Visual surround suppression in schizophrenia

Compared to unaffected observers patients with schizophrenia (SZ) show characteristic differences in visual perception, including a reduced susceptibility to the influence of context on judgments of contrast – a manifestation of weaker surround suppression (SS). To examine the generality of this phenomenon we measured the ability of 24 individuals with SZ to judge the luminance, contrast, orientation, and size of targets embedded in contextual surrounds that would typically influence the target’s appearance. Individuals with SZ demonstrated weaker SS compared to matched controls for stimuli defined by contrast or size, but not for those defined by luminance or orientation. As perceived luminance is thought to be regulated at the earliest stages of visual processing our findings are consistent with a suppression deficit that is predominantly cortical in origin. In addition, we propose that preserved orientation SS in SZ may reflect the sparing of broadly tuned mechanisms of suppression. We attempt to reconcile these data with findings from previous studies.

Modulation of somatosensory processing by action

Psychophysical evidence suggests that sensations arising from our own movements are diminished when predicted by motor forward models and that these models may also encode the timing and intensity of movement. Here we report a functional magnetic resonance imaging study in which the effects on sensation of varying the occurrence, timing and force of movements were measured. We observed that tactile-related activity in a region of secondary somatosensory cortex is reduced when sensation is associated with movement and further that this reduction is maximal when movement and sensation occur synchronously. Motor force is not represented in the degree of attenuation but rather in the magnitude of this region's response. These findings provide neurophysiological correlates of previously-observed behavioural forward-model phenomena, and advocate the adopted approach for the study of clinical conditions in which forward-model deficits have been posited to play a crucial role.

Aging effects on functional auditory and visual processing using fMRI with variable sensory loading

INTRODUCTION

Traditionally, studies investigating the functional implications of age-related structural brain alterations have focused on higher cognitive processes; by increasing stimulus load, these studies assess behavioral and neurophysiological performance. In order to understand age-related changes in these higher cognitive processes, it is crucial to examine changes in visual and auditory processes that are the gateways to higher cognitive functions. This study provides evidence for age-related functional decline in visual and auditory processing, and regional alterations in functional brain processing, using non-invasive neuroimaging.

METHODS

Using functional magnetic resonance imaging (fMRI), younger (n=11; mean age=31) and older (n=10; mean age=68) adults were imaged while observing flashing checkerboard images (passive visual stimuli) and hearing word lists (passive auditory stimuli) across varying stimuli presentation rates.

RESULTS

Younger adults showed greater overall levels of temporal and occipital cortical activation than older adults for both auditory and visual stimuli. The relative change in activity as a function of stimulus presentation rate showed differences between young and older participants. In visual cortex, the older group showed a decrease in fMRI blood oxygen level dependent (BOLD) signal magnitude as stimulus frequency increased, whereas the younger group showed a linear increase. In auditory cortex, the younger group showed a relative increase as a function of word presentation rate, while older participants showed a relatively stable magnitude of fMRI BOLD response across all rates. When analyzing participants across all ages, only the auditory cortical activation showed a continuous, monotonically decreasing BOLD signal magnitude as a function of age.

CONCLUSIONS

Our preliminary findings show an age-related decline in demand-related, passive early sensory processing. As stimulus demand increases, visual and auditory cortex do not show increases in activity in older compared to younger people. This may negatively impact on the fidelity of information available to higher cognitive processing. Such evidence may inform future studies focused on cognitive decline in aging.

It's not what you say but the way that you say it: an fMRI study of differential lexical and non-lexical prosodic pitch processing

BACKGROUND

This study aims to identify the neural substrate involved in prosodic pitch processing. Functional magnetic resonance imaging was used to test the premise that prosody pitch processing is primarily subserved by the right cortical hemisphere.Two experimental paradigms were used, firstly pairs of spoken sentences, where the only variation was a single internal phrase pitch change, and secondly, a matched condition utilizing pitch changes within analogous tone-sequence phrases. This removed the potential confounder of lexical evaluation. fMRI images were obtained using these paradigms.

RESULTS

Activation was significantly greater within the right frontal and temporal cortices during the tone-sequence stimuli relative to the sentence stimuli.

CONCLUSION

This study showed that pitch changes, stripped of lexical information, are mainly processed by the right cerebral hemisphere, whilst the processing of analogous, matched, lexical pitch change is preferentially left sided. These findings, showing hemispherical differentiation of processing based on stimulus complexity, are in accord with a 'task dependent' hypothesis of pitch processing.

Patients with schizophrenia show increased aversion to angry faces in an associative learning task

BACKGROUND

We were interested in examining the relationship between socially relevant stimuli and decision processes in patients with schizophrenia.

METHOD

We tested patients with schizophrenia and healthy controls on a stochastically rewarded associative learning task. Participants had to determine, through trial and error, which of two faces was associated with a higher chance of reward: one face was angry, the other happy.

