The Merging Tracks of Anosognosia and Neglect.

Anosognosia and hemineglect are among the most startling neurological phenomena identified during the 20th century. Though both are associated with right hemisphere cerebral dysfunction, notably stroke, each disorder had its own distinct literature. Anosognosia, as coined by Babinski in 1914, describes patients who seem to have no idea of their paralysis, despite general cognitive preservation. Certain patients seem more than unaware, with apparent resistance to awareness. More extreme, and qualitatively distinct, is denial of hemiplegia. Various interpretations of pathogenesis are still deliberated. As accounts of its captivating manifestations grew, anosognosia was established as a prominent symbol of neurological and psychic disturbance accompanying (right-hemisphere) stroke. Although reports of specific neglect-related symptomatology appeared earlier, not until nearly 2 decades after anosognosia's inaugural definition was neglect formally defined by Brain, paving a path spanning some years, to depict a class of disorder with heterogeneous variants. Disordered awareness of body and extrapersonal space with right parietal lesions, and other symptom variations, were gathered under the canopy of neglect. Viewed as a disorder of corporeal awareness, explanatory interpretations involve mechanisms of extinction and perceptual processing, disturbance of spatial attention, and others. Odd alterations involving apparent concern, attitudes, or belief characterize many right hemisphere conditions. Anosognosia and neglect are re-examined, from the perspective of unawareness, the nature of belief, and its baffling distortions. Conceptual parallels between these 2 distinct disorders emerge, as the major role of the right hemisphere in mental representation of self is highlighted by its most fascinating syndromes of altered awareness.

History of Amusia.

We live in a world surrounded by sound. Throughout life, we are exposed to music: from lullabies and songs taught at school to instrumental music both heard and played for pleasure. Every nation, along with its own language, has unique forms of music and dance. "Music knows no boundaries," as the saying goes. Just as language impairment is known as "aphasia," impairment of the perception of music is called "amusia." In this article, we will first classify the types of amusia. This will be followed by an introduction to the classical research of Salomon Eberhard Henschen (1847-1930), and to a discussion of higher auditory functions in which we highlight cases of amusia encountered in a person and through the literature.

Hemineglect and Attentional Dysfunction.

Tracing the history of neglect is intriguing, as diverse terminologies have been used to characterize a multi-factorial disorder with rather startling manifestations. In part, heterogeneous terms may have hinted at distinct subtypes. Thus, different variants of hemi-inattention and neglect relate conceptually, but may be functionally dissociable. Patients with neglect, acting as if the world-space they perceive is full, do not phenomenally experience the omissions or absences so patently obvious to an observer. From the late 19th century, hemi-inattention was described according to its prominent manifestations, visual, bodily or spatial. Since then, diverse terms including imperception, inattention, unilateral visual inattention, unilateral spatial agnosia, and neglect, among others, reflected proposed underlying mechanisms. Major theories presented to account for this curious, even astonishing, neurological disorder, included disruption of body-scheme, perceptual rivalry and extinction, forgetting or amnesia for half the body, and highly nuanced models of distribution of directed spatial attention, and of disrupted perceptual processes. Unlike neurological counterparts, already designated as hemi-syndromes by the first part of the 20th century, not until about 1970 did neglect become so broadly recognized as a syndrome. Earlier, commonalities were identified, features conceptually clustered, and then subtypes were distinguished. Neglect was designated as an overarching term for a class of disorder with distinct subtypes, including visual, motor, extrapersonal, bodily or personal, other somatosensory, and representational. Specificity for modality, chronology, material, and symptom severity was noted. Remarkable clinical, neuropsychological, and behavioral manifestations of hemi-inattention and neglect may involve varying proposed mechanisms of higher cognitive functions, all within a spectrum of clinical disorder. Concepts of connectivity and interaction, neural networks, and functional integration enhance understanding of dysfunction, recovery, and compensation in neglect and inattention. Focus on distinct manifestations clustered under the umbrella of neglect offers a vantage point for examining historical trends in approach to the phenomenon.

Optic ataxia: beyond the dorsal stream cliché.

This chapter reviews clinical and scientific approaches to optic ataxia. This double historic track allows us to address important issues such as the link between Bálint syndrome and optic ataxia, the alleged double dissociation between optic ataxia and visual agnosia, and the use of optic ataxia to argue for a specific vision-for-action occipitoposterior parietal stream. Clinical cases are described and reveal that perceptual deficits have been long shown to accompany ataxia. Importantly, the term ataxia appears to be misleading as patients exhibit a combination of visual and nonvisual perceptual, attentional, and visuomotor guidance deficits, which are confirmed by experimental approaches. Three major features of optic ataxia are described. The first is a spatial feature whereby the deficits exhibited by patients appear to be specific to peripheral vision, akin to the field effect. Visuomotor field examination allows us to quantify this deficit and reveals that it consists of a highly reliable retinocentric hypometria. The third is a temporal feature whereby these deficits are exacerbated under temporal constraints, i.e., when attending to dynamic stimuli. These two aspects combine in a situation where patients have to quickly respond to a target presented in peripheral vision that is experimentally displaced upon movement onset. In addition to the field effect, a hand effect can be described in conditions where the hand is not visible. Spatial and temporal aspects as well as field and hand effects may rely on several posterior parietal modules that remain to be precisely identified both anatomically and functionally. It is concluded that optic ataxia is not a visuomotor deficit and there is no dissociation between perception and action capacities in optic ataxia, hence a fortiori no double dissociation between optic ataxia and visual agnosia. Future directions for understanding the basic pathophysiology of optic ataxia are proposed.

