Meta-analysis Of Functional Neuroimaging Studies Research Articles

Functional dissociation of pre-SMA and SMA-proper in temporal processing

The ability to assess temporal structure is crucial in order to adapt to an ever-changing environment. Increasing evidence suggests that the supplementary motor area (SMA) is involved in both sensory and sensorimotor processing of temporal structure. However, it is not entirely clear whether the structural differentiation of the SMA translates into functional specialization, and how the SMA relates to other systems that engage in temporal processing, namely the cerebellum and cortico-striatal circuits. Anatomically, the SMA comprises at least two subareas, the rostral pre-SMA and the caudal SMA-proper. Each displays a characteristic pattern of connections to motor and non-motor structures. Crucially, these connections establish a potential hub among cerebellar and cortico-striatal systems, possibly forming a dedicated subcortico-cortical temporal processing network. To further explore the functional role of each SMA subarea, we performed a meta-analysis of functional neuroimaging studies by contrasting activations according to whether they linked with either sensory, sensorimotor, sequential, non-sequential, explicit, non-explicit, subsecond, or suprasecond temporal processing. This procedure yielded a set of functional differences, which mirror the rostro-caudal anatomical dimension. Activations associated with sensory, non-sequential, and suprasecond temporal processing tend to locate to the rostral SMA, while the opposite is true for the caudal SMA. These findings confirm a functional dissociation of pre-SMA and SMA-proper in temporal processing.

Meta-Analysis of Functional Neuroimaging Studies of Emotion Perception and Experience in Schizophrenia

Neuroimaging studies of emotion in schizophrenia have reported abnormalities in amygdala and other regions, although divergent results and heterogeneous paradigms complicate conclusions from single experiments. To identify more consistent patterns of dysfunction, a meta-analysis of functional imaging studies of emotion was undertaken. Searching Medline and PsycINFO databases through January 2011, 88 potential articles were identified, of which 26 met inclusion criteria, comprising 450 patients with schizophrenia and 422 healthy comparison subjects. Contrasts were selected to include emotion perception and emotion experience. Foci from individual studies were subjected to a voxelwise meta-analysis using multilevel kernel density analysis. For emotional experience, comparison subjects showed greater activation in the left occipital pole. For emotional perception, schizophrenia subjects showed reduced activation in bilateral amygdala, visual processing areas, anterior cingulate cortex, dorsolateral frontal cortex, medial frontal cortex, and subcortical structures. Schizophrenia subjects showed greater activation in the cuneus, parietal lobule, precentral gyrus, and superior temporal gyrus. Combining across studies and eliminating studies that did not balance on effort and stimulus complexity eliminated most differences in visual processing regions as well as most areas where schizophrenia subjects showed a greater signal. Reduced reactivity of the amygdala appeared primarily in implicit studies of emotion, whereas deficits in anterior cingulate cortex activity appeared throughout all contrasts. Processing emotional stimuli, schizophrenia patients show reduced activation in areas engaged by emotional stimuli, although in some conditions, schizophrenia patients exhibit increased activation in areas outside those traditionally associated with emotion, possibly representing compensatory processing.

The “paradoxical” engagement of the primary auditory cortex in patients with auditory verbal hallucinations: A meta-analysis of functional neuroimaging studies

The existing literature on neuroimaging studies of auditory verbal hallucinations (AVHs) in patients with schizophrenia contains an apparent “paradox” in that the same areas in the auditory cortex seem to be both activated and deactivated in relation to AVHs, depending on whether an external auditory stimulus is present or not. We performed meta-analyses of neuroimaging studies examining patients with schizophrenia during the processing of auditory stimuli and in individuals experiencing hallucinations in the absence of auditory stimuli to examine whether the auditory cortex shows the paradoxical decrease/increase pattern across studies. Databases PubMed and ISI Web of Knowledge were queried with the combination of the keywords “auditory verbal hallucinations”, “auditory hallucinations”, “fMRI”, “PET”, “imaging”, yielding 11 studies involving comparison between schizophrenia and control group during external auditory stimulation, and 12 studies of hallucinating subjects experiencing AVHs and resting in the absence of auditory stimulation. The data were analyzed using Activation Likelihood Estimation method. The results showed overlapping increased activation in the absence of an external stimulus, and decreased activation in the presence of an external auditory stimulus in the left primary auditory cortex and in the right rostral prefrontal cortex, confirming the “paradoxical” brain activation in relation to AVHs. It is suggested that the “paradox” may be caused by an attentional bias towards internally generated information and failure of down- and up-regulation of the default mode and auditory processing networks, respectively, with the consequence that the spontaneous activation in the absence of an external stimulus shuts down the perceptual apparatus for further processing.

Are networks for residual language function and recovery consistent across aphasic patients?

