It is known that small and large numbers facilitate left/right respectively (the SNARC effect). Recently, it has been proposed that numerical magnitude is just one example of a range of quantities, which have a common cognitive/neural representation. To investigate this proposition, response congruency effects were explored for stimuli which differed according to their: (a) numerical size, (b) physical size, (c) luminance, (d) conceptual size and (e) auditory intensity. In a series of experiments, groups of undergraduate participants made two-alternative forced choice discriminations with their left or right hands. There were clear interactions between magnitude and responding hand whereby right hand responses were faster for stimuli with (a) large numbers, (b) large physical size, (c) low luminance, and (d) a reference to large objects. There was no congruency effect for the auditory stimuli. The data demonstrate that the response congruency effect observed for numbers also occurs for a variety of other non-numerical visual quantities. These results support models of general magnitude representation and suggest that the association between magnitude and the left/right sides of space may not be related to culture and/or directional reading habits.
APOE4 and mild cognitive impairment (MCI) are major risk factors for Alzheimer's disease (AD) related neurodegenerative process. However, not every APOE4 carrier or individuals with MCI will phenoconvert to AD. Scaffolding Theory of Aging and Cognition suggests the possibility of protecting cognitive performance against the neurodegeneration-associated pathology by heavily involving frontal brain regions in old age. However, such hypotheses have not been tested among older adults at high risk for AD. Seventy-five individuals (mean age = 74) from the Alzheimer's Disease Neuroimaging Initiative (ADNI) were categorized into four subgroups based on their APOE4 (+ vs. -), and diagnostic (healthy control (HC) vs. MCI) statuses. Applying voxel-based approach, we analyzed fractional amplitude of low-frequency fluctuations (fALFF) of the resting-state fMRI data using a 2 (APOE4 status) × 2 (diagnostic status) ANCOVA, controlling for age. We also obtained measures of memory and cerebrospinal fluid levels of β-amyloid and tau. Four brain regions were identified (alphasim: p < 0.005, voxel > 8, corrected p< 0.01): L-insular, L-inferior frontal gyrus (IFG), R-precentral gyrus (PG), and R-superior parietal lobe (SPL) (see Fig. 1). Controlling for age, sex, education, APOE4 and diagnostic statuses, there were interaction effects between L-insular or L-IFG and β-amyloid on memory such that there was a significantly positive relationship between β-amyloid and memory among only individuals with low fALFF of L-insular or L-IFG. Such interaction effect was also found between β-amyloid and the functional connectivity of L-insular and L-IFG on memory.
Vision-based speed of processing (VSOP) training can result in broad cognitive improvements in older adults with amnestic mild cognitive impairment (aMCI). What remains unknown, however, is what neurophysiological mechanisms account for the observed training effect. Much of the work in this area has focused on the central nervous system, neglecting the fact that the peripheral system can contributes to changes of the central nervous system and vice versa.We examined the prospective relationship between an adaptive parasympathetic nervous system response to cognitive stimuli and VSOP training-induced plasticity.Twenty-one participants with aMCI (10 for VSOP training, and 11 for mental leisure activities (MLA) control) were enrolled. We assessed high-frequency heart rate variability (HF-HRV) during training sessions, and striatum-related neural networks and cognition at baseline and post-training.Compared to MLA, the VSOP group showed a significant U-shaped pattern of HF-HRV response during training, as well as decreases in connectivity strength between bilateral striatal and prefrontal regions. These two effects were associated with training-induced improvements in both the trained (attention and processing speed) and transferred (working memory) cognitive domains.This work provides novel support for interactions between the central and the peripheral nervous systems in relation to cognitive training, and motivates further studies to elucidate the causality of the observed link.
AIM To explore the action mechanism of traditional Chinese medicine (TCM) remedy in vivo , and to provide further experimental evidence for “qualitative and quantitative view”, the one of six key elements of “TCM syndrome and recipe” hypothesis. METHODS Boiled water extract of TCMR of Ligustici wallichii Franch was administered to the atria of healthy dogs and the dogs with coronary artery stenosis respectively. RESULTS Double-peak phenomena of concentration-time curve tetramethylpyrazine (TMP) in serum were observed; the second peak of TMP concentration in serum of the dog with coronary artery stenosis, which was related to the increase in coronary blood flow, was higher than that in the healthy dog ( P 0.05). CONCLUSION There is likely particular effects of physiological and pathophysiological state on the blood drug concentration of TCMR.