Bilateral parietal dysfunctions and disconnections in simultanagnosia and Bálint syndrome.

In 1909 Rezsö Bálint published an extraordinary case study of a man with complex visuospatial deficits resulting from bilateral parietal lesions. Despite some controversies over the nature of reported symptoms, in 1954 Hecaen and Ajuriaguerra conceived the term "Bálint syndrome," not only to honor Bálint's influential work but to firmly conceptualize this striking neurologic disorder. Nowadays it is largely agreed that, while Bálint syndrome may result from multiple etiologies, it is principally diagnosed based on the presence of three symptoms: simultanagnosia, optic ataxia, and ocular apraxia. One of the most striking characteristics of Bálint syndrome, perfectly capturing the nature of this remarkable disorder, is that affected patients cannot perceive more than one object at a time or comprehend multiobject visual scenes due to a lack of ability to detect several objects concurrently and to grasp the spatial relationships between them. This chapter gives an overview of the cognitive mechanisms and neuroanatomy underlying Bálint syndrome, which provides key insights into our understanding of the role of parietal cortex in human attention, visual perception, and visuomotor control. This chapter also pays homage to Glyn Humphreys (1954-2016), who pioneered contributions to the knowledge about complexity of visual and spatial deficits associated with Bálint syndrome.

Théodore Flournoy on synesthetic personification.

In 1893, Théodore Flournoy published a landmark book on synesthesia - Des phénomènes de synopsie [Of Synoptic Phenomena]. The book presented a pioneering chapter on synesthetic personification, including numerous striking case examples, and it is frequently cited by twenty-first-century researchers as providing some of the earliest examples of the phenomenon. Flournoy employed a broad definition of personification - the representation of stimuli as concrete and specific individuals or inanimate objects. This definition encompassed a more extensive set of phenomena than the definition used by researchers today and was illustrated by cases that would fall outside of contemporary subtypes of synesthetic personification. Yet, Flournoy's seminal work remains unavailable in English, and the extent of the phenomenon that he described has not been discussed in the contemporary literature. We provide an unabridged translation of Flournoy's chapter "Des personnifications" ["Of Personifications"].

Alexander Nikolaevich Scriabin (1872-1915): Enlightenment or illness?

The similarity between psychotic symptoms and aspects of mystical experiences is well known. It has long been recognized that there are similarities between mystical and spiritual and psychotic experiences. The content of an experience alone usually does not determine whether an individual is psychotic. The Russian composer Scriabin (1872-1915) was among the most famous artists of his time. Scriabin infused his music with mysticism, evolving a modernistic idiom through which he created a musical counterpart to the Symbolist literature of that period. In this paper, we discuss the question that arises from perusing Scriabin's life is whether the composer was a mystic genius or whether he suffered from affective psychopathology with psychotic features.

Description and clinical application of the Pulfrich effect.

BACKGROUND: In 1922, German physicist Carl Pulfrich described an illusory binocular perceptual disturbance in which an object moving across an observer's field of vision is perceived as traveling along a curved trajectory. OBJECTIVE: To review the discovery of the Pulfrich effect, and subsequent clinical applications. METHODS: We translated Pulfrich's description and searched for subsequent publications using electronic databases and review of reference lists in identified publications. RESULTS: In 1901, Pulfrich developed an optical device to accurately compare stereoscopic photographs, but brightness difference between plates caused distance misperceptions that interfered with precise measurements. Pulfrich proposed that this Stereo-Effekt resulted from interocular differences in perceptual latency. He induced the effect by placing a smoked glass in front of one eye. The resulting perceptual disparity creates an apparently curved trajectory of an object moving sideways across the field of vision. Pulfrich also recognized that visual pathway disorders can produce a pathologic Stereo-Effekt. In 1925, Grimsdale demonstrated this in a man with unilateral retrobulbar optic neuritis and suggested treatment with a neutral density filter (NDF) over the good eye. Not until the 1970s, however, was the Pulfrich effect evaluated as a diagnostic test for retrobulbar optic neuritis and the therapeutic efficacy of an NDF confirmed. CONCLUSION: Although the clinical importance of the Pulfrich effect was suggested by Pulfrich and quickly confirmed, it took decades before its diagnostic utility and the efficacy of an NDF were assessed. Recognition remains clinically important to minimize safety risks and mislabeling, and because resulting misperceptions can be easily treated.

