lea_hazel: Neuron cell (Science: Brains)
[personal profile] lea_hazel
Excerpted from Bipolar disorder: A neural network perspective on a disorder of emotion and motivation

Michele Wessa, Philipp Kanske and Julia Linke

At InTech:

Based on our own and previous data we further propose that functional and anatomical alterations in orbitofrontal cortex and amygdala as well as the connection between these two regions represents a biological vulnerability marker of bipolar disorder.
lea_hazel: Neuron cell (Science: Brains)
[personal profile] lea_hazel
Excerpted from Mesocorticolimbic Circuits are Impaired in Chronic Cocaine Users as Demonstrated by Resting State Functional Connectivity

Elliot A. Stein and Yihong Yang

At National Institute on Drug Abuse's Neuroimaging Research Branch:

Using whole-brain resting-state fMRI connectivity analysis with ‘seed voxels’ placed within individual nodes of the MCL system, we report network-specific functional connectivity strength decreases in cocaine users within distinct circuits of the system, including between ventral tegmental area (VTA) and a region encompassing thalamus, lentiform nucleus, and nucleus accumbens, between amygdala and medial prefrontal cortex (mPFC), and between hippocampus and dorsal mPFC. Further, regression analysis on regions showing significant functional connectivity decrease in chronic cocaine users revealed that the circuit strength between VTA and thalamus-lentiform nucleus-nucleus accumbens was negatively correlated with years of cocaine use.
lea_hazel: Neuron cell (Science: Brains)
[personal profile] lea_hazel
Excerpted from Positive Affect Versus Reward: Emotional and Motivational Influences on Cognitive Control

Kimberly S. Chiew and Todd S. Braver

At Frontiers in Psychology:

The neural mechanisms underlying positive emotion’s effects on cognition remain unclear. Different theories have been posited to explain these effects. One influential theory, the dopaminergic theory of positive affect (Ashby et al., 1999) was developed to address findings that positive emotion is linked to broadened cognition. Ashby and colleagues extrapolated from the literature on the neural substrates of reward processing to propose that the psychological effects of positive emotion are specifically linked to increased dopamine (DA) release (via the substantia nigra and ventral tegmental area) in these states. The particular cognitive effects of increased DA release during positive affect were postulated to occur through mesocorticolimbic system projections to the anterior cingulate cortex (ACC) and substantia nigra projections to striatum, with increased DA facilitating the ability of ACC and striatum to initiate a switch among active task sets, rules, or goal representations maintained in lateral prefrontal cortex (PFC). This facilitation of switching among task-set representations under positive affect enables unusual or non-dominant sets to become active with a greater probability than under neutral affect conditions, which then facilitates creative problem-solving. In connectionist simulations, the account was tested and exhibited an ability to account for certain behavioral performance patterns observed by Isen and colleagues under positive affect manipulations (i.e., improved performance on creative problem-solving and semantic association tasks; Ashby et al., 1999, 2002).

The limbic system's regulation of positive affect influences the prefrontal cortex's role in novel problem-solving.
lea_hazel: Neuron cell (Science: Brains)
[personal profile] lea_hazel
Daniel R. Weinberger, MD; Karen Faith Berman, MD; Ronald F. Zec, PhD

At the Archives of General Psychiatry:

To evaluate dorsolateral prefrontal cortex (DLPFC) physiology and function simultaneously, 20 medication-free patients with chronic schizophrenia and 25 normal controls underwent three separate xenon Xe 133 inhalation procedures for determination of regional cerebral blood flow (rCBF): first at rest, then while performing an automated version of the Wisconsin Card Sort (WCS), a DLPFC-specific cognitive test, and while peforming a simple number-matching (NM) test. During rest, patients had significantly reduced relative, but not absolute, rCBF to DLPFC. During NM, no specific region differentiated patients from controls. During WCS, however, both absolute and relative rCBF to DLPFC significantly distinguished patients from controls. While controls showed a clear increase in DLPFC rCBF, patients did not. The changes were regionally specific, involving only DLPFC. Furthermore, in patients, DLPFC rCBF correlated positively with WCS cognitive performance, suggesting that the better DLPFC was able to function, the better patients could perform. Autonomic arousal measures, the pattern of WCS errors, and results of complementary studies suggest that the DLPFC finding is linked to regionally specific cognitive function and is not a nonspecific epiphenomenon.

This is a study from 1986 that appears to go to the core of examining the role of the dlPFC in schizophrenia.

Physiological Dysfunction of the Dorsolateral Prefrontal Cortex in Schizophrenia Revisited

Joseph H. Callicott, Alessandro Bertolino, Venkata S. Mattay, Frederick J.P. Langheim, Jeffrey Duyn, Richard Coppola, Terry E. Goldberg and Daniel R. Weinberger

At Cerebral Cortex:

Evidence implicates subtle neuronal pathology of the prefrontal cortex (PFC) in schizophrenia, but how this pathology is reflected in physiological neuroimaging experiments remains controversial. We investigated PFC function in schizophrenia using functional magnetic resonance imaging (fMRI) and a parametric version of the n-back working memory (WM) task. In a group of patients who performed relatively well on this task, there were three fundamental deviations from the ‘healthy’ pattern of PFC fMRI activation to varying WM difficulty. The first characteristic was a greater magnitude of PFC fMRI activation in the context of slightly impaired WM performance (i.e. physiological inefficiency). The second was that the significant correlations between behavioral WM performance and dorsal PFC fMRI activation were in opposite directions in the two groups. Third, the magnitude of the abnormal dorsal PFC fMRI response was predicted by an assay of N-acetylaspartate concentrations (NAA) in dorsal PFC, a measure of neuronal pathology obtained using proton magnetic resonance spectroscopy. Patients had significantly lower dorsal PFC NAA than controls and dorsal PFC NAA inversely predicted the fMRI response in dorsal PFC (areas 9, 46) to varying WM difficulty — supporting the assumption that abnormal PFC responses arose from abnormal PFC neurons. These data suggest that under certain conditions the physiological ramifications of dorsal PFC neuronal pathology in schizophrenia includes exaggerated and inefficient cortical activity, especially of dorsal PFC.
lea_hazel: Neuron cell (Science: Brains)
[personal profile] lea_hazel
John D. Beaver, Andrew D. Lawrence, Luca Passamonti, and Andrew J. Calder

At the Journal of Neuroscience:

The "behavioral approach system" (BAS) (Gray, 1990) has been primarily associated with reward processing and positive affect. However, additional research has demonstrated that the BAS plays a role in aggressive behavior, heightened experience of anger, and increased attention to facial signals of aggression. Using functional magnetic resonance imaging, we show that variation in the BAS trait in healthy participants predicts activation in neural regions implicated in aggression when participants view facial signals of aggression in others. Increased BAS drive (appetitive motivation) was associated with increased amygdala activation and decreased ventral anterior cingulate and ventral striatal activation to facial signals of aggression, relative to sad and neutral expressions. In contrast, increased behavioral inhibition was associated with increased activation in the dorsal anterior cingulate, a region involved in the perception of fear and threat. Our results provide the first demonstration that appetitive motivation constitutes a significant factor governing the function of neural regions implicated in aggression, and have implications for understanding clinical disorders of aggression.

Note: This study only peripherally examines the role of the vmPFC in aggression, but I decided to start with something I was already working on.
lea_hazel: Neuron cell (Science: Brains)
[personal profile] lea_hazel
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