The dorsolateral prefrontal cortex (DLPFC) is considered to play a crucial role in many high-level functions, such as cognitive control and emotional regulation. Many studies have reported that the DLPFC can be activated during the processing of emotional information in tasks requiring working memory. However, it is still not clear whether modulating the activity of the DLPFC influences emotional perception in a detection task. In the present study, using transcranial direct-current stimulation (tDCS), we investigated (1) whether modulating the right DLPFC influences emotional face processing in a detection task, and (2) whether the DLPFC plays equal roles in processing positive and negative emotional faces. The results showed that anodal tDCS over the right DLPFC specifically facilitated the perception of positive faces, but did not influence the processing of negative faces. In addition, anodal tDCS over the right primary visual cortex enhanced performance in the detection task regardless of emotional valence. Our findings suggest, for the first time, that modulating the right DLPFC influences emotional face perception, especially faces showing positive emotion.
Transcranial direct current stimulation (tDCS) is a noninvasive neuromodulation technique that can modulate cortical excitability and behavioral performance. However, its effects on spontaneous low-frequency fluctuations of brain activity are still poorly understood. Here, we systematically investigated the frontopolar tDCS effects on resting-state brain activity and connectivity. Twelve healthy participants were recruited and received anode, cathode, and sham stimulation in a randomized order. Resting-state functional magnetic resonance imaging was performed before and after stimulation. Functional connectivity was calculated to examine tDCS effects within and beyond the frontopolar network. To assess the frequency-dependent changes of brain activity, fractional amplitude of low-frequency fluctuations (fALFF) was computed in the slow-4 (0.027-0.073 Hz) and slow-5 (0.01-0.027 Hz) bands. The results showed anodal tDCS-induced widespread connectivity reduction within and beyond the frontopolar network. Regardless of tDCS polarity, stimulation effect on fALFF was significantly larger in slow-5 band compared with the slow-4. Notably, anodal tDCS-induced connectivity changes were associated with pre-tDCS fALFF in slow-4 band, showing positive correlations in the frontal regions and negative correlations in the temporal regions. Our findings imply that tDCS-induced brain alterations may be frequency-dependent, and pre-tDCS regional brain activity could be used to predict post-tDCS connectivity changes.
The hippocampus regulates learning and memory formation and storage, while also playing a significant role in regulating the Hypothalamic-Pituitary-Adrenal axis and stress responses. AD-associated neurodegeneration is known to affect all of these aspects. However, it’s still unclear how different types of stress (chronic vs. acute) mediate the hippocampal regulation of learning and memory, especially in AD associated neurodegeneration. The present study combined neuropsychological testing, resting state functional MRI, structural MRI, acute stress tests, and self-report chronic stress questionnaires to compare MCI subjects (n = 18) to their age-, sex-, and education-matched healthy controls (HC, n = 21). The MCI group had significantly smaller right hippocampal grey matter volumes (t = 2.50, df = 30, p = .018) than the HC group. The connectivity between the right hippocampus and the inferior frontal gyrus (Rhipp-IFG) was significantly positively related to both acute and chronic stress for the entire sample. After testing our mediation model for the two groups separately, we found that acute and chronic stress showed significant mediating effects in the association between Rhipp-IFG and learning (before adding mediators: t = -2.56, p = .022; when including mediators: t = 0.21, p = .84) in the HC group, but not in the MCI group. This suggests that chronic and acute stress act as mediators for the right hippocampus-involved neural network for learning and memory, and this mediating effect may be disrupted in the AD-associated neurodegeneration process.
Coping with cognitively demanding everyday activities with cognitive demands can be stressful for older adults with mild cognitive impairment (MCI). Cognitive impairment, stress dysregulation, and stress-related biological alterations may accelerate the progression to Alzheimer's disease in individuals with MCI. Cardiovascular reactivity to acute stress is a critical indicator for stress regulation, and has implications in multiple health outcomes. However, evidence is inconsistent regarding the normality of cardiovascular reactivity in MCI. Based on our previous work, we targeted mental fatigability as a potentially important determinant of cardiovascular stress reactivity in individuals with MCI. We also examined the frontal basal ganglia circuitry as a potential neural basis supporting the link between mental fatigability and cardiovascular reactivity. Mental fatigability and parasympathetic control of cardiovascular reactivity, high frequency heart rate variability (HF-HRV), were assessed during a 60-minute cognitive stress protocol in 19 individuals with MCI. The resting state functional connectivity of intra- and inter-networks within frontal basal ganglia circuitry was assessed using BOLD fMRI two weeks earlier among 7 of the individuals with MCI and 6 age-, gender-, and education-matched healthy controls. We found that high level mental fatigability disrupted the normal U shape of HF-HRV reactivity to cognitive stress in individuals with MCI. Furthermore, the stronger connectivity of intra-network of central executive network and the inter-network between central executive network and basal ganglia network (especially between the bilateral middle prefrontal cortex and left putamen) within the frontal basal ganglia circuitry (Figure 1) were related to lower mental fatigability and stronger HF-HRV reactivity in both MCI and healthy control (Figure 2). These results indicate that mental fatigability may contribute to abnormal cardiovascular reactivity to acute stress in MCI, and frontal basal ganglia circuitry may support such a link.
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