A systematic study of personification in synaesthesia: Behavioural and neuroimaging studies

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel UniversityIn synaesthetic personification, personality traits and other human characteristics are attributed to linguistic sequences and objects. Such non-perceptual concurrents are different from those found in most frequently studied types of synaesthesia, in which the eliciting stimuli induce sensory experiences. Here, subjective reports from synaesthetes were analysed and the cognitive and neural mechanisms underlying personification were investigated. Specifically, the neural bases of personification were examined using functional MRI in order to establish whether brain regions implicated in social cognition are involved in implementing personification. Additional behavioural tests were used to determine whether personification of inanimate objects is automatic in synaesthesia. Subjective reports describing general characteristics of synaesthetic personification were collected using a semi-structured questionnaire. A Stroop-like paradigm was developed in order to examine the automaticity of object personification, similarly to the previous investigations. Synaesthetes were significantly slower in responding to incongruent than to congruent stimuli. This difference was not found in the control group. The functional neuroimaging investigations demonstrated that brain regions involved in synaesthetic personification of graphemes and objects partially overlap with brain areas activated in normal social cognition, including the temporo-parietal junction, precuneus and posterior cingulate cortex. Activations were observed in areas known to be correlated with mentalising, reflecting the social and affective character of concurrents described in subjective reports. Psychological factors linked with personification in previous studies were also assessed in personifiers, using empathy, mentalising and loneliness scales. Neither heightened empathy nor mentalising were found to be necessary for personification, but personifying synaesthetes in the study felt lonelier than the general population, and this was more pronounced in those who personified more. These results demonstrate that personification shares many defining characteristics with classical forms of synaesthesia. Ascribing humanlike characteristics to graphemes and objects is a spontaneous and automatic process, inducer-concurrent pairings are consistent over time and the phenomenological character of concurrents is reflected in functional neuroanatomy. Furthermore, the neuroimaging findings are consistent with the suggestions that synaesthetes have a lower threshold for activation brain regions implicated in self-projection and mentalising, which may facilitate the personification processes in synaesthesia.Brunel University - Isambard Scholarshi

Cerebro-Cerebellar Pathways for Verbal Working Memory

The current study examined the structural and functional connectivity of the cerebro-cerebellar network of verbal working memory as proposed by Chen and Desmond (2005a). Diffusion spectrum imaging was employed to establish structural connectivity between cerebro-cerebellar regions co-activated during a verbal working memory task. The inferior frontal gyrus, inferior parietal lobule, pons, thalamus, superior cerebellum and inferior cerebellum were used as regions of interest to reconstruct and segment the contralateral white matter cerebro-cerebellar circuitry. The segmented pathways were examined further to establish the relationship between structural and effective connectivity as well as the relationship between structural connectivity and verbal working memory performance. No direct relationship between structural and effective connectivity was found but the results demonstrated that structural connectivity is indirectly related to effective connectivity as DCM models that resembled more closely with underlying white matter pathways had a higher degree of model inference confidence. Additionally, it was demonstrated that the structural connectivity of the ponto-cerebellar tract was associated with individual differences in response time for verbal working memory. The findings of the study contribute to further our understanding of the relationship between structural and functional connectivity and the impact of variability in verbal working memory performance

Cerebro-cerebellar pathways for verbal working memory

The current study examined the structural and functional connectivity of the cerebro-cerebellar network of verbal working memory as proposed by Chen and Desmond (2005a). Diffusion spectrum imaging was employed to establish structural connectivity between cerebro-cerebellar regions co-activated during a verbal working memory task. The inferior frontal gyrus, inferior parietal lobule, pans, thalamus, superior cerebellum and inferior cerebellum were used as regions of interest to reconstruct and segment the contralateral white matter cerebro-cerebellar circuitry. The segmented pathways were examined further to establish the relationship between structural and effective connectivity as well as the relationship between structural connectivity and verbal working memory performance. No direct relationship between structural and effective connectivity was found but the results demonstrated that structural connectivity is indirectly related to effective connectivity as DCM models that resembled more closely with underlying white matter pathways had a higher degree of model inference confidence. Additionally, it was demonstrated that the structural connectivity of the ponto-cerebellar tract was associated with individual differences in response time for verbal working memory. The findings of the study contribute to further our understanding of the relationship between structural and functional connectivity and the impact of variability in verbal working memory performance

Cerebro-cerebellar pathways for verbal working memory

The current study examined the structural and functional connectivity of the cerebro-cerebellar network of verbal working memory as proposed by Chen and Desmond (2005a). Diffusion spectrum imaging was employed to establish structural connectivity between cerebro-cerebellar regions co-activated during a verbal working memory task. The inferior frontal gyrus, inferior parietal lobule, pons, thalamus, superior cerebellum and inferior cerebellum were used as regions of interest to reconstruct and segment the contralateral white matter cerebro-cerebellar circuitry. The segmented pathways were examined further to establish the relationship between structural and effective connectivity as well as the relationship between structural connectivity and verbal working memory performance. No direct relationship between structural and effective connectivity was found but the results demonstrated that structural connectivity is indirectly related to effective connectivity as DCM models that resembled more closely with underlying white matter pathways had a higher degree of model inference confidence. Additionally, it was demonstrated that the structural connectivity of the ponto-cerebellar tract was associated with individual differences in response time for verbal working memory. The findings of the study contribute to further our understanding of the relationship between structural and functional connectivity and the impact of variability in verbal working memory performance.MOE (Min. of Education, S’pore)Published versio