RESULTS

Both patients and healthy controls were able to perform the task at above-chance accuracy, and there was no significant difference in overall accuracy between the groups. Both groups also reliably preferred the happy face, such that they selected it more often than the angry face on the basis of the same amount of positive versus negative feedback. However, patients were significantly more averse to the angry face, such that they chose it less often than control participants when the reward feedback strongly supported the angry face as the best choice.

CONCLUSIONS

Patients show an increased aversion to angry faces, in a task in which they must learn to associate rewards with expressions.

Probabilistic learning and inference in schizophrenia

Patients with schizophrenia make decisions on the basis of less evidence when required to collect information to make an inference, a behavior often called jumping to conclusions. The underlying basis for this behavior remains controversial. We examined the cognitive processes underpinning this finding by testing subjects on the beads task, which has been used previously to elicit jumping to conclusions behavior, and a stochastic sequence learning task, with a similar decision theoretic structure. During the sequence learning task, subjects had to learn a sequence of button presses, while receiving a noisy feedback on their choices. We fit a Bayesian decision making model to the sequence task and compared model parameters to the choice behavior in the beads task in both patients and healthy subjects. We found that patients did show a jumping to conclusions style; and those who picked early in the beads task tended to learn less from positive feedback in the sequence task. This favours the likelihood of patients selecting early because they have a low threshold for making decisions, and that they make choices on the basis of relatively little evidence.

Functional magnetic resonance imaging investigation of the amphetamine sensitization model of schizophrenia in healthy male volunteers

CONTEXT

Recent work suggests that the amphetamine sensitization model of schizophrenia can safely be induced in healthy volunteers and is associated both with behavioral and dopaminergic hypersensitivity to amphetamine. However, the effects of a sensitization on brain function remain unclear.

OBJECTIVE

To assess the impact of a sensitizing dosage regimen of dextroamphetamine on human cortical functioning and cognition.

DESIGN

Randomized, double-blind, parallel-groups design using pharmacological functional magnetic resonance imaging.

SETTING

The neuroimaging research unit at the Institute of Psychiatry, King's College London, London, England.

PARTICIPANTS

Healthy male volunteers (n = 22).

INTERVENTIONS

Dextroamphetamine (20 mg) or placebo administration at 4 testing sessions, using a dosage regimen shown to induce sensitization (ie, 3 doses administered with a 48-hour interdose interval and a final dose after a 2-week washout period).

MAIN OUTCOME MEASURES

Sensitization was characterized by enhanced subjective response to the drug, changes in behavioral performance (reaction time and accuracy), and functional magnetic resonance imaging measurements of brain activity during an N-back working memory task.

RESULTS

Sensitization was associated with more rapid responding during the performance of an intermediate-load working memory challenge. During a high-load cognitive challenge, sensitization did not produce performance deficits, but functional magnetic resonance imaging showed hyperactivity of the dorsolateral prefrontal cortex and aberrant recruitment of the superior temporal gyrus, caudate nucleus, and thalamus. Furthermore, the change in striatal activity was negatively correlated with the enhanced subjective effects of the drug, whereas prefrontal hyperactivity was positively correlated with sensitized measures of alertness.

CONCLUSIONS

These transient load-dependent abnormalities of frontal and temporal activity induced by amphetamine sensitization support neuroimaging findings in schizophrenic patients, implying that amphetamine sensitization may help to bridge pathophysiological theories of schizophrenia that focus on pharmacological (dopaminergic) and cognitive mechanisms, respectively.

Oxytocin decreases aversion to angry faces in an associative learning task

Social and financial considerations are often integrated when real life decisions are made, and recent studies have provided evidence that similar brain networks are engaged when either social or financial information is integrated. Other studies, however, have suggested that the neuropeptide oxytocin can specifically affect social behaviors, which would suggest separable mechanisms at the pharmacological level. Thus, we examined the hypothesis that oxytocin would specifically affect social and not financial information in a decision making task, in which participants learned which of the two faces, one smiling and the other angry or sad, was most often being rewarded. We found that oxytocin specifically decreased aversion to angry faces, without affecting integration of positive or negative financial feedback or choices related to happy vs sad faces.

Cortical thickness reduction of normal appearing cortex in patients with polymicrogyria

OBJECTIVE

To examine cortical thickness and volumetric changes in the cortex of patients with polymicrogyria, using an automated image analysis algorithm.

METHODS

Cortical thickness of patients with polymicrogyria was measured using magnetic resonance imaging (MRI) cortical surface-based analysis and compared with age- and sex-matched healthy subjects. We studied 3 patients with disorder of cortical development (DCD), classified as polymicrogyria, and 15 controls. Two experienced neuroradiologists performed a conventional visual assessment of the MRIs. The same data were analyzed using an automated algorithm for tissue segmentation and classification. Group and individual average maps of cortical thickness differences were produced by cortical surface-based statistical analysis.

