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Biomedical subjects

Peter W R Woodruff

Publications and source records attributed to Peter W R Woodruff.

At least 19 recordsLinked to original sources
PubMed2007

The role of the cerebellum in subsecond time perception: evidence from repetitive transcranial magnetic stimulation.

In three experiments, we investigated the role of the cerebellum in sub- and suprasecond time perception by using repetitive transcranial magnetic stimulation (rTMS). In Experiment 1, subjects underwent four 8-min 1-Hz rTMS sessions in a within-subject design. rTMS sites were the medial cerebellum (real and sham rTMS), left lateral cerebellum, and right lateral cerebellum. Following each rTMS session, subjects completed a subsecond temporal bisection task (stimuli in the range 400-800 msec). Compared with sham rTMS, rTMS applied over the right lateral or medial cerebellum induced a leftward shift of the psychophysical function (perceived lengthening of time). In Experiment 2, a separate sample of subjects underwent the identical rTMS procedure and completed a suprasecond bisection task (stimuli in the 1000-2000 msec range). In this experiment, rTMS to the cerebellar sites did not produce any significant changes compared with sham rTMS. Experiment 3 employed a within-subject design to replicate findings from Experiments 1 and 2. Subjects underwent four rTMS conditions (sub- and suprabisection tasks following medial cerebellar and sham rTMS). rTMS induced a significant leftward shift of psychophysical function in the subsecond bisection, but not in the suprasecond bisection. In this study, we have demonstrated that transient cerebellar stimulation can differently affect the ability to estimate time intervals below and above a duration of 1 sec. The results of this study provide direct evidence for the role of the cerebellum in processing subsecond time intervals. This study further suggests that the perception of sub- and suprasecond intervals is likely to depend upon distinct neural systems.

Adult↗
PubMed2006

Increased cerebellar vermis white-matter volume in men with schizophrenia.

We aimed to investigate cerebellar structural abnormalities and their functional significance in patients with schizophrenia. Forty right-handed men with schizophrenia and 40 sex, age and handedness matched controls underwent a volumetric magnetic resonance scan with 1 mm3 isotropic spatial resolution. Cerebellar grey- and white-matter volumes were analysed using voxel-based morphometry. Patients with schizophrenia completed a battery of neuropsychological tests assessing sustained attention (continuous performance test), memory (Hopkins memory test) and executive function (verbal fluency and Wisconsin card sorting tests). Patients with schizophrenia exhibited significantly increased cerebellar vermis white-matter volume compared with controls. By contrast, total cerebellar volume, and grey- and white-matter volumes of cerebellar hemispheres were not significantly different between groups. Increased vermis white-matter volume in patients was associated with poor verbal fluency performance. We concluded that increased white-matter in the cerebellar vermis, possibly suggesting anomalous connectivity, may be associated with verbal executive dysfunction in men with chronic schizophrenia.

Adult↗
PubMed2006

A new dissimilarity measure for finding semantic structure in category fluency data with implications for understanding memory organization in schizophrenia.

The ordering of words in category fluency lists is indicative of the semantic distance between items in conceptual memory. Several studies have concluded from structural analyses of such data, using cluster analysis or multidimensional scaling, that the semantic memory of patients with schizophrenia is more disorganized than that of controls. Previous studies have based their analyses on a measure of average interitem dissimilarity devised by A. S. Chan et al. (1993). Here the authors derive a new and improved method of determining dissimilarity and show that when this measure is applied to the fluency lists of patients with schizophrenia, the average pattern of organization for the animal category has similar structure to that of controls, but with greater variability between individuals.

Adult↗
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↗
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

Male and female voices activate distinct regions in the male brain.

In schizophrenia, auditory verbal hallucinations (AVHs) are likely to be perceived as gender-specific. Given that functional neuro-imaging correlates of AVHs involve multiple brain regions principally including auditory cortex, it is likely that those brain regions responsible for attribution of gender to speech are invoked during AVHs. We used functional magnetic resonance imaging (fMRI) and a paradigm utilising 'gender-apparent' (unaltered) and 'gender-ambiguous' (pitch-scaled) male and female voice stimuli to test the hypothesis that male and female voices activate distinct brain areas during gender attribution. The perception of female voices, when compared with male voices, affected greater activation of the right anterior superior temporal gyrus, near the superior temporal sulcus. Similarly, male voice perception activated the mesio-parietal precuneus area. These different gender associations could not be explained by either simple pitch perception or behavioural response because the activations that we observed were conjointly activated by both 'gender-apparent' and 'gender-ambiguous' voices. The results of this study demonstrate that, in the male brain, the perception of male and female voices activates distinct brain regions.

Acoustic Stimulation↗
PubMed2004

Gender-specific sensitivity to low frequencies in male speech.

The perception of human voices as naturally occurring sound objects may correspond to the detection of specific components of the frequency spectrum. In the current study, a psychophysical experiment was undertaken to investigate whether male and female listeners differed with respect to which frequencies were important in the perception of a male voice as a natural sound object. For females (but not males) the presence of low frequencies (<220 Hz), but not high frequencies (>4 kHz), was most crucial in the perception of a male voice as natural. This finding could be compatible with a neuroethological interpretation: low frequencies in the range that were studied are important in distinguishing male from female voices and mature from immature male voices.

