Cerebral cortex
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Neural processing of fearful faces: effects of anxiety are gated by perceptual capacity limitations.
Debate continues as to the automaticity of the amygdala's response to threat. Accounts taking a strong automaticity line suggest that the amygdala's response to threat is both involuntary and independent of attentional resources. Building on these accounts, prominent models have suggested that anxiety modulates the output of an amygdala-based preattentive threat evaluation system. ⋯ Neither high- nor low-anxious volunteers showed an increased amygdala response to threat distractors under high perceptual load, contrary to a strong automaticity account of amygdala function. Under low perceptual load, elevated state anxiety was associated with a heightened response to threat distractors in the amygdala and superior temporal sulcus, whereas individuals high in trait anxiety showed a reduced prefrontal response to these stimuli, consistent with weakened recruitment of control mechanisms used to prevent the further processing of salient distractors. These findings suggest that anxiety modulates processing subsequent to competition for perceptual processing resources, with state and trait anxiety having distinguishable influences upon the neural mechanisms underlying threat evaluation and "top-down" control.
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Pain naturally draws one's attention. However, humans are capable of engaging in cognitive tasks while in pain, although it is not known how the brain represents these processes concurrently. There is some evidence for a cortical interaction between pain- and cognitive-related brain activity, but the outcome of this interaction may depend on the relative load imposed by the pain versus the task. ⋯ However, during the more intense pain, activity in primary sensorimotor cortex, secondary somatosensory cortex/posterior insula, anterior insula, paracentral lobule, caudal anterior cingulate cortex, cerebellum, and supplementary motor area was modestly attenuated by the easy task and in some cases the difficult task. Conversely, cognitive-related activity was not modulated by pain, except when cognitive load was minimal during the control task. These findings support the notion that brain networks supporting pain perception and cognition can be simultaneously active.
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Recent proposals have conceptualized piriform cortex as an association cortex, capable of integrating incoming olfactory information with descending input from higher order associative regions such as orbitofrontal cortex and basolateral amygdala (ABL). If true, encoding in piriform cortex should reflect associative features prominent in these areas during associative learning involving olfactory cues. We recently reported that neurons in anterior piriform cortex (APC) in rats exhibited significant plasticity in their responses to odor cues during associative learning. ⋯ Consistent with this hypothesis, we found that PPC neurons were highly associative and appeared to be somewhat more likely than neurons recorded in APC to alter their responses to the odor cues after reversal of the odor-outcome associations in the task. Further, odor-selective PPC populations exhibited markedly different firing patterns based on the valence of the odor cue. These results suggest associative encoding in piriform cortex is represented in a topographical fashion, reflecting the stronger and more specific input from olfactory bulb concerning the sensory features of odors in anterior regions and stronger input from ABL concerning the meaning of odors in posterior regions.
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Pain is an unpleasant sensation, and at the same time, it is always subjective and affective. Ten healthy subjects viewed 3 counterbalanced blocks of images from the International Affective Picture System: images showing painful events and those evoking emotions of fear and rest. ⋯ The results show that the imagination of pain is associated with increased activity in several brain regions involved in the pain-related neural network, notably the anterior cingulate cortex (ACC), right anterior insula, cerebellum, posterior parietal cortex, and secondary somatosensory cortex region, whereas increased activity in the ACC and amygdala is associated with the viewing of images evoking fear. Our results indicate that the imagination of pain even without physical injury engages the cortical representations of the pain-related neural network more specifically than emotions of fear and rest; it also engages the common representation (i.e., in ACC) between the imagination of pain and the emotion of fear.
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The coupling of neuronal cellular activity to its blood supply is of critical importance to the physiology of the human brain and has been under discussion for more than a century. Linearity in this relationship has been demonstrated in some animal studies, but evidence is lacking in humans. In this study, we compared scalp evoked potentials and the functional magnetic resonance imaging (fMRI) blood oxygen level-dependent (BOLD) signal from healthy human volunteers with changes in the intensity of a somatosensory stimulus. ⋯ Hemodynamic changes in primary somatosensory cortex covaried positively with neuronal activity in a predominantly linear manner, with a small quadratic contribution. Simultaneously, other cortical areas corresponding to the nonstimulated limbs were found to covary negatively and linearly in the hemispheres ipsilateral and contralateral to the stimulus. These concurrent and bilateral cortical dynamics, as well as the intraregional features of this neurovascular coupling, are both more complex than had been considered to date, with considerable implications.