European Journal of Neuroscience最新文献

Timing and architecture of sleep are co-driven by circadian rhythms modulated by their major Zeitgeber light and darkness. In a natural environment, one is exposed to 3.000 lx (cloudy winter sky) to 100.000 lx (bright sunny sky). The aim of the study was to assess (1) habitual daytime light exposure in urban winter and (2) impact of daytime urban light on objective night-time sleep. Eleven healthy participants (mean age ± SD: 25.4 ± 2.8 years; 6 male) wore eyeglass frames continuously recording daytime illuminance levels vertically to the eye by mounted sensors (range: 1–40.000 lx) during four consecutive days in winter 2008 in Berlin, Germany. In-lab polysomnography was performed over two nights in nine participants. Median light exposure over 4 days was the following: full day 7:00–19:00 h: 23 lx (12–37 lx); morning 7:00–11:00 h: 81 lx (19–201 lx); midday 11:00–15:00 h: 68 lx (19–164 lx); afternoon 15:00–19:00 h: 22 lx (6–58 lx), resulting in only 36 min > 500 lx per day. Timing of daytime light intensity was significantly associated with subsequent sleep: lower midday illuminance with shorter REM latency (Rho = 0.817; p = 0.049) and earlier REM polarity (less prevalence of REM at end-of-sleep; Rho = 0.817; p = 0.049). Humans, living in an urban environment, appear to be exposed to extremely low light levels, which we named as ‘Living in Biological Darkness’. Most fascinating, physiology seems to adapt and responds to variation in light intensity on such low levels. Interestingly, the observed changes in sleep architecture with low light levels are reminiscent of those suspected to constitute biological markers of depression some 40–50 years ago.

Communication sound processing in mouse AC is lateralized. Both left and right AC are highly specialised and differ in auditory stimulus representation, functional connectivity and field topography. Previous studies have highlighted intracortical functional circuits that explain hemispheric stimulus preference. However, the underlying microstructure remains poorly understood. In this study, we examine structural lateralization of AC on the basis of immunohistochemically stained and tissue-cleared adult mouse brains (n = 11). We found hemispheric asymmetries of intracortical myelination, most prominently in layer 2/3, which featured more intercolumnar connections in the right AC. Furthermore, we found a larger structural asymmetry in the right AC. We also investigated sex differences. In male mice, myelination direction in the right AC is tilted to the anterior side. This pattern is inverted in female mice. However, the spatial distribution of neuronal cell bodies in the left and right AC along the laminar axis of the cortex was remarkably symmetric in all samples. These results suggest that basic developmentally defined structures such as cortical columns remain untouched by lateral specialisation, but more plastic myelinated axons show diverse hemispheric asymmetries. These asymmetries may contribute to specialisation on lateralized tasks such as vocal communication processing or specialisation on spectral or temporal complexity of stimuli.

Lightly touching a solid object reduces postural sway. Here, we determine the effect of artificially modifying haptic feedback for balance. Participants stood with their eyes closed, lightly gripping a manipulandum that moved synchronously with body sway to systematically enhance or attenuate feedback gain between +2 and −2, corresponding to motion in the same or opposite direction to the body, respectively. This intervention had a systematic effect on postural sway, which exhibited an asymmetric u-shape function with respect to haptic feedback gain. Sway was minimal around zero gain, corresponding to a static object. Sway increased slightly at gains below −0.25 but increased greatly at gains above +0.25. At +2, it was approximately double that of a no-touch condition. Mean interaction force between the hand and manipulandum remained < 0.9 N throughout, although it increased slightly at extreme gains. Cross-correlations between hand force and trunk position were highest during conditions of least sway, suggesting that higher quality haptic feedback is associated with greater sway reduction. We successfully replicated the sway behaviour using a feedback control model that attenuated haptic feedback signals when the discrepancy between haptic and proprioceptive signals reached a threshold. Our findings suggests the CNS can utilise augmented haptic feedback for balance, but only with relatively small changes to natural feedback gain. In healthy volunteers, it offers minimal benefit over a static object. Haptic feedback is therefore optimal when motion is physiologically realistic and subtle enough to be misinterpreted as self-motion.

