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Biomedical subjects

Sean A Spence

Publications and source records attributed to Sean A Spence.

At least 19 recordsLinked to original sources
PubMed2007

A systematic review of cognition in homeless children and adolescents.

Objectives The cognitive function of homeless children and adolescents may be overlooked, albeit understandably, when societal interventions focus on their immediate housing needs. Nevertheless, homelessness might be hypothesized to carry many risks for the developing mind and brain. We wanted to discover whether this hypothesis had been tested previously. Design A systematic review to examine whether cognitive impairments were reported in homeless children and adolescents. Setting Objective, systematic review of standard databases, examined by key word searches. Participants Children and adolescents. Main outcome measures Formal assessments of cognition. Results We found that in spite of there being many homeless children in the world, fewer than 2000 have been assessed cognitively and reported in the literature. Yet when compared with those who are domiciled, these children tend to have lower intellectual functioning and decreased academic achievement. Furthermore, adolescents evince cognitive impairments in the contexts of drug, physical, and sexual abuse. Conclusions We suggest that cognitive and mental health screening be incorporated into those intervention programs deployed to facilitate societal reintegration of homeless children and adolescents.

Adolescent↗
PubMed2006

A functional magnetic resonance imaging study of social cognition in schizophrenia during an acute episode and after recovery.

OBJECTIVE: Difficulty with social interactions is a characteristic of schizophrenia. The authors used functional magnetic resonance imaging (fMRI) to investigate brain activation changes during a social cognition paradigm in patients with schizophrenia during and after an acute episode and their association with social and executive function. METHOD: In a longitudinal study design, 14 patients with schizophrenia experiencing an acute episode had an fMRI scan. They returned for a follow-up scan after clinical improvement. Fourteen healthy comparison subjects were also scanned twice with approximately the same time interval between scans as in the patient group. The authors employed a social cognition fMRI paradigm involving empathic and forgivability judgments. Schizophrenia symptoms, social functioning and illness insight scales, and the Wisconsin Card Sorting Test were used to examine whether improvement on these measures was associated with recovery of brain activation in response to the social cognition paradigm. RESULTS: After recovery from the acute episode, patients exhibited increased activation in the left medial prefrontal cortex, which was, in turn, significantly correlated with improved insight and social functioning. Decreased symptom severity and improved performance on the Wisconsin Card Sorting Test were not significantly associated with increased left medial prefrontal cortex activation. CONCLUSIONS: This is the first study to the authors' knowledge to use a social cognition paradigm to reveal improved left medial prefrontal cortex activation in schizophrenia after recovery from an acute episode. These results suggest that restored left medial prefrontal cortex activation may mediate improvement of insight and social functioning in patients with schizophrenia.

Adult↗
PubMed2006

Impact of modafinil on prefrontal executive function in schizophrenia.

OBJECTIVE: The purpose of this study was to investigate the acute effects of modafinil on prefrontal activation and cognitive control of motor activity in people with schizophrenia and prominent negative symptoms. METHOD: In a crossover design, 12 subjects with schizophrenia were studied twice, receiving either modafinil or placebo prior to functional magnetic resonance imaging (fMRI). Inside the scanner, they performed a task probing cognitive control that required deliberate variation of motor activity in time. RESULTS: Modafinil administration was associated with significantly greater activation of the dorsolateral prefrontal cortex during fMRI. Its physiological and behavioral effects were correlated. This was most evident in individuals with worse baseline executive function. Focal response to modafinil in the left dorsolateral prefrontal cortex and baseline letter fluency scores predicted most of the variance in the drug's effect on cognitive control. CONCLUSIONS: Modafinil did not improve cognitive control in all schizophrenia patients. Increased activation in the dorsolateral prefrontal cortex and in neuropsychological performance were observed in patients with suboptimal baseline function.

Adult↗
PubMed2006

Modafinil and unconstrained motor activity in schizophrenia: double-blind crossover placebo-controlled trial.

Avolition affects quality of life in chronic schizophrenia. We investigated the effect of modafinil upon unconstrained motor activity in 18 male patients. In a randomised crossover design study, wrist-worn actigraphic monitors were used to objectively record motor activity over a 20 h period. Patients' total activity was significantly greater when given the drug. These data suggest that modafinil increases quantifiable motor behaviour in schizophrenia and may have an impact on avolition.

Benzhydryl Compounds↗
PubMed2005

Quantifiable change in functional brain response to empathic and forgivability judgments with resolution of posttraumatic stress disorder.