Adult↗
PubMed2004

Smaller hippocampal volume in patients with recent-onset posttraumatic stress disorder.

BACKGROUND: Previous structural magnetic resonance (MR) research in patients with posttraumatic stress disorder (PTSD) has found smaller hippocampal volumes in patients compared with control subjects. These studies have mostly involved subjects who have had PTSD for a number of years, such as war veterans or adult survivors of childhood abuse. Patients with recent-onset PTSD have rarely been investigated. To our knowledge only one other study has investigated such a group. The aim of this study was to compare hippocampal volumes of patients with recent onset PTSD and nontrauma-exposed control subjects. METHODS: Fifteen patients with PTSD, recruited from an accident and emergency department, were compared with 11, non-trauma-exposed, healthy control subjects. Patients underwent a structural MR scan soon after trauma (mean time = 158 +/- 41 days). Entire brain volumes, voxel size 1 x 1 x 1 mm, were acquired for each subject. Point counting and stereology were used to measure the hippocampal and amygdala volume of each subject. RESULTS: Right-sided hippocampal volume was significantly smaller in PTSD patients than control subjects after controlling for effects of whole brain volume and age. Neither left nor total hippocampal volume were significantly smaller in the PTSD group after correction. Whole brain volume was also found to be significantly smaller in patients. There were no differences in amygdala or white matter volumes between patients and control subjects. CONCLUSIONS: This result replicates previous findings of smaller hippocampal volumes in PTSD patients, but in an underinvestigated population, suggesting that either smaller hippocampal volume is a predisposing factor in the development of PTSD or that damage occurs within months of trauma, rather than a number of years. Either of these two hypotheses have significant implications for the treatment of PTSD. For instance, if it could be shown that screening for hippocampal volume may, in some cases, predict those likely to develop clinical PTSD.

Adult↗
PubMed2004

Corpus callosum size and very preterm birth: relationship to neuropsychological outcome.

Thinning of the corpus callosum (CC) is often observed in individuals who were born very preterm. Damage to the CC during neurodevelopment may be associated with poor neuropsychological performance. This study aimed to explore any evidence of CC pathology in adolescents aged 14-15 years who were born very preterm, and to investigate the relationship between CC areas and verbal skills. Seventy-two individuals born before 33 weeks of gestation and 51 age- and sex-matched full-term controls received structural MRI and neuropsychological assessment. Total CC area in very preterm adolescents was 7.5% smaller than in controls, after adjusting for total white matter volume (P = 0.015). The absolute size of callosal subregions differed between preterm and full-term adolescents: preterm individuals had a 14.7% decrease in posterior (P < 0.0001) and an 11.6% decrease in mid-posterior CC quarters (P = 0.029). Preterm individuals who had experienced periventricular haemorrhage and ventricular dilatation in the neonatal period showed the greatest decrease in CC area. In very preterm boys only, verbal IQ and verbal fluency scores were positively associated with total mid-sagittal CC size and mid-posterior surface area. These results suggest that very preterm birth adversely affects the development of the CC, particularly its posterior quarter, and this impairs verbal skills in boys.

Adolescent↗
PubMed2004

The effects of ageing on stereopsis. A VEP study.

Differences in brain activation between young (n = 11, ages 21-35) and elderly (n = 8, ages 70-84) healthy participants were studied using visual evoked potentials (VEPs) to different kinds of computer generated random-dot patterns. The main stimulus of interest was a 2 x 2 array of rectangles whose rectangles moved to and fro in depth. Control conditions were similar 2 x 2 arrays, one with side-to-side lateral motion (LM) of the rectangles, and one a stationary baseline condition. The third non-stereo stimulus was an expanding field of small dots in radial motion (RM). Significant stereo related activation was found in both age groups. The stereo VEPs showed a longer latency of depth reversal triggered VEP peaks compared to control LM VEPs. The amplitudes of LM VEPs were larger than the baseline VEPs. Age-related differences were found not only in stereo but also in the other conditions. Thus the latency of early VEP peaks was shorter and their amplitude higher in the elderly for LM and baseline conditions, and the younger participants showed significantly higher activation in the later VEP peaks of all conditions. Our main finding is no evidence for age related stereo specific effects in brain activation, but instead more general and subtle changes that affect widely different visual stimulus conditions.

Adult↗
PubMed2004

Neural response to emotional prosody in schizophrenia and in bipolar affective disorder.

