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In this article the author discusses the brain activity in the intrinsic default network that includes medial temporal lobe, medial prefrontal subsystems and posterior cingulate cortex of the brain during an idle mode. The author states that the activity in the default network is associated with the activity in the attention system, an another intrinsic network being activated during goal-directed cognition. The author discusses definitions for doodling and studies of the aspects of doodles.

Competing Interests: Competing interests: None declared.

The tondo, a circular work of art, comprises a geometry that is said to increase the visual concentration on the picture's centre, a concentration that is enhanced by a picture frame. The present contribution discusses these observations from the perspective of the psychologist and the art historian, notes the perceptual differences between circular and other shapes of pictures, and refers to studies including eye-tracking methods, neurophysiological experiments on the visual cortex in man and macaques, and consideration of ocular factors. These studies provide considerable support for the "Power of the Center" when viewing tondi.

For over a century the arrow has appeared in illustrations of cerebral function, yet the implications of using such symbols have not been previously considered. This review seeks to outline the nature, evolution, applications and limitations of this deceptively simple graphic device when it is used to picture functions of the brain. The arrow is found to have been used in several different ways: as a means of endowing anatomical structures with functional properties; as a method of displaying neural function either in free-standing form or in a structural or spatial framework; as a device for correlating functional data with underlying brain topography; and as a technique for linking functions of the brain with the world outside and with various philosophical concepts. For many of these uses the essential feature of the arrow is its directional characteristic. In contrast to the line, it is direction that enables the arrow to display information about time, which in turn can be exploited to depict functional rather than structural data. However, the use of the arrow is fraught with difficulties. It is often unclear whether an arrow has been used to illustrate fact, hypothesis, impression or possibility, or merely to provide a decorative flourish. Furthermore, the powerful symbolic nature of the arrow can so easily confer a spurious validity on the conjectural. Increasingly now there are insuperable difficulties when attempting to illustrate complex mechanisms of brain function. In the iconography of cerebral function, therefore, arrows with all their ambiguities may in certain circumstances become superseded by more non-representational symbols such as the abstract devices of the computational neuroscientist.

Eight patients suffering from various forms of idiopathic dystonia are described whose initial referral was for an orthopaedic opinion. The diagnoses of these patients, who were seen over a two-year period, comprised dystonia musculorum deformans, dystonia of the foot, spasmodic torticollis and occupational cramps. Although various musculoskeletal sequelae often occur, the primary underlying neurological cause of these unusual conditions is emphasised.

Neurogenic facial pain can be classified as either paroxysmal or persistent. Trigeminal neuralgia is the commonest example of the former, and postherpetic neuralgia, atypical facial pain, and tension head and facial pains are examples of the latter. The cause of many of these pains is poorly understood, the complex neuroanatomy of the head and neck being a contributory factor. Even when the aetiology is known, the mechanism whereby pain is produced is usually obscure. While treatment with drugs and surgical measures for trigeminal neuralgia are often satisfactory, and acupuncture for pain due to "muscle tension" may be beneficial, there is often little effective treatment for a considerable proportion of patients with neurogenic facial pain.

Ten patients are described in whom various involuntary movement disorders developed after trauma that was predominantly or entirely peripheral. The interval between injury and onset of movement disorder ranged from 48 hours to 3 years; the injured and painful part was the area initially affected by involuntary movements, although more widespread involvement subsequently occurred. These clinical features resemble the phenomena experienced by some patients with causalgia and suggest the possibility of common mechanisms.

The muscle weakness that frequently accompanies osteomalacia and rickets may arise from a variety of causes. Particularly in patients with muscle weakness, identification of the metabolic disorder is important, since effective treatment is often possible.

Certain normal individuals when scratching a small area of skin often experience simultaneously an additional punctate sensation (Mitempfindung) at a remote site on the body. Four patients are described with acquired Mitempfindungen, the sensation being referred to the region that had been rendered abnormal by damage to the nervous system. The differences between normal and pathological Mitempfindungen and other patterns of cutaneous referral are considered, and mechanisms underlying Mitempfindungen, including the possible role of the spinocervical tract, are discussed.

The definition of causalgia as a pain state following peripheral nerve injury has been accepted since the term was introduced by Weir Mitchell over a century ago. In the present paper, problems of nomenclature and nosology are discussed, and attention is drawn to the fact that the same clinical features can occur spontaneously, in nontraumatic nerve lesions, in the absence of a part as in phantom limb states, and in diseases confined to the central nervous system. Attention is also drawn to the lack of correlation of pain with the effects mediated by catecholamines in the sympathetic nervous system and with the response to sympathetic blockade. Concerning mechanisms, a number of peripheral mechanisms have been postulated. These are reviewed, and while they might be correct when causalgia arises from peripheral nerve damage, they cannot provide adequate explanation for at least some instances of causalgia. The relevance of the neuroma as a model for chronic pain in general, and causalgia, is questioned. Also questioned is the view that causalgia is a state that depends on peripheral involvement of the sympathetic nerve supply. Certain authors in the past considered that the central nervous system (CNS) played an important part in causalgia, and current evidence supporting this view is assessed. Involvement of the CNS is suggested by the development of causalgia in diseases confined to the CNS and in phantom pain states; the unusual distribution of pain sometimes experienced; the paradoxical development of widespread pain that can occur after damage to the sympathetic nervous system; the effects of peripheral sympathetic blockade even when the cause lies centrally; and central interactions with motor, sensory and psychological phenomena. Reservations concerning the role of catecholamines in causalgia are outlined, and the possibility is considered that nonadrenergic substances may be implicated.

The present study concerns neuropsychological aspects of the handwriting of Leonardo da Vinci. The evidence for Leonardo's left handedness is considered, and a critical appraisal of his mirror writing and its underlying mechanism is presented. The relationship between Leonardo's sinistrality, mirror writing and certain aspects of localisation of cerebral function are discussed. From these considerations and from new evidence obtained from contemporary historical sources, it is proposed that Leonardo's language skills were lateralised to the more unusual right hemisphere.