Previous functional neuroimaging studies of posttraumatic stress disorder (PTSD) have mainly focused on symptom-provocation paradigms in combat-related PTSD. We sought to elucidate the effect of non-combat-related PTSD on the physiology of social cognition. Thirteen patients with PTSD underwent functional magnetic resonance imaging (fMRI) while they engaged in tasks that (i) involve speculation on another's intention, (ii) invoke empathy and (iii) involve making judgments of the forgivability of others' actions; each versus 'baseline' social reasoning judgments. A post-therapy fMRI scan followed a course of modified cognitive behavioural therapy. Post-therapy, we found increased activation in brain regions predicted on the basis of foregoing work in healthy subjects. These included significant left middle temporal gyrus activation in post-therapy response to empathy judgments and posterior cingulate gyrus activation in post-therapy response to forgivability judgments. The specific regions of the human brain activated by empathy and forgivability judgments changed with symptom resolution in PTSD. Time and therapy are likely contributory factors that lead to a degree of 'normalisation' of the neural response to these social cognition tasks.

Adult↗
PubMed2005

Expanding the response space in chronic schizophrenia: the relevance of left prefrontal cortex.

OBJECTIVE: This study probed the ability of people with chronic schizophrenia to control their behavior in time by requiring them to deliberately vary responses within the temporal domain (i.e., to avoid regular inter-response intervals). METHODS: Thirteen schizophrenia patients performed single finger movements (at moments of their own choosing) in an event-related functional magnetic resonance imaging paradigm. Their performance was computed using the coefficient of variation of inter-response interval duration. RESULTS: Task performance was positively correlated with activation of left lateral prefrontal cortex. Post hoc analyses revealed an inverse correlation between activation in this region and severity of attentional impairment. CONCLUSION: These findings implicate left lateral prefrontal cortex in the modulation of the temporal response space in schizophrenia and imply greater attentional (executive) impairment among those who fail to modulate their behavior in time.

Adult↗
PubMed2005

Modafinil modulates anterior cingulate function in chronic schizophrenia.

BACKGROUND: Schizophrenia is associated with widespread cognitive deficits that have an impact on social function. Modafinil promotes wakefulness and is reported to enhance cognition. AIMS: To study the acute effects of modafinil administration upon brain activity and cognitive performance in people with chronic schizophrenia. METHOD: In a randomised double-blind placebo-controlled crossover design, 19 patients received either modafinil (100 mg) or placebo prior to undertaking a working memory task with functional magnetic resonance imaging. RESULTS: Seventeen patients completed the study and another underwent acute relapse 4 days post-drug. Modafinil administration was associated with significantly greater activation in the anterior cingulate cortex during the working memory task. The anterior cingulate cortex signal correlated with cognitive performance, although only a subset of patients exhibited 'enhancement'. CONCLUSIONS: Modafinil modulates anterior cingulate cortex function in chronic schizophrenia but its beneficial cognitive effects may be restricted to a subset of patients requiring further characterisation.

Adolescent↗
PubMed2005

Structural brain correlates of unconstrained motor activity in people with schizophrenia.

Avolition affects quality of life in chronic schizophrenia. We investigated the relationship between unconstrained motor activity and the volume of key executive brain regions in 16 male patients with schizophrenia. Wristworn actigraphy monitors were used to record motor activity over a 20 h period. Structural magnetic resonance imaging brain scans were parcellated and individual volumes for anterior cingulate cortex and dorsolateral prefrontal cortex extracted. Patients'total activity was positively correlated with volume of left anterior cingulate cortex. These data suggest that the volume of specific executive structures may affect (quantifiable) motor behaviours, having further implications for models of the 'will' and avolition.

Adult↗
PubMed2004

A cognitive neurobiological account of deception: evidence from functional neuroimaging.