BACKGROUND: Evidence suggests a reversal of the normal left-lateralised response to speech in schizophrenia. AIMS: To test the brain's response to emotional prosody in schizophrenia and bipolar disorder. METHOD: BOLD contrast functional magnetic resonance imaging of subjects while they passively listened or attended to sentences that differed in emotional prosody. RESULTS: Patients with schizophrenia exhibited normal right-lateralisation of the passive response to 'pure' emotional prosody and relative left-lateralisation of the response to unfiltered emotional prosody. When attending to emotional prosody, patients with schizophrenia activated the left insula more than healthy controls. When listening passively, patients with bipolar disorder demonstrated less activation of the bilateral superior temporal gyri in response to pure emotional prosody, and greater activation of the left superior temporal gyrus in response to unfiltered emotional prosody. In both passive experiments, the patient groups activated different lateral temporal lobe regions. CONCLUSIONS: Patients with schizophrenia and bipolar disorder may display some left-lateralisation of the normal right-lateralised temporal lobe response to emotional prosody.

Adult↗
PubMed2003

The neural response to emotional prosody, as revealed by functional magnetic resonance imaging.

Prosody is an important feature of language, comprising intonation, loudness, and tempo. Emotional prosodic processing forms an integral part of our social interactions. The main aim of this study was to use bold contrast fMRI to clarify the normal functional neuroanatomy of emotional prosody, in passive and active contexts. Subjects performed six separate scanning studies, within which two different conditions were contrasted: (1) "pure" emotional prosody versus rest; (2) congruent emotional prosody versus 'neutral' sentences; (3) congruent emotional prosody versus rest; (4) incongruent emotional prosody versus rest; (5) congruent versus incongruent emotional prosody; and (6) an active experiment in which subjects were instructed to either attend to the emotion conveyed by semantic content or that conveyed by tone of voice. Data resulting from these contrasts were analysed using SPM99. Passive listening to emotional prosody consistently activated the lateral temporal lobe (superior and/or middle temporal gyri). This temporal lobe response was relatively right-lateralised with or without semantic information. Both the separate and direct comparisons of congruent and incongruent emotional prosody revealed that subjects used fewer brain regions to process incongruent emotional prosody than congruent. The neural response to attention to semantics, was left lateralised, and recruited an extensive network not activated by attention to emotional prosody. Attention to emotional prosody modulated the response to speech, and induced right-lateralised activity, including the middle temporal gyrus. In confirming the results of lesion and neuropsychological studies, the current study emphasises the importance of the right hemisphere in the processing of emotional prosody, specifically the lateral temporal lobes.

Adolescent↗
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

Laterality effects in perceived spatial location of hallucination-like voices.

Aydin and colleagues reported a reversal of physiological 'right-ear advantage' in a group of right-handed patients with schizophrenia, using an auditory acuity test. In schizophrenia, auditory hallucinations may appear to be spatially located inside or outside the patient's head. Here we show, using virtual acoustic space techniques, that normal right-handed subjects have a right-ear advantage for correctly locating the 'source' of hallucination-like voices as from either inside or outside the head. We propose a model for understanding lateralised, external hallucinations in schizophrenia based upon reversal of normal cortical asymmetry for auditory spatial processing.

Adult↗
PubMed2003

Sex and personality traits influence the difference between time taken to tell the truth or lie.

A necessary component of lying is the withholding of a truthful response. Hence, lying may be conceptualised as involving the inhibition of an initial, automatic response (the truth) while an alternative response (the lie) is generated. We investigated response times to visually and auditorially presented questions probing recent episodic memory, when subjects answered questions truthfully or with lies. We also investigated whether the absolute response times or difference between time taken to tell the truth or lie was affected by participants' sex or correlated with personality scores on the Eysenck Personality Questionnaire Revised-Short Scale. 61 subjects answered the same 36 questions five times. The first time involved answering all questions truthfully, which allowed post hoc analysis of whether subjects had been consistent in their lying and truth-telling on the following four occasions. These latter four occasions involved answering all questions (one each with 'truth' or 'lie') for both types of presentation. Regardless of type of presentation or subjects' sex, subjects took approximately 200 msec. longer to lie than to tell the truth in response to each question (p<.001). There were significant correlations between truthful response times to auditorially presented questions and Eysenck 'Neuroticism' scores. There was also a significant correlation for women between mean individual lie-minus-truth time to auditorially presented questions and Eysenck 'Lie' scores. These preliminary data suggest that response time is systematically longer when telling a lie and that personality variables may play a part in this process.

Adult↗
PubMed2002

Study of the effect of CSF suppression on white matter diffusion anisotropy mapping of healthy human brain.

Healthy human brain diffusion anisotropy maps derived from standard spin echo diffusion tensor imaging (DTI) were compared with those using fluid-attenuated inversion recovery (FLAIR) preparation prior to DTI to null the signal from cerebrospinal fluid (CSF). Consistent comparisons entailed development of DTI postprocessing methods, image masking based on fitting quality, and an objective region-of-interest-based method for assessment of white matter extent. FLAIR DTI achieved an extended delineation of major white-matter tracts (genu, splenium, and body of the corpus callosum) close to large CSF-filled spaces (lateral ventricles), but did not affect representation of tracts remote from CSF (internal and external capsules and coronal radiation). This result, which was detectable qualitatively (visual inspection), was verified quantitatively by analyses of the relative anisotropy (RA) distribution over white matter structures for 11 subjects. FLAIR DTI thus suppresses the CSF signal that otherwise masks underlying anisotropic parenchymal tissue through partial volume averaging.

Adult↗