A common finding in human functional brain-imaging studies is that damage to neural systems paradoxically results in enhanced functional connectivity between network regions, a phenomenon commonly ...referred to as ‘hyperconnectivity’. Here, we describe the various ways that hyperconnectivity operates to benefit a neural network following injury while simultaneously negotiating the trade-off between metabolic cost and communication efficiency. Hyperconnectivity may be optimally expressed by increasing connections through the most central and metabolically efficient regions (i.e., hubs). While adaptive in the short term, we propose that chronic hyperconnectivity may leave network hubs vulnerable to secondary pathological processes over the life span due to chronically elevated metabolic stress. We conclude by offering novel, testable hypotheses for advancing our understanding of the role of hyperconnectivity in systems-level brain plasticity in neurological disorders.
A primary aim in the neuroscientific study of depression is to identify the brain areas involved in the pathogenesis of symptoms. In this review, we describe evidence from studies employing various ...experimental approaches in humans (functional imaging, lesion method, and brain stimulation) that converge to implicate the ventromedial and dorsolateral sectors of prefrontal cortex as critical neural substrates for depression, albeit with distinct functional contributions. The putative roles of ventromedial and dorsolateral prefrontal cortex in depression are discussed in light of the results.
Long-Term Follow-up of TBI Grafman, Jordan
New England journal of medicine/The New England journal of medicine,
2016-Oct-20, Letnik:
375, Številka:
16
Journal Article
Although neuroscience has made remarkable progress in understanding the involvement of prefrontal cortex (PFC) in human memory, the necessity of dorsolateral PFC (dlPFC) for key competencies of ...working memory remains largely unexplored. We therefore studied human brain lesion patients to determine whether dlPFC is necessary for working memory function, administering subtests of the Wechsler Memory Scale, the Wechsler Adult Intelligence Scale, and the N-Back Task to three participant groups: dlPFC lesions (n = 19), non-dlPFC lesions (n = 152), and no brain lesions (n = 54). DlPFC damage was associated with deficits in the manipulation of verbal and spatial knowledge, with left dlPFC necessary for manipulating information in working memory and right dlPFC critical for manipulating information in a broader range of reasoning contexts. Our findings elucidate the architecture of working memory, providing key neuropsychological evidence for the necessity of dlPFC in the manipulation of verbal and spatial knowledge.
Posttraumatic stress disorder (PTSD) is characterized by recurrent distressing memories of an emotionally traumatic event. In this review, the authors present neuroscientific data highlighting the ...function of two brain areas—the amygdala and ventromedial prefrontal cortex (vmPFC)—in PTSD and related emotional processes. A convergent body of human and nonhuman studies suggests that the amygdala mediates the acquisition and expression of conditioned fear and the enhancement of emotional memory, whereas the vmPFC mediates the extinction of conditioned fear and the volitional regulation of negative emotion. It has been theorized that the vmPFC exerts inhibition on the amygdala, and that a defect in this inhibition could account for the symptoms of PTSD. This theory is supported by functional imaging studies of PTSD patients, who exhibit hypoactivity in the vmPFC but hyperactivity in the amygdala. A recent study of brain-injured and trauma-exposed combat veterans confirms that amygdala damage reduces the likelihood of developing PTSD. But contrary to the prediction of the top-down inhibition model, vmPFC damage also reduces the likelihood of developing PTSD. The putative roles of the amygdala and the vmPFC in the pathophysiology of PTSD, as well as implications for potential treatments, are discussed in light of these results.
According to the Gestalt theorists, restructuring is an essential component of insight problem-solving, contributes to the "Aha!" experience, and is similar to the perceptual switch experienced when ...reinterpreting ambiguous figures. Previous research has demonstrated that pupil diameter increases during the perceptual switch of ambiguous figures, and indexes norepeinephrine functioning mediated by the locus coeruleus. In this study, we investigated if pupil diameter similarly predicts the switch into awareness people experience when solving a problem via insight. Additionally, we explored eye movement dynamics during the same task to investigate if the problem-solving strategies used are linked to specific oculomotor behaviors. In 38 participants, pupil diameter increased about 500 msec prior to solution only in trials for which subjects report having an insight. In contrast, participants increased their microsaccade rate only prior to non-insight solutions. Pupil dilation and microsaccades were not reliably related, but both appear to be robust markers of how people solve problems (with or without insight). The pupil size change seen when people have an "Aha!" moment represents an indicator of the switch into awareness of unconscious processes humans depend upon for insight, and suggests important involvement of norepinephrine, via the locus coeruleus, in sudden insight.
