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Many agrammatic aphasics have a specific syntactic comprehension deficit involving processing syntactic transformations. It has been proposed that this deficit is due to a dysfunction of Broca's area, an area that is thought to be critical for comprehension of complex transformed sentences. The goal of this study was to investigate the role of Broca's area in processing canonical and non-canonical sentences in healthy subjects. The sentences were presented auditorily and were controlled for task difficulty. Subjects were asked to judge the grammaticality of the sentences while their brain activity was monitored using event-related functional magnetic resonance imaging. Processing both kinds of sentences resulted in activation of language-related brain regions. Comparison of non-canonical and canonical sentences showed greater activation in bilateral temporal regions; a greater activation of Broca's area in processing antecedent-gap relations was not found. Moreover, the posterior part of Broca's area was conjointly activated by both sentence conditions. Broca's area is thus involved in general syntactic processing as required by grammaticality judgments and does not seem to have a specific role in processing syntactic transformations. (C) 2004 Wiley-Liss, Inc
Moral decision-making is central to everyday social life because the evaluation of the actions of another agent or our own actions made with respect to the norms and values guides our behavior in a community. There is previous evidence that the presence of bodily harm-even if irrelevant for a decision-may affect the decision-making, process. While recent neuroimaging studies found a common neural substrate of moral decision-making, the role of bodily harm has not been systematically studied so far. Here we used event-related functional magnetic resonance imaging (fMRI) to investigate how behavioral and neural correlates of semantic and moral decision-making processes are modulated by the presence of direct bodily harm or violence in the stimuli. Twelve participants made moral and semantic decisions about sentences describing actions of agents that either contained bodily harm or not and that could easily be judged as being good or bad or correct/incorrect, respectively. During moral and semantic decision-making, the presence of bodily harm resulted in faster response times (RT) and weaker activity in the temporal poles relative to trials devoid of bodily harm/violence, indicating a processing advantage and reduced processing depth for violence-related linguistic stimuli. Notably, there was no increase in activity in the amygdala and the posterior cingulate cortex (PCC) in response to trials containing bodily harm. These findings might be a correlate of limited generation of the semantic and emotional context in the anterior temporal poles during the evaluation of actions of another agent related to violence that is made with respect to the norms and values guiding our behavior in a community. (C) 2004 Elsevier Inc. All rights reserved
The flexible learning of stimulus-reward associations when required by situational context is essential for everyday behavior. Older adults experience a progressive decline in several cognitive functions and show deficiencies in neuropsychological tasks requiring flexible adaptation to external feedback, which could be related to impairments in reward association learning. To study the effect of aging on stimulus-reward association learning 20 young and 20 older adults performed a probabilistic object reversal task (pORT) along with a battery of tests assessing executive functions and general intellectual abilities. The pORT requires learning and reversing associations between actions and their outcomes. Older participants collected fewer points, needed more trials to reach the learning criterion, and completed less blocks successfully compared to young adults. This difference remained statistically significant after correcting for the age effect of other tests assessing executive functions. This suggests that there is an age-related difference in reward association learning as measured using the pORT, which is not closely related to other executive functions with respect to the age effect. In human aging, structural alterations of reward detecting structures and functional changes of the dopaminergic as well as the serotonergic system might contribute to the deficit in reward association learning observed in this study. (C) 2004 Elsevier Ltd. All rights reserved
There is increasing interest ill understanding the neural systems that mediate analogical thinking, which is essential for learning and fluid intelligence. The aim of the present study was to shed light on the cerebral correlates of geometric analogical processing and on training-induced changes at the behavioral and brain level. In healthy participants a bilateral fronto-parietal network was engaged in processing geometric analogies and showed greater blood oxygenation dependent (BOLD) signals as resource demands increased. This network, as well as fusiform and subcortical brain regions, additionally showed training-induced decreases in the BOLD signal over time. The general finding that brain regions were modulated by the amount of resources demanded by the task, and/or by the reduction of allocated resources due to short term training, reflects increased efficiency - in terms of more focal and more specialized brain activation - to more economically process the geometric analogies. Our data indicate a rapid adaptation of the cognitive system which is efficiently modulated by short term training based on a positive correlation of resource demands and brain activation.
Understanding the rapidly developing building blocks of speech perception in infancy requires a close look at the auditory prerequisites for speech sound processing. Pioneering studies have demonstrated that hemispheric specializations for language processing are already present in early infancy. However, whether these computational asymmetries can be considered a function of linguistic attributes or a consequence of basic temporal signal properties is under debate. Several studies in adults link hemispheric specialization for certain aspects of speech perception to an asymmetry in cortical tuning and reveal that the auditory cortices are differentially sensitive to spectrotemporal features of speech. Applying concurrent electrophysiological (EEG) and hemodynamic (near-infrared spectroscopy) recording to newborn infants listening to temporally structured nonspeech signals, we provide evidence that newborns process nonlinguistic acoustic stimuli that share critical temporal features with language in a differential manner. The newborn brain preferentially processes temporal modulations especially relevant for phoneme perception. In line with multi-time-resolution conceptions, modulations on the time scale of phonemes elicit strong bilateral cortical responses. Our data furthermore suggest that responses to slow acoustic modulations are lateralized to the right hemisphere. That is, the newborn auditory cortex is sensitive to the temporal structure of the auditory input and shows an emerging tendency for functional asymmetry. Hence, our findings support the hypothesis that development of speech perception is linked to basic capacities in auditory processing. From birth, the brain is tuned to critical temporal properties of linguistic signals to facilitate one of the major needs of humans: to communicate.
Normal aging is associated with a decline in different cognitive domains and local structural atrophy as well as decreases in dopamine concentration and receptor density. To date, it is largely unknown how these reductions in dopaminergic neurotransmission affect human brain regions responsible for reward-based decision making in older adults. Using a learning criterion in a probabilistic object reversal task, we found a learning stage by age interaction in the dorsolateral prefrontal cortex (dIPFC) during decision making. While young adults recruited the dlPFC in an early stage of learning reward associations, older adults recruited the dlPFC when reward associations had already been learned. Furthermore, we found a reduced change in ventral striatal BOLD signal in older as compared to younger adults in response to high probability rewards. Our data are in line with behavioral evidence that older adults show altered stimulus-reward learning and support the view of an altered fronto-striatal interaction during reward-based decision making in old age, which contributes to prolonged learning of reward associations.
People differ with regard to how they perceive, experience, and express negative affect. While trait negative affect reflects a stable, sustained personality trait, state negative affect represents a stimulus limited and temporally acute emotion. So far, little is known about the neural systems mediating the relationship between negative affect and acute emotion processing. To address this issue we investigated in a healthy female sample how individual differences in state negative affect are reflected in changes in blood oxygen level-dependent responses during passive viewing of emotional stimuli. To assess autonomic arousal we simultaneously recorded changes in skin conductance level. At the psychophysiological level we found increased skin conductance level in response to aversive relative to neutral pictures. However, there was no association of state negative affect with skin conductance level. At the neural level we found that high state negative affect was associated with increased left insular activity during passive viewing of aversive stimuli. The insula has been implicated in interoceptive processes and in the integration of sensory, visceral, and affective information thus contributing to subjective emotional experience. Greater recruitment of the insula in response to aversive relative to neutral stimuli in subjects with high state negative affect may represent increased processing of salient aversive stimuli.