"The El Greco fallacy" fallacy.

To what extent does an artist's work represent his or her perceptual world, and to what extent can attributes of his or her work be ascribed to sensory defects? These issues lie at the center of a conjecture more than a century old, which has been termed the El Greco fallacy. The El Greco fallacy posits that the elongation evident in El Greco's art reflects an underlying perceptual elongation of objects caused by astigmatism. The "logical" refutation of this theory argues that any perceptual elongation that El Greco might have experienced as a result of astigmatism would have caused not only his subjects to be elongated but also his canvas. Hence, it should have been unnecessary for him to elongate his paintings to match his perception. This objection is important because it warns us against drawing the erroneous conclusion that an artist's work represents a facsimile of his or her perception. However, an analysis of the effects of astigmatism on the retinal image suggests that this "logical" refutation of the El Greco fallacy promulgates another fallacy--that of astigmatism as a source of a constant perceptual error.

Wiley Post, around the world with no stereopsis.

In 1933, famed aviator Wiley Post (1898-1935) was the first pilot to fly around the world solo. In addition, during one of his many stratospheric flights, he discovered the jet stream. What makes his accomplishments even more remarkable is that he did this monocularly, having lost his left eye from traumatic endophthalmitis following an oil rig accident. He underwent a period of self-imposed visual training to maximize his depth perception, and then accomplished what no one had before.

The development of a scientific understanding of synesthesia from early case studies (1849-1873).

The first case of synesthesia was reported in 1812 ( Jewanski, Day, & Ward, 2009 ). However, it took almost seven decades before the idea of synesthesia entered the mainstream of science and, subsequently, art. There are no known new cases described between 1812 and 1848, but in the following three decades there are at least 11 reported cases of synesthesia and many reviews of these cases. This comes at an important period in the history of the neurosciences, and for sensory physiology in particular. However, the literature that describes synesthesia during this period is largely unknown to contemporary researchers and historians. The aim of this review is to discuss the reports of synesthesia during this period, providing translations of some key passages, and to place these reports within the contextual framework of nineteenth-century neuroscience.

Phantom penis: historical dimensions.

Interest in sensations from removed body parts other than limbs has increased with modern surgical techniques. This applies particularly to operations (e.g., gender-changing surgeries) that have resulted in phantom genitalia. The impression given in modern accounts, especially those dealing with phantoms associated with penis amputation, is that this is a recently discovered phenomenon. Yet the historical record reveals several cases of phantom penises dating from the late-eighteenth century and the early-nineteenth century. These cases, recorded by some of the leading medical and surgical figures of the era, are of considerable historical and theoretical significance. This is partly because these phantoms were associated with pleasurable sensations, in contrast to the loss of a limb, which for centuries had been associated with painful phantoms. We here present several early reports on phantom penile sensations, with the intent of showing what had been described and why more than 200 years ago.

Chapter 32: sensory and perceptual disorders.

Disorders of perception can be examined appropriately only after the normal operations of the senses have been appreciated. There was a long descriptive history of perceptual phenomena before theories were formed and experiments were performed. The phases through which phenomena pass in progressing from description to dissection are charted. The first stage is a description of phenomena, followed by attempts to incorporate them into the body of extant theory. Finally, the phenomena are accepted and utilized to gain more insights into the functioning of the senses and of the brain. In many cases, the phenomena have been described in the distant past, and no clear origin can be determined. In others, there is an obvious break with the past and a phenomenon is described and investigated for the first time. For most of the history of the senses, interest was usually restricted to illusions or oddities of experience: the commonplace characteristics of constant perception were ignored. These factors are taken into consideration with regard to the classification of the senses, phantom limbs, vertigo, and developmental disorders. Imposing some order on the senses was a long but necessary precursor to examining their disorders. Once order was established then a range of fascinating phenomena came to light (particularly in vision). Others that had long been known became open to more detailed scrutiny.

Kaethe Kollwitz (1867-1945): the artist who may have suffered from Alice in Wonderland Syndrome.

Kaethe Kollwitz was a 20th century German artist who grew to fame for her socio-political impressions of Germany during World Wars I and II. In her diary, Kollwitz self-described symptoms of Alice in Wonderland Syndrome during her childhood. She complained of episodes where objects appeared to grow larger or smaller and perceptual distortions where she felt she was diminishing in size. This may explain why Kollwitz's artistic style appeared to shift from naturalism to expressionism, and why her artistic subjects are often shaped with large hands and faces. The distortion present in her visual art may have less to do with a deliberate emphasis of the artist's feelings and more to do with her perceptual experience.