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Left frontal activation
Abstract
We read with considerable interest the paper by Shergill et al ([2004][1]) about the temporal course of brain activity associated with auditory verbal hallucinations. The researchers used functional magnetic resonance imaging to reveal those brain regions activated before, during and after such
... Such a proposal is supported by evidence that brain areas implicated in inner speech, such as the left inferior frontal gyrus (including Broca's area) and the right temporal cortex (Huang, Carr, & Cao, 2001; Jones, in press; McGuire, Silbersweig, Murray, et al., 1996) are activated during AVHs (McGuire, Shah, & Murray, 1993; Shergill et al., 2004; Shergill, Brammer, Williams, Murray, & McGuire, 2000). Although some have questioned whether the finding of inferior frontal gyrus activation during AVHs is an artifact of using a button-press to signal onset of AVHs during imaging (Hunter & Spence, 2005), other studies which have not used a button-press to signal onset, but have instead asked post-imaging whether an AVH was experienced, have also shown inferior frontal gyrus activation in AVHs (Shergill, Brammer, et al., 2000). This said, several other imaging studies have failed to replicate the finding that inferior frontal gyrus activation is associated with the experience of AVHs (e.g., Lennox et al., 2000; Silbersweig et al., 1995). ...
The neuroimaging and neurophysiological literature on inner speech in healthy participants and those who experience auditory verbal hallucinations (AVHs) is reviewed. AVH-hearers in remission and controls do not differ neurologically on tasks involving low levels of verbal self-monitoring (VSM), such as reciting sentences in inner speech. In contrast, on tasks involving high levels of VSM, such as auditory verbal imagery, AVH-hearers in remission show less activation in areas including the middle and superior temporal gyri. This pattern of findings leads to a conundrum, given that mentation involving low levels of VSM is typically held to form the raw material for AVHs. We address this by noting that existing neuroimaging and neurophysiological studies have been based on unexamined assumptions about the form and developmental significance of inner speech. We set out a Vygotskian approach to AVHs which can account for why they are generally experienced as the voice of another person, with specific acoustic properties, and a tendency to take the form of commands. On this approach, which we argue is consistent with the neural correlates evidence, AVHs result from abnormalities in the transition between condensed and expanded dialogic inner speech. Further potential empirical tests of this model are discussed.
... At this point, it can be considered a replicated finding (McGuire et al., 1993; Shergill et al., 2004). Hunter and Spence (2005) suggested that the activation of frontal area could be related not only to the hallucinations but also to the intention to activate the motor area when the button is pressed in functional MRI studies. However, according to the results in this study, it could be considered that the inferior frontal gyrus area is thought to participate in the first stages of the hallucination by the genesis of auditory verbal contents. ...
Many studies have shown widespread but subtle pathological changes in gray matter in patients with schizophrenia. Some of these studies have related specific alterations to the genesis of auditory hallucinations, particularly in the left superior temporal gyrus, but none has analysed the relationship between morphometric data and a specific scale for auditory hallucinations. The present study aims to define the presence and characteristics of structural abnormalities in relation with the intensity and phenomenology of auditory hallucinations by means of magnetic resonance voxel-based morphometry (MR-VBM) method applied on a highly homogeneous group of 18 persistent hallucinatory patients meeting DSM-IV criteria for schizophrenia compared to 19 healthy matched controls. Patients were evaluated using the PSYRATS scale for auditory hallucinations. Reductions of gray matter concentration in patients to controls were observed in bilateral insula, bilateral superior temporal gyri and left amygdala. In addition, specific relationships between left inferior frontal and right postcentral gyri reductions and the severity of auditory hallucinations were observed. All these areas might be implicated in the genesis and/or persistence of auditory hallucinations through specific mechanisms. Precise morphological abnormalities may help to define reliable MR-VBM biomarkers for the genesis and persistence of auditory hallucinations.
The pathophysiology of auditory verbal hallucinations remains poorly understood.
To characterise the time course of regional brain activity leading to auditory verbal hallucinations.
During functional magnetic resonance imaging, 11 patients with schizophrenia or schizoaffective disorder signalled auditory verbal hallucination events by pressing a button. To control for effects of motor behaviour, regional activity associated with hallucination events was scaled against corresponding activity arising from random button-presses produced by 10 patients who did not experience hallucinations.