Problem-solving is essential for advances in cultural, social, and scientific knowledge. It is also one of the most challenging cognitive processes to facilitate. Some problem-solving is deliberate, ...but frequently people solve problems with a sudden insight, also known as a Eureka or "Aha!" moment. The advantage of solving problems via insight is that these solutions are more accurate, relying on a unique pattern of neural activity, compared to deliberative strategies. The right Anterior Temporal Lobe (rATL), putatively involved in semantic integration, is distinctively activated when people experience an insight. The rATL may contribute to the recognition of distant semantic relations that support insight solutions, although fMRI and EEG evidence for its involvement is, by nature, correlational. In this study, we investigate if focal sub-threshold neuromodulation to the rATL facilitates insight problem-solving. In three different groups, using a within- and between-subjects design, we tested the causal role of this brain region in problem-solving, by applying High Definition Transcranial Direct Current Stimulation to the rATL (active and sham condition) or the left frontopolar region while participants attempted to solve Compound Remote Associates problems before, during and after stimulation. Participants solved a higher percentage of problems, overall, and specifically by insight when they received rATL stimulation, compared to pre-stimulation, and compared to sham and left frontopolar stimulation. These results confirm the crucial role played by the rATL in insight problem-solving.
In recent years, theoretical perspectives on posterior parietal function have evolved beyond the traditional visuospatial processing models to include more diverse cognitive operations, such as ...long-term and working memory. However, definitive neuropsychological evidence supporting the superior parietal lobule's purported role in working memory has been lacking. Here, we studied human brain lesion patients to determine whether the superior parietal lobule is indeed necessary for working memory. We assessed a wide range of memory functions in three participant groups: superior parietal lesions (n = 19), lesions not involving superior parietal cortex (n = 146), and no brain lesions (n = 55). Superior parietal damage was reliably associated with deficits on tests involving the manipulation and rearrangement of information in working memory, but not on working memory tests requiring only rehearsal and retrieval processes, nor on tests of long-term memory. These results indicate that superior parietal cortex is critically important for the manipulation of information in working memory.
Results from functional magnetic resonance imaging and lesion studies indicate that the prefrontal cortex (PFC) is essential for successful navigation through a complex social world inundated with ...intricate norms and moral values. This review examines regions of the PFC that are critical for implicit and explicit social cognitive and moral judgment processing. Considerable overlap between regions active when individuals engage in social cognition or assess moral appropriateness of behaviors is evident, underscoring the similarity between social cognitive and moral judgment processes in general. Findings are interpreted within the framework of structured event complex theory, providing a broad organizing perspective for how activity in PFC neural networks facilitates social cognition and moral judgment. We emphasize the dynamic flexibility in neural circuits involved in both implicit and explicit processing and discuss the likelihood that neural regions thought to uniquely underlie both processes heavily interact in response to different contextual primes.
Human memory is thought to depend on a circuit of connected brain regions, but this hypothesis has not been directly tested. We derive a human memory circuit using 53 case reports of strokes causing ...amnesia and a map of the human connectome (n = 1000). This circuit is reproducible across discovery (n = 27) and replication (n = 26) cohorts and specific to lesions causing amnesia. Its hub is at the junction of the presubiculum and retrosplenial cortex. Connectivity with this single location defines a human brain circuit that incorporates > 95% of lesions causing amnesia. Lesion intersection with this circuit predicts memory scores in two independent datasets (N1 = 97, N2 = 176). This network aligns with neuroimaging correlates of episodic memory, abnormalities in Alzheimer's disease, and brain stimulation sites reported to enhance memory in humans.
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