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NeuroImage Jun 2024After more than 30 years of extensive investigation, impressive progress has been made in identifying the neural correlates of consciousness (NCC). However, the...
After more than 30 years of extensive investigation, impressive progress has been made in identifying the neural correlates of consciousness (NCC). However, the functional role of spatiotemporally distinct consciousness-related neural activity in conscious perception is debated. An influential framework proposed that consciousness-related neural activities could be dissociated into two distinct processes: phenomenal and access consciousness. However, though hotly debated, its authenticity has not been examined in a single paradigm with more informative intracranial recordings. In the present study, we employed a visual awareness task and recorded the local field potential (LFP) of patients with electrodes implanted in cortical and subcortical regions. Overall, we found that the latency of visual awareness-related activity exhibited a bimodal distribution, and the recording sites with short and long latencies were largely separated in location, except in the lateral prefrontal cortex (lPFC). The mixture of short and long latencies in the lPFC indicates that it plays a critical role in linking phenomenal and access consciousness. However, the division between the two is not as simple as the central sulcus, as proposed previously. Moreover, in 4 patients with electrodes implanted in the bilateral prefrontal cortex, early awareness-related activity was confined to the contralateral side, while late awareness-related activity appeared on both sides. Finally, Granger causality analysis showed that awareness-related information flowed from the early sites to the late sites. These results provide the first LFP evidence of neural correlates of phenomenal and access consciousness, which sheds light on the spatiotemporal dynamics of NCC in the human brain.
PubMed: 38944172
DOI: 10.1016/j.neuroimage.2024.120699 -
NeuroImage Jun 2024Research indicates that hearing loss significantly contributes to tinnitus, but it alone doesn't fully explain its occurrence, as many people with hearing loss do not...
Research indicates that hearing loss significantly contributes to tinnitus, but it alone doesn't fully explain its occurrence, as many people with hearing loss do not experience tinnitus. To identify a secondary factor for tinnitus generation, we examined a unique dataset of individuals with intermittent chronic tinnitus, who experience fluctuating periods of tinnitus. EEGs of healthy controls were compared to EEGs of participants who reported perceiving tinnitus on certain days, but no tinnitus on other days.. The EEG data revealed that tinnitus onset is associated with increased theta activity in the pregenual anterior cingulate cortex and decreased theta functional connectivity between the pregenual anterior cingulate cortex and the auditory cortex. Additionally, there is increased alpha effective connectivity from the dorsal anterior cingulate cortex to the pregenual anterior cingulate cortex. When tinnitus is not perceived, differences from healthy controls include increased alpha activity in the pregenual anterior cingulate cortex and heightened alpha connectivity between the pregenual anterior cingulate cortex and auditory cortex. This suggests that tinnitus is triggered by a switch involving increased theta activity in the pregenual anterior cingulate cortex and decreased theta connectivity between the pregenual anterior cingulate cortex and auditory cortex, leading to increased theta-gamma cross-frequency coupling, which correlates with tinnitus loudness. Increased alpha activity in the dorsal anterior cingulate cortex correlates with distress. Conversely, increased alpha activity in the pregenual anterior cingulate cortex can transiently suppress the phantom sound by enhancing theta connectivity to the auditory cortex. This mechanism parallels chronic neuropathic pain and suggests potential treatments for tinnitus by promoting alpha activity in the pregenual anterior cingulate cortex and reducing alpha activity in the dorsal anterior cingulate cortex through pharmacological or neuromodulatory approaches.
PubMed: 38944171
DOI: 10.1016/j.neuroimage.2024.120713 -
Biological Psychiatry Jun 2024Insomnia disorder is the most common sleep disorder. A better understanding of insomnia-related deviations in the brain could inspire better treatment. Insufficiently...
OBJECTIVE
Insomnia disorder is the most common sleep disorder. A better understanding of insomnia-related deviations in the brain could inspire better treatment. Insufficiently recognized heterogeneity within the insomnia population could obscure detection of involved brain circuits. The present study investigated whether structural brain connectivity deviations differ between recently discovered and validated insomnia subtypes.
METHODS
Structural and diffusion weighted 3-Tesla MRI data of four independent studies were harmonized. The sample consisted of 73 controls without sleep complaints and 204 participants with insomnia grouped into five subtypes based on their fingerprint of mood and personality traits assessed with the Insomnia Type Questionnaire. Linear regression correcting for age and sex evaluated group differences in structural connectivity strength, indicated by fractional anisotropy, streamline volume density and mean diffusivity, and evaluated within three different atlases.
