The term "neglect" designates various kinds of failure to orient or respond to or to re... more The term "neglect" designates various kinds of failure to orient or respond to or to report stimuli appearing at the side contralateral to a cerebral lesion. This failure cannot be explained by primary sensory or motor disorders. Essentially the following symptoms of neglect have been reported: inattention to visual (or) acoustical stimuli in one hemifield under unilateral and simultaneous bilateral presentation reduction in orienting responses (eye and head movements) to the neglected hemispace and deviation of head and gaze axes towards the intact hemispace omission or incomplete reproduction of one side of a figure of a text when copying or drawing from memory omission of one half of a well-known scene or picture when reporting from memory deviation of the egocentre as tested by visual, acoustic and somatesthetic stimuli towards the intact hemispace reduction of motor activities, especially for the extremities of one half of the body, which cannot be attributed to a sensory motor deficit inattention to somatesthetic stimuli presented on one side of the body displacement of somatesthetic stimuli, presented on the affected body side, to the intact body side lack of "awareness" of the existence of one half of the body, resulting in, e.g., ignoring this body half when washing or dressing "reference" of the neglected body half to another person unawareness or denial of severe sensorimotor deficits (e.g. hemiparesis) in the affected body half. The syndrome of neglect should be carefully differentiated from inattention phenomena resulting from primary sensory (e.g. hemianopia, restriction of field of search) and motor deficits (hemiparesis, hemiakinesis). In some cases this differentiation is rather difficult, because both types of inattention may be combined. Thus, detailed testing of sensory and motor disorders is needed in order to avoid any precipitate diagnosis of "neglect". The neuropathology of the neglect syndrome is not yet known precisely. Damage to the parietal lobe (presumably of the nondominant hemisphere) is the most common cause for neglect. Lesions at the bank of the sulcus intraparietalis seem especially crucial. Lesions in the dorsolateral frontal lobe causing neglect are mainly situated in Brodmann's premotor areas 8, 9 and 46. Furthermore, lesions of the anterior cingular cortex (area 24), of the thalamus (intralaminar nuclei, nucleus ventralis lateralis, pulvinar) and of the basal ganglia seem to induce neglect.
In recent decades, theories have been presented to explain the nature of dyslexia, but the causes... more In recent decades, theories have been presented to explain the nature of dyslexia, but the causes of dyslexia remained unclear. Although the investigation of the causes of dyslexia presupposes a clear understanding of the concept of cause, such an understanding is missing. The present paper proposes the absence of at least one necessary condition or the absence of all sufficient conditions as causes for impaired reading. The causes of impaired reading include: an incorrect fixation location, too short a fixation time, the attempt to recognize too many letters simultaneously, too large saccade amplitudes, and too short verbal reaction times. It is assumed that a longer required fixation time in dyslexic readers results from a functional impairment of areas V1, V2, and V3 that require more time to complete temporal summation. These areas and areas that receive input from them, such as the fusiform gyrus, are assumed to be impaired in their ability to simultaneously process a string of...
Although subjective conscious experience and introspection have long been considered unscientific... more Although subjective conscious experience and introspection have long been considered unscientific and banned from psychology, they are indispensable in scientific practice. These terms are used in scientific contexts today; however, their meaning remains vague, and earlier objections to the distinction between conscious experience and unconscious processing, remain valid. This also applies to the distinction between conscious visual perception and unconscious visual processing. Damage to the geniculo-striate pathway or the visual cortex results in a perimetrically blind visual hemifield contralateral to the damaged hemisphere. In some cases, cerebral blindness is not absolute. Patients may still be able to guess the presence, location, shape or direction of movement of a stimulus even though they report no conscious visual experience. This “unconscious” ability was termed “blindsight”. The present paper demonstrates how the term conscious visual experience can be introduced in a log...
