (3) differences in sleep and its characteristics during cuing. Acknowledgements Ovidiu Lungu, Bradley King, Arnaud Boré.
In this work, we consider the case of a strongly coupled dark/hidden sector, which extends the Standard Model (SM) by adding an additional non-Abelian gauge group. These extensions generally contain ...matter fields, much like the SM quarks, and gauge fields similar to the SM gluons. We focus on the exploration of such sectors where the dark particles are produced at the LHC through a portal and undergo rapid hadronization within the dark sector before decaying back, at least in part and potentially with sizeable lifetimes, to SM particles, giving a range of possibly spectacular signatures such as emerging or semi-visible jets. Other, non-QCD-like scenarios leading to soft unclustered energy patterns or glueballs are also discussed. After a review of the theory, existing benchmarks and constraints, this work addresses how to build consistent benchmarks from the underlying physical parameters and present new developments for the
pythia
Hidden Valley module, along with jet substructure studies. Finally, a series of improved search strategies is presented in order to pave the way for a better exploration of the dark showers at the LHC.
Abstract To study age-related differences in neural activation during motor learning, functional magnetic resonance imaging (fMRI) scans were acquired from 25 young (mean 21.5 years old) and 18 older ...adults (mean 68.6 years old) while performing a bimanual coordination task before (pre-test) and after (post-test) a 2-week training intervention on the task. We studied whether task-related brain activity and training-induced brain activation changes differed between age groups, particularly with respect to the hyperactivation typically observed in older adults. Findings revealed that older adults showed lower performance levels than younger adults but similar learning capability. At the cerebral level, the task-related hyperactivation in parieto-frontal areas and underactivation in subcortical areas observed in older adults were not differentially modulated by the training intervention. However, brain activity related to task planning and execution decreased from pre- to post-test in temporo-parieto-frontal areas and subcortical areas in both age-groups, suggesting similar processes of enhanced activation efficiency with advanced skill level. Furthermore, older adults who displayed higher activity in prefrontal regions at pre-test demonstrated larger training-induced performance gains. In conclusion, in spite of prominent age-related brain activation differences during movement planning and execution, the mechanisms of learning-related reduction of brain activation appear to be similar in both groups. Importantly, cerebral activity during early learning can differentially predict the amplitude of the training-induced performance benefit between young and older adults.
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