RESULTS
Insomnia subtypes showed differentiating profiles of deviating structural connectivity which concentrated in different functional networks. Permutation testing against randomly drawn heterogeneous subsamples indicated significant specificity of deviation profiles in four of the five subtypes: highly distressed, moderately distressed reward sensitive, slightly distressed low reactive and slightly distressed high reactive. Connectivity deviation profile significance ranged from p= 0.001 to p=0.049 for different resolutions of brain parcellation and connectivity weight.
CONCLUSIONS
Our results provide a first indication that different insomnia subtypes exhibit distinct profiles of deviations in structural brain connectivity. Subtyping of insomnia could be essential for a better understanding of brain mechanisms that contribute to insomnia vulnerability.
PubMed: 38944140
DOI: 10.1016/j.biopsych.2024.06.014 -
Behavioural Processes Jun 2024Two experiments compared the reinforcing effects of sucrose and maltose across a range of concentrations. The results were interpreted using the Multiplicative...
Two experiments compared the reinforcing effects of sucrose and maltose across a range of concentrations. The results were interpreted using the Multiplicative Hyperbolic Model of reinforcer value (MHM). In Experiment 1, rats were exposed to a discrete-trials schedule in which they chose between the test compound (sucrose or maltose) and a standard sucrose solution (0.4M, delivered after a 4-s delay). Percentage choice of each test compound increased as a function of concentration. The maximum percentage choice of maltose was significantly less than that of sucrose; the concentration corresponding to the half-maximal selection of the test compound was lower for maltose than for sucrose. In Experiment 2 the preference function for sucrose alone was compared with the preference function for a sucrose solution to which a fixed concentration of maltose had been added. The presence of maltose elevated the function and shifted it leftwards (i.e. towards lower concentrations). The results were interpreted in terms of MHM using two alterntive models 'borrowed' from classical pharmacological receptor theory. It was concluded that maltose and sucrose are not fully substitutable reinforcers and that the reinforcing effect of maltose may be mediated by an action at more than one species of sweet taste receptor. (200 words).
PubMed: 38944130
DOI: 10.1016/j.beproc.2024.105075 -
Appetite Jun 2024People often fail to acknowledge external influences on their food intake, but there might be some circumstances in which people are willing to report that those...
People often fail to acknowledge external influences on their food intake, but there might be some circumstances in which people are willing to report that those external factors influenced their behavior. This study examined whether participants who believed that they had overeaten would indicate that the portion size they were served influenced their food intake. Participants (119 women) ate a pasta lunch at two separate sessions, one week apart. At the second session, participants were randomly assigned to receive either a regular portion of pasta (the same portion as the first session) or a large portion of pasta (a portion that was twice the size), and to receive false feedback about their food intake indicating that they had either eaten about the same as or substantially more than they had at the previous session. Participants were then asked to indicate the extent to which the amount of food served influenced how much they ate at that second session. Compared to participants who were informed that they had eaten the same amount across the two sessions, those who were informed that they ate more at the second session reported a stronger influence of the amount of food served if they also received a large portion of pasta, but not if they received a regular portion of pasta. These findings suggest that the willingness to implicate external influences (e.g., portion size) on one's food intake may be driven by a self-serving bias, providing an "excuse" for overeating. However, the external cue must be salient enough to be a plausible explanation for one's behavior.
PubMed: 38944056
DOI: 10.1016/j.appet.2024.107583 -
The Lancet. Rheumatology Jun 2024
PubMed: 38944052
DOI: 10.1016/S2665-9913(24)00166-8 -
Ecotoxicology and Environmental Safety Jun 2024Millions of adults and children are exposed to high levels of lead, a neurotoxicant, each year. Recent evidence suggests that lead exposure may precipitate...
Millions of adults and children are exposed to high levels of lead, a neurotoxicant, each year. Recent evidence suggests that lead exposure may precipitate neurodegeneration, particularly if the exposure occurs early or late in life, with unique alterations to the structure or function of specific subfields of the hippocampus, a region involved in memory and Alzheimer's disease. It has been proposed that specific hippocampal subfields may thus be useful biomarkers for lead-associated neurological disease. We turned to a population-representative New Zealand birth cohort where the extent of lead exposure was not confounded by social class (the Dunedin Study; born 1972-1973 and followed to age 45) to test the hypothesis that early life lead exposure (blood-lead level at age 11 years) is associated with smaller MRI-assessed gray matter volumes of specific subfields of the hippocampus at age 45 years. Among the 508 Dunedin Study members with childhood lead data and adult MRI data passing quality control (93.9 % of those with lead data who attended the age-45 assessment wave, 240[47.2 %] female), childhood blood-lead levels ranged from 4 to 31 µg/dL (M[SD]=10.9[4.6]). Total hippocampal volumes were lower among adults with higher childhood blood-lead levels (b=-102.6 mm per 5 ug/dL-unit greater blood-lead level, 95 %CI: -175.4 to -29.7, p=.006, β=-.11), as were all volumes of the 24 hemisphere-specific subfields of the hippocampus. Of these 24 subfields, 20 demonstrated negative lead-associations greater than β=-.05 in size, 14 were statistically significant after adjustment for multiple comparisons (p<.05), and 9 remained significant after adjustment for potential confounders and multiple comparisons. Children exposed to lead demonstrate smaller volumes across all subfields of the hippocampus in midlife. The hypothesis that lead selectively impairs specific subfields of the hippocampus, or that specific subfields may be markers for lead-associated neurological disease, requires further evaluation.