Sixteen children aged 1 to 15 years who were blind due to an ischemic postgeniculate cerebral les... more Sixteen children aged 1 to 15 years who were blind due to an ischemic postgeniculate cerebral lesion after perinatal asphyxia and 6 children aged 1 to 13 years who were blinded after a postgeniculate traumatic cerebral lesion participated in a systematic visual field training. Thirty-one children who were blind due to a postgeniculate lesion following perinatal asphyxia and 12 children who suffered from blindness after a traumatic postgeniculate lesion served as controls. These children received no visual field training or an ineffective visual field training. The extension of the functional visual field and the functional luminance difference threshold were assessed with a specially designed arc perimeter. In all children blindness had already persisted for at least one year. Visual functions developed within a training period of three months in 15 of 22 children who received visual field training whereas there was no spontaneous recovery in the control group. The functional lumina...
This paper explores whether the child's visual system is more or less vulnerable than the adu... more This paper explores whether the child's visual system is more or less vulnerable than the adult's visual system, whether the capacity of the child's visual system to recover from cerebral blindness exceeds the capacity of the adult's, and which brain structures can mediate visual functions after damage to the geniculostriate visual system. Reports about the development of visual functions in normal and in visually-deprived children and about the recovery of visual functions after incomplete damage to the occipital lobe, unilateral hemispherectomy, and in the absence of both cerebral hemispheres in early life, are reviewed. In addition, 2 new cases are reported. A child (patient 1) is described, who was blindfolded, but had normal visual experience for 2 hours daily between the 24 and the 30 months of age. Despite the daily visual experience, there was an elevation of the luminance difference threshold (LDT) in the periphery of the visual field. An adult patient (pati...
Durch neue Entwicklungen in der Experimentalpsychologie, Neurobiologie und Wissenschaftstheorie w... more Durch neue Entwicklungen in der Experimentalpsychologie, Neurobiologie und Wissenschaftstheorie wurden Methoden und Ergebnisse bereitgestellt, die es erlauben, wesentliche Aspekte dessen, was gewohnlich als bewufit. unbe wufit oder als das Bewuj1tsein bezeichnet wird, unter naturwissenschaftlichen Gesichtspunkten zu betrachten. Die Probleme, die sich dabei stellen, sind so wohl experimentalpsychologischer als auch neurobiologischer und wissen schaftstheoretischer Art. Bereits die Frage nach der Adaquatheit naturwissen schaftlicher Methoden zur Untersuchung von BewuBtsein ist eine wissen schaftstheoretische Frage. Da sie von grundlegender Bedeutung ist, wUJ: "de sie der Behandlung experimentalpsychologischer und neurobiologischer Aspekte vorangestellt. Die sich anschlieBende Diskussion behavioristischer und kogni tiver Standpunkte dient der Darstellung der Problematik einer naturwissen schaftlichen Rekonstruktion von Begriffen wie bewufit. unbewufit. das Bewufit sein. Die Rekons...
Background: Flawless reading presupposes the ability to simultaneously recognize a sequence of le... more Background: Flawless reading presupposes the ability to simultaneously recognize a sequence of letters, to fixate words at a given location for a given time, to exert eye movements of a given amplitude, and to retrieve phonems rapidly from memory. Poor reading performance may be due to an impairment of at least one of these abilities. Objectives: It was investigated whether reading performance of dyslexic children can be improved by changing the reading strategy without any previous training. Methods: 60 dyslexic German children read a text without and with the help of a computer. A tailored computer program subdivided the text into segments that consisted of no more letters than the children could simultaneously recognize, indicated the location in the segments to which the gaze should be directed, indicated how long the gaze should be directed to each segment, which reading saccades the children should execute, and when the children should pronounce the segments. The computer aide...
It is a widely held belief that developmental dyslexia (DD) is a phonological disorder in which r... more It is a widely held belief that developmental dyslexia (DD) is a phonological disorder in which readers have difficulty associating graphemes with their corresponding phonemes. In contrast, the magnocellular theory of dyslexia assumes that DD is a visual disorder caused by dysfunctional magnocellular neural pathways. The review explores arguments for and against these theories. Recent results have shown that DD is caused by (1) a reduced ability to simultaneously recognize sequences of letters that make up words, (2) longer fixation times required to simultaneously recognize strings of letters, and (3) amplitudes of saccades that do not match the number of simultaneously recognized letters. It was shown that pseudowords that could not be recognized simultaneously were recognized almost without errors when the fixation time was extended. However, there is an individual maximum number of letters that each reader with DD can recognize simultaneously. Findings on the neurobiological bas...
