In individuals diagnosed with schizophrenia (SZ), there is a reduced sensitivity towards endogenous or exogenous pain stimuli. This hypoalgesic phenotype is considered to be a major cause as to why patients fail to seek clinical treatment for conditions such as cardiovascular (CVD) or metabolic diseases, where pain is often a presenting symptom. An unfortunate, yet likely preventable outcome of poorly treated physical conditions is premature mortality in the SZ patient population. In fact, delayed treatment or an absence of clinical care all together of CVDs in SZ has been reported to cause 12 and 15 years of reduced lifespans in female and male patients, respectively. Currently, the clinical characteristics across the SZ spectrum or the aberrant neurobiological mechanisms linked with reduced pain perception in SZ patients are in large part unknown. Clinical feature of SZ such as positive and negative symptoms may be involved in reducing the overall salience of pain and as a result, produce what is in the end observed as a hypoalgesic effect. Moreover, domains such as reward- aversion, cognitive, autonomic or sensorimotor processing are important to consider in the context of hypoalgesia in SZ as these are dysregulated in this population as well as are intertwined with salience and pain perception. In the current proposal, we outline a thorough approach to identify how positive and negative clinical symptoms measured in SZ patients relate to hypoalgesia. Moreover, we define a strategy that aims to determine the central, neurobiological constructs that are functionally and structurally altered in SZ and that underpin a hypoalgesic state. We propose to cross-sectionally evaluate 30 SZ patients and matched, healthy subjects (N=30) using a combination of evoke heat pain, blood-oxygenated level dependent functional magnetic resonance imaging in conjunction with clinical (Scale for the Assessment of Negative Symptoms), behavioral (quantitative sensory testing, effort expenditure for rewards task, and emotion mapping) and physiological (skin conductance and heart rate) measures. Our central hypothesis is that the severity of negative symptoms, particularly anhedonia and reduced self-awareness, will coincide with hypoalgesic responses to experimentally evoked pain. We further hypothesize that a down-regulation of brain systems mediating pain salience (e.g., autonomic, mesolimbic and nigrostriatal) drive altered pain perception in SZ.
Our Specific Aims are:
Aim 1 : Identify clinical, cognitive, physiological and behavioral predictors of hypoalgesic response to noxious heat stimuli in SZ.
Aim 2 : Characterize central, evoked pain responses in SZ.
Aim 3 : Using resting-state fMRI, identify circuit abnormalities that are associated with hypoalgesia in SZ. To carry out this work, we have formed a team of clinical researchers with robust experience in investigation of pain mechanism, treatment and investigation of SZ patients and utilization of neuroimaging methodology.
Dissecting Central Mechanisms of Hypoalgesia in Schizophrenia NARRATIVE Individuals diagnosed with schizophrenia have reduced sensitivity towards pain, which can prevent early diagnosis of critical illnesses as well as increase the risk of early mortality. We hypothesize that the severity of negative symptoms in schizophrenia (i.e., anhedonia) will coincide with hypoalgesic responses, while a down- regulation of brain systems mediating pain salience (e.g., autonomic, mesolimbic and nigrostriatal) facilitates altered pain perception. The proposed work will utilize functional neuroimaging in conjunction with clinical, behavioral and physiological methods in order to determine factors that underlie hypoalgesia in schizophrenia.