Immediately prior to the hallucinations, motor-adjusted activity in the left inferior frontal gyrus was significantly greater than corresponding activity in the right inferior frontal gyrus. In contrast, motor-adjusted activity in a right posterior temporal region overshadowed corresponding activity in the left homologous temporal region. Robustly elevated motor-adjusted activity in the left temporal region associated with auditory verbal hallucinations was also detected, but only subsequent to hallucination events. At the earliest time shift studied, the correlation between left inferior frontal gyrus and right temporal activity was significantly higher for the hallucination group compared with non-hallucinating patients.
Findings suggest that heightened functional coupling between the left inferior frontal gyrus and right temporal regions leads to coactivation in these speech processing regions that is hallucinogenic. Delayed left temporal activation may reflect impaired corollary discharge contributing to source misattribution of resulting verbal images.
The time course of brain activation prior to onset of auditory/verbal hallucinations was characterised using functional magnetic resonance imaging in six dextral patients with schizophrenia. Composite maps of pre-hallucination periods revealed activation in the left anterior insula and in the right middle temporal gyrus, partially replicating two previous case reports, as well as deactivation in the anterior cingulate and parahippocampal gyri. These findings may reflect brain events that trigger or increase vulnerability to auditory/verbal hallucinations.
Verbal auditory hallucinations are common in schizophrenia but little is known about how they arise. We have used single photon emission tomography (SPET) to measure regional cerebral blood flow with the aim of identifying brain areas that are especially active during auditory hallucinations. We scanned twelve men with schizophrenia while they were experiencing hallucinations. The subjects were rescanned under identical conditions when their hallucinations had resolved (mean 19 weeks later). Blood flow was significantly greater during hallucinations than in the non-hallucinating state in Broca's area (mean count density on SPET 1.18 [SD 0.04] vs 1.13 [0.06]; p < 0.001); flow was also higher during hallucinations in the left anterior cingulate cortex and regions in the left temporal lobe, but these differences did not achieve significance. The increased flow in Broca's area was not accounted for by changes in other clinical variables nor by changes in the dose of neuroleptic drugs. These findings suggest that the production of auditory hallucinations in schizophrenia is associated with increased activity in a network of cortical areas specialised for language.
Mild learning disability is associated with an increased risk of affective disorder. This study examines the extent to which adult socio-economic disadvantage and ill health contribute to this risk. Samples were drawn from the 1958 National Child Development Study. Relative to a comparison group, mild learning disability at age 11 was associated with elevated rates of depressive symptoms throughout adult life, and carried a six-fold risk of chronic depressed mood. The group difference in depressed mood at age 43 years was in large part mediated by variations in adult socio-economic disadvantage and ill health.
It is widely accepted that dorsolateral prefrontal cortex (DLPFC) is activated at the time of action generation in humans. However, the previous functional neuroimaging studies that have supported this hypothesis temporally integrated brain dynamics and therefore could not demonstrate when DLPFC underwent activation relative to the emergence of voluntary behavior. Data that are time-locked to the instant of voluntary action execution do not reveal DLPFC activation at that moment. Rather, activated foci are seen at the frontal poles. We investigated this apparent conundrum through three differentially constrained experiments, utilizing functional magnetic resonance imaging to identify those prefrontal areas exhibiting functional change at the moment of spontaneous action execution. We observed profound functional dissociation between anterior and dorsolateral regions, compatible with their involvement at different points during the temporal evolution of action: bilaterally the frontal poles activated at the moment of execution, while simultaneously (and relative to a prior activation state) left DLPFC 'deactivated.'
We used functional magnetic resonance imaging to examine how brain activity associated with auditory verbal hallucinations in schizophrenia changed during hallucinatory events. Activation in the left inferior frontal and right middle temporal gyri was evident 6-9 s before the person signalled the onset of the hallucination, whereas activation in the bilateral temporal gyri and the left insula coincided with the perception of the hallucination. This supports the hypothesis that during hallucinations activation in cortical regions mediating the generation of inner speech may precede the engagement of areas implicated in the perception of auditory verbal material.