If neuroplastic changes in aphasia are consistent across studies, this would imply relatively stereotyped mechanisms of recovery which could guide the design of more efficient noninvasive brain stimulation treatments. To address this question, we performed a meta-analysis of functional neuroimaging studies of chronic aphasia after stroke. Functional neuroimaging articles using language tasks in patients with chronic aphasia after stroke (n = 105) and control subjects (n = 129) were collected. Activation likelihood estimation meta-analysis determined areas of consistent activity in each group. Functional homology between areas recruited by aphasic patients and controls was assessed by determining whether they activated under the same experimental conditions. Controls consistently activated a network of left hemisphere language areas. Aphasic patients consistently activated some spared left hemisphere language nodes, new left hemisphere areas, and right hemisphere areas homotopic to the control subjects' language network. Patients with left inferior frontal lesions recruited right inferior frontal gyrus more reliably than those without. Some areas, including right dorsal pars opercularis, were functionally homologous with corresponding control areas, while others, including right pars triangularis, were not. The network of brain areas aphasic patients recruit for language functions is largely consistent across studies. Several recruitment mechanisms occur, including persistent function in spared nodes, compensatory recruitment of alternate nodes, and recruitment of areas that may hinder recovery. These findings may guide development of brain stimulation protocols that can be applied across populations of aphasic patients who share common attributes.

New approaches for coordinate-based meta-analysis of functional neuroimaging studies

New approaches for coordinate-based meta-analysis of functional neuroimaging studies

Cerebellum and auditory function: an ALE meta-analysis of functional neuroimaging studies.

Over the past two decades neuroimaging data have accumulated showing that the cerebellum, traditionally viewed only as a motor structure, is also active in a wide variety of sensory and cognitive tasks. We have proposed that instead of explicit involvement in any particular motor, sensory, or cognitive task, the cerebellum performs a much more fundamental computation involving the active acquisition of sensory data. We carried out an activation likelihood estimate (ALE) meta-analysis to determine whether neuroimaging results obtained during a wide range of auditory tasks support this proposal. Specifically, we analyzed the coordinates of 231 activation foci obtained in 15 different auditory studies selected through an extensive search of the positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) literature. The studies selected represent a wide variety of purely auditory tasks using highly controlled synthesized acoustic stimuli. The results clearly revealed that in addition to temporal auditory areas of cerebral cortex, specific regions in the cerebellum are activated consistently across studies regardless of the particular auditory task involved. In particular, one area in left lateral crus I area showed the greatest volume and ALE peak value among the extratemporal regions. A subanalysis was carried out that ruled out the specific association of this cerebellar cluster with attentional demand. The results are consistent with the hypothesis that the cerebellum may play a role in purely sensory auditory processing, and are discussed in light of the broader idea of the cerebellum subserving a fundamental sensory function.

Albemarle to enter Japanese market with co-catalysts

It remains unclear whether and to what extent the default network subregions involved in episodic memory (EM) and semantic memory (SM) processes overlap or are separated from one another. This study addresses this issue through a controlled meta-analysis of functional neuroimaging studies involving healthy participants. Various EM and SM task paradigms differ widely in the extent of default network involvement. Therefore, the issue at hand cannot be properly addressed without some control for this factor. In this regard, this study employs a two-stage analysis: a preliminary meta-analysis to select EM and SM task paradigms that recruit relatively extensive default network regions and a main analysis to compare the selected task paradigms. Based on a within-EM comparison, the default network contributed more to recollection/familiarity effects than to old/new effects, and based on a within-SM comparison, it contributed more to word/pseudoword effects than to semantic/phonological effects. According to a direct comparison of recollection/familiarity and word/pseudoword effects, each involving a range of default network regions, there were more overlaps than separations in default network subregions involved in these two effects. More specifically, overlaps included the bilateral posterior cingulate/retrosplenial cortex, left inferior parietal lobule, and left anteromedial prefrontal regions, whereas separations included only the hippocampal formation and the parahippocampal cortex region, which was unique to recollection/familiarity effects. These results indicate that EM and SM retrieval processes involving strong memory signals recruit extensive and largely overlapping default network regions and differ mainly in distinct contributions of hippocampus and parahippocampal regions to EM retrieval.

Habit Formation and Dynamic Demand Functions

Most economists would agree that past consumption patterns are an important determinant of present consumption patterns, and that one ought to distinguish between long-run and short-run demand functions. But although the distinction between long-run and short-run behavior is traditional in the theory of the firm, it is seldom made in the theory of consumer behavior. If we regard demand theory as a theory of how a given amount of money (expenditure, called income) is allocated among goods, then-in a world without consumer durables-there are three reasons why longand shortrun demand functions might differ. (i) The consumer may have contractually fixed commitments which prevent him from adjusting some portion of his consumption (for example, housing) in response to changes in prices or income. When these fixed commitments lapse, he is able to adjust to his long-run equilibrium. (ii) The consumer may be ignorant of consumption possibilities or of his own tastes outside the range of his past consumption experience. In this case his adjustment to a new price-income situation will involve a time-consuming learning process. (iii) Finally, goods may be "habit forming" so that an individual's current preferences depend on his past consumption patterns. In this case a change in prices or income will cause a change-in consumption which will induce a change in tastes, which will cause a further change in consumption. In this paper I formulate a model of consumer behavior based on habit formation, beginning with a specific class of demand functions derived from the "modified Bergson family" of utility functions. The properties of these utility functions and the corresponding demand functions are briefly summarized in Section 1. I then postulate that the parameters