RESULTS

Patients with polymicrogyria showed increased thickness of the cortex in the same areas identified as abnormal by radiologists. We also identified a reduction in the volume and thickness of cortex within additional areas of apparently normal cortex relative to controls.

CONCLUSIONS

Our findings indicate that there may be regions of reduced cortical thickness, which appear normal from radiological analysis, in the cortex of patients with polymicrogyria. This finding suggests that alterations in neuronal migration may have an impact in the cortical formation of the cortical areas that are visually normal. These areas are associated or occur concurrently with polymicrogyria.

The effects of reality distortion syndrome on salient stimuli processing in patients with schizophrenia: an fMRI study

Schizophrenia is associated with interpersonal difficulties related to impairments in the processing of facial emotional expressions. The aim of the present study was to identify brain regions associated with reality distortion syndrome reduction in a group of patients with schizophrenia during processing of emotionally salient stimuli. We used functional magnetic resonance imaging to measure cerebral blood oxygenation changes during an implicit emotional task in 11 patients with schizophrenia, who were scanned twice with an interval of 6-8 weeks. We found that reality distortion syndrome reduction was associated with increases in the activation of the affective division of the anterior cingulate and lateral prefrontal cortices. Our findings may indicate that changes in the activation of these regions during processing of emotionally salient stimuli may represent neural markers of patients' symptomatic improvement.

Functional magnetic resonance imaging of inner speech in schizophrenia

BACKGROUND

Auditory verbal hallucinations in schizophrenia have been linked to defective monitoring of one's own verbal thoughts. Previous studies have shown that patients with auditory verbal hallucinations show attenuated activation of brain regions involved with auditory processing during the monitoring of inner speech. However, there are no functional magnetic resonance imaging studies explicitly comparing the perception of external speech with internal speech in the same patients with schizophrenia. The present study investigated the functional neuroanatomy of inner and external speech in both patients with schizophrenia and healthy control subjects.

METHODS

Fifteen patients with schizophrenia and 12 healthy control subjects were studied using functional magnetic resonance imaging while listening to sentences or imagining sentences.

RESULTS

Significant interactions between group (control subjects vs. patients) and task (listening vs. inner speech) were seen for the left superior temporal gyrus, as well as regions within the cingulate gyrus.

CONCLUSIONS

Attenuated deactivation of the left superior temporal gyrus in schizophrenia patients during the processing of inner speech may reflect deficits in the forward models subserving self-monitoring.

Subjective cognitive impairment: increased prefrontal cortex activation compared to controls during an encoding task

OBJECTIVE

Subjective cognitive impairment (SCI) has been proposed as a clinical stage which may precede mild cognitive impairment in the clinical continuum of AD, and is characterised by the presence of subjective memory complaints in the absence of objective cognitive deficits. Specific memory-related brain activation differences have been reported in mild cognitive impairment and in cognitively normal individuals at known genetic risk of AD; our objective was to determine whether similar differences are present in people with SCI.

METHODS

We compared brain activation in a memory clinic sample of 10 SCI subjects and 10 controls during a verbal episodic memory encoding task using functional magnetic resonance imaging (fMRI).

RESULTS

There were no differences between groups on measures of encoding success (recognition accuracy) nor was there evidence of altered semantic processing. Both groups activated left prefrontal cortex (PFC) and cerebellum during encoding. The SCI group also demonstrated activation in left medial temporal, occipitoparietal and medial frontal cortex. Group comparisons revealed increased activation in SCI in left PFC, where activation strength correlated with memory task performance.

CONCLUSIONS

The activation differences reported in this study may reflect the employment of compensatory strategies in the face of early AD pathology, although a number of alternative explanations need to be considered. Further studies with larger samples may help to determine whether the observed activation changes are likely to be associated with early neuropathological processes or with other unrelated factors.

Neural substrates of letter fluency processing in young adults who were born very preterm: alterations in frontal and striatal regions

Several studies have described poorer performance in executive-type tasks in individuals who were born very preterm compared to controls. As there is evidence that high-order executive functions may be underpinned by neuronal activity in frontal-striatal circuits, we investigated with functional MRI a group of young adults who were born very preterm (n=28, gestational age <33 weeks) and controls (n=26) in order to detect possible alterations in brain activation during completion of a letter fluency task with differential cognitive loading ("easy" and "hard" letter trials). Structural MRI data were also collected to clarify whether any functional changes were associated with structural brain volume changes. Group membership, level of task difficulty and gestational age had significant effects on brain activation. In the absence of significant between-group differences in task performance, during "easy" letter trials, very preterm-born individuals showed attenuated activation in anterior cingulate gyrus, right caudate nucleus and left inferior frontal gyrus compared to controls. During "hard" letter trials, very preterm-born individuals showed both decreased and increased BOLD signal compared to controls, in left middle frontal and anterior cingulate gyrus, respectively. BOLD signal in caudate nucleus and anterior cingulate gyrus, in regions with peaks close to areas where between-group differences were observed, was linearly associated with gestational age. Analysis of structural MRI data showed altered grey matter distribution in the preterm-born group compared to controls. However, fMRI results were only partly explained by structural changes, and may reflect processes of functional plasticity for the successful completion of executive-type operations.

