Spatiotemporal processing of somatosensory stimuli in schizotypy

Unusual interaction behaviors and perceptual aberrations, like those occurring in schizotypy and schizophrenia, may in part originate from impaired remapping of environmental stimuli in the body space. Such remapping is contributed by the integration of tactile and proprioceptive information about current body posture with other exteroceptive spatial information. Surprisingly, no study has investigated whether alterations in such remapping occur in psychosis-prone individuals. Four hundred eleven students were screened with respect to schizotypal traits using the Schizotypal Personality Questionnaire. A subgroup of them, classified as low, moderate, and high schizotypes were to perform a temporal order judgment task of tactile stimuli delivered on their hands, with both uncrossed and crossed arms. Results revealed marked differences in touch remapping in the high schizotypes as compared to low and moderate schizotypes. For the first time here we reveal that the remapping of environmental stimuli in the body space, an essential function to demarcate the boundaries between self and external world, is altered in schizotypy. Results are discussed in relation to recent models of 'self-disorders' as due to perceptual incoherence

Bayesian Cue Integration as a Developmental Outcome of Reward Mediated Learning

Average human behavior in cue combination tasks is well predicted by Bayesian inference models. As this capability is acquired over developmental timescales, the question arises, how it is learned. Here we investigated whether reward dependent learning, that is well established at the computational, behavioral, and neuronal levels, could contribute to this development. It is shown that a model free reinforcement learning algorithm can indeed learn to do cue integration, i.e. weight uncertain cues according to their respective reliabilities and even do so if reliabilities are changing. We also consider the case of causal inference where multimodal signals can originate from one or multiple separate objects and should not always be integrated. In this case, the learner is shown to develop a behavior that is closest to Bayesian model averaging. We conclude that reward mediated learning could be a driving force for the development of cue integration and causal inference

Pleomorphic adenoma of the lacrimal gland: is there a role for biopsy?

Aim To review the literature on biopsy of lacrimal gland pleomorphic adenoma (LGPA) and to examine the validity of the prohibition against biopsy in LGPA. Method Literature review. Results LGPA is usually diagnosed preoperatively based on clinical and radiological characteristics, as current teaching advises complete excision without prior incisional biopsy. The caveat against biopsy is based on older studies that reported increased recurrence rates with increased risk of malignant transformation after incomplete excision or biopsy. On the basis of a detailed examination of the literature on biopsy of both LGPA and pleomorphic adenoma of the salivary glands, it appears that there is no clear evidence to support the claim that biopsy increases the risk of recurrence or of malignant transformation of LGPA. Conclusion Lacrimal gland tumours are uncommon lesions and optimal management depends to a great extent on a definite preoperative diagnosis. Preoperative biopsy should therefore be considered in all lacrimal gland mass lesions and management should be tailored to the biopsy findings. If surgical resection is then required, it may be prudent to excise the biopsy tract to ensure complete removal of the tumour.T Lai, V C Prabhakaran, R Malhotra and D Selv