PubMed: 38944006
DOI: 10.1016/j.ecoenv.2024.116658 -
Behaviour Research and Therapy Jun 2024Relevant implicit markers of suicidal thoughts and behaviors (STBs) have only been studied in isolation with mixed evidence. This is the first study that investigated a...
Implicit measures of suicide vulnerability: Investigating suicide-related information-processing biases and a deficit in behavioral impulse control in a high-risk sample and healthy controls.
OBJECTIVE
Relevant implicit markers of suicidal thoughts and behaviors (STBs) have only been studied in isolation with mixed evidence. This is the first study that investigated a suicide attentional bias, a death-identity bias and a deficit in behavioral impulsivity in a high-risk sample and healthy controls.
METHOD
We administered the Death Implicit Association Test, the Modified Suicide Stroop Task, and a Go/No-Go Task to inpatient suicide ideators (n = 42), suicide attempters (n = 40), and community controls (n = 61).
RESULTS
Suicide ideators and attempters showed a suicide attentional bias and a death-identity bias compared to healthy controls. Ideators and attempters did not differ in these implicit information-processing biases. Notably, only attempters were more behaviorally impulsive compared to controls; however, ideators and attempters did not significantly differ in behavioral impulsivity. Moreover, implicit scores were positively intercorrelated in the total sample.
CONCLUSION
In line with the Cognitive Model of Suicide, ideators and attempters display suicide-related information processing biases, which can be considered as implicit cognitive markers of suicide vulnerability. Furthermore, attempters have elevated levels of behavioral impulsiveness. These results are highly relevant in the context of crisis intervention strategies and warrant further research.
PubMed: 38943987
DOI: 10.1016/j.brat.2024.104601 -
Brain and Language Jun 2024A key aspect of linguistic communication involves semantic reference to objects. Presently, we investigate neural responses at objects when reference is disrupted, e.g.,...
A key aspect of linguistic communication involves semantic reference to objects. Presently, we investigate neural responses at objects when reference is disrupted, e.g., "The connoisseur tasted *that wine"… vs. "…*that roof…" Without any previous linguistic context or visual gesture, use of the demonstrative determiner "that" renders interpretation at the noun as incoherent. This incoherence is not based on knowledge of how the world plausibly works but instead is based on grammatical rules of reference. Whereas Event-Related Potential (ERP) responses to sentences such as "The connoisseur tasted the wine …" vs. "the roof" would result in an N400 effect, it is unclear what to expect for doubly incoherent "…*that roof…". Results revealed an N400 effect, as expected, preceded by a P200 component (instead of predicted P600 effect). These independent ERP components at the doubly violated condition support the notion that semantic interpretation can be partitioned into grammatical vs. contextual constructs.
PubMed: 38943944
DOI: 10.1016/j.bandl.2024.105438 -
Food Chemistry Jun 2024This pilot study evaluated the impact of pistachio consumption on cognitive performance and mood in overweight young adults. Pistachios were characterized (chemical and...
This pilot study evaluated the impact of pistachio consumption on cognitive performance and mood in overweight young adults. Pistachios were characterized (chemical and nutraceutical), and a baseline-final, uncontrolled nutritional intervention was performed (28 g of pistachio/28 days). Psychometric tests were applied to estimate cognitive performance and mood; anthropometric evaluation, biochemical analysis, and plasma antioxidant activity were included. The main component of nuts was lipids (48.1%). Pistachios consumption significantly (p ≤ 0.05) reduced waist circumference (-1.47 cm), total cholesterol (-10.21 mg/dL), LDL (-6.57 mg/dL), and triglycerides (-21.07 mg/dL), and increased plasma antioxidant activity. Pistachio supplementation improved risk tolerance (p ≤ 0.006) and decision-making strategy (p ≤ 0.002; BART-task), executive functions (BCST-task; p ≤ 0.006), and selective and sustained attention (Go/No-Go-test; p ≤ 0.016). The mood state was positively modulated (p ≤ 0.05) for anxiety, anger-hostility, and sadness-depression. These results show for the first time the benefits of pistachio consumption on cognitive performance and mood in overweight young adults.
PubMed: 38943918
DOI: 10.1016/j.foodchem.2024.140211