Task-dependent posterior cingulate activation in mild cognitive impairment

Neuroimaging research has demonstrated that the posterior cingulate cortex (PCC) is functionally compromised in individuals diagnosed with amnestic mild cognitive impairment (MCI), a major risk factor for the development of Alzheimer\u27s disease (AD). In functional MRI studies with healthy participants, this same region is active during self-appraisal (requiring retrieval of semantic knowledge about the self) as well as episodic recognition of previously learned information. Administering both types of tasks to people with MCI may reveal important information on the role of the PCC in recollection. This study investigated fMRI activation in the PCC in individuals with MCI and matched controls across two tasks. The first task was a visual episodic recognition task. The second task was an autobiographical self-appraisal task in which subjects rated themselves on a set of trait adjectives. Results of a conjunction analysis revealed the PCC as the sole region commonly active during both tasks in the healthy older adults. Furthermore, additional analysis revealed an interaction in the PCC, indicating a task-dependent response in the MCI group. MCI participants showed PCC activation during self-appraisal, but not episodic retrieval. This result suggests in MCI that the PCC shows functional degradation during episodic retrieval; however, the PCC\u27s role in retrieval and evaluation of highly elaborated information regarding the self is more well-preserved. © 2005 Elsevier Inc. All rights reserved

The cerebral response during subjective choice with and without self-reference

The anterior medial prefrontal (AMPFC) and retrosplenial (RSC) cortices are active during self-referential decision-making tasks such as when participants appraise traits and abilities, or current affect. Other appraisal tasks requiring an evaluative decision or mental representation, such as theory of mind and perspective-taking tasks, also involve these regions. In many instances, these types of decisions involve a subjective opinion or preference, but also a degree of ambiguity in the decision, rather than a strictly veridical response. However, this ambiguity is generally not controlled for in studies that examine self-referential decision-making. In this functional magnetic resonance imaging experiment with 17 healthy adults, we examined neural processes associated with subjective decision-making with and without an overt self-referential component. The task required subjective decisions about colors - regarding self-preference (internal subjective decision) or color similarity (external subjective decision) under conditions where there was no objectively correct response. Results indicated greater activation in the AMPFC, RSC, and caudate nucleus during internal subjective decision-making. The findings suggest that self-referential processing, rather than subjective judgments among ambiguous response alternatives, accounted for the AMPFC and RSC response. © 2005 Massachusetts Institute of Technology

Neural correlates of self-evaluative accuracy after traumatic brain injury

Individuals who have sustained a traumatic brain injury (TBI) often exhibit an array of cognitive deficits, yet perhaps most maladaptive of these sequelae is the frequent occurrence of reduced insight into one\u27s own condition. In such cases, TBI individuals may overestimate their post-injury level of socio-cognitive functioning, leading to disparities between how they perceive themselves and what others observe. This functional MRI (fMRI) investigation examined the relationship between level of insight into one\u27s post-injury condition (i.e. trait/ability status) and neural activation evoked during an fMRI task involving self-appraisal of one\u27s traits and abilities. Twenty TBI patients (8-12 weeks post-injury, ER Glasgow Coma Scale Average = 10.9 ± 2.8) were selected on the criterion that they overestimate their current trait/abilities (as detected on the patient competency rating scale, PCRS). fMRI activation on the self-appraisal task was compared between the TBI patients and 20 matched controls. For both groups, the fMRI task evoked activation at mid-line prefrontal and retrosplenial cortices. TBI patients exhibited greater signal change in the anterior cingulate, precuneus and right temporal pole. Subsequently, a linear regression analysis was conducted for the TBI group, with the PCRS and a measure of cognitive speed entered as predictor variables to determine the selective effect of insight on self-evaluative brain activation. A more accurate level of trait/ability-based insight was related to increased signal change in the right anterior dorsal prefrontal cortex (PFC). The results suggest that one\u27s post-injury level of self-referential insight is related to a network inclusive of the medial and right dorsal PFC. © 2005 Elsevier Ltd. All rights reserved

Metacognitive evaluation, self-relevance, and the right prefrontal cortex

The capability to foster metacognitive evaluations (MEs) of oneself and others represents a major component of conscious awareness. Separate emerging lines of brain activation research examining ME have converged on the medial prefrontal cortex as a common finding. The current functional magnetic resonance imaging (fMRI) study utilized a task that directly compared ME associated with two referentially discrete targets: oneself and a significant other (e.g., close friend or relative). Nineteen healthy young adult participants (mean age 24; 9 female, 10 male) were required to make yes/no decisions based on individually presented trait adjectives across two separate referential conditions and a nonreferential control condition: self-evaluation (SE), significant other-evaluation (OE), and semantic positivity-evaluation (SPE), respectively. Results of random-effects group analyses indicated a common area of medial prefrontal activation during the ME conditions of self- and other-evaluation versus the baseline semantic positivity-evaluation condition. A direct comparison of brain activation between the self and other evaluative conditions revealed a right dorsolateral prefrontal response that was significantly more active when making evaluations about the self. The present study extends upon the prior findings of separate research domains by directly comparing the cerebral response to ME about the self and others, and finding right PFC activation increases as a function of self-relevance. © 2004 Elsevier Inc. All rights reserved