A new comparator account of auditory verbal hallucinations: how motor prediction can plausibly contribute to the sense of agency for inner speech

The comparator account holds that processes of motor prediction contribute to the sense of agency by attenuating incoming sensory information and that disruptions to this process contribute to misattributions of agency in schizophrenia. Over the last 25 years this simple and powerful model has gained widespread support not only as it relates to bodily actions but also as an account of misattributions of agency for inner speech, potentially explaining the etiology of auditory verbal hallucination (AVH). In this paper we provide a detailed analysis of the traditional comparator account for inner speech, pointing out serious problems with the specification of inner speech on which it is based and highlighting inconsistencies in the interpretation of the electrophysiological evidence commonly cited in its favor. In light of these analyses we propose a new comparator account of misattributed inner speech. The new account follows leading models of motor imagery in proposing that inner speech is not attenuated by motor prediction, but rather derived directly from it. We describe how failures of motor prediction would therefore directly affect the phenomenology of inner speech and trigger a mismatch in the comparison between motor prediction and motor intention, contributing to abnormal feelings of agency. We argue that the new account fits with the emerging phenomenological evidence that AVHs are both distinct from ordinary inner speech and heterogeneous. Finally, we explore the possibility that the new comparator account may extend to explain disruptions across a range of imagistic modalities, and outline avenues for future research.

Judging Time Intevals using a model of perceptuo-motor control

Estimating a time interval and temporally coordinating movements in space are fundamental skills, but the relationships between these different forms of timing, and the neural processes that they incur, are not well understood. While different theories have been proposed to account for time perception, time estimation, and the temporal patterns of coordination, there are no general mechanisms which unify these various timing skills. This study considers whether a model of perceptuo-motor timing, the tau(GUIDE), can also describe how certain judgements of elapsed time are made. To evaluate this, an equation for determining interval estimates was derived from the tau(GUIDE) model and tested in a task where participants had to throw a ball and estimate when it would hit the floor. The results showed that in accordance with the model, very accurate judgements could be made without vision (mean timing error -19.24 msec), and the model was a good predictor of skilled participants' estimate timing. It was concluded that since the tau(GUIDE) principle provides temporal information in a generic form, it could be a unitary process that links different forms of timing.

Caged birds and cloning machines: how student imagery 'speaks' to us about cultures of schooling and student participation

With the advent of the United Nations Convention on the Rights of the Child (CRC), there is an increasing requirement that schools ensure children and young people's views are voiced, listened to and taken seriously on matters of significance. Encouraging these shifts by law is one thing; changing the culture in schools is another. For a significant proportion of schools, actively engaging students' voices on how they experience education poses a significant challenge and crucial gaps may exist between the rhetoric espoused and a school's readiness for genuine student involvement. This ethnographic study illuminates tensions that persist between headteachers' espoused views of how students are valued and students' creative images of their actual post-primary schooling experience. If cultures of schooling are to nurture the true spirit of democratic pupil participation implied by changes in the law, there is a need to develop genuine processes of student engagement in which students and staff can collaborate towards greater shared understandings of a school's priorities.

Oxaliplatin induces hyperexcitability at motor and autonomic neuromuscular junctions through effects on voltage-gated sodium channels

Oxaliplatin, an effective cytotoxic treatment in combination with 5-fluorouracil for colorectal cancer, is associated with sensory, motor and autonomic neurotoxicity. Motor symptoms include hyperexcitability while autonomic effects include urinary retention, but the cause of these side-effects is unknown. We examined the effects on motor nerve function in the mouse hemidiaphragm and on the autonomic system in the vas deferens. In the mouse diaphragm, oxaliplatin (0.5 mM) induced multiple endplate potentials (EPPs) following a single stimulus, and was associated with an increase in spontaneous miniature EPP frequency. In the vas deferens, spontaneous excitatory junction potential frequency was increased after 30 min exposure to oxaliplatin; no changes in resting Ca(2+) concentration in nerve terminal varicosities were observed, and recovery after stimuli trains was unaffected.In both tissues, an oxaliplatin-induced increase in spontaneous activity was prevented by the voltage-gated Na(+) channel blocker tetrodotoxin (TTX). Carbamazepine (0.3 mM) also prevented multiple EPPs and the increase in spontaneous activity in both tissues. In diaphragm, beta-pompilidotoxin (100 microM), which slows Na(+) channel inactivation, induced multiple EPPs similar to oxaliplatin's effect. By contrast, blockers of K(+) channels (4-aminopyridine and apamin) did not replicate oxaliplatin-induced hyperexcitability in the diaphragm. The prevention of hyperexcitability by TTX blockade implies that oxaliplatin acts on nerve conduction rather than by effecting repolarisation. The similarity between beta-pompilidotoxin and oxaliplatin suggests that alteration of voltage-gated Na(+) channel kinetics is likely to underlie the acute neurotoxic actions of oxaliplatin.

Interobserver agreement of the Gross Motor Function Classification System in an ambulant population of children with cerebral palsy

Gross Motor Function Classification System (GMFCS) level was reported by three independent assessors in a population of children with cerebral palsy (CP) aged between 4 and 18 years (n=184; 112 males, 72 females; mean age 10y 10mo [SD 3y 7mo]). A software algorithm also provided a computed GMFCS level from a regional CP registry. Participants had clinical diagnoses of unilateral (n=94) and bilateral (n=84) spastic CP, ataxia (n=4), dyskinesia (n=1), and hypotonia (n=1), and could walk independently with or without the use of an aid (GMFCS Levels I-IV). Research physiotherapist (n=184) and parent/guardian data (n=178) were collected in a research environment. Data from the child's community physiotherapist (n=143) were obtained by postal questionnaire. Results, using the kappa statistic with linear weighting (?1w), showed good agreement between the parent/guardian and research physiotherapist (?1w=0.75) with more moderate levels of agreement between the clinical physiotherapist and researcher (?1w=0.64) and the clinical physiotherapist and parent/guardian (?1w=0.57). Agreement was consistently better for older children (>2y). This study has shown that agreement with parent report increases with therapists'experience of the GMFCS and knowledge of the child at the time of grading. Substantial agreement between a computed GMFCS and an experienced therapist (?1w=0.74) also demonstrates the potential for extrapolation of GMFCS rating from an existing CP registry, providing the latter has sufficient data on locomotor ability.