The term "neglect" designates various kinds of failure to orient or respond to or to re... more The term "neglect" designates various kinds of failure to orient or respond to or to report stimuli appearing at the side contralateral to a cerebral lesion. This failure cannot be explained by primary sensory or motor disorders. Essentially the following symptoms of neglect have been reported: inattention to visual (or) acoustical stimuli in one hemifield under unilateral and simultaneous bilateral presentation reduction in orienting responses (eye and head movements) to the neglected hemispace and deviation of head and gaze axes towards the intact hemispace omission or incomplete reproduction of one side of a figure of a text when copying or drawing from memory omission of one half of a well-known scene or picture when reporting from memory deviation of the egocentre as tested by visual, acoustic and somatesthetic stimuli towards the intact hemispace reduction of motor activities, especially for the extremities of one half of the body, which cannot be attributed to a sensory motor deficit inattention to somatesthetic stimuli presented on one side of the body displacement of somatesthetic stimuli, presented on the affected body side, to the intact body side lack of "awareness" of the existence of one half of the body, resulting in, e.g., ignoring this body half when washing or dressing "reference" of the neglected body half to another person unawareness or denial of severe sensorimotor deficits (e.g. hemiparesis) in the affected body half. The syndrome of neglect should be carefully differentiated from inattention phenomena resulting from primary sensory (e.g. hemianopia, restriction of field of search) and motor deficits (hemiparesis, hemiakinesis). In some cases this differentiation is rather difficult, because both types of inattention may be combined. Thus, detailed testing of sensory and motor disorders is needed in order to avoid any precipitate diagnosis of "neglect". The neuropathology of the neglect syndrome is not yet known precisely. Damage to the parietal lobe (presumably of the nondominant hemisphere) is the most common cause for neglect. Lesions at the bank of the sulcus intraparietalis seem especially crucial. Lesions in the dorsolateral frontal lobe causing neglect are mainly situated in Brodmann's premotor areas 8, 9 and 46. Furthermore, lesions of the anterior cingular cortex (area 24), of the thalamus (intralaminar nuclei, nucleus ventralis lateralis, pulvinar) and of the basal ganglia seem to induce neglect.
In recent decades, theories have been presented to explain the nature of dyslexia, but the causes... more In recent decades, theories have been presented to explain the nature of dyslexia, but the causes of dyslexia remained unclear. Although the investigation of the causes of dyslexia presupposes a clear understanding of the concept of cause, such an understanding is missing. The present paper proposes the absence of at least one necessary condition or the absence of all sufficient conditions as causes for impaired reading. The causes of impaired reading include: an incorrect fixation location, too short a fixation time, the attempt to recognize too many letters simultaneously, too large saccade amplitudes, and too short verbal reaction times. It is assumed that a longer required fixation time in dyslexic readers results from a functional impairment of areas V1, V2, and V3 that require more time to complete temporal summation. These areas and areas that receive input from them, such as the fusiform gyrus, are assumed to be impaired in their ability to simultaneously process a string of...
Although subjective conscious experience and introspection have long been considered unscientific... more Although subjective conscious experience and introspection have long been considered unscientific and banned from psychology, they are indispensable in scientific practice. These terms are used in scientific contexts today; however, their meaning remains vague, and earlier objections to the distinction between conscious experience and unconscious processing, remain valid. This also applies to the distinction between conscious visual perception and unconscious visual processing. Damage to the geniculo-striate pathway or the visual cortex results in a perimetrically blind visual hemifield contralateral to the damaged hemisphere. In some cases, cerebral blindness is not absolute. Patients may still be able to guess the presence, location, shape or direction of movement of a stimulus even though they report no conscious visual experience. This “unconscious” ability was termed “blindsight”. The present paper demonstrates how the term conscious visual experience can be introduced in a log...