Cannabinoid receptor 1 (CB1) regulates synaptic transmission through presynaptic receptors in nerve terminals, and its physiological roles are of clinical relevance. The cellular sources and synaptic targets of CB1-expressing terminals in the human cerebral cortex are undefined. We demonstrate a variable laminar pattern of CB1-immunoreactive axons and electron microscopically show that CB1-positive GABAergic terminals make type-2 synapses innervating dendritic shafts (69%), dendritic spines (20%) and somata (11%) in neocortical layers 2–3. Of the CB1-immunopositive GABAergic terminals, 25% were vesicular-glutamate-transporter-3 (VGLUT3)-immunoreactive, suggesting GABAergic/glutamatergic co-transmission on dendritic shafts. In vitro recorded and labelled VGLUT3 or CB1-positive GABAergic interneurons expressed cholecystokinin, vasoactive-intestinal-polypeptide and calretinin, had diverse firing, axons and dendrites, and included rosehip, neurogliaform and basket cells, but not double bouquet or axo-axonic cells. CB1-positive interneurons innervated pyramidal cells and GABAergic interneurons. Glutamatergic synaptic terminals formed type-1 synapses and some were positive for CB1 receptor with a distribution that appeared different from that in GABAergic terminals. From the sampled VGLUT3-positive terminals, 60% formed type-1 synapses with dendritic spines (80%) or shafts (20%) and 52% were also positive for VGLUT1, suggesting intracortical origin. Some VGLUT3-positive terminals were immunopositive for vesicular-monoamine-transporter-2, suggesting 5-HT/glutamate co-transmission. Overall, the results show that CB1 regulates GABA release mainly to dendritic shafts of both pyramidal cells and interneurons and predict CB1-regulated co-release of GABA and glutamate from single cortical interneurons. We also demonstrate the co-existence of multiple vesicular glutamate transporters in a select population of terminals probably originating from cortical neurons and innervating dendritic spines in the human cerebral cortex.

Previous research on resting muscles has shown that inter-pulse interval (IPI) duration influences transcranial magnetic stimulation (TMS) responses, which can introduce serious confounding variables into investigations if not accounted for. However, it is far less clear how IPI influences TMS responses in active muscles. Thus, the purpose of this study was to examine the relationship between IPI and corticospinal excitability during submaximal isometric elbow flexion. Corticospinal excitability to the biceps and triceps brachii was measured using motor evoked potentials (MEPs) elicited via TMS. Stimulation intensity was set to 120% of the biceps brachii's active motor threshold while participants produced 10% of their biceps' maximal muscle activity. TMS was delivered as separate trains of five stimulations, with experimental conditions differing between IPIs of 4, 6, 8, 10, 12 or 14 s. Results demonstrated that IPI had no influence on MEP amplitudes for either the biceps or triceps. However, when MEP amplitudes were expressed as a unitless ratio to pre-stimulus muscle activity, a main effect of time was found for the biceps; MEP amplitudes progressively decreased with successive stimulations (MEP 1:32.8 ± 5.9; MEP 5:27.7 ± 4.3, p < 0.05). These results suggest that IPI is unlikely to represent a confounding variable in TMS studies utilizing active contractions. However, studies looking to compare the amplitudes of single MEPs over time should be aware of the possibility that amplitudes may decrease with continuous stimulation. Future research should seek to examine even longer IPIs and explore the influence of higher stimulation intensities.

Conceptual review is a method to address issues of task comparability and task validity in cognitive neuroscience. Meta-analyses within cognitive neuroscience (CNS) as well as integration of neuroscientific findings with findings from adjacent disciplines both involve gathering studies that have purportedly investigated the same mental concept. After all, it is no use comparing apples and oranges. Tasks, and in particular the experimental contrasts implemented through tasks, determine whether studies are in fact comparable. Yet studies tend to be grouped together or kept apart based on the mental label researchers have applied and unfortunately, labels are an unreliable proxy for experimental contrasts. Different contrasts may receive the same label: ‘working memory’ studies rely on a variety of contrasts, derived from a variety of tasks. Vice versa, the same contrast may receive different labels: ‘task switching’ and ‘working memory’ studies can be exactly the same in terms of their experimental contrast. Label use thus obscures comparability problems. What is more, even when experimental contrasts are comparable, they may be invalid operationalizations of the mental label attached to them. In this paper, I introduce conceptual review as a method for task analysis. It can stand on its own or be combined with a cognitive ontology. Conceptual review applies philosophical strategies for analysing concepts to methodological choices in CNS studies, to uncover their conceptual implications. Conceptual review thus sheds light on the precise concept that was studied and thereby, on the comparability of CNS studies and the validity of tasks.

Target odorant detection in mixtures has been shown to become more difficult as the number of background odorants increases and falls below chance level in mixtures with 16 components. Our aim was to investigate target odorant detection in mixtures among healthy people and compare it between dysosmic patients and age- and gender-matched controls. Participants underwent extensive olfactory testing and performed two target odorant detection tasks. Eugenol (‘clove’) and phenylethanol (PEA, ‘rose’) were target odorants for all participants, whereas a third target was randomised. For each target odorant in task one (task two), there were four steps. Mixtures contained two (three) odorants in the first step and up to seven (eight) odorants in the fourth step. In each step, participants were asked to choose the sample with the target odorant from the three (two) jars presented. The study included 90 healthy people and 40 patients. As expected, probability of successful target odorant detection decreased as the number of odorants in the mixture increased. However, even when there were seven (eight) odorants in the mixture, around 50% (50%) of healthy people detected Eugenol and around 30% (40%) detected PEA. Furthermore, both distributions of successful target odorant detection differed from the expected binominal distribution of chance (p < 0.001). Patients performed worse at detecting Eugenol or PEA at each step than controls. Furthermore, there were significant positive correlations between task scores and olfactory function. In conclusion, target odorant detection is influenced by the target odorant, number of background odorants, and individual olfactory function.