Using the Stroop task to investigate the neural correlates of symptom change in schizophrenia

This study examined brain activation during a cognitive inhibition task in patients with schizophrenia following changes in their positive symptoms. A Stroop task was used during functional magnetic resonance imaging in 11 patients with schizophrenia (patient group) and 9 healthy volunteers (control group). At baseline, the patient group showed significantly attenuated activation within the anterior cingulate gyrus, left pre-/postcentral gyrus and inferior frontal junction. At follow-up, there was a significant increase in activation in the left inferior frontal junction associated with a decrease in positive symptoms, suggesting this region plays a role in the development of these symptoms.

Facial fear processing and psychotic symptoms in schizophrenia: functional magnetic resonance imaging study

BACKGROUND

The recognition of negative facial affect is impaired in people with schizophrenia. The neural underpinnings of this deficit and its relationship to the symptoms of psychosis are still unclear.

AIMS

To examine the association between positive and negative psychotic symptoms and activation within the amygdala and extrastriate visual regions of patients with schizophrenia during fearful and neutral facial expression processing.

METHOD

Functional magnetic resonance imaging was used to measure neural responses to neutral and fearful facial expressions in 11 patients with schizophrenia and 9 healthy volunteers during an implicit emotional task.

RESULTS

No association between amygdala activation and positive symptoms was found; the activation within the left superior temporal gyrus was negatively associated with the negative symptoms of the patients.

CONCLUSIONS

Our results indicate an association between impaired extrastriate visual processing of facial fear and negative symptoms, which may underlie the previously reported difficulties of patients with negative symptoms in the recognition of facial fear.

Brain structural changes in schizophrenia patients with persistent hallucinations

Schizophrenia is characterised by the presence of a heterogeneous range of symptoms. Although there is a consensus regarding ventricular enlargement and regional grey matter deficits, the brain structural correlates of specific symptoms, such as auditory hallucinations, are not clearly defined. We used an automated voxel-wise analysis of dual-echo spin-echo MRI data from 28 patients with schizophrenia characterised by persistent hallucinations and 32 healthy controls. Patients demonstrated grey matter (GM) volume decrements in the insula bilaterally, and in the right superior temporal and fusiform gyri, and left inferior temporal gyrus. With the exception of the insula, these GM volume losses were correlated with severity of auditory hallucinations. GM excesses were observed in the right caudate nucleus and middle temporal gyrus. White matter deficits were observed adjacent to the left superior temporal gyrus, in the right internal capsule and inferior longitudinal fasciculus. These findings support the proposition that there are structural changes in the neural circuits underlying broader processing of affect-laden information in patients with schizophrenia prone to experiencing auditory hallucinations. Such deficits may obscure important cues for recognition of internal speech, contributing to failures of self-monitoring.

A diffusion tensor imaging study of fasciculi in schizophrenia

OBJECTIVE

Cognitive models propose that the symptoms and psychological impairments associated with schizophrenia arise as a consequence of impaired communication between brain regions, especially the prefrontal cortex and the temporal and parietal lobes. Functional imaging and electrophysiological data have provided evidence of functional dysconnectivity, but it is unclear whether this reflects an underlying problem with anatomical connectivity. This study used diffusion tensor imaging to examine the integrity of the major white matter fasciculi, which connects the frontal and temporal-parietal cortices, and the corpus callosum in patients with schizophrenia.

METHOD

A 1.5-T magnetic resonance scanner was used to acquire diffusion tensor images giving whole brain coverage at an isotropic 2.5-mm voxel size. Fractional anisotropy was measured in 33 patients with schizophrenia and 40 healthy comparison subjects with an automated voxel-based method of analysis.

RESULTS

There was reduced fractional anisotropy in patients with schizophrenia in regions corresponding to the superior longitudinal fasciculi bilaterally and in the genu of the corpus callosum. However, within the patient group, the propensity to experience auditory hallucinations was associated with relatively increased fractional anisotropy in superior longitudinal fasciculi and in the anterior cingulum.

CONCLUSIONS

Schizophrenia is associated with altered white matter integrity in the tracts connecting the frontal cortex with the temporal and parietal cortices and with the contralateral frontal and temporal lobes. The severity of these changes may vary with the pattern of symptoms associated with the disorder.