Sixteen children aged 1 to 15 years who were blind due to an ischemic postgeniculate cerebral les... more Sixteen children aged 1 to 15 years who were blind due to an ischemic postgeniculate cerebral lesion after perinatal asphyxia and 6 children aged 1 to 13 years who were blinded after a postgeniculate traumatic cerebral lesion participated in a systematic visual field training. Thirty-one children who were blind due to a postgeniculate lesion following perinatal asphyxia and 12 children who suffered from blindness after a traumatic postgeniculate lesion served as controls. These children received no visual field training or an ineffective visual field training. The extension of the functional visual field and the functional luminance difference threshold were assessed with a specially designed arc perimeter. In all children blindness had already persisted for at least one year. Visual functions developed within a training period of three months in 15 of 22 children who received visual field training whereas there was no spontaneous recovery in the control group. The functional lumina...
This paper explores whether the child's visual system is more or less vulnerable than the adu... more This paper explores whether the child's visual system is more or less vulnerable than the adult's visual system, whether the capacity of the child's visual system to recover from cerebral blindness exceeds the capacity of the adult's, and which brain structures can mediate visual functions after damage to the geniculostriate visual system. Reports about the development of visual functions in normal and in visually-deprived children and about the recovery of visual functions after incomplete damage to the occipital lobe, unilateral hemispherectomy, and in the absence of both cerebral hemispheres in early life, are reviewed. In addition, 2 new cases are reported. A child (patient 1) is described, who was blindfolded, but had normal visual experience for 2 hours daily between the 24 and the 30 months of age. Despite the daily visual experience, there was an elevation of the luminance difference threshold (LDT) in the periphery of the visual field. An adult patient (pati...
Durch neue Entwicklungen in der Experimentalpsychologie, Neurobiologie und Wissenschaftstheorie w... more Durch neue Entwicklungen in der Experimentalpsychologie, Neurobiologie und Wissenschaftstheorie wurden Methoden und Ergebnisse bereitgestellt, die es erlauben, wesentliche Aspekte dessen, was gewohnlich als bewufit. unbe wufit oder als das Bewuj1tsein bezeichnet wird, unter naturwissenschaftlichen Gesichtspunkten zu betrachten. Die Probleme, die sich dabei stellen, sind so wohl experimentalpsychologischer als auch neurobiologischer und wissen schaftstheoretischer Art. Bereits die Frage nach der Adaquatheit naturwissen schaftlicher Methoden zur Untersuchung von BewuBtsein ist eine wissen schaftstheoretische Frage. Da sie von grundlegender Bedeutung ist, wUJ: "de sie der Behandlung experimentalpsychologischer und neurobiologischer Aspekte vorangestellt. Die sich anschlieBende Diskussion behavioristischer und kogni tiver Standpunkte dient der Darstellung der Problematik einer naturwissen schaftlichen Rekonstruktion von Begriffen wie bewufit. unbewufit. das Bewufit sein. Die Rekons...
Background: Flawless reading presupposes the ability to simultaneously recognize a sequence of le... more Background: Flawless reading presupposes the ability to simultaneously recognize a sequence of letters, to fixate words at a given location for a given time, to exert eye movements of a given amplitude, and to retrieve phonems rapidly from memory. Poor reading performance may be due to an impairment of at least one of these abilities. Objectives: It was investigated whether reading performance of dyslexic children can be improved by changing the reading strategy without any previous training. Methods: 60 dyslexic German children read a text without and with the help of a computer. A tailored computer program subdivided the text into segments that consisted of no more letters than the children could simultaneously recognize, indicated the location in the segments to which the gaze should be directed, indicated how long the gaze should be directed to each segment, which reading saccades the children should execute, and when the children should pronounce the segments. The computer aide...
It is a widely held belief that developmental dyslexia (DD) is a phonological disorder in which r... more It is a widely held belief that developmental dyslexia (DD) is a phonological disorder in which readers have difficulty associating graphemes with their corresponding phonemes. In contrast, the magnocellular theory of dyslexia assumes that DD is a visual disorder caused by dysfunctional magnocellular neural pathways. The review explores arguments for and against these theories. Recent results have shown that DD is caused by (1) a reduced ability to simultaneously recognize sequences of letters that make up words, (2) longer fixation times required to simultaneously recognize strings of letters, and (3) amplitudes of saccades that do not match the number of simultaneously recognized letters. It was shown that pseudowords that could not be recognized simultaneously were recognized almost without errors when the fixation time was extended. However, there is an individual maximum number of letters that each reader with DD can recognize simultaneously. Findings on the neurobiological bas...
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