Detecting an intention to communicate: using ToMas to test Theory of Mind in people with schizophrenia and healthy controls

Introduction: Impairments in Theory of Mind (ToM), for example, in schizophrenia, are evidenced in studies which typically use variants of story comprehension tasks (e.g., Hinting, Corcoran et al, 1995). These tasks can be complex and may depend upon IQ and executive functioning (Ducato et al, 2008). So far, it is unknown what parts of the human brain are responsible for detecting an intention to communicate from sounds, and distinguishing these from those sounds produced without such intent. We developed a much simpler auditory ToM task to assess the specific ability to detect whether a sound conveyed an ‘intention to communicate’: Theory-of-Mind-auditory-stimuli (ToMas). Our aim was to identify brain regions associated with the detection of an intention to communicate in people with schizophrenia and healthy controls when they responded to ToMas. We hypothesised firstly, that mentally healthy people would perceive and rate auditory stimuli in similar ways and distinguish sounds with an intention to communicate (ITC) from those without. Secondly, we believed that there was insufficient evidence to assume there would be any differences on this task between mentally healthy controls and participants with schizophrenia who were matched on age, gender and IQ. Thirdly, we expected that mentally healthy controls would use language-specific brain regions for ITC stimuli which were not used for non-ITC stimuli, when recorded using functional brain imaging. Lastly, we expected the differential activation seen in the healthy controls would be markedly absent in the people with schizophrenia, even though they would be matched on similar variables and their behavioural responses would be the same. Method: Participants: The behavioural study involved testing 50 mentally healthy participants (18 male) from Research Registers and the community (mean age 38.5, SD=15.1); a subset was matched on age and gender to 14 people with schizophrenia (10 male; mean age 40.0, SD=11.6). Then nine participants (6 male) from each group, matched on age and gender, were scanned whilst performing ToMas (mean age 37, SD=9.9). Procedure: Initially, healthy adults and those with schizophrenia were asked to listen to sounds played and answer qualitative questions about them. Twenty fMRIpilot participants of ToMas rated sounds on familiarity, source, emotional salience, meaningfulness, and intention to communicate (ITC), leading to a subset of 30 stimuli, where the ITC was either clearly evident, clearly absent, or ambiguous. The aim of Detecting an intention to communicate; Using ToMas to test Theory of Mind in people with schizophrenia and healthy controls Author: Mary-Claire Hanlon Date: 5 September 2013 Page 7 of 267 ToMas was to distinguish sounds with an ITC from those without. In the neuroimaging paradigm, participants were presented with a sound, then asked “Message? ”, to which they responded yes/no via button-press. Apparata and stimuli: Haemodynamic responses to stimuli were collected using a Siemens Avanto 1.5Tesla MR scanner in an event-related paradigm. Group-level random effect analyses were performed separately on each contrast after each individual’s data were analysed (GLM, regressors=stimulus categories, covariates=motion parameters). Data were analysed using SPM8 and Matlab 7.1. Results: Healthy adults aged 18-65 years (N=50) showed qualitative elements such as familiarity, source, emotion, and meaning were used when deciding if a stimulus had an ITC. Our schizophrenia group (N=14) showed no behavioural difference in ToMas from the 14 healthy controls matched on age, gender and IQ: no group differences suggested that our schizophrenia participants were not hampered in identifying stimuli with an ITC from those without. Using a shorter version of ToMas (30 auditory stimuli), in functional neuroimaging (fMRI), we ascertained which parts of the brain were responsible for both perceiving the stimuli, and subtracting out the known brain regions to reveal those which managed the discernment of ITC. Data from mentally healthy participants (N=14) highlighted the impact of the superior temporal and middle temporal gyri (especially right STG and left MTG) in how mentally healthy adults chose between ITC-absent and ITC-present stimuli, and as predicted, the differential activation seen in the healthy group (of right STG & left MTG at p<.001) was remarkably absent in the schizophrenia group