Assessments of anterior cingulate cortex in experimental animals and humans have led to unifying theories of its structural organization and contributions to mammalian behaviour. The anterior cingulate cortex forms a large region around the rostrum of the corpus callosum that is termed the anterior executive region. This region has numerous projections into motor systems, however, since these projections originate from different parts of anterior cingulate cortex and because functional studies have shown that it does not have a uniform contribution to brain functions, the anterior executive region is further subdivided into ‘affect’ and ‘cognition’ components. The affect division includes areas 25, 33 and rostral area 24, and has extensive connections with the amygdala and periaqueductal grey, and parts of it project to autonomic brainstem motor nuclei. In addition to regulating autonomic and endocrine functions, it is involved in conditioned emotional learning, vocalizations associated with expressing internal states, assessments of motivational content and assigning emotional valence to internal and external stimuli, and maternal—infant interactions. The cognition division includes caudal areas 24' and 32', the cingulate motor areas in the cingulate sulcus and nociceptive cortex. The cingulate motor areas project to the spinal cord and red nucleus and have premotor functions, while the nociceptive area is engaged in both response selection and cognitively demanding information processing. The cingulate epilepsy syndrome provides important support of experimental animal and human functional imaging studies for the role of anterior cingulate cortex in movement, affect and social behaviours. Excessive cingulate activity in cases with seizures confirmed in anterior cingulate cortex with subdural electrode recordings, can impair consciousness, alter affective state and expression, and influence skeletomotor and autonomic activity. Interictally, patients with anterior cingulate cortex epilepsy often display psychopathic or sociopathic behaviours. In other clinical examples of elevated anterior cingulate cortex activity it may contribute to tics, obsessive—compulsive behaviours, and aberrent social behaviour. Conversely, reduced cingulate activity following infarcts or surgery can contribute to behavioural disorders including akinetic mutism, diminished self-awareness and depression, motor neglect and impaired motor initiation, reduced responses to pain, and aberrent social behaviour. The role of anterior cingulate cortex in pain responsiveness is suggested by cingulumotomy results and functional imaging studies during noxious somatic stimulation. The affect division of anterior cingulate cortex modulates autonomic activity and internal emotional responses, while the cognition division is engaged in response selection associated with skeletomotor activity and responses to noxious stimuli. Overall, anterior cingulate cortex appears to play a crucial role in initiation, motivation, and goal-directed behaviours. The anterior cingulate cortex is part of a larger matrix of structures that are engaged in similar functions. These structures form the rostral limbic system and include the amygdala, periaqueductal grey, ventral striatum, orbitofrontal and anterior insular cortices. The system formed by these interconnected areas assesses the motivational content of internal and external stimuli and regulates context-dependent behaviours.

Contributions of anterior cingulate cortex to behaviour.

A monograph communicating the current realities and future possibilities of unifying basic studies on anatomy and cellular physiology with investigations of the behavioral and physiological events of waking and sleep. Steriade established the Laboratory of Neurophysiology at Laval U., Quebec; McCarl

Brainstem control of wakefulness and sleep

PERSISTENT VEGETATIVE STATE AFTER BRAIN DAMAGE: A Syndrome in Search of a Name

The concept of consciousness continues to defy definition and elude the grasp of philosophical and scientific efforts to formulate a testable construct that maps to human experience. Severe acquired brain injury results in the dissolution of consciousness, providing a natural model from which key insights about consciousness may be drawn. In the clinical setting, neurologists and neurorehabilitation specialists are called on to discern the level of consciousness in patients who are unable to communicate through word or gesture, and to project outcomes and recommend approaches to treatment. Standards of care are not available to guide clinical decision-making for this population, often leading to inconsistent, inaccurate and inappropriate care. In this Review, we describe the state of the science with regard to clinical management of patients with prolonged disorders of consciousness. We review consciousness-altering pathophysiological mechanisms, specific clinical syndromes, and novel diagnostic and prognostic applications of advanced neuroimaging and electrophysiological procedures. We conclude with a provocative discussion of bioethical and medicolegal issues that are unique to this population and have a profound impact on care, as well as raising questions of broad societal interest.

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D. Whitteridge

Papers

Akinetic mutism with an epidermoid cyst of the 3rd ventricle