An organism may use misinformation, knowingly (through deception) or unknowingly (as in the case of camouflage), to gain advantage in a competitive environment. From an evolutionary perspective, greater tactical deception occurs among primates closer to humans, with larger neocortices. In humans, the onset of deceptive behaviours in childhood exhibits a developmental trajectory, which may be regarded as 'normal' in the majority and deficient among a minority with certain neurodevelopmental disorders (e.g. autism). In the human adult, deception and lying exhibit features consistent with their use of 'higher' or 'executive' brain systems. Accurate detection of deception in humans may be of particular importance in forensic practice, while an understanding of its cognitive neurobiology may have implications for models of 'theory of mind' and social cognition, and societal notions of responsibility, guilt and mitigation. In recent years, functional neuroimaging techniques (especially functional magnetic resonance imaging) have been used to study deception. Though few in number, and using very different experimental protocols, studies published in the peer-reviewed literature exhibit certain consistencies. Attempted deception is associated with activation of executive brain regions (particularly prefrontal and anterior cingulate cortices), while truthful responding has not been shown to be associated with any areas of increased activation (relative to deception). Hence, truthful responding may comprise a relative 'baseline' in human cognition and communication. The subject who lies may necessarily engage 'higher' brain centres, consistent with a purpose or intention (to deceive). While the principle of executive control during deception remains plausible, its precise anatomy awaits elucidation.

Brain↗
PubMed2004

Spatial and temporal dissociation in prefrontal cortex during action execution.

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.'

Adult↗
PubMed2003

Approaching an ecologically valid functional anatomy of spontaneous "willed" action.

We used functional magnetic resonance imaging of healthy subjects to investigate the neural basis for spontaneous "willed" action. We hypothesised that such action involves prefrontal cortex (PFC) and supplementary motor area (SMA), in addition to primary motor cortex. Furthermore, we predicted that PFC and SMA would demonstrate similar temporal response dynamics, distinct from primary motor cortex. Specifically, we predicted earlier activation in PFC and SMA, manifest as shorter response latencies compared with primary motor cortex. Six right-handed males participated in an event-related design and were required to generate spontaneous motor acts inside the scanner. By deciding "which" of two buttons to press, and "when" to press them, subjects generated sequences of action that were of high information content ("novelty" or "randomness"). Utilising a short repetition time (1 s), we acquired functional images that covered most of the frontal and parietal cortices. The onset of action was associated with significant activation in bilateral PFC, left primary motor cortex, and, close to the midline, SMA. Following action, mean time to half-maximum blood oxygenation level-dependent response was significantly earlier in left PFC and SMA than primary motor cortex. Our findings suggest that neural correlates of spontaneous willed action are distributed in executive and motor centres, and that temporal response dynamics differentiate "higher" regions from subordinate motor areas.

Adult↗
PubMed2003

A neural basis for the perception of voices in external auditory space.

We used functional imaging of normal subjects to identify the neural substrate for the perception of voices in external auditory space. This fundamental process can be abnormal in psychosis, when voices that are not true external auditory objects (auditory verbal hallucinations) may appear to originate in external space. The perception of voices as objects in external space depends on filtering by the outer ear. Psychoses that distort this process involve the cerebral cortex. Functional magnetic resonance imaging was carried out on 12 normal subjects using an inside-the-scanner simulation of 'inside head' and 'outside head' voices in the form of typical auditory verbal hallucinations. Comparison between the brain activity associated with the two conditions allowed us to test the hypothesis that the perception of voices in external space ('outside head') is subserved by a temperoparietal network comprising association auditory cortex posterior to Heschl's gyrus [planum temporale (PT)] and inferior parietal lobule. Group analyses of response to 'outside head' versus 'inside head' voices showed significant activation solely in the left PT. This was demonstrated in three experiments in which the predominant lateralization of the stimulus was to the right, to the left or balanced. These findings suggest a critical involvement of the left PT in the perception of voices in external space that is not dependent on precise spatial location. Based on this, we suggest a model for the false perception of externally located auditory verbal hallucinations.

Acoustics↗
PubMed2003

Re-examining thought insertion. Semi-structured literature review and conceptual analysis.

BACKGROUND: Thought insertion is commonly regarded as diagnostic of schizophrenia. Little is known of its aetiology or pathophysiology. AIMS: To examine the definition and application of thought insertion in psychiatric and allied literatures. METHOD: A semi-structured literature review and conceptual analysis. RESULTS: When 'narrowly' defined, thought insertion is reliably identified but not specific to schizophrenia. There is a range of related phenomena ('alienated', 'influenced', 'made' and 'passivity' thinking), less consistently defined but also not specific to schizophrenia. Whether thought insertion is solely an abnormal belief (or may also be an experience) is open to question. Nevertheless, the symptom has been used to explain schizophrenia, predict dangerousness and advance theories of 'normal' agency. Most applications have been subject to critique. CONCLUSIONS: Despite its widespread occurrence and diagnostic application, thought insertion is an ill-understood and under researched symptom of psychosis. Its pathophysiology remains obscure.

Adaptation, Psychological↗