Prosodic discrimination in patients with schizophrenia

Fifteen patients with prominent positive symptoms of schizophrenia and 15 normal controls performed verbal prosodic and pure musical discrimination tasks, with changes in pitch and timing parameters. The patients' performance was comparable to that of controls on the discrimination of terminal pitch changes, but significantly poorer on the more difficult internal pitch discrimination. The latter deficit was positively correlated with the severity of their positive symptoms. The results suggest that patients have a deficit in processing fundamental aspects of prosody, which is associated with the presence of positive symptoms.

Age effects on diffusion tensor magnetic resonance imaging tractography measures of frontal cortex connections in schizophrenia

Diffusion tensor magnetic resonance imaging (DT-MRI) has previously been used to investigate white matter tracts in schizophrenia, with inconsistent results. The aim of the study was to use a novel method for tract-specific measurements of fronto-temporal fasciculi in early-onset schizophrenia. We hypothesized that by making tract-specific measurements, clear diffusion abnormalities would be revealed in specific fasciculi in schizophrenia. Measurements of diffusion anisotropy and mean diffusivity were localized within fronto-temporal fasciculi by forming 3-D reconstructions of the cingulum, uncinate, superior longitudinal, and inferior fronto-occipital fasciculi using diffusion tensor tractography. We were limited in our ability to test our hypothesis by the important and surprising finding that age affected DT-MRI-based measures in schizophrenia patients in a different way from comparison subjects, most notably in the left superior longitudinal fasciculus. The youngest schizophrenia patients that we studied had lower diffusion anisotropy than age-matched comparison subjects, but this difference diminished with increasing age. The main conclusion of this study was that direct comparisons of absolute DT-MRI-based measures between individuals with schizophrenia and comparison subjects may be problematic and misleading because of underlying age-related differences in brain maturation between groups.

Imaging auditory hallucinations in schizophrenia

It is increasingly recognized that there are a heterogeneous range of symptoms within the syndrome of schizophrenia and that some of these also occur frequently within other psychiatric conditions. An approach similar to that in neuropsychology, where cases are grouped based on a discrete deficit, or in this case a discrete symptom, rather than a cause or diagnosis, may be useful in exploring the neural correlates of psychotic symptomatology. Functional neuroimaging provides an excellent tool for investigating the in vivo cortical function of patients with schizophrenia. Auditory verbal hallucinations are one of the most commonly occurring psychotic symptoms in schizophrenia; and this paper examines the progress that has been made in utilizing neuroimaging techniques to investigate auditory hallucinations in schizophrenia and review potential implications for treatment and future directions for research.

Tract-specific anisotropy measurements in diffusion tensor imaging

Diffusion tensor magnetic resonance imaging (DT-MRI) has been used to examine the microstructure of individual white matter tracts, often in neuropsychiatric conditions without identifiable focal pathology. However, the voxel-based group-mapping and region-of-interest (ROI) approaches used to analyse the data have inherent conceptual and practical difficulties. Taking the example of the genu of the corpus callosum in a sample of schizophrenic patients, we discuss the difficulties in attempting to replicate a voxel-based finding of reduced anisotropy using two ROI methods. Firstly we consider conventional ROIs; secondly, we present a novel tractography-based approach. The problems of both methods are explored, particularly of high variance and ROI definition. The potential benefits of the tractographic method for neuropsychiatric conditions with subtle and diffuse pathology are outlined.

Timing of covert articulation: An fMRI study

Timing is an important constituent of speech and language. Different brain regions have been associated with time management functions such as time estimation and motor timing. This study aims to identify the less well known neural networks associated with timing of internally paced covert articulation. Functional MRI was performed on subjects who either spontaneously, or in response to a visual cue, covertly generated words every 2 s. Results show the involvement of anterior cingulate gyrus, right dorsolateral and inferior frontal and right inferior parietal cortices in a putatively modality independent circuit associated with timing of covert speech. Modality specific activation in the right temporal cortex may have reflected the involvement of this region in auditory-verbal processing.

A diffusion tensor magnetic resonance imaging study of frontal cortex connections in very-late-onset schizophrenia-like psychosis

OBJECTIVE

Onset of psychosis after the age of 60 may be associated with structural abnormalities within cerebral white matter. The authors looked within white-matter tracts, which mediate connectivity of the frontal lobes, in psychotic patients for evidence of loss of fiber integrity consistent with degenerative damage.

METHODS

Fourteen patients with very-late-onset schizophrenia-like psychosis and an age-matched control group underwent diffusion tensor magnetic resonance imaging. Tract maps were constructed for each subject from the imaging data, and measurements of fractional anisotropy and mean diffusivity were made within the uncinate, superior longitudinal, and inferior occipito-frontal fasciculi, and the cingulum.

RESULTS

There were no significant differences in fractional anisotropy, a measure of the ordering of axons within fiber tracts, nor in mean diffusivity, an orientationally-averaged measure of the bulk diffusivity within each voxel, between patients and control subjects.

CONCLUSION

The lack of difference in fractional anisotropy and mean diffusivity measures between patients and controls argues against the presence of structural abnormalities within these tracts and the notion that a focal white-matter abnormality within the tracts investigated underpins the onset of psychosis.

Evidence for sensory prediction deficits in schizophrenia

OBJECTIVE

Patients with schizophrenia experiencing delusions and hallucinations can misattribute their own actions to an external source. The authors test the hypothesis that patients with schizophrenia have defects in their ability to predict the sensory consequences of their actions.

METHOD

The authors measured sensory attenuation of self-produced stimuli by patients with schizophrenia and by healthy subjects.

RESULTS

Patients with schizophrenia demonstrated significantly less sensory attenuation than healthy subjects.

CONCLUSIONS

Patients with a diagnosis of schizophrenia have a dysfunction in their predictive mechanisms.

The functional anatomy of divided attention in amnestic mild cognitive impairment

Recent neuroimaging studies have demonstrated changes in brain function in cognitively normal subjects at increased risk of developing Alzheimer's disease. Amnestic mild cognitive impairment (AMCI) carries a high risk of developing into Alzheimer's disease. In AMCI altered cortical activation has been demonstrated during memory tasks, using functional MRI (fMRI). Memory and attention are closely related cognitive functions. It is unclear whether the memory impairment of AMCI is associated with attentional deficits of the sort likely to be revealed by tasks requiring divided attention. Ten older adults (mean age 72 years, range 57-81 years) with AMCI were compared with healthy matched controls on divided attention and passive sensory processing tasks using fMRI. During the divided attention task both groups activated similar regions of left hemispheric prefrontal and extrastriate visual cortex. However, the AMCI group had attenuated prefrontal activation compared with age matched controls. On the passive sensory processing task there was no difference between the AMCI and control groups. We conclude that there are changes in the functional network subserving divided attention in patients with AMCI as reflected in the attenuation of prefrontal cortical activation. These findings have implications for evaluating cognition in AMCI and also for monitoring the effects of future treatments in AMCI.

Temporal course of auditory hallucinations

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.

Engagement of brain areas implicated in processing inner speech in people with auditory hallucinations

BACKGROUND

The neurocognitive basis of auditory hallucinations is unclear, but there is increasing evidence implicating abnormalities in processing inner speech. Previous studies have shown that people with schizophrenia who were prone to auditory hallucinations demonstrated attenuated activation of brain areas during the monitoring of inner speech.

AIMS

To investigate whether the same pattern of functional abnormalities would be evident as the rate of inner speech production was varied.

METHOD

Eight people with schizophrenia who had a history of prominent auditory hallucinations and eight control participants were studied using functional magnetic resonance imaging while the rate of inner speech generation was varied experimentally.

RESULTS

When the rate of inner speech generation was increased, the participants with schizophrenia showed a relatively attenuated response in the right temporal, parietal, parahippocampal and cerebellar cortex.

CONCLUSIONS

In people with schizophrenia who are prone to auditory hallucinations, increasing the demands on the processing of inner speech is associated with attenuated engagement of the brain areas implicated in verbal self-monitoring.

Modulation of activity in temporal cortex during generation of inner speech

Monitoring one's thoughts (in the verbal modality) is thought to be critically dependent on the interaction between areas that generate and perceive inner speech in the frontal and temporal cortex, respectively. We used functional magnetic resonance imaging (fMRI) to examine the relationship between activity in these areas while the rate of inner speech generation was varied experimentally. The faster rate was associated with activation in the left inferior frontal gyrus, the right pre- and postcentral gyri and both superior temporal gyri. Thus, temporal cortical activation was associated with increasing the rate of covert articulation, in the absence of external auditory input, suggesting that there is effective fronto-temporal connectivity. Furthermore, this may provide support for the existence of feed forward models, which suggest that activity in regions responsible for verbal perception is modulated by activity in areas that generate inner speech.

Modality specific neural correlates of auditory and somatic hallucinations

Somatic hallucinations occur in schizophrenia and other psychotic disorders, although auditory hallucinations are more common. Although the neural correlates of auditory hallucinations have been described in several neuroimaging studies, little is known of the pathophysiology of somatic hallucinations. Functional magnetic resonance imaging (fMRI) was used to compare the distribution of brain activity during somatic and auditory verbal hallucinations, occurring at different times in a 36 year old man with schizophrenia. Somatic hallucinations were associated with activation in the primary somatosensory and posterior parietal cortex, areas that normally mediate tactile perception. Auditory hallucinations were associated with activation in the middle and superior temporal cortex, areas involved in processing external speech. Hallucinations in a given modality seem to involve areas that normally process sensory information in that modality.

A functional study of auditory verbal imagery

BACKGROUND

We used functional MRI to examine the functional anatomy of inner speech and different forms of auditory verbal imagery (imagining speech) in normal volunteers. We hypothesized that generating inner speech and auditory verbal imagery would be associated with left inferior frontal activation, and that generating auditory verbal imagery would involve additional activation in the lateral temporal cortices.

METHODS

Subjects were scanned, while performing inner speech and auditory verbal imagery tasks, using a 1.5 Tesla magnet.

RESULTS

The generation of inner speech was associated with activation in the left inferior frontal/insula region, the left temporo-parietal cortex, right cerebellum and the supplementary motor area. Auditory verbal imagery in general, as indexed by the three imagery tasks combined, was associated with activation in the areas engaged during the inner speech task, plus the left precentral and superior temporal gyri (STG), and the right homologues of all these areas.

CONCLUSIONS

These results are consistent with the use of the 'articulatory loop' during both inner speech and auditory verbal imagery, and the greater engagement of verbal self-monitoring during auditory verbal imagery.

Mapping auditory hallucinations in schizophrenia using functional magnetic resonance imaging

BACKGROUND

Perceptions of speech in the absence of an auditory stimulus (auditory verbal hallucinations) are a cardinal feature of schizophrenia. Functional neuroimaging provides a powerful means of measuring neural activity during auditory hallucinations, but the results from previous studies have been inconsistent. This may reflect the acquisition of small numbers of images in each subject and the confounding effects of patients actively signaling when hallucinations occur.

METHODS

We examined 6 patients with schizophrenia who were experiencing frequent auditory hallucinations, using a novel functional magnetic resonance imaging method that permitted the measurement of spontaneous neural activity without requiring subjects to signal when hallucinations occurred. Approximately 50 individual scans were acquired at unpredictable intervals in each subject while they were intermittently hallucinating. Immediately after each scan, subjects reported whether they had been hallucinating at that instant. Neural activity when patients were and were not experiencing hallucinations was compared in each subject and the group as a whole.

RESULTS

Auditory hallucinations were associated with activation in the inferior frontal/insular, anterior cingulate, and temporal cortex bilaterally (with greater responses on the right), the right thalamus and inferior colliculus, and the left hippocampus and parahippocampal cortex (P<.0001).

CONCLUSIONS

Auditory hallucinations may be mediated by a distributed network of cortical and subcortical areas. Previous neuroimaging studies of auditory hallucinations may have identified different components of this network.

Functional anatomy of auditory verbal imagery in schizophrenic patients with auditory hallucinations

OBJECTIVE

This study investigated the functional neuroanatomy of inner speech and auditory verbal imagery in schizophrenic patients predisposed to auditory hallucinations.

METHOD

Eight patients with schizophrenia with a history of prominent auditory hallucinations and six comparison subjects underwent functional magnetic resonance imaging while generating inner speech or imagining external speech.

RESULTS

Patients showed no differences while generating inner speech but experienced a relatively attenuated response in the posterior cerebellar cortex, hippocampi, and lenticular nuclei bilaterally and the right thalamus, middle and superior temporal cortex, and left nucleus accumbens during auditory verbal imagery.

CONCLUSIONS

Patients with schizophrenia who were prone to auditory hallucinations show attenuated activation when processing inner speech in areas implicated in verbal self-monitoring.

Outcome in refractory depression

BACKGROUND

Failure to respond to first-line antidepressant treatment can occur in up to 40% of patients with depressive illness. A proven strategy for managing this refractory depression is lithium augmentation. The long-term outcome and optimal management of patients treated with lithium augmentation remains unclear. We describe a 4-8 year naturalistic follow-up of patients treated with lithium augmentation in two controlled studies of its efficacy in refractory depression.

METHOD

Cases were followed up with personal interview where possible, and by telephone and general practitioner contact otherwise. Lifetime clinical status was ascertained using the Schedule for Affective Disorders and Schizophrenia-Lifetime (SADS-L).

RESULTS

We obtained outcome data on 53 of the original eligible 76 patients. There was a good outcome in 38 (72%) patients. Good outcome was associated with a less endogenous nature of depression and an absence of previous hospitalisations.

CONCLUSIONS

There do not seem to be any specific prognostic indicators of long-term outcome to lithium augmentation beyond those recognised to be relevant in the outcome of depression generally.

LIMITATIONS

The conclusions are limited by incomplete follow-up of the total original sample and lack of objective illness and medication data for the intervening period.

Auditory hallucinations: a review of psychological treatments

Auditory hallucinations (AH) occur frequently amongst psychiatric patients, being most common in schizophrenia. In 25-30% of cases they are refractory to traditional antipsychotic drugs. A variety of psychosocial treatments have been used, but their efficacy remains unclear. This review aims to bring together the more recent studies of psychological treatments and discuss them in the context of recent cognitive models of hallucinations and functional imaging studies. The search strategy included the following sources: MEDLINE, Embase and Psychlit. Strategies reported by patients can be categorised as: (1) distracting activities, such as listening to music; (2) behavioural tasks, such as taking exercise; (3) cognitive tasks, such as ignoring AH. Almost all the strategies produced some benefit in some patients: treatment often improved AH-associated distress, rather than frequency of AH. There are many difficulties in conducting research on AH. Treatment should be individually tailored and used as an adjunct to pharmacotherapy. Future theory-driven studies need to be based on complex aetiological models and incorporate functional imaging to elucidate the physiological changes induced by therapeutic interventions.

Communication of psychiatric diagnosis

We examined whether psychiatric patients knew their diagnosis, the significance they attached to it, and the impact of being informed in a systematic fashion according to their wishes. We also assessed whether the nature of the psychiatric diagnosis influenced what patients were told by their psychiatrists. The three parts of the study included questionnaire responses from 28 consultant psychiatrists: case-note reviews and questionnaire responses of 200 adult psychiatric in-patients: and a pilot study informing 28 adult psychiatric day hospital patients of their diagnosis according to their wishes. The results showed that of 126 in-patients, 53% had not been told their diagnosis, although most wanted to know. Of those informed, 75% agreed with their diagnosis. The majority of patients considered a psychiatric diagnosis to be as real as a physical diagnosis and helpful in their treatment. Patients with schizophrenia were less likely to have been informed of their diagnosis, and psychiatrists were also more reticent regarding the diagnosis of personality disorder. All patients who were systematically informed, in the pilot study agreed with their diagnosis. We conclude that most patients agree with their diagnosis and its usefulness. All patients should be asked whether they want to know their diagnosis and be informed appropriately.

Pharmacological choices after one antidepressant fails: a survey of UK psychiatrists

BACKGROUND

At least 30% of depressed patients fail to respond to adequate first-line anti-depressant medication. Several pharmacological strategies have been suggested to treat such refractory depression. There has been no survey of United Kingdom psychiatrists' treatment preferences for refractory depression. This study was carried out to determine both experience and preference of various strategies for management of refractory depression.

METHOD

A total of 300 fellows, members and inceptors of the Royal College of Psychiatrists were randomly selected and approached by postal questionnaire. They were asked to comment on management of a detailed clinical vignette of a case of depression with initial treatment failure.

RESULTS

The response rate was 63% (n = 175). The most popular treatment choices were increasing dosage of tricyclic medication and change of medication of SSRI. The most rarely selected were augmentation with triiodothyronine (T3) and augmentation with tryptophan or MAOIs. Treatment choice was significantly influenced by previous experience. A large number (39%) of psychiatrists were not confident in treating refractory depression.

CONCLUSION

Surprisingly few psychiatrists chose to use the best proven pharmacological treatments such as augmentation with lithium or T3. In view of this and the considerable proportion of psychiatrists lacking confidence in the management of refractory depression, this topic deserves priority as a topic for continuing professional development (CPD) courses.

Patients' views towards care received from psychiatrists

BACKGROUND

Measurement of the quality of psychiatric care including assessment of patients' views have become increasingly important as expectations of the standard of care rises.

METHODS

Attitudes and satisfaction of acute psychiatric in-patients were investigated using a questionnaire looking at satisfaction, patients' views on personal and professional qualities of psychiatrists, empowerment and insight.

RESULTS

The response rate was 79.2% (137 out of 173). Patients with a diagnosis of a non-affective psychotic illness, particularly those lacking insight were significantly less satisfied with their care. Respondents were more satisfied with the personal rather than the professional qualities of the doctors, and less satisfied with their empowerment and doctors' availability.

CONCLUSIONS

In-patients' attitudes towards their psychiatric care involves a complex relationship between clinical and sociocultural characteristics. Satisfaction studies can serve as an important monitor and reminder of patient dissent.

A comparative study of ophthalmodynamometry in hypertensive and non-hypertensive cases

Ophthalmodynamometry was done on 100 hypertensive cases and 100 non-hypertensive cases who had clear media and no glaucoma. The ratio of the pressure mean ophthalmic: pressure mean brachial in the non-hypertensive group was 0.71:1.0, which rose to 0.78:1.0 in the hypertensive group. The ophthalmic humeral diastolic ratio increased with the severity of fundus changes. The pressure mean ophthalmic showed higher values with increasing grades of fundus changes. Those cases having a pressure mean opthalmic higher than the expected value in the hypertensive group as compared to the cases having a pressure mean ophthalmic lower than the expected value, were at a greater risk or had a graver prognosis. The importance of ophthalmodynamometry is stressed for the prognosis of hypertension along with the fundus examination.