• Consciousness is often conceptualized as en-compassing two cardinal elements (Laureys2005):– wakefulness: refer to the level of consciousness– Awareness: refer to its contents
Introduction• disorders of consciousness (DOC)(Monti. 2012)– Coma: lack both awareness and wakefulness– Vegetative State(VS): basic vegetative nervousfunctions are preserved, but in the absence of anysensation and thought– Minimally Conscious State(MCS): not only to bewakeful (like vegetative-state patients) but also exhibitinconsistent but reproducible signs of awareness ofthemselves or their surroundings– locked-in syndrome(LIS): both awake and aware butare either unable to produce any motor response
Introduction• self-referential processing in DOC:– Di et al. (2007): five out of seven VS patients exhibited primaryauditory activity in response to their own name. In addition, intwo VS patients (and all MCS patients),activations in higher-levelposterior temporal cortices were also detected.– Qin et al. (2010) reported significant activations for six out ofseven VS patients in one or more of three medial prefrontalregions previously linked to processing self-related stimuli• Resting state in DOC:– alterations in cortical midline structures, abnormally lowfunctional connectivity (Boly et al., 2009; Cauda et al., 2009;Vanhaudenhuyse et al., 2010) and effective connectivity(Rosanova et al., 2012).
Questions• 1) In DOC, the temporal dynamics of resting stateactivity, such as the amplitude of low-frequencyfluctuations (ALFF)(Kannurpatti and Biswal, 2008;Zang et al., 2007) and standard deviation ofneural activity changes across time (Garrett et al.,2011), remain to be thoroughly investigated.Importantly, the functional implications ofabnormalities in the resting state remain unclear• 2) It is unclear how to relate self-referentialprocessing, resting state activity andconsciousness in DOC patients.
Hypothesis and Aim• (1) the neural response to self-referential stimuli in themidline regions would be present though abnormallyreduced in DOC patients; a particularly strong linkbetween neural responses in midline brain regions andthe level of consciousness,• (2) abnormal brain responses while processing self-referential tasks may be related to impairments notonly in the spatial domain but also with temporalabnormalities in neuronal measures of resting stateactivity, e.g. lower ALFF and standard deviation withinthe midline regions
Materials and Methods• Participants and patients– 12 healthy control subjects– 11 patients (six VS and five MCS)
fMRI scan procedureResting6mintask8’8’’task8’8’’task8’8’’task8’8’’T1Trial Trial8s,10s,12s20 self-referential & 20 non-self-referential,delivered in a pseudo-random order.
Results• Behavioral data: from longitudinal behavioralassessments (CRS-R)– VS5 and VS6 exhibited clinical improvement andwere classified as MCS two months after the fMRIstudy– Patients MCS3 and MCS4 recovered 2 monthsafter the fMRI, and were able to repeatedly followa command to move and verbally answer to theirnames.
Conclusion• DOC patients exhibit reduced cortical responsescompared with healthy controls during activeself-referential processing in anterior andposterior midline regions.• The magnitude of cortical responses in theanterior midline regions (e.g. PACC) wassignificantly correlated with DOC patients’ degreeof consciousness.• PACC displayed major resting-state abnormalitiesas manifested by reduced ALFF, FC